Semi-aromatic CPI film and preparation method thereof

Abstract

The invention relates to the technical field of flexible display materials, in particular to a semi-aromatic CPI film and a preparation method thereof. The invention relates to a semi-aromatic CPI film. The semi-aromatic CPI film is prepared by carrying out polymerization reaction on alicyclic dianhydride and diamine, the diamine comprises a diamine containing trifluoromethyl, a diamine containing benzimidazole and a diamine containing vinyl phenoxy; the alicyclic dianhydride comprises one or two of norbornane-2-spiro-alpha-cyclopentanone-alpha '-spiro-2'-norbornane-5, 5 ', 6, 6'-tetracarboxylic dianhydride and cyclobutane tetracarboxylic dianhydride, and the alicyclic dianhydride comprises one or two of norbornane-2-spiro-alpha-cyclopentanone-alpha '-spiro-2'-norbornane-5, 5 ', 6, in order to solve the problem that application of an existing polyimide film in a flexible substrate is limited due to the fact that optical properties, high temperature resistance, mechanical properties and dimensional thermal stability of the existing polyimide film are difficult to consider, the temperature resistance, the dimensional stability and the mechanical properties are enhanced while the optical properties of colorless transparent polyimide are kept, and the application prospect is wide. And the application of the flexible display substrate in the field of flexible display substrates is widened.

Description

Technical Field

[0001] The present application relates to the technical field of flexible display materials, and in particular to a semi-aromatic CPI film and a preparation method thereof. Background Art

[0002] With the rapid development of technologies such as flexible electronics and 5G, flexible displays have become a key direction for the transformation and upgrading of my country's display industry. Flexible display devices stand out among many display devices due to their many advantages, such as deformability, bendability, foldability, low energy consumption, ultra-lightness, unbreakableness, and changeable shape. Currently, the mainstream technologies for realizing flexible displays include organic light-emitting diodes (OLEDs), electronic paper (e-Paper), and liquid crystal displays (LCDs), among which organic light-emitting diodes (OLEDs) are the most widely used. In the implementation of flexible OLEDs, yellow polyimide slurry is usually used as a TFT backplane. However, the existing yellow substrate cannot meet the requirements of full visible light transmittance for under-screen cameras, making it difficult to solve the problem of opening the front camera hole. Therefore, CPI slurry film was developed to replace yellow PI film as a TFT substrate. Transparent polyimide (CPI) has the characteristics of high light transmittance and light color, and is a key material for the next generation of flexible display substrates such as under-screen cameras and transparent displays.

[0003] Because electronic components must be manufactured under high-temperature conditions and undergo multiple cycles of high and low temperatures, polyimides are required to possess excellent high-temperature resistance and dimensional thermal stability. However, the optical properties, high-temperature resistance, mechanical properties, and dimensional thermal stability of current polyimide films often conflict with each other, making it difficult to achieve a balance, limiting their widespread application in flexible substrates. Therefore, the development of colorless, transparent polyimide (CPI) with excellent heat resistance, high optical transparency, and dimensional thermal stability is urgent. Summary of the Invention

[0004] In order to improve the high temperature resistance of colorless and transparent polyimide, maintain its own optical properties while enhancing the temperature resistance, dimensional stability and mechanical properties, the present application provides a semi-aromatic CPI film and a preparation method thereof.

[0005] In a first aspect, the present application provides a semi-aromatic CPI film, which adopts the following technical solution: A semi-aromatic CPI film is prepared by polymerization reaction of an alicyclic dianhydride and a diamine; the diamine includes a trifluoromethyl-containing diamine, a benzimidazole-containing diamine, and a vinylphenoxy-containing diamine; the alicyclic dianhydride includes one or two of norbornane-2-spiro-α-cyclopentanone-α'-spiro-2'-norbornane-5,5',6,6'-tetracarboxylic dianhydride and cyclobutanetetracarboxylic dianhydride.

[0006] By adopting the above technical solution, the present application contains alicyclic dianhydride and benzene ring-containing diamine connected with specific functional groups and positional relationships, which can not only improve the transparency and mechanical properties of the prepared polyimide film, but also reduce the expansion coefficient of the polyimide film, thereby improving the dimensional stability; and taking into account the strength, thermal stability and light transmittance of the polyimide film to the greatest extent. Through the characteristics and symmetry of the spatial structure of the spiro ring in the alicyclic dianhydride, the movement of the molecular chain is restricted. After combining with the diamine containing trifluoromethyl, the diamine containing benzimidazole and the diamine containing vinylphenoxy, a molecular structure with good regularity can be formed, which significantly improves the glass transition temperature. In addition, the alicyclic structure of the alicyclic dianhydride gives the molecular chain a certain flexibility, which can improve the toughness of the film. At the same time, when combined with the diamine containing benzimidazole, the benzimidazole structure and the alicyclic dianhydride form a tight stack, which enhances the interaction between the molecules, making it difficult for the molecular chain to slide when the film is subjected to external force, further optimizing the heat resistance and dimensional stability of the film. In addition, the vinyl groups in the vinylphenoxy-containing diamine further optimize the cross-linking structure to form a more stable three-dimensional network structure, further improving the thermal stability, mechanical properties and chemical stability of the polyimide, and jointly participating in the polymerization reaction of alicyclic diamines and trifluoromethyl-containing diamines, further improving the regularity of the molecular chain structure, promoting uniform intermolecular interactions, and forming a uniform microstructure, thereby ensuring the uniformity of optical properties; it is not easy to cause light absorption and scattering, so that the film has good optical transparency, and together prepares a semi-aromatic colorless and transparent polyimide film to meet the demand for high-performance materials in the field of flexible displays.

[0007] In a specific embodiment, the molar ratio of the alicyclic dianhydride to the diamine is 1:(0.9-1.1).

[0008] By adopting the above technical solution, the alicyclic dianhydride and diamine in the proportion of the present application, the polymer molecular chains generated by the reaction are arranged in a relatively orderly manner, the regularity between the molecular chains is good, and a stable cross-linked network is formed between the polymer molecular chains, which can limit the movement of the molecular chains. When the polymer is heated, the molecular chains are not easy to slide and break, and a higher energy is required to destroy its chemical bonds and intermolecular forces, thereby having better thermal stability. A small amount of alicyclic dianhydride reduces the cross-linking density between the molecular chains, making the molecular chains more likely to slide when heated, resulting in the material being deformed at lower temperatures. A small amount of diamine will lead to limited molecular chain growth, a wider molecular weight distribution, and the low molecular weight portion is easily volatilized or decomposed when heated, resulting in side reactions, affecting the thermal stability of the material.

[0009] In a specific embodiment, the molar ratio of the trifluoromethyl-containing diamine, the benzimidazole-containing diamine, and the vinylphenoxy-containing diamine is (9-14):(5-9):2.

[0010] Preferably, the trifluoromethyl-containing diamine is TFMB; the benzimidazole-containing diamine is BIA; and the vinylphenoxy-containing diamine is DFPTM. The monomer structural formulas are as follows: By adopting the above technical solution, this application selects trifluoromethyl donor diamine TFMB. Due to the strong electronegativity of fluorine atoms, most of the electron cloud is concentrated near the fluorine atom group, which strongly weakens the electron cloud conjugation in the main chain and significantly weakens the CTC effect within and between chains, making the PI film generally lighter in color; at the same time, a rigid diamine BIA with a kinked benzimidazole structure is introduced. The rigid imidazole structure can effectively improve the heat resistance and dimensional stability of polyimide, and the kinked rigid imidazole structure can also effectively reduce the packing density of the polymer chain and increase the free volume, which can improve the thermal stability of the material while ensuring optical properties. On this basis, by selecting the monomer DFPTM containing vinylphenoxy, the presence of the vinylphenoxy group in DFPTM forms a cross-linked network between the molecular chains of the latently cross-linkable third monomer polyimide, adjusting the thermal expansion properties of the film and achieving mutual coordination between optical properties, heat resistance and dimensional stability.

[0011] The applicant has found that when the BIA content exceeds the range of this application, the optical properties of the polymer are significantly reduced. A too low DFP™ content can affect crosslinking between molecular chains, thereby affecting thermal stability and mechanical properties. A too high DFP™ content can hinder the molecular weight of the polymer, resulting in a decline in overall performance and impaired film processing. Furthermore, a reduced fluorine content can also affect the optical properties of the polymer.

[0012] In a second aspect, the present application provides a method for preparing a semi-aromatic CPI film, which adopts the following technical solution: A method for preparing a semi-aromatic CPI film comprises the following steps: adding a diamine to a polar solvent, then sequentially adding a catalyst and an alicyclic dianhydride, wherein the content of the polar solvent is 10-25% of the solid content of the system; stirring and refluxing at 90-100° C. for 2-4 hours, heating to 170-180° C. for reaction and continuing to react for 8-10 hours to obtain a mixed solution; filtering the mixed solution, casting, and subjecting the mixed solution to programmed temperature to obtain a polyimide film; naturally cooling and annealing to room temperature, and immersing the mixture in water for 30-60 minutes to obtain the semi-aromatic CPI film.

[0013] In a specific embodiment, the polar solvent includes one or more of N-methylpyrrolidone, mesitylene, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, and dimethyl sulfoxide.

[0014] The catalyst is benzoic acid.

[0015] The mass ratio of the catalyst to the alicyclic dianhydride is (0.07-0.1):1.

[0016] By adopting the above technical solution, benzoic acid transfers a proton to a carbonyl oxygen atom in the anhydride group of the alicyclic dianhydride, thereby protonating it, thereby increasing the positive charge of the carbonyl carbon, making it more susceptible to nucleophilic attack by the amino group in the diamine, and further optimizing the polymerization reaction of the alicyclic dianhydride and the diamine under relatively mild conditions.

[0017] The programmed temperature rise includes 60-70°C, constant temperature for 3-4h, 80-90°C, constant temperature for 1-2h, 100-110°C, constant temperature for 1-2h, 200-220°C, constant temperature for 1-2h, 300-320°C, constant temperature for 1-2h, 350-360°C, constant temperature for 30-45min.

[0018] In summary, this application has the following beneficial effects: 1. The present invention relates to alicyclic dianhydrides and benzene ring-containing diamines connected by specific functional groups and positional relationships. This not only improves the transparency and mechanical properties of the prepared polyimide film, but also reduces the expansion coefficient of the polyimide film, thereby improving dimensional stability. This maximizes the balance between the strength, thermal stability, and light transmittance of the polyimide film. The spatial structural characteristics and symmetry of the spiro rings in the alicyclic dianhydride restrict the movement of the molecular chain. When combined with trifluoromethyl-containing diamines, benzimidazole-containing diamines, and vinylphenoxy-containing diamines, a well-regularized molecular structure can be formed, significantly increasing the glass transition temperature and optimizing the film's heat resistance and dimensional stability. Together, these materials produce a semi-aromatic, colorless, and transparent polyimide film that meets the demand for high-performance materials in the flexible display field.

[0019] 2. The trifluoromethyl donor diamine TFMB was selected. Due to the strong electronegativity of the fluorine atom, most of the electron cloud is concentrated near the fluorine atom group, which strongly weakens the electron cloud conjugation in the main chain and significantly reduces the CTC effect within and between chains, resulting in a generally lighter color for the PI film. Simultaneously, a rigid diamine BIA with a kinked benzimidazole structure was introduced. The rigid imidazole structure effectively improves the heat resistance and dimensional stability of the polyimide. The kinked rigid imidazole structure also effectively reduces the packing density of the polymer chains and increases the free volume, thereby improving the thermal stability of the material while maintaining optical properties. Furthermore, the vinylphenoxy-containing monomer DFPTM was selected. The presence of the vinylphenoxy group in DFPTM creates a crosslinked network between the molecular chains of the latently crosslinkable third monomer polyimide, regulating the thermal expansion properties of the film and achieving a balance between optical properties, heat resistance, and dimensional stability. DETAILED DESCRIPTION

[0020] The present application is further described in detail below with reference to the embodiments.

[0021] The relevant raw materials used in the examples and comparative examples are all conventional products that can be purchased from the market.

[0022] Example 1 0.014 mol of TFMB, 0.009 mol of BIA, and 0.0025 mol of DFPTM were weighed respectively and added into a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0259 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system. The system was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0023] Example 2 0.011475 mol of TFMB, 0.011475 mol of BIA, and 0.00255 mol of DFPTM were weighed respectively and added into a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0259 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system. The mixture was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. The mixed solution was filtered and cast onto a glass plate. After programmed temperature treatment at 70°C for 3 h, 80°C for 2 h, 100°C for 1 h, 220°C for 1 h, 320°C for 1 h, and 350°C for 30 min, the mixture was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 60 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0024] Example 3 0.014 mol of TFMB, 0.009 mol of BIA, and 0.0025 mol of DFPTM were weighed respectively and added into a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0188 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system. The system was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0025] Example 4 0.014 mol of TFMB, 0.009 mol of BIA, and 0.0025 mol of DFPTM were weighed respectively and added into a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.03 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system. The system was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0026] Example 5 0.018 mol of TFMB, 0.005 mol of BIA, and 0.0025 mol of DFPTM were weighed respectively and added into a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0259 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system. The system was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0027] Example 6 0.0155 mol of TFMB, 0.01125 mol of BIA, and 0.00125 mol of DFPTM were weighed respectively and added into a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0259 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system. The mixture was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0028] Comparative Example 1 0.0165 mol of TFMB and 0.009 mol of BIA were weighed respectively and added to a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0259 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system, and the mixture was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0029] Comparative Example 2 0.023 mol of TFMB and 0.0025 mol of DFPTM were weighed respectively and added to a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0259 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system. The system was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0030] Comparative Example 3 0.0255 mol of TFMB was weighed and added to a 250 mL three-necked flask. In a N2 atmosphere, 70 g of NMP was added and mechanically stirred until completely dissolved. Then 0.7 g of benzoic acid and 0.0259 mol of dianhydride monomer CpODA were added in sequence. 30 g of NMP was added to adjust the solid content of the system, and the mixture was stirred and refluxed at 90°C for 2 h. The system temperature was raised to 180°C and reacted for 8 h to obtain a mixed solution. After filtering the mixed solution, the solution was cast onto a glass plate and subjected to a programmed temperature increase of 60°C for 4 h, 80°C for 1 h, 100°C for 1 h, 200°C for 1 h, 300°C for 1 h, and 350°C for 30 min. The solution was naturally cooled and annealed to room temperature. The glass plate with the film was immersed in deionized water for 45 min to obtain a semi-aromatic CPI film with a thickness of 20 μm.

[0031] Performance testing The properties of the semi-aromatic CPI films prepared in Examples 1-6 and Comparative Examples 1-3 were tested using the following method: (1) Optical properties: measured using an X-rite Ci7800 colorimeter, using a D65 illuminant, transmittance Tr (550 nm), and haze. (2) Mechanical properties: tested using Shimadzu AG-X plus universal tensile electronic testing machine, sample size 10 mm width, test speed 100 mm / min, tensile strength Ts; (3) Glass transition temperature Tg: TA Instruments DMA800, heating rate 3 K / min; (4) The semi-aromatic CPI film was subjected to a thermogravimetric curve test under a N2 atmosphere, and the temperature at which the thermal weight loss was 5% was calculated and recorded as the thermal decomposition temperature (Td).

[0032] (5) Coefficient of linear expansion (CTE): TA Instruments Q400, temperature range 50-400°C, heating rate 10K / min; the comparison results are as follows: Table 1 Performance test results Haze / % <![CDATA[T 450 %]]> CTE (ppm / K) Tg(℃) Td5% Ts(MPa) Example 1 0.34 85 8.29 433 478 220 Example 2 0.35 84.25 8.55 432 476 218 Example 3 0.37 82.87 11.58 422 457 209 Example 4 0.38 81.41 12.24 424 460 207 Example 5 0.34 83.91 9.95 430 467 215 Example 6 0.33 83.31 10.22 426 462 213 Comparative Example 1 0.42 81.21 14.79 415 443 197 Comparative Example 2 0.39 81.88 16.22 412 441 195 Comparative Example 3 0.45 78.29 17.75 391 432 171 As can be seen from Table 1, the semi-aromatic CPI films prepared in the examples of the present application maintain their own optical properties and improve temperature resistance, dimensional stability, and mechanical properties. Comparing Example 1 with Examples 3-4, it can be seen that the spatial structure characteristics and symmetry of the spiro ring in the alicyclic dianhydride restrict the movement of the molecular chain. After combining with the diamine containing trifluoromethyl, the diamine containing benzimidazole, and the diamine containing vinylphenoxy, a molecular structure with good regularity can be formed, which significantly increases the glass transition temperature. When the polymer is heated, the molecular chain is not easy to slide and break, and a high energy is required to destroy its chemical bonds and intermolecular forces, thereby having good thermal stability. A small amount of alicyclic dianhydride reduces the cross-linking density between the molecular chains, making the molecular chains more likely to slide when heated, resulting in the material being deformed at lower temperatures and reducing mechanical properties such as tensile strength.

[0033] By comparing Example 1 with Examples 5-6 and Comparative Examples 1-3, it can be seen that the trifluoromethyl donor diamine TFMB is selected. The trifluoromethyl group in TFMB has a strong electron-withdrawing effect and is more likely to react with the anhydride group in the alicyclic dianhydride. Furthermore, by selecting the donor DFPTM containing vinylphenoxy groups, the presence of vinylphenoxy groups in DFPTM and the introduction of fluorine atoms will change the spatial arrangement of the vinylphenoxy groups, thereby enhancing the interaction between the molecular chains and making the cross-linking and stacking of the molecular chains more compact, thereby improving the thermal stability and dimensional stability, and also greatly improving the optical properties of the polymer. On this basis, the rigid diamine BIA with a kinked benzimidazole structure is introduced, so that the molecular chains are interconnected through the benzimidazole ring to form a three-dimensional network structure. When the BIA content is lower than the range of this application, the degree of cross-linking of the polymer is reduced, the molecular chain segments are more likely to move, the thermal stability is weakened, the hardness and modulus are also reduced to a certain extent, the material's load-bearing capacity and deformation resistance are weakened, and the dimensional stability is reduced. A low DFPTM content will affect the stacking between molecular chains, thereby affecting thermal stability and mechanical properties, and a reduced fluorine atom content will also affect the optical properties of the polymer.

[0034] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A semi-aromatic CPI film, characterized in that: The semi-aromatic CPI film is prepared by a polymerization reaction between an alicyclic dianhydride and a diamine; the diamine includes a trifluoromethyl-containing diamine, a benzimidazole-containing diamine, and a vinylphenoxy-containing diamine; the alicyclic dianhydride includes one or two of norbornane-2-spiro-α-cyclopentanone-α'-spiro-2'-norbornane-5,5',6,6'-tetracarboxylic dianhydride and cyclobutanetetracarboxylic dianhydride.

2. The semi-aromatic CPI film according to claim 1, characterized in that: The molar ratio of the alicyclic dianhydride to the diamine is 1:(0.9-1.1).

3. The semi-aromatic CPI film according to claim 1, characterized in that: The molar ratio of the trifluoromethyl-containing diamine, the benzimidazole-containing diamine, and the vinylphenoxy-containing diamine is (9-14):(5-9):

2.

4. The method for preparing the semi-aromatic CPI film according to any one of claims 1 to 3, characterized in that: The following steps are included: The method comprises the following steps: adding a diamine to a polar solvent, then sequentially adding a catalyst and an alicyclic dianhydride, wherein the content of the polar solvent is 10-25% of the solid content of the system; stirring and refluxing at 90-100° C. for 2-4 hours, heating to 170-180° C. and continuing the reaction for 8-10 hours to obtain a mixed solution; filtering the mixed solution, casting, and obtaining a polyimide film through programmed temperature increase; naturally cooling and annealing to room temperature, and immersing in water for 30-60 minutes to obtain a semi-aromatic CPI film.

5. The method for preparing a semi-aromatic CPI film according to claim 4, wherein: The polar solvent includes one or more of N-methylpyrrolidone, mesitylene, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, and dimethyl sulfoxide.

6. The method for preparing a semi-aromatic CPI film according to claim 4, wherein: The catalyst is benzoic acid.

7. The method for preparing a semi-aromatic CPI film according to claim 4, wherein: The mass ratio of the catalyst to the alicyclic dianhydride is (0.07-0.1):

1.

8. The method for preparing a semi-aromatic CPI film according to claim 4, wherein: The programmed temperature rise includes 60-70°C, constant temperature for 3-4h, 80-90°C, constant temperature for 1-2h, 100-110°C, constant temperature for 1-2h, 200-220°C, constant temperature for 1-2h, 300-320°C, constant temperature for 1-2h, 350-360°C, constant temperature for 30-45min.

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