Asymmetric polyimide composite film and its preparation method and application

Abstract

This invention belongs to the field of thin film preparation technology and discloses an asymmetric polyimide composite film, its preparation method, and its application. By adjusting the degree of film asymmetry based on the SiO2 content, the film can achieve varying hardness and transparency. This method is simple, environmentally friendly, and universally applicable. The asymmetric polyimide film developed in this invention has broad application prospects in optical devices, broadband devices, humidity sensors, insulating coatings, and even biomimetic actuators.

Description

Technical Field

[0001] The present invention belongs to the technical field of film preparation, relates to a material modification method, and specifically relates to an asymmetric high-transparency polyimide composite film and a preparation method and application thereof. Background Art

[0002] Currently, PI composites are primarily prepared and obtained in high-boiling-point organic solvents. However, organic solvents are less environmentally friendly than aqueous solutions. Furthermore, while pure polyimide currently offers excellent overall performance, including thermal stability, good mechanical properties, good transparency, and a low coefficient of thermal expansion, and is widely used in microelectronic integrated circuits, flexible circuit boards, aerospace, and communications, its low hardness limits its application.

[0003] In addition, some asymmetric films currently require multiple layers and complex preparation processes. Therefore, how to provide an asymmetric, highly transparent polyimide composite film with simple process and wide application range is a technical challenge that needs to be solved in this field. Summary of the Invention

[0004] In view of this, the first object of the present invention is to provide a method for preparing an asymmetric high-transparency polyimide composite film in order to address the problems existing in the prior art.

[0005] It should be noted that the preparation method of this patent is green and environmentally friendly, can be applied in many fields, and has good transparency and high hardness. The asymmetric film broadens the application field of PI; moreover, the present invention only requires a single layer to prepare an asymmetric film, the process is simple, and is suitable for promotion and application.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing an asymmetric high-transparency polyimide composite film comprises the following steps:

[0008] a. Preparation of a polyimide precursor: Under a nitrogen environment, the diamine and 1,2-dimethylimidazole were dissolved in water, and after complete dissolution, the dianhydride was added to react to obtain a polyamic acid salt solution;

[0009] b. Modified silica nanoparticles: adding a coupling agent solution diluted with alcohol to the silica nanoparticle sol to obtain modified silica nanoparticles;

[0010] c. The modified silica nanoparticles were thoroughly mixed with a polyimide precursor to obtain a polyamic acid salt mixture, and then the polyamic acid salt mixture was coated on a glass plate and placed in an air drying oven to dry the solvent to prepare a composite film;

[0011] d. heating the composite film prepared in step c to complete the imidization process, and finally preparing the asymmetric highly transparent polyimide composite film.

[0012] It is worth noting that the film prepared in this patent has asymmetry, high transparency and high hardness, which can broaden the application range of PI composite materials.

[0013] Preferably, in step a, the molar ratio of the diamine to the dianhydride is in the range of 0.5-1.5:0.5-1.5, the molar ratio of the added base to the diamine is 1-3:1, and the solution concentration is 5%-25%, but the present invention is not limited thereto.

[0014] Further preferably, the dianhydride includes 3,3',4,4'-biphenyltetracarboxylic dianhydride s-BPDA, 2,3,3',4'-biphenyltetracarboxylic dianhydride a-BPDA, pyromellitic dianhydride PMDA, 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride BTDA, 4,4-oxyphthalic anhydride ODPA, diphenyl sulfide dianhydride TDPA, and isomeric triphenyl diether dianhydride HQDPA; and the diamine includes p-phenylenediamine PDA and p-aminodiphenyl ether ODA.

[0015] Preferably, in step b, the mass concentration of the coupling agent solution is 1-20%, the mass ratio of the coupling agent to the silica is 0-10%; and the coupling agent is KH550 or KH560;

[0016] The size of the silicon dioxide nanoparticles is 20-200 nm, the porosity is 0-90%, and the alcohol is methanol, ethanol or isopropanol.

[0017] Preferably, in step c, the mass ratio of silicon dioxide to polyimide is 1-45%, the drying temperature is 25° C.-100° C., and the drying time is 30-120 min.

[0018] Furthermore, the coating process is as follows:

[0019] Wire rod coating 100, 150 microns;

[0020] Alternatively, blade coating is used, with a wet film thickness of 50-500 μm. The final film thickness is 5-50 μm corresponding to the concentration of the polyamic acid salt mixture.

[0021] Preferably, in step d, the heating temperature is 200° C.-450° C., and the heating time is 0.5-3 h.

[0022] The second object of the present invention is to provide an asymmetric high-transparency polyimide composite film prepared by the above method.

[0023] The third object of the present invention is to provide an application of the asymmetric high-transparency polyimide composite film as described above in the fields of optical devices, broadband, humidity sensors, insulating coatings, and bionic actuators.

[0024] Compared with the prior art, the present invention discloses an asymmetric polyimide composite film and its preparation method and application, which has the following excellent effects:

[0025] The present invention provides a transparent polyimide film with asymmetric morphology and different hardness on both sides of the film, and a preparation method thereof. The resulting polyimide film not only exhibits flexibility, high transparency, and high thermal stability, but also can be controlled by varying the SiO2 content to achieve different hardnesses and refractive indices. This method is simple, environmentally friendly, and universally applicable. The asymmetric polyimide film developed by the present invention has broad application prospects in optical devices, environmental protection, sensors, and insulating coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0027] Figure 1 Scanning electron microscope images of the air-contacting side (a) and the substrate-contacting side (b) of the asymmetric high-transparency polyimide composite film prepared in Example 1 of the present invention.

[0028] Figure 2 Scanning electron microscope images of the air-contacting side (a) and the substrate-contacting side (b) of the asymmetric high-transparency polyimide composite film prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The invention discloses a method for preparing an asymmetric high-transparency polyimide composite film.

[0031] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing an asymmetric high-transparency polyimide composite film comprises the following steps:

[0034] 10 mmol of p-phenylenediamine (PDA) and 26 mmol of 1,2-dimethylimidazole were dissolved in deionized water. After complete dissolution, 10.1 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added in batches to prepare a 12 wt% PAAS solution, which was fully reacted for 12 hours. 11.48 g of silica sol (35 wt%) was dropwise added with 0.60 mL of KH550 diluted with 36.1 g of methanol. After sufficient reaction, the solution was added to the PAAS solution and fully reacted for 2 hours to prepare a SiO2 / PAAS mixture solution. The polyamic acid salt mixture was coated on a glass plate and placed in a forced air drying oven to dry the solvent at 80 degrees for 30 minutes to prepare a composite membrane. The prepared composite membrane was further heated at 450 degrees for 0.5 hours to complete the imidization process and prepare an asymmetric polyimide composite film.

[0035] Example 2

[0036] A method for preparing an asymmetric high-transparency polyimide composite film comprises the following steps:

[0037] 10 mmol of p-phenylenediamine (PDA) and 26 mmol of 1,2-dimethylimidazole were dissolved in deionized water. After complete dissolution, 10.1 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added in batches to prepare a 12 wt% PAAS solution, which was fully reacted for 12 hours. 22.97 g of silica sol (35 wt%) was dropwise added with 0.120 mL of KH550 diluted with 72.2 g of methanol. After sufficient reaction, the solution was added to the PAAS solution and fully reacted for 2 hours to prepare a SiO2 / PAAS mixture solution. The polyamic acid salt mixture was coated on a glass plate and placed in a forced air drying oven to dry the solvent at 80 degrees for 30 minutes to prepare a composite membrane. The prepared composite membrane was further heated at 450 degrees for 0.5 hours to complete the imidization process and prepare an asymmetric polyimide composite film.

[0038] Example 3

[0039] A method for preparing an asymmetric high-transparency polyimide composite film comprises the following steps:

[0040] 10 mmol of p-phenylenediamine (PDA) and 26 mmol of 1,2-dimethylimidazole were dissolved in deionized water. After complete dissolution, 10.1 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added in batches to prepare a 12 wt% PAAS solution, which was fully reacted for 12 hours. 11.48 g of silica sol (35 wt%) was diluted with 36.1 g of methanol, mixed thoroughly, and added to the PAAS solution. The mixture was fully reacted for 2 hours to prepare a SiO2 / PAAS mixture solution. The polyamic acid salt mixture was coated on a glass plate and placed in a forced air drying oven to dry the solvent at 80 degrees for 30 minutes to prepare a composite membrane. The prepared composite membrane was further heated at 450 degrees for 0.5 hours to complete the imidization process and prepare an asymmetric polyimide composite film.

[0041] Example 4

[0042] A method for preparing an asymmetric high-transparency polyimide composite film comprises the following steps:

[0043] 10 mmol of p-phenylenediamine (PDA) and 26 mmol of 1,2-dimethylimidazole were dissolved in deionized water. After complete dissolution, 10.1 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added in batches to prepare a 12 wt% PAAS solution, which was fully reacted for 12 hours. 11.48 g of silica sol (35 wt%) was dropwise added with 0.60 mL of KH560 diluted with 36.1 g of methanol. After sufficient reaction, the solution was added to the PAAS solution and fully reacted for 2 hours to prepare a SiO2 / PAAS mixture solution. The polyamic acid salt mixture was coated on a glass plate and placed in a forced air drying oven to dry the solvent at 80 degrees for 30 minutes to prepare a composite membrane. The prepared composite membrane was further heated at 450 degrees for 0.5 hours to complete the imidization process and prepare an asymmetric polyimide composite film.

[0044] In addition, in order to further verify the excellent effect of the technology of the present invention, the inventors also conducted experimental measurements, the specific contents of which are as follows:

[0045] Scanning electron microscopy (SEM) of the surface reveals that the whitish color is SiO2. In Examples 1 and 2, silica particles are abundant on the film surface on the air-exposed side (a). Silica particles are also present on the glass-exposed side (b), but their concentration is significantly lower than on side (a). This is because during the solvent removal and thermal imidization process, the polyimide and silica shrink somewhat, but the shrinkage of silica is not as strong as that of polyimide, so the silica gradually emerges. Furthermore, the film has a distinct asymmetry, resulting in different hardnesses on both sides.

[0046] As the silicon dioxide content increases, Example 2 shows a significantly higher SiO2 content than Example 1, and the film's hardness and transparency also increase. Common commercial PI films have a hardness between B and HB. The present invention introduces varying SiO2 contents to regulate the hardness of both sides of the film.

[0047] The thickness of the test film sample is 12 microns. The degree of film asymmetry can be adjusted according to the different contents of SiO2 to ensure that the film has different hardness and transparency.

[0048]

[0049] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an asymmetric high-transparency polyimide composite film, characterized in that: The method specifically comprises the following preparation steps: a. Preparation of a polyimide precursor: Under a nitrogen atmosphere, diamine and 1,2-dimethylimidazole were dissolved in water, and after complete dissolution, dianhydride was added to react to obtain a polyamic acid salt solution; b. Modified silica nanoparticles: A coupling agent solution diluted with alcohol was added dropwise to the hollow silica nanoparticle sol to obtain modified hollow silica nanoparticles; c. The modified hollow silica nanoparticles were thoroughly mixed with a polyimide precursor to obtain a polyamic acid salt mixture, and then the polyamic acid salt mixture was coated on a glass plate and placed in a blast drying oven to dry the solvent to prepare a composite film; d. The composite film prepared in step c is heated to complete the imidization process, and finally the asymmetric high transparency polyimide composite film is prepared; The dianhydride is selected from 3,3',4,4'-biphenyltetracarboxylic dianhydride s-BPDA, 2,3,3',4'-biphenyltetracarboxylic dianhydride a-BPDA, pyromellitic dianhydride PMDA, 3,3',4,4'-benzophenone tetracarboxylic dianhydride BTDA, 4,4-oxyphthalic anhydride ODPA, diphenyl sulfide dianhydride TDPA or isomeric triphenyl diether dianhydride HQDPA; the diamine is selected from p-phenylenediamine PDA or p-aminodiphenyl ether ODA; The size of the hollow silica nanoparticles is 20-200 nm, and the porosity is 0-90%; The coating process is as follows: Doctor blade coating, wet film 50-500 microns, the obtained film is 5-50 microns.

2. The method for preparing an asymmetric high-transparency polyimide composite film according to claim 1, characterized in that: In step a, the molar ratio of the diamine to the dianhydride is 0.5-1.5:0.5-1.5, the molar ratio of 1,2-dimethylimidazole to the diamine is 1-3:1, and the solution concentration is 5%-25%.

3. The method for preparing an asymmetric high-transparency polyimide composite film according to claim 1, characterized in that: In the step b, the mass concentration of the coupling agent solution is 1-20%, and the mass ratio of the coupling agent to the silica is 1-10%; and the coupling agent is KH550 or KH560; The alcohol is methanol, ethanol or isopropanol.

4. The method for preparing an asymmetric high-transparency polyimide composite film according to claim 1, characterized in that: In the step c, the mass ratio of silicon dioxide to polyimide is 1-45%, the drying temperature is 25° C.-100° C., and the drying time is 30-120 minutes.

5. The method for preparing an asymmetric high-transparency polyimide composite film according to claim 1, characterized in that: In the step d, the heating temperature is 200° C.-450° C., and the heating time is 0.5-3 h.

6. An asymmetric high-transparency polyimide composite film prepared by the method of claim 1.

7. Application of the asymmetric high-transparency polyimide composite film prepared by the method of claim 1 in the fields of optical devices, broadband, humidity sensors, insulating coatings, and bionic actuators.

Images