High-transmittance colorless transparent polyimide film and preparation method thereof

Abstract

The invention relates to the technical field of polyimide materials, in particular to a high-transmittance colorless transparent polyimide film and a preparation method thereof. The preparation method comprises the following steps: polymerizing a diamine monomer containing fluorine and amide groups, a fluorine-containing or ester ring dianhydride monomer and a triamine cross-linking agent to generate polyimide; and then carrying out gradient heating on the polyimide solution to form a film, so as to prepare the transparent polyimide film containing the intermolecular hydrogen bond and the micro-crosslinking structure. According to the invention, through the strong electron withdrawing capability and the large volume characteristic of the fluorine-containing group, the intramolecular and intermolecular charge transfer effect is effectively reduced so as to guarantee high transmittance; an intermolecular hydrogen bond is constructed by means of an amide group in the diamine monomer containing fluorine and the amide group, and a structural support is provided for the regular formation of a subsequent micro-crosslinking structure; and finally, a triamine cross-linking agent is combined to form a micro-cross-linked structure, so that the polyimide film keeps high transmittance, the dielectric property and the mechanical property are improved, and the polyimide film has high glass transition temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyimide materials, in particular to a high-transmittance colorless transparent polyimide film and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid iteration of the flexible electronic industry, flexible display technology has gradually penetrated into many fields such as folding terminals, wearable devices, transparent displays, and flexible energy devices. These application scenarios have put forward diversified requirements for the performance of the core material, i.e., the polymer flexible substrate. In addition to meeting the basic flexibility requirements, the substrate material also needs to have excellent optical properties to ensure the display effect, reliable mechanical strength to cope with repeated bending, stable size performance to adapt to high-temperature processing procedures, and low dielectric-related properties, which are also the key to adapting to high-frequency microelectronic signal transmission. The coordinated compliance of these performance indicators is the core prerequisite for promoting the landing of flexible electronic technology.

[0003] Polyimide is a classic high-performance polymer formed by the polymerization of diamine and dianhydride. The rigid conjugated aromatic backbone and strong intermolecular forces in its molecular structure endow the material with excellent heat stability and basic mechanical properties, and it has long played a key role in the fields of aerospace, precision electronics, etc. However, due to the significant charge transfer complex effect within and between molecules, traditional polyimides generally exhibit varying degrees of yellow-brown appearance, poor light transmission, and are difficult to meet the needs of high light transmittance and colorless appearance in optical application scenarios such as flexible display, which greatly restricts its application expansion in emerging flexible electronic fields.

[0004] To break through the optical limitations of traditional polyimides, the industry has carried out a lot of research around the preparation of transparent polyimides. By regulating the molecular structure to effectively suppress the charge transfer complex effect, certain progress has been made in improving the transparency of the material.

[0005] However, the existing technical solutions generally have performance imbalance problems: some methods weaken the intermolecular forces when optimizing the optical properties, resulting in a decrease in material mechanical strength; some solutions can maintain mechanical properties, but improper molecular structure design can cause a decrease in glass transition temperature, affecting the feasibility of high-temperature processing; at the same time, the regulation of dielectric constant and dielectric loss is often ignored, making it difficult to meet the application standards of high-frequency microelectronics. In addition, the lack of processability in material synthesis and film formation process also increases the difficulty and cost of industrial production. How to realize the coordinated optimization of multiple performance indicators has become the core challenge of transparent polyimide material research and development.

[0006] In summary, developing a preparation technology of polyimide film capable of synchronously realizing colorless transparent appearance, high light transmittance, excellent mechanical properties, heat resistance and good dielectric properties is not only the key to solve the performance bottleneck of current flexible electronic materials, but also has a promoting effect on the upgrading of high-end optical and microelectronic industries. SUMMARY

[0007] In view of the above problems or deficiencies, the present application provides a high-transmittance colorless transparent polyimide film and a preparation method thereof, to solve the problem that colorless transparent appearance, high light transmittance, good mechanical properties and dielectric properties of polyimide film cannot be achieved simultaneously.

[0008] A preparation method of a high-transmittance colorless transparent polyimide film, comprising the following steps:

[0009] Step 1: under the protection of inert gas at -5-0℃, a diamine monomer containing fluorine and amide groups and a fluorine-containing or ester ring dianhydride monomer are added to an organic solvent, and a linear polyamic acid solution is obtained after reacting for 12-24h; then a triamine crosslinking agent is added, and the reaction is continued for 12-24h to obtain a polyamic acid solution with a micro-crosslinked structure and a solid content of 10wt.%-20wt.%;

[0010] The molar ratio of the diamine monomer containing fluorine and amide groups to the fluorine-containing or ester ring dianhydride monomer is 1:1-1.075; and the molar ratio of the diamine monomer containing fluorine and amide groups to the triamine crosslinking agent is 1:0.01-0.05.

[0011] Step 2: after adjusting the reaction temperature to room temperature, a dehydrating agent and a catalyst are added to the polyamic acid solution obtained in step 1 to perform a dehydration reaction, and after 5-14h, polyimide powder is obtained by precipitation and drying treatment;

[0012] The molar amount of the dehydrating agent is 3-5 times the molar amount of the diamine containing fluorine and amide groups; and the molar amount of the catalyst is 3-5 times the molar amount of the diamine containing fluorine and amide groups.

[0013] Step 3: the polyimide powder obtained in step 2 is dissolved in an organic solvent to obtain a homogeneous polyimide solution, and the solid content of the solution is 10wt.%-25wt.%.

[0014] Step 4: the homogeneous polyimide solution obtained in step 3 is coated on a substrate, and heat treatment is performed under vacuum to obtain a high-transmittance colorless transparent polyimide film.

[0015] Further, the diamine monomer containing fluorine and amide group is one or more of N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide) (AB-TFMB), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-N-methylbenzamide), N,N'-(1,4-phenylene)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(1,4-phenylene)bis(4-amino-2-(trifluoromethyl)benzamide), and the specific structural formula is:

[0016]

[0017] Further, the diamine monomer containing fluorine and amide group is one or more of N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide) (AB-TFMB), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-N-methylbenzamide), N,N'-(1,4-phenylene)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(1,4-phenylene)bis(4-amino-2-(trifluoromethyl)benzamide), and the specific structural formula is:

[0018]

[0019] Further, the diamine monomer containing fluorine and amide group is one or more of N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide) (AB-TFMB), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-N-methylbenzamide), N,N'-(1,4-phenylene)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(1,4-phenylene)bis(4-amino-2-(trifluoromethyl)benzamide), and the specific structural formula is:

[0020]

[0021] Further, the diamine monomer containing fluorine and amide group is one or more of N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide) (AB-TFMB), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-N-methylbenzamide), N,N'-(1,4-phenylene)bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(1,4-phenylene)bis(4-amino-2-(trifluoromethyl)benzamide), and the specific structural formula is:

[0022]

[0023] Further, the dehydrating agent is one or more of acetic anhydride, propionic anhydride, butyric anhydride, and the specific structural formula is:

[0024]

[0025] Further, the catalyst is one or more of pyridine, quinoline, isoquinoline, and triethylamine, and the specific structural formula is:

[0026]

[0027] Further, the process of precipitation and drying treatment in step 2 is as follows: the dehydrated reaction solution is added into a precipitant for precipitation treatment, wherein the precipitant is one or more of deionized water, methanol, ethanol, propanol, butanol, and isopropanol; and the process of drying treatment is as follows: the polyimide after precipitation treatment is heated in a vacuum drying oven at 100-120 DEG C for 12-24 h.

[0028] Further, the process of heat treatment in step 4 is as follows: vacuum drying at 50-70 DEG C for 2-5 h, vacuum drying at 90-110 DEG C for 1-2.5 h, vacuum drying at 140-160 DEG C for 1-2 h, vacuum drying at 190-210 DEG C for 1-2 h, and finally vacuum drying at 220-250 DEG C for 1-3 h.

[0029] Further, the high-transmittance colorless transparent polyimide film prepared by the above method has the advantages of colorless transparent appearance, high light transmittance, good mechanical properties and dielectric properties.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] 1) The present application first introduces a fluorine-containing strong electronegative and bulky group, which on the one hand reduces the close packing degree of the molecular chain and increases the interchain free volume through steric hindrance effect, and on the other hand weakens the intramolecular and intermolecular charge transfer effect and reduces the material color-related micro factors by virtue of the strong electron-withdrawing property of the fluorine-containing group. Ultimately, the prepared polyimide film has good transmittance in the visible light range and presents a colorless appearance, which lays a foundation for subsequent optimization of performance in cooperation with other structures.

[0032] 2) Unlike existing technologies that only introduce fluorine-containing and bulky groups, this invention further introduces diamine monomers containing both fluorine and amide groups. The synergistic effect of these two groups is key to performance improvement. The loose molecular packing environment created by the fluorine-containing groups prevents local structural rigidity caused by excessive aggregation of amide groups, resulting in more uniform and stable intermolecular hydrogen bonds. Furthermore, hydrogen bonds between molecular chains can compensate for insufficient intermolecular bonding that might result from the fluorine-containing groups, ensuring that the overall molecular chain arrangement is both moderately loose and structurally stable. This synergistic effect not only improves the material's thermal stability and chemical corrosion resistance but also allows thermal properties to complement other fundamental properties, avoiding performance imbalances caused by single-structure optimization. It positively impacts the dimensional matching and thermal tolerance of flexible substrates during high-temperature fabrication processes, improving the performance balance issues present in existing technologies.

[0033] 3) This invention further introduces a triamine crosslinking agent to construct a micro-crosslinked structure. Here, the fluorinated groups, amide structure, and micro-crosslinked structure form a triple synergistic effect. In existing technologies, when constructing a micro-crosslinked structure alone, the uneven distribution of crosslinking points is easily caused by excessively sparse molecular chain stacking, affecting performance stability. In this invention, the steric hindrance of the fluorinated groups can regulate the molecular chain spacing, providing spatial conditions for the uniform distribution of crosslinking points. The intermolecular forces generated by the amide groups through hydrogen bonds can stabilize the local arrangement of molecular chains in advance, providing structural support for the subsequent micro-crosslinking reaction to form a regular three-dimensional network. Under the synergistic effect of the three structures, the micro-crosslinked structure effectively restricts the disordered movement of molecular chains through the covalent bonds between molecular chains. Compared with linear polyimide films with the same main chain structure, it can significantly improve the strength and modulus of the film, enhance mechanical properties, and maintain the structural stability of the material through a regular crosslinked network, avoiding the degradation of transparency and thermal properties after the improvement of mechanical properties. This represents a breakthrough in multi-performance synergistic optimization, improving the problem of balancing mechanical properties with other key properties in existing technologies. Attached Figure Description

[0034] Figure 1 The optical properties of the polyimide films prepared in Comparative Examples 1-2 and Example 1 are shown in the figure.

[0035] Figure 2 Dielectric constant diagrams of the polyimide films prepared in Comparative Examples 1-2 and Example 1;

[0036] Figure 3 The dielectric loss diagrams are for the polyimide films prepared in Comparative Examples 1-2 and Example 1.

[0037] Figure 4 The images show physical photos of the polyimide films prepared in Comparative Examples 1-2 and Example 1.

[0038] Figure 5 Dynamic mechanical analysis graph of the polyimide film prepared for Example 1. DETAILED DESCRIPTION

[0039] The present application is further explained in detail by the accompanying drawings and examples.

[0040] Comparative Example 1

[0041] (1) A three-necked flask was charged with 1.01 g (3.15 mmol) of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB) and 15 ml of N,N-dimethylacetamide (DMAc), and stirred under nitrogen until completely dissolved.

[0042] The temperature was lowered to 0°C, and 1.47 g (3.3 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was further added, and the reaction was continued at the temperature for 24 h after dissolution. After 1 g (12.61 mmol) of acetic anhydride and 1 g (12.61 mmol) of pyridine were added, the dehydration reaction was performed at room temperature for 12 h, and the resulting 15 wt.% linear polyimide solution was precipitated into 500 ml of ethanol, washed with ethanol three times, and finally subjected to vacuum drying at 120°C.

[0043] (2) A three-necked flask was charged with 1 g of polyimide and 9 g of N,N-dimethylacetamide (DMAc) to obtain a linear polyimide solution having a solid content of 10 wt.%. After the solution was filtered through a needle filter to remove impurities, a homogeneous polyimide solution was obtained. Then, it was coated on a glass substrate having a smooth surface, and sequentially subjected to heat treatment at 60°C for 2 h, 100°C for 1 h, 150°C for 1 h, 200°C for 1 h, and 220°C for 1 h under vacuum. The resulting glass substrate was removed from the mold by placing it in warm water at 30°C, washed with ethanol three times after the removal was completed, and left to stand in a drying oven at 60°C for 24 h, and finally a polyimide film was obtained, which was designated as PI-1.

[0044] Comparative Example 2

[0045] (1) A three-necked flask was charged with 1.35 g (2.42 mmol) of N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide) (AB-TFMB) and 15 ml of N,N-dimethylacetamide (DMAc), and stirred under nitrogen until completely dissolved.

[0046] The temperature was lowered to 0°C, and then 1.13 g (2.54 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was added, and after dissolution, the reaction was continued at this temperature for 24 h; after 0.99 g (9.69 mmol) of acetic anhydride and 0.77 g (9.69 mmol) of pyridine were added, the dehydration reaction was carried out at room temperature for 12 h, and then the obtained 15 wt.% linear polyimide solution was precipitated into 500 ml of ethanol, the precipitate was washed with ethanol three times, and finally vacuum drying treatment was carried out at 120°C.

[0047] (2) 1 g of polyimide and 9 g of N,N-dimethylacetamide (DMAc) were added to a three-necked flask to obtain a linear polyimide solution having a solid content of 10 wt.%; after the solution was filtered through a needle filter to remove impurities, a homogeneous polyimide-containing solution was obtained. Then, it was coated onto a glass substrate having a smooth surface, and was sequentially subjected to heat treatment at 60°C for 2 h, 100°C for 1 h, 150°C for 1 h, 200°C for 1 h, and 220°C for 1 h under vacuum. The obtained glass substrate was removed from the mold by placing it in warm water at 30°C, and after the removal was completed, it was washed with ethanol three times, was left to stand in a drying oven at 60°C for 24 h, and finally a polyimide film was obtained, and the polyimide film was named PI-2.

[0048] Example 1

[0049] (1) 1.35 g (2.42 mmol) of N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4- aminobenzamide) (AB-TFMB) and 15 ml of N,N-dimethylacetamide (DMAc) were added to a three-necked flask, and stirring was carried out under nitrogen until complete dissolution.

[0050] The temperature was lowered to 0°C, and then 1.13 g (2.54 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was added, and after dissolution, the reaction was continued at this temperature for 24 h; after 0.99 g (9.69 mmol) of acetic anhydride and 0.77 g (9.69 mmol) of pyridine were added, the dehydration reaction was carried out at room temperature for 12 h, and then the obtained 15 wt.% linear polyimide solution was precipitated into 500 ml of ethanol, the precipitate was washed with ethanol three times, and finally vacuum drying treatment was carried out at 120°C.

[0051] (2) 1 g of the polyimide was added into a 9 g of N, N-dimethylacetamide (DMAc) in a three-neck flask to obtain a polyimide solution with a solid content of 10 wt.%, and then the solution was filtered through a needle filter to remove impurities to obtain a homogeneous polyimide solution; then, the solution was coated on a glass substrate with a smooth surface, and then was sequentially subjected to 60°C for 2 h, 100°C for 1 h, 150°C for 1 h, 200°C for 1 h, and 220°C for 1 h under vacuum. The obtained glass substrate was placed in warm water at 30°C for demolding, and then was washed with ethanol for three times, and was placed in a drying box at 60°C for 24 h, to obtain a polyimide film, which was named as PI-3.

[0052] The optical properties of the film samples prepared in the above Comparative Example 1-2 and Example 1 were determined by using an ultraviolet-visible spectrophotometer; the dielectric properties of the film samples were determined by using a broadband dielectric impedance spectrometer; and the tensile properties of the film samples were determined by using a universal material testing machine according to the standard of ASTM D882.

[0053] The actual polyimide films prepared in Comparative Example 1-2 and Example 1 were as shown in Figure 4 The optical properties of the polyimide films prepared in Comparative Example 1-2 and Example 1 were as shown in Figure 1 The dielectric constant of the polyimide films prepared in Comparative Example 1-2 and Example 1 was as shown in Figure 2 The dielectric loss of the polyimide films prepared in Comparative Example 1-2 and Example 1 was as shown in Figure 3 Figure 5 The dynamic mechanical analysis graph of the polyimide film prepared in Example 1 was as shown in

[0054] Table 1, optical properties, dielectric properties and mechanical properties of the samples of Comparative Example 1-2 and Example 1

[0055]

[0056] As can be seen from the data in Table 1, the polyimide film after adding the diamine monomer containing fluorine and amide groups and the triamine crosslinking agent has improved dielectric properties and mechanical properties on the basis of maintaining the optical properties.

[0057] As can be seen from the test results of the above examples and comparative examples, the high-transmittance colorless transparent polyimide film provided by the present application has improved dielectric properties and mechanical properties while retaining high transmittance, and has a high glass transition temperature.​

Claims

1. A method for preparing a high-transmittance colorless and transparent polyimide film, characterized in that, Includes the following steps: Step 1: Under -5 to 0°C and inert gas protection, diamine monomers containing fluorine and amide groups and fluorine-containing or ester ring dianhydride monomers are added to an organic solvent and reacted for 12 to 24 hours to obtain a linear polyamic acid solution; then a triamine crosslinking agent is added and the reaction continues for 12 to 24 hours to obtain a polyamic acid solution with a micro-crosslinked structure and a solid content of 10 wt.% to 20 wt.%. The molar ratio of the diamine monomer containing fluorine and amide groups to the fluorine-containing or ester-ring dianhydride monomer is 1:1 to 1.075; the molar ratio of the diamine monomer containing fluorine and amide groups to the triamine crosslinking agent is 1:0.01 to 0.

05. Step 2: After adjusting the reaction temperature to room temperature, add a dehydrating agent and a catalyst to the polyamic acid solution obtained in Step 1 to carry out a dehydration reaction. After 5-14 hours, after precipitation and drying, polyimide powder is obtained. The molar amount of the dehydrating agent is 3 to 5 times the molar amount of the diamine containing fluorine and amide groups; the molar amount of the catalyst is 3 to 5 times the molar amount of the diamine containing fluorine and amide groups. Step 3: Dissolve the polyimide powder obtained in Step 2 in an organic solvent to obtain a homogeneous polyimide solution with a solid content of 10 wt.% to 25 wt.%. Step 4: Coat the homogeneous polyimide solution obtained in Step 3 onto the substrate and heat-treat it under vacuum to obtain a high-transmittance colorless and transparent polyimide film.

2. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that: The diamine monomer containing fluorine and amide groups is N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide)AB-TFMB, N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-3-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-methylbenzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl) One or more of bis(4-amino-3-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-2-(trifluoromethyl)benzamide), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-amino-N-methylbenzamide), N,N'-(1,4-phenylene)bis(4-amino-3-(trifluoromethyl)benzamide), and N,N'-(1,4-phenylene)bis(4-amino-2-(trifluoromethyl)benzamide), with the specific structural formula as follows:

3. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that: The fluorine-containing or ester-cyclic dianhydride monomer is one or more of 4,4'-(hexafluoroisopropene)phthalic anhydride 6FDA, cyclobutanetetracarboxylic dianhydride CBDA, 1,2,4,5-cyclohexanetetracarboxylic dianhydride PMDA, and cyclopentanone dispironorbornenetetracarboxylic dianhydride CpODA, with the specific structural formula as follows:

4. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that: The triamine crosslinking agent is one or more of 4,4',4”-[benzene-1,3,5-triyltri(oxy)]tris[3-(trifluoromethyl)aniline]TFAPOB, 1,3,5-tris(4-aminophenoxy)benzene, 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, tri(4-aminophenyl)amine, and melamine, with the specific structural formula as follows:

5. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that: The organic solvent is one or more of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), γ-butyrolactone (GBL), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO), with the specific structural formula as follows:

6. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that: The dehydrating agent is one or more of acetic anhydride, propionic anhydride, and butyric anhydride, with the following specific structural formula:

7. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that: The catalyst is one or more of pyridine, quinoline, isoquinoline, and triethylamine, with the following specific structural formula:

8. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that, The precipitation and drying process in step 2 is as follows: the dehydrated reaction solution is added to a precipitant for precipitation treatment, wherein the precipitant is one or more of deionized water, methanol, ethanol, propanol, butanol and isopropanol; the drying process is as follows: the polyimide after precipitation treatment is dried in a vacuum drying oven at 100-120°C for 12-24 hours.

9. The method for preparing a high-transmittance colorless and transparent polyimide film as described in claim 1, characterized in that, The heat treatment process in step 4 is as follows: first, vacuum dry at 50-70℃ for 2-5 hours, then vacuum dry at 90-110℃ for 1-2.5 hours, then vacuum dry at 140-160℃ for 1-2 hours, then vacuum dry at 190-210℃ for 1-2 hours, and finally vacuum dry at 220-250℃ for 1-3 hours.

10. A high-transmittance colorless and transparent polyimide film, characterized in that: Prepared using any one of the methods described in claims 1-9.

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