Preparation method and application of electromagnetic shielding film material with photochromic effect

Abstract

The application provides a preparation method of electromagnetic shielding film material with photochromic effect, which comprises the following steps: mixing phosphotungstic acid particles and tetrahydrofuran to obtain a mixed solution, adding a polymethyl methacrylate dissolving solution into the mixed solution, and stirring by magnetic force to obtain P-PW 12 The silver nanowire dispersion is diluted in an ethanol solution to different concentrations to form several portions of silver nanowire suspensions, and the concentration range of the different concentrations is 1 mg / mL-5 mg / mL; the P-PW 12 mixed solution is poured into a petri dish to obtain a casting film; the casting film is cut into several portions, and each portion is sprayed with a silver nanowire suspension of one concentration to obtain P-PW 12 / AgNWs-x composite film, wherein x corresponds to the concentration of AgNWs; the remaining portions are respectively formed into upper and lower matrices and are respectively arranged on both sides of each P-PW 12 / AgNWs-x composite film, and hot pressing to obtain P-PW 12 / AgNWs / P-PW 12 -x composite film containing different concentrations of AgNWs.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding reflective materials, and in particular to a method for preparing an electromagnetic shielding film material with a photochromic effect. Background Art

[0002] Currently, photochromic materials based on polyoxometalates have been widely used in different application fields, such as optical storage, smart windows, and UV sensors. Polyoxometalate phosphotungstic acid (PWA) has been incorporated into many hybrid matrices to provide the properties required by composite materials. In recent years, people's interest has been focused on polymer matrices such as polyacrylamide (PAM) and polyvinylpyrrolidone (PVP). Polymethyl methacrylate (PMMA), a well-known thermoplastic polymer for engineering plastics and polymer glasses, is a good choice. It has a wide range of applications, mainly due to its high transparency, thermal stability, good impact resistance and the ability to incorporate a large number of additives.

[0003] Espindola et al. studied the combination of PMMA and PWA to prepare photochromic films, demonstrating that these highly transparent and photosensitive photochromic films have broad application prospects as cast coatings and inkjet printing. However, they lack specific shielding effects. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for preparing an electromagnetic shielding film material with a photochromic effect and its application. The method uses PMMA particles as the raw material, which are dissolved in dichloromethane. A photochromic material (PWA) is introduced and blended in a tetrahydrofuran (THF) organic solution to form a photochromic film. A conductive network of interconnected silver nanowires with welded joints is affixed to a PMMA substrate by spraying and hot pressing.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing an electromagnetic shielding film material having a photochromic effect comprises the following steps:

[0007] The mixture of transition metal oxide and polar organic solvent is added to polymethyl methacrylate solution and magnetically stirred to obtain P-PW 12 Mixing solution;

[0008] The silver nanowire dispersion was diluted in an ethanol solution to different concentrations to form several silver nanowire suspensions, wherein the different concentrations ranged from 1 mg / mL to 5 mg / mL;

[0009] In a petri dish, pour P-PW 12mixing the solutions to obtain a cast film;

[0010] Part of the cast film is cut into several parts, and each part is sprayed with a concentration of silver nanowire suspension to obtain P-PW 12 / AgNWs-x composite film, where x corresponds to the concentration of AgNWs;

[0011] The rest of the parts form upper and lower bases, which are respectively set on each P-PW 12 / AgNWs-x composite film on both sides, hot pressing, to obtain P-PW containing different concentrations of AgNWs 12 / AgNWs / P-PW 12 -x composite film.

[0012] Furthermore, the method also includes the preparation of a polymethyl methacrylate solution, specifically, the polymethyl methacrylate particles and a halogenated hydrocarbon solvent are mixed and stirred to disperse uniformly, and then the polymethyl methacrylate solution is added and magnetically stirred to obtain a P-PW12 mixed solution.

[0013] Furthermore, the mass ratio of the phosphotungstic acid particles to the polymethyl methacrylate particles is 15:1-25:1.

[0014] Furthermore, the transition metal oxide includes phosphotungstic acid particles, and the polar organic solvent includes tetrahydrofuran, dichloromethane, acetone, ethyl acetate or N,N-dimethylformamide.

[0015] Furthermore, the magnetic stirring time is 3-7 min and the speed is 400-600 rpm.

[0016] Furthermore, the P-PW 12 The mixed solution has a solid content of 0.08 mg / mL to 0.1 mg / mL.

[0017] Furthermore, during the spraying, the cast film is fixed on a tinplate sheet that is heated at a constant temperature, and the temperature of the constant heating is 60-80°C.

[0018] Furthermore, during spraying, the distance between the spray gun and the film is at least 9-12 cm, and the spraying pressure is 0.2-0.5 MPa.

[0019] On the other hand, the P-PW obtained by the above-mentioned preparation method of the electromagnetic shielding film material with photochromic effect 12 / AgNWs / P-PW 12 -x composite film applications in the field of electronic equipment.

[0020] Furthermore, the application is specifically as a screen, which can be used in different light environments by adjusting the transmittance state.

[0021] The present invention has the following beneficial effects:

[0022] The preparation method of the present invention produces a film with excellent electromagnetic shielding performance and light transmittance, and also has a photochromic effect. By controlling the loading amount of silver nanowires, the optical properties and electromagnetic shielding properties of the composite film can be jointly regulated. At the same time, it is hot-pressed with another layer of PMMA film to form a "sandwich" structure with an interlayer, which protects the silver nanowires from oxidation and falling off. A polymethyl methacrylate / phosphotungstic acid electromagnetic shielding composite film (P-PW12 / AgNWs / P-PW12) with a photochromic effect was successfully prepared. This chapter characterizes and analyzes the various properties of the composite film. The prepared composite film not only has high light transmittance and good mechanical strength, but also has an excellent photochromic effect.

[0023] The present invention uses PMMA as a substrate, which not only has the good mechanical properties of traditional polymer materials, but also has the advantage of high light transmittance.

[0024] The present invention uses silver nanowires as conductive fillers and loads the silver nanowire conductive network on a PMMA substrate through spraying and hot pressing techniques to achieve the electromagnetic shielding performance of the material.

[0025] The present invention uses a typical sandwich structure of a thin film to wrap the silver nanowire network, avoiding displacement and corrosion caused by contact of the conductive network with moisture and oxygen in the air. This gives the material reliable durability, thereby giving the material certain anti-oxidation properties and improving the service life of the composite film.

[0026] The present invention introduces the photochromic material phosphotungstic acid to give the material excellent photochromic properties. The composite film changes from colorless to blue after being irradiated with ultraviolet light, and the photochromic effect is reversible. After repeated color change and recolor cycles for 10 times, its photochromic performance does not show obvious attenuation, showing excellent anti-fatigue performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1a Figure 2 is a network structure diagram composed of silver nanowires (AgNWs);

[0028] Figure 1b P-PW 12 / AgNWs / P-PW 12 -x smooth surface covering structure diagram;

[0029] Figure 1c The prepared P-PW 12 / AgNWs / P-PW 12 Cross-sectional view of the composite film;

[0030] Figure 1dThe X-ray spectra of tungsten and phosphorus under energy dispersion are shown in Figure 2.

[0031] Figure 1e is the X-ray spectrum of tungsten under energy dispersion;

[0032] Figure 1f is the X-ray spectrum of phosphorus under energy dispersion;

[0033] Figure 2a P-PW in the stress-strain curve 12 / AgNWs / P-PW 12 -1 Curve strain diagram of different concentrations;

[0034] Figure 2b The tensile stress histogram and the tensile stress data diagram of the strain line with different AgNWs concentrations;

[0035] Figure 2c The prepared P-PW 12 / AgNWs / P-PW 12 One of the structural diagrams of the composite membrane;

[0036] Figure 2d The prepared P-PW 12 / AgNWs / P-PW 12 Schematic diagram of the structure of the composite membrane (part 2);

[0037] Figure 3a The prepared P-PW with different concentrations 12 / AgNWs / P-PW 12 Transmittance variation diagram of composite film;

[0038] Figure 3b The prepared P-PW 12 / AgNWs / P-PW 12 Transmittance variation of composite film at concentrations of 1-2 mg / mL;

[0039] Figure 3c The prepared P-PW 12 / AgNWs / P-PW 12 Photograph of the composite film on the first reference;

[0040] Figure 3d The prepared P-PW 12 / AgNWs / P-PW 12 Photograph of the composite film on the second reference;

[0041] Figure 3e The prepared P-PW 12 / AgNWs / P-PW 12Photograph of the composite film on the third reference;

[0042] Figure 4a P-PW before hot pressing 12 / AgNWs and P-PW 12 / AgNWs / P-PW 12 -x resistance change trend diagram;

[0043] Figure 4b P-PW with different concentrations 12 / AgNWs / P-PW 12 EMI change curve diagram;

[0044] Figure 4c P-PW corresponding to different concentrations of AgNWs 12 / AgNWs / P-PW 12 The change diagram of shielding effectiveness;

[0045] Figure 4d P-PW 12 / AgNWs / P-PW 12-4 Shielding performance change diagram;

[0046] Figure 5a The temperature change curve when the voltage gradually increases and decreases;

[0047] Figure 5b The temperature change curve when the voltage point data increases and decreases;

[0048] Figure 5c The temperature change curve when the voltage is gradually increased and decreased;

[0049] Figure 5d This is the infrared thermal imaging image of the composite film;

[0050] Figure 5e The temperature distribution diagram at constant voltage;

[0051] Figure 6a One of the schematic diagrams of the photochromic properties of the P-PW12 / AgNWs / P-PW12 composite film;

[0052] Figure 6b The second schematic diagram of the photochromic performance of the P-PW12 / AgNWs / P-PW12 composite film;

[0053] Figure 6c The third schematic diagram of the photochromic performance of the P-PW12 / AgNWs / P-PW12 composite film;

[0054] Figure 6dThe fourth schematic diagram of the photochromic performance of the P-PW12 / AgNWs / P-PW12 composite film;

[0055] Figure 6e Irradiate P-PW with ultraviolet light 400-800nm 12 / AgNWs / P-PW 12 -3 UV-vis absorption spectrum of composite film;

[0056] Figure 6f P-PW after different times of cycling 12 / AgNWs / P-PW 12 -3 Absorbance change diagram of composite film. DETAILED DESCRIPTION

[0057] The present invention is described in detail below with reference to the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in this field based on these embodiments are all within the scope of protection of the present invention.

[0058] Referring to Figures 1-6, the present invention utilizes a transparent electromagnetic shielding material as its core material, adding a photochromic function to this material to produce a polymer-based electromagnetic shielding composite film with a photochromic effect. PMMA particles are dissolved in dichloromethane, along with the photochromic material PWA. These are then blended in a tetrahydrofuran (THF) organic solution to form the photochromic film. A conductive network of interconnected silver nanowires with welded joints is affixed to the PMMA substrate via spray coating and hot pressing.

[0059] In view of this, it is necessary to design and prepare a film with excellent electromagnetic shielding performance and light transmittance, and also with photochromic effect. By controlling the loading amount of silver nanowires, the optical properties and electromagnetic shielding properties of the composite film can be jointly regulated. At the same time, it is hot-pressed with another layer of PMMA film to form a "sandwich" structure with an interlayer to protect the silver nanowires from oxidation and falling off. The polymethyl methacrylate / phosphotungstic acid electromagnetic shielding composite film (P-PW) with photochromic effect was successfully prepared. 12 / AgNWs / P-PW 12 ). This chapter characterizes and analyzes the various properties of the composite film. The prepared composite film not only has high transmittance and good mechanical strength, but also has excellent photochromic effect.

[0060] The method for preparing the electromagnetic shielding film material with photochromic effect in the present invention is characterized by comprising the following steps:

[0061] The first step is to prepare a polymethyl methacrylate solution. Specifically, the polymethyl methacrylate particles and a halogenated hydrocarbon solvent are mixed and stirred until uniformly dispersed. The polymethyl methacrylate solution is then added and magnetically stirred to obtain a P-PW12 mixed solution. The mass ratio of the phosphotungstic acid particles to the polymethyl methacrylate particles is 15:1-25:1.

[0062] In the second step, the mixture of transition metal oxide and polar organic solvent is added to the polymethyl methacrylate solution and magnetically stirred to obtain a P-PW12 mixed solution; at this time, the transition metal oxide includes phosphotungstic acid particles, the polar organic solvent includes tetrahydrofuran, dichloromethane, acetone, ethyl acetate or N,N-dimethylformamide; the halogenated hydrocarbon includes dichloromethane.

[0063] In this embodiment, the purpose of using magnetic stirring is to promote the mixing of phosphotungstic acid and polymethyl methacrylate solution to obtain P-PW 12 Mix the solution. Stir magnetically for 3-7 minutes at a speed of 400-600 rpm.

[0064] The third step is to dilute the silver nanowire dispersion in an ethanol solution to different concentrations to form several silver nanowire suspensions, wherein the different concentrations range from 1 mg / mL to 5 mg / mL;

[0065] Step 4: Pour P-PW into the culture dish 12 Mix the solutions to obtain a cast film; in this embodiment, P-PW 12 The mixed solution has a solid content of 0.08 mg / mL to 0.1 mg / mL.

[0066] The fifth step is to cut part of the cast film into several parts, and spray a silver nanowire suspension of a certain concentration on each part to obtain P-PW 12 / AgNWs-x composite film, where x corresponds to the concentration of AgNWs; in this embodiment, the cast film is fixed on a tinplate sheet heated at a constant temperature. The cast film is fixed on a tinplate sheet heated at a constant temperature of 60-80°C.

[0067] During spraying, the distance between the spray gun and the film should be at least 9-12 cm, and the spraying pressure should be 0.2-0.5 MPa.

[0068] In the sixth step, the remaining parts are formed into upper and lower bases, which are respectively set on each type of P-PW 12 / AgNWs-x composite film on both sides, hot pressing, to obtain P-PW containing different concentrations of AgNWs 12 / AgNWs / P-PW 12 -x composite film.

[0069] In this embodiment, the temperature during hot pressing is 50-70° C., the pressure is 10-15 MPa, and the total hot pressing time is 20 s-30 s.

[0070] The P-PW obtained by the preparation method of the electromagnetic shielding film material with photochromic effect prepared in this embodiment 12 / AgNWs / P-PW 12 -x composite film applications in the field of electronic equipment.

[0071] The application is specifically as a screen, which can be used in different light environments by adjusting the transmittance state.

[0072] Example 1

[0073] (1) First, weigh 1g of polymethyl methacrylate (PMMA) particles in a beaker, add 10mL of dichloromethane (CH2Cl2) organic solvent, and stir quickly with a glass rod for 1min to make it evenly dispersed. Then stir with a magnetic stirrer (speed 650rpm) at room temperature for 0.5h until PMMA is completely dissolved and set aside. At the same time, weigh 0.05g of phosphotungstic acid (PWA) particles in a beaker, add 0.68mL of tetrahydrofuran (THF) organic solvent, and shake thoroughly to completely dissolve it. Pour it into the previously prepared PMMA solution and stir it with a magnetic stirrer (speed 500rpm) at room temperature for 5min. Get P-PW 12 Mix the solution.

[0074] (2) The silver nanowire dispersion (20 mg / mL) was diluted to different concentrations (1, 2, 3, 4 and 5 mg / mL) in ethanol solution for use. The P-PW12 mixed solution was then evenly poured into a culture dish, dried for 6 hours, and peeled off to obtain a cast film. The PMMA film was cut into five parts, each with a size of 30 mm × 30 mm, and fixed on a tinplate sheet placed on a constant temperature heating platform (70°C). Then, a spray gun was used to evenly spray the silver nanowire suspension (1 mL) of different concentrations on the surface of the PMMA film at a distance of 10 cm and a pressure of 0.2 MPa. P-PW was obtained. 12 / AgNWs-x composite films, where x corresponds to the concentration of AgNWs.

[0075] In this example, within a concentration range of 1-5 mg / mL, silver nanowires exhibited excellent synergy with other film components (such as polymethyl methacrylate and phosphotungstic acid). An appropriate silver nanowire concentration ensures electromagnetic shielding performance while maintaining the performance of other components, such as the excellent mechanical properties of polymethyl methacrylate and the photochromic properties of phosphotungstic acid. However, excessive silver nanowire concentrations may disrupt the structure or properties of other components, affecting the overall film performance balance.

[0076] (3) In order to effectively protect the exposed silver nanowire conductive network, the prepared P-PW 12 The / AgNWs-x composite film and PMMA film were hot pressed under the conditions of temperature (68 ° C), pressure (12 MPa), and time (20 s), and the coating structure was realized, and P-PW was successfully prepared. 12 / AgNWs / P-PW 12 -x composite film.

[0077] Figure 1a-Figure 1c is a scanning electron microscope image, where Figure 1a The researchers show a densely and evenly distributed network of silver nanowires (AgNWs) on a substrate surface. The nanowires intertwine to form conductive pathways. The nanowires are thin and uniform in diameter, randomly distributed. The nanowire density is uniform, with no apparent agglomeration. This network structure can significantly improve the electrical conductivity and mechanical properties of the composite material. The uniform distribution contributes to stable electrical and optical properties.

[0078] Figure 1b Demonstrated P-PW 12 / AgNWs / P-PW 12 -x smooth surface covering structure, with Figure 1a The surface appears quite smooth and uniform, with no obvious defects or cracks. There are no signs of silver nanowires protruding from the surface, indicating that the nanowires are efficiently coated. The smooth surface may help improve the material's transparency and resistance to environmental corrosion. 12 As a covering layer, it can well conceal the internal structure and form a smooth surface.

[0079] Figure 1c The cross-section of the composite film is shown, including two layers of polymer (PMMA) and a silver nanowire layer (AgNWs) in the middle. It can be clearly seen that the material is divided into two layers of PMMA matrix, upper and lower, with a nanowire network layer in the middle. The AgNWs layer is displayed as a highlighted linear area in the middle, indicating that the silver nanowires are mainly concentrated in a specific position. Interface bonding: The interface between the upper and lower layers of PMMA and the AgNWs layer is smooth and well bonded, with no obvious stratification or gaps. The design of the layered structure enhances the comprehensive properties of the composite material (such as conductivity, mechanical properties and transparency). It can be seen from the opening that the tightly bonded interface in this embodiment indicates that the preparation process is proper, which helps to improve the overall mechanical strength and stability.

[0080] Figure 1d Energy dispersive X-ray spectroscopy (EDS): Figure 1dThe composite distribution of tungsten (W) and phosphorus (P) elements is shown.

[0081] Figure 1e Energy dispersive X-ray spectroscopy (EDS) only shows the individual distribution of tungsten (W). Figure 1f The individual distribution of phosphorus (P) elements is shown, from which it can be concluded that tungsten elements are evenly distributed on the substrate.

[0082] pass Figures 1a-1f It can be seen that the prepared P-PW 12 / AgNWs / P-PW 12 The silver nanowires of the composite film are uniformly distributed on the substrate, and the tungsten element is uniformly distributed on the substrate.

[0083] Figure 2a P-PW in stress-strain curve 12 / AgNWs / P-PW 12 -1 (lowest AgNWs concentration): The initial stress is the smallest, but when stretched to a higher strain, it shows the highest stress peak, indicating that the material is relatively tough. 12 / AgNWs / P-PW 12 -2: Slightly reduced strength compared to the lowest concentration material, but still maintains good stress levels. 12 / AgNWs / P-PW 12 -3: The stress is slightly reduced, but the tensile strength is still high. 12 / Ag NWs / P-PW 12 -4: The stress intensity is further reduced, and the curve declines significantly, indicating that the material performance has deteriorated. 12 / AgNWs / P-PW 12 -5 (highest AgNWs concentration): shows the lowest tensile strength and strain capacity, indicating that excessively high AgNWs concentration can weaken the mechanical properties of the composite. It can be seen that with increasing AgNWs concentration, the tensile stress of the material shows an overall downward trend. An appropriate amount of AgNWs (e.g., 1 or 2 mg / mL) can enhance the mechanical properties of the composite, while excessive concentrations can lead to performance degradation, likely due to excessive nanowire accumulation, which affects the uniformity and structural integrity of the composite.

[0084] Figure 2b The tensile stress bar graph and strain line (from left to right) show the tensile stress data for AgNWs concentrations of 1, 2, 3, 4, and 5 mg / mL, respectively. The tensile stress gradually decreases from 25.98 MPa (concentration 1) to 22.36 MPa (concentration 5), indicating that the material's load-bearing capacity decreases with increasing AgNWs concentration. The line graph (fracture strain %) shows the material's ability to deform before tensile fracture.

[0085] The strain remained relatively low from concentrations of 1 to 5, concentrated below 2.5%. This suggests that increasing the AgNW concentration has little significant effect on the material's ductility. Lower AgNW concentrations (1 or 2 mg / mL) help improve the material's tensile strength, but higher concentrations can reduce the composite's mechanical properties. The strain capacity did not change significantly at different concentrations, indicating that the material's ductility was relatively stable.

[0086] like Figures 2a-2d As shown, it can be seen that the obtained P-PW 12 / AgNWs / P-PW 12 The composite film has good tensile strength (25MPa), which meets the mechanical properties of transparent electromagnetic shielding film P-PW 12 / AgNWs / P-PW 12 The composite film still exhibits good mechanical strength and high optical transparency when bent.

[0087] Example 2

[0088] (1) First, weigh 1g of polymethyl methacrylate (PMMA) particles in a beaker, add 10mL of dichloromethane (CH2Cl2) organic solvent, and stir quickly with a glass rod for 1min to make it evenly dispersed. Then stir with a magnetic stirrer (speed 650rpm) at room temperature for 0.5h until PMMA is completely dissolved and set aside. At the same time, weigh 0.05g of phosphotungstic acid (PWA) particles in a beaker, add 0.68mL of tetrahydrofuran (THF) organic solvent, and shake thoroughly to completely dissolve it. Pour it into the previously prepared PMMA solution and stir it with a magnetic stirrer (speed 500rpm) at room temperature for 5min. Get P-PW 12 Mix the solution.

[0089] (2) The silver nanowire dispersion (20 mg / mL) was diluted to different concentrations (1, 2, 3, 4 and 5 mg / mL) in ethanol solution for use. The P-PW12 mixed solution was then evenly poured into a culture dish, dried for 6 hours, and peeled off to obtain a cast film. The PMMA film was cut into five parts, each with a size of 30 mm × 30 mm, and fixed on a tinplate sheet placed on a constant temperature heating platform (70°C). Then, a spray gun was used to evenly spray the silver nanowire suspension (1 mL) of different concentrations on the surface of the PMMA film at a distance of 10 cm and a pressure of 0.2 MPa. P-PW was obtained. 12 / AgNWs-x composite films, where x corresponds to the concentration of AgNWs.

[0090] (3) In order to effectively protect the exposed silver nanowire conductive network, the prepared P-PW12 The / AgNWs-x composite film and PMMA film were hot pressed under the conditions of temperature (68 ° C), pressure (12 MPa) and time (20 s), achieving the coating of the "sandwich" structure and successfully preparing P-PW 12 / AgNWs / P-PW 12 -x composite film.

[0091] The optical properties of the composite films prepared in the examples of the present invention were tested, and the transmittance of the composite films with different silver nanowire loadings was measured in the visible light wavelength range (400-800 nm).

[0092] Refer to the attached Figure 3a At low concentrations (1 mg / mL), transmittance decreases slightly, ranging from 85% to 90%. Transmittance is low at approximately 85% at 400 nm, but gradually increases as wavelength increases, reaching nearly 90% at 800 nm. Compared to PMMA, transparency is slightly reduced, but the material still maintains good optical properties. At a concentration of 2 mg / mL, transmittance decreases further, ranging from 80% to 85%. At a concentration of 3 mg / mL, transmittance drops to 78% to 83%. The increase in transmittance with increasing wavelength slows with increasing concentration. High-concentration AgNWs (4-5 mg / mL) curves show a significant decrease in transmittance at 4 mg / mL, ranging from 75% to 80%, demonstrating a significant drop in optical transparency compared to the low-concentration sample. At a concentration of 5 mg / mL, transmittance decreases further, reaching approximately 70% at 400 nm and only reaching 75% at 800 nm. The drop in transparency is even more pronounced, and the material gradually becomes opaque.

[0093] Refer to the attached Figure 3b As shown, low concentrations (1-2 mg / mL) offer excellent transparency and are suitable for applications requiring both optical clarity and shielding performance. High concentrations (3-5 mg / mL) significantly reduce optical clarity, but may significantly improve electromagnetic shielding performance. For applications requiring both transparency and electromagnetic shielding performance, 1-2 mg / mL is a good choice. For applications requiring lower transparency but prioritizing shielding performance, 3-5 mg / mL is a good choice.

[0094] like Figures 3a-3e As shown in the following figure, especially the photos of the composite membrane under different reference materials in 3c-3c, when the silver nanowire loading is 1 mg / mL, P-PW 12 / AgNWs / P-PW 12 The transmittance of the composite film reached a maximum of 87.7%, but even at a silver nanowire loading of 5 mg / mL, the composite film still maintained a relatively high transmittance (>79.7%), which indicates that the invention has excellent optical properties.

[0095] Example 3

[0096] (1) First, weigh 1g of polymethyl methacrylate (PMMA) particles in a beaker, add 10mL of dichloromethane (CH2Cl2) organic solvent, and stir quickly with a glass rod for 1min to make it evenly dispersed. Then stir with a magnetic stirrer (speed 650rpm) at room temperature for 0.5h until PMMA is completely dissolved and set aside. At the same time, weigh 0.05g of phosphotungstic acid (PWA) particles in a beaker, add 0.68mL of tetrahydrofuran (THF) organic solvent, and shake thoroughly to completely dissolve it. Pour it into the previously prepared PMMA solution and stir it with a magnetic stirrer (speed 500rpm) at room temperature for 5min. Get P-PW 12 Mix the solution.

[0097] (2) The silver nanowire dispersion (20 mg / mL) was diluted to different concentrations (1, 2, 3, 4 and 5 mg / mL) in ethanol solution for use. The P-PW12 mixed solution was then evenly poured into a culture dish, dried for 6 hours, and peeled off to obtain a cast film. The PMMA film was cut into five parts, each with a size of 30 mm × 30 mm, and fixed on a tinplate sheet placed on a constant temperature heating platform (70°C). Then, a spray gun was used to evenly spray the silver nanowire suspension (1 mL) of different concentrations on the surface of the PMMA film at a distance of 10 cm and a pressure of 0.2 MPa. P-PW was obtained. 12 / AgNWs-x composite films, where x corresponds to the concentration of AgNWs.

[0098] (3) In order to effectively protect the exposed silver nanowire conductive network, the prepared P-PW 12 The / AgNWs-x composite film and PMMA film were hot pressed under the conditions of temperature (68 ° C), pressure (12 MPa), and time (20 s), achieving the coating of the "sandwich" structure and successfully preparing P-PW 12 / AgNWs / P-PW 12 -x composite film.

[0099] The electromagnetic shielding performance of the composite film prepared in the embodiment of the present invention was tested, and the electromagnetic shielding performance exhibited in the X-band is shown in FIG4 , where Figure 4a Before hot pressing: the surface density of Ag NWs is 0.1 mg / cm 2 When the surface density increases to 0.6mg / cm 2 , the sheet resistance gradually decreased to 48.9Ω / sq. The overall trend is downward, but the conductivity before hot pressing is significantly lower than after hot pressing. After hot pressing: at 0.1mg / cm 2When the sheet resistance is significantly reduced from 160.2Ω / sq to 92.5Ω / sq, the surface density is 0.6mg / cm 2 When the AgNWs are heated to 100°C, the sheet resistance is further reduced to 38.4Ω / sq. Hot pressing significantly improves the connectivity and conductivity of the AgNW network. Conductivity increases with increasing AgNW density: increased density means more AgNWs form a dense network, reducing resistance. Hot pressing significantly improves conductivity: the compaction process reduces contact resistance between AgNWs.

[0100] Refer to the attached Figure 4b As shown, EMI SE values ​​gradually increase with increasing AgNW concentration, while shielding effectiveness slightly decreases with increasing frequency. At a concentration of 1 mg / mL, EMI SE is lowest, approximately 12-14 dB. At 5 mg / mL, it reaches its highest value, approximately 24-26 dB. Shielding effectiveness significantly improves with increasing Ag NW concentration. High concentrations form a denser shielding layer, enhancing both reflection and absorption. Frequency dependence is minimal, and within the 8-12 GHz range, the effect of frequency on shielding effectiveness is relatively limited.

[0101] Refer to the attached Figure 4c As shown in the figure, the total shielding effectiveness increases from 13.5 dB (1 mg / mL) to 24.1 dB (5 mg / mL) with increasing AgNWs concentration. The absorption efficiency (SE_A) gradually becomes dominant, increasing from 8.0 dB (1 mg / mL) to 16.2 dB (5 mg / mL). The reflection efficiency (SE_R) varies slightly, ranging from approximately 3.5 to 5.0 dB. The absorption / reflection ratio increases with concentration, from 68% (1 mg / mL) to 75% (5 mg / mL). The reflection ratio decreases accordingly, from 32% to 25%. Absorption is the dominant mechanism: The shielding layer with a high concentration of AgNWs has a higher absorption efficiency, primarily achieving shielding by dissipating electromagnetic wave energy. Reflection contributes less: Reflection is primarily due to the good conductivity of AgNWs, but its contribution is limited compared to absorption.

[0102] Refer to the attached Figure 4d As shown, the shielding effectiveness is highest in the initial state, approximately 24-26 dB, and decreases slightly with increasing frequency. After 20 days of storage, the shielding effectiveness decreases slightly, by approximately 1-2 dB. After 40 days of storage, the overall shielding effectiveness decreases further, by approximately 3-4 dB. Variation: The attenuation of shielding effectiveness gradually increases over time, but the decline is small, indicating that the material performance is relatively stable. Good long-term stability: The AgNWs-based shielding film maintains a high shielding effectiveness (approximately 20 dB or more) even after 40 days. The slight attenuation may be due to oxidation of the AgNWs or a slightly loose network structure.

[0103] The electromagnetic shielding performance of the composite film prepared in the embodiment of the present invention was tested, and the electromagnetic shielding performance exhibited in the X-band was as follows: Figures 4a-4d As shown, when the silver nanowire content is 5 mg / mL, P-PW 12 / AgNWs / P-PW 12 The electromagnetic shielding effectiveness value of the composite film increases to a maximum value of 24.1 dB, and the effective shielding bandwidth can cover the entire X-band (8.2 to 12.4 GHz), which indicates that the invention has excellent shielding performance.

[0104] Example 4

[0105] (1) First, weigh 1g of polymethyl methacrylate (PMMA) particles in a beaker, add 10mL of dichloromethane (CH2Cl2) organic solvent, and stir quickly with a glass rod for 1min to make it evenly dispersed. Then stir with a magnetic stirrer (speed 650rpm) at room temperature for 0.5h until PMMA is completely dissolved and set aside. At the same time, weigh 0.05g of phosphotungstic acid (PWA) particles in a beaker, add 0.68mL of tetrahydrofuran (THF) organic solvent, and shake thoroughly to completely dissolve it. Pour it into the previously prepared PMMA solution and stir it with a magnetic stirrer (speed 500rpm) at room temperature for 5min. Get P-PW 12 Mix the solution.

[0106] (2) The silver nanowire dispersion (20 mg / mL) was diluted to different concentrations (1, 2, 3, 4 and 5 mg / mL) in ethanol solution for use. The P-PW12 mixed solution was then evenly poured into a culture dish, dried for 6 hours, and peeled off to obtain a cast film. The PMMA film was cut into five parts, each with a size of 30 mm × 30 mm, and fixed on a tinplate sheet placed on a constant temperature heating platform (70°C). Then, a spray gun was used to evenly spray the silver nanowire suspension (1 mL) of different concentrations on the surface of the PMMA film at a distance of 10 cm and a pressure of 0.2 MPa. P-PW was obtained. 12 / AgNWs-x composite films, where x corresponds to the concentration of AgNWs.

[0107] (3) In order to effectively protect the exposed silver nanowire conductive network, the prepared P-PW 12 The / AgNWs-x composite film and PMMA film were hot pressed under the conditions of temperature (68 ° C), pressure (12 MPa), and time (20 s), achieving the coating of the "sandwich" structure and successfully preparing P-PW 12 / AgNWs / P-PW 12 -x composite film.

[0108] The Joule heating performance test was performed on the composite film prepared in the embodiment of the present invention. Figures 5a-5e The material was shown to be able to reach a stable surface temperature from room temperature in a short time (about 20s). Figure 5a It can be seen that as the voltage increases, the peak temperature gradually increases. The temperature rises rapidly after power is applied and stabilizes after reaching the peak. When the voltage is low (2.5V), the temperature rises slowly and the peak temperature is low. Therefore, the higher the voltage, the faster the material heats up and the higher the final temperature, indicating that the voltage is positively correlated with the material's heating capacity. Figure 5b As shown in the figure, the data points are basically distributed linearly and are represented by a linear fitting curve. The temperature rise characteristics of the material are proportional to the square of the voltage. Figure 5c As shown in the figure, it shows the temperature change curve when the voltage is gradually increased and decreased. The voltage is sequentially increased to 4.5V and then gradually decreased to 2.5V, and the temperature rises and falls in a step-like manner. The temperature response voltage changes rapidly, indicating that the material has a high thermal response speed. The material has good reversibility in the heating and cooling process, indicating that its thermal performance is stable. Figure 5d As shown in the figure, it is an infrared thermal image showing the thermal distribution of the material under high temperature conditions. The image shows the uniformity of the temperature distribution and the hot spots. The maximum temperature is 48.7°C and the minimum temperature is 18.5°C. It can be concluded that the thermal imaging shows that the material surface is heated evenly, with some slight hot spots. Figure 5e The figure shows the material's temperature stability over time under a long-term constant voltage (e.g., 4.5V), along with thermal profiles at multiple times. After an initial temperature increase, the temperature gradually stabilizes between 51.2°C and 52.2°C, with minimal fluctuations. The temperature distribution shows little variation. The material exhibits excellent thermal stability and uniformity over long periods of operation.

[0109] It was found that there is an approximately linear relationship between its saturation temperature and the square of the input voltage, and the surface temperature remains evenly distributed during bending deformation, and the steady-state temperature can last for nearly 720 seconds, indicating that the composite film of this invention has excellent Joule heating performance.

[0110] Example 5

[0111] (1) First, weigh 1g of polymethyl methacrylate (PMMA) particles in a beaker, add 10mL of dichloromethane (CH2Cl2) organic solvent, and stir quickly with a glass rod for 1min to make it evenly dispersed. Then stir with a magnetic stirrer (speed 650rpm) at room temperature for 0.5h until PMMA is completely dissolved and set aside. At the same time, weigh 0.05g of phosphotungstic acid (PWA) particles in a beaker, add 0.68mL of tetrahydrofuran (THF) organic solvent, and shake thoroughly to completely dissolve it. Pour it into the previously prepared PMMA solution and stir it with a magnetic stirrer (speed 500rpm) at room temperature for 5min. Get P-PW 12 Mix the solution.

[0112] (2) The silver nanowire dispersion (20 mg / mL) was diluted to different concentrations (1, 2, 3, 4 and 5 mg / mL) in ethanol solution for use. The P-PW12 mixed solution was then evenly poured into a culture dish, dried for 6 hours, and peeled off to obtain a cast film. The PMMA film was cut into five parts, each with a size of 30 mm × 30 mm, and fixed on a tinplate sheet placed on a constant temperature heating platform (70°C). Then, a spray gun was used to evenly spray the silver nanowire suspension (1 mL) of different concentrations on the surface of the PMMA film at a distance of 10 cm and a pressure of 0.2 MPa. P-PW was obtained. 12 / AgNWs-x composite films, where x corresponds to the concentration of AgNWs.

[0113] (3) In order to effectively protect the exposed silver nanowire conductive network, the prepared P-PW 12 The / AgNWs-x composite film and PMMA film were hot pressed under the conditions of temperature (68 ° C), pressure (12 MPa), and time (20 s), achieving the coating of the "sandwich" structure and successfully preparing P-PW 12 / AgNWs / P-PW 12 -x composite film.

[0114] The photochromic performance of the composite film prepared in the embodiment of the present invention was tested. Figure 6a-6f As shown, the P-PW was measured under ultraviolet light (λ = 400 ~ 800nm) 12 / AgNWs / P-PW 12 -3 composite film UV-vis absorption spectrum, the absorption intensity at 470nm and 730nm wavelength gradually increases. The UV dose is 120kJ / m 2The absorbance reached saturation at 0.58. After irradiation with ultraviolet light, the absorbance at a wavelength of 730 nm did not decrease significantly after 10 repetitions, indicating that the composite film has excellent fatigue resistance. This indicates that the composite film of the present invention can be applied to the field of smart windows. While ensuring high transparency and shielding electromagnetic waves, the modulation of ultraviolet light can also improve indoor daylight comfort, save energy, and achieve low-carbon and environmentally friendly effects.

[0115] This study, centered around transparent electromagnetic shielding materials, combines PMMA and PWA to create photochromic films. The study demonstrates the addition of photochromic functionality to these highly transparent and photosensitive photochromic films, already used for cast coatings and inkjet printing, to create polymer-based electromagnetic shielding composite films with photochromic properties. By controlling the silver nanowire loading, the composite film's optical and electromagnetic shielding properties can be controlled.

[0116] The electromagnetic shielding film material with photochromic effect prepared by the present invention can be used in the field of electronic equipment. With the popularity of smart phones and tablet computers, people have higher and higher requirements for the functions and performance of the equipment. The film material prepared in the present invention can be applied to the surface of the screen as a protective and function-enhancing layer. In daily use, it can effectively shield external electromagnetic interference, prevent damage to the electronic components inside the device, and improve the stability of the device operation. At the same time, its photochromic effect can automatically adjust the transparency and color of the screen according to the intensity of the ambient light. It darkens in strong light to reduce glare, improve screen visibility, and protect the user's eyes; it brightens in low-light environments to ensure the clarity of the screen display. For example, when the sunlight is strong outdoors, the screen automatically adjusts to a low transmittance state, so that the screen content is still clearly visible, and can effectively prevent the aging effect of ultraviolet rays on the screen; when the light indoors is dim, the screen restores high transmittance to provide a good visual experience.

[0117] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0118] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing an electromagnetic shielding film material having a photochromic effect, characterized in that: The following steps are included: The mixture of phosphotungstic acid particles and polar organic solvent is added to the polymethyl methacrylate solution and magnetically stirred to obtain P-PW 12 Mixing solution; The silver nanowire dispersion was diluted in an ethanol solution to different concentrations to form several silver nanowire suspensions, wherein the concentration range of the different concentrations was 1 mg / mL to 5 mg / mL; In a petri dish, pour P-PW 12 mixing the solutions to obtain a cast film; Part of the cast film is cut into several parts, and each part is sprayed with a concentration of silver nanowire suspension to obtain P-PW 12 / AgNWs-x composite film, where x corresponds to the concentration of AgNWs; Several copies of P-PW 12 The cast film forms the upper and lower substrates respectively, and is set on each P-PW 12 / AgNWs-x composite film on both sides, hot pressing, to obtain P-PW containing different concentrations of AgNWs 12 / AgNWs / P-PW 12 -x composite film.

2. The method for preparing an electromagnetic shielding film material having a photochromic effect according to claim 1, wherein: The method also includes the preparation of polymethyl methacrylate solution, specifically, the polymethyl methacrylate particles and halogenated hydrocarbon solvent are mixed and stirred to disperse uniformly.

3. The method for preparing an electromagnetic shielding film material having a photochromic effect according to claim 2, characterized in that: The mass ratio of the phosphotungstic acid particles to the polymethyl methacrylate particles is 15:1-25:

1.

4. The method for preparing an electromagnetic shielding film material having a photochromic effect according to claim 1, wherein: The polar organic solvent includes tetrahydrofuran, dichloromethane, acetone, ethyl acetate or N,N-dimethylformamide.

5. The method for preparing an electromagnetic shielding film material having a photochromic effect according to claim 1, wherein: The magnetic stirring time is 3-7 min, and the speed is 400-600 rpm.

6. The method for preparing an electromagnetic shielding film material having a photochromic effect according to claim 1, wherein: The P-PW 12 The mixed solution has a solid content of 0.08 mg / mL to 0.1 mg / mL.

7. The method for preparing an electromagnetic shielding film material having a photochromic effect according to claim 1, characterized in that: During the spraying, the cast film is fixed on a tinplate sheet that is heated at a constant temperature, and the temperature of the constant temperature heating is 60-80°C.

8. The method for preparing an electromagnetic shielding film material having a photochromic effect according to claim 1, wherein: During the spraying, the distance between the spray gun and the film is at least 9-12 cm, and the spraying pressure is 0.2-0.5 MPa.

9. P-PW obtained by the method for preparing an electromagnetic shielding film material with photochromic effect according to any one of claims 1 to 8 12 / AgNWs / P-PW 12 -x composite film applications in the field of electronic equipment.

10. The use according to claim 9, characterized in that The application is specifically as a screen, which can be used in different light environments by adjusting the transmittance state.

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