A transparent film having electromagnetic field shielding performance and a method for manufacturing the same

Abstract

The present application relates to the field of electromagnetic shielding layered material, and provides a transparent film for electromagnetic field shielding and a preparation method thereof, the film is a three-layer structure, sequentially comprising a polycarbonate / polyetherimide blended base layer, a shielding functional layer containing surface modified GO / ITO composite filler and a fluorinated ethylene propylene copolymer protective layer. The GO / ITO composite filler is composed of ITO nanorods loaded with graphene oxide and is modified by sodium benzoate, and has good dispersibility and conductivity. The filler content and additives in the functional layer are optimized to improve the electromagnetic shielding and mechanical properties, and the overall film has excellent transparency, strength and shielding effect. The preparation process includes melt extrusion of the base, solution coating and multi-stage temperature control curing of the functional layer, gravure coating of the protective layer and hot pressing and stretching shaping, and the prepared product is suitable for electromagnetic interference protection of high-performance electronic devices, the process is stable, and has good industrialization prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic shielding layered materials, in particular to a transparent film for electromagnetic field shielding and a preparation method thereof. BACKGROUND

[0002] With the rapid development of 5G communication, wearable devices, flexible displays and high-integration electronic modules, devices have put forward more stringent requirements for electromagnetic compatibility in high-frequency, high-density and high-sensitivity working environments. Especially in the application scenarios such as smart phones, medical diagnostic instruments, aerospace equipment, etc., which have extremely high space utilization rate and extremely high requirements for signal stability, the traditional metal shielding materials have been difficult to meet the needs of modern electronic products for lightweight, integration and visualization due to their opacity, high weight and processing complexity. Therefore, it is particularly crucial to develop new thin film materials with high transparency, electromagnetic shielding function and excellent mechanical properties. In practical applications, such materials not only need to have effective shielding ability to a wide range of electromagnetic waves, but also need to maintain good mechanical strength, flexibility and environmental stability in long-term use to adapt to complex working conditions and frequent operation. In addition, its processing performance and interface adaptability also directly affect the integration efficiency with devices. Achieving the dual breakthrough of transparent electromagnetic shielding materials in strength and shielding performance not only can significantly improve the anti-interference ability and use reliability of electronic products, but also will accelerate the evolution of high-end electronic equipment towards intelligence and lightness, which has important technical value and industrial significance.

[0003] Although some progress has been made in the research of transparent electromagnetic shielding materials in recent years, there are still obvious deficiencies in the synergistic improvement of strength and electromagnetic shielding performance in the existing technology. For example, the electromagnetic wave shielding film disclosed in the Chinese patent with publication number CN116419847A has a certain shielding ability, but its mechanical strength is low and it is difficult to withstand stress impact in complex environments, and it is easy to cause structural damage during long-term use, affecting the shielding stability. The main reason is that the material system design fails to build an effective interface enhancement mechanism, the interface bonding force between the conductive components and the matrix is weak, resulting in loose overall structure of the film, which cannot balance the shielding effect and mechanical strength. In addition, the electromagnetic wave shielding film proposed in the patent with publication number CN118140606A has achieved certain optimization in the preparation process, but the dispersion and stability of the shielding filler are insufficient, which makes it difficult to achieve high-efficiency shielding without sacrificing optical transparency, further limiting its application in high-end electronic devices. Therefore, it is urgent to start from the two aspects of material structure design and process control to develop transparent thin film materials with good strength and electromagnetic shielding performance, in order to meet the urgent needs of new generation electronic products for high-performance shielding materials. SUMMARY

[0004] (1) Technical problems solved

[0005] The present application aims to provide an electromagnetic field shielding transparent film and a preparation method thereof, and solve the problem of insufficient strength and electromagnetic shielding performance of the current film.

[0006] (2) Technical scheme

[0007] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0008] An electromagnetic field shielding transparent film, the transparent film is a multilayer structure, comprising a substrate layer, a functional shielding layer and a protective layer which are stacked in turn, wherein:

[0009] The substrate layer is formed by a blend of polycarbonate and polyetherimide, and the thickness is 15-25 μm;

[0010] The functional shielding layer takes polyethylene terephthalate as a matrix, wherein the surface modified GO / ITO composite filler is dispersed therein; the thickness of the functional shielding layer is 2.0-5.0 μm;

[0011] The surface modified GO / ITO composite filler is obtained by treating GO / ITO composite filler with sodium benzoate surface modifier;

[0012] The GO / ITO composite filler is composed of ITO nanorods and graphene oxide loaded on the surface of the nanorods;

[0013] The protective layer is selected from fluorinated ethylene propylene copolymer, and the thickness is 0.5-4.0 μm.

[0014] The present application adopts a multi-layer structure design, and is mainly used for enhancing the electromagnetic shielding performance and mechanical strength performance required by the device in use. By constructing a transparent film structure sequentially stacked by a substrate layer, a functional shielding layer and a protective layer, the synergistic effect between the components of the material is systematically realized. The substrate layer is composed of a blend of polycarbonate and polyetherimide, and the complementarity of the two in thermoplasticity and heat resistance not only improves the overall structural stability and mechanical strength of the film, but also provides a good support matrix for the upper functional material; the functional shielding layer takes polyethylene terephthalate as the matrix, and takes into account the film-forming property and transparency, and disperses the GO / ITO composite filler modified by sodium benzoate in it, the composite filler is composed of ITO nanorods and graphene oxide loaded on the surface of the ITO nanorods, the ITO nanorods have excellent electrical conductivity, and the graphene oxide provides high specific surface area and lamellar structure, and the interface complementarity and electromagnetic wave multiple scattering absorption are realized by the composite mode, which significantly improves the electromagnetic interference suppression ability of the shielding layer; after the surface modification treatment of sodium benzoate, the composite filler is more uniformly dispersed in the polyester matrix, and the interface is more closely combined, which further enhances the overall stability and shielding efficiency of the composite system; the outermost protective layer is formed by fluorinated ethylene propylene, which has excellent weather resistance and chemical inertness, effectively prolongs the service life of the film in complex environment and prevents the performance degradation of the functional layer. The overall structural design effectively realizes the synchronous improvement of the electromagnetic shielding function and the mechanical property on the basis of maintaining excellent optical transparency, through the structural matching and interface synergy between the multi-component materials, which reflects the supporting role of material structure design on the development of functional integration.

[0015] Further, the preparation method of the surface modified GO / ITO composite filler is as follows: 100.0-120.0 parts of GO / ITO composite filler and 1.0-2.5 parts of sodium dodecyl sulfate are added to a three-necked reaction flask equipped with a mechanical stirrer, 200.0-300.0 parts of anhydrous ethanol is added for ultrasonic dispersion, the ultrasonic power is 300.0-500.0 W, and the ultrasonic time is 30.0-60.0 min, then 50.0-100.0 parts of a 0.5-1.0 wt% sodium benzoate aqueous solution is added to the dispersion liquid, and continuously stirred at a stirring rate of 200.0-400.0 rpm for 2.0-4.0 h at room temperature, then the reaction mixture is centrifuged at a speed of 8000.0-12000.0 rpm for 10.0-20.0 min to remove the supernatant, then the precipitate is washed with deionized water for 2-3 times to remove the unreacted sodium benzoate, and after each washing, it is centrifuged at a speed of 6000.0-10000.0 rpm for 5.0-10.0 min, finally the obtained precipitate is vacuum dried at a temperature of 60.0-80.0°C for 12.0-24.0 h to obtain the surface modified GO / ITO composite filler.

[0016] Further, the preparation method of the GO / ITO composite filler is as follows: 10.0-30.0 parts of ITO nanorods are added into 100.0-200.0 parts of a 2.0 wt% γ-aminopropyltriethoxysilane anhydrous ethanol solution, and surface amination is carried out under nitrogen protection at 80.0-100.0°C for 2.0-4.0 h, then centrifugal washing is performed to remove unreacted silane coupling agent, then the aminated ITO nanorods are redispersed in 150.0-250.0 parts of deionized water, 5.0-15.0 parts of natural graphite powder is added, 30.0-50.0 parts of concentrated sulfuric acid is added dropwise under ice bath, then 2.0-5.0 parts of sodium nitrate is added, 8.0-15.0 parts of potassium permanganate is added in batches at 15.0-25.0°C, and the graphite is oxidized and peeled to generate graphene oxide and simultaneously loaded on the surface of the ITO nanorods at 35.0-45.0°C for 2.0-4.0 h, then 10.0-20.0 parts of 30.0% hydrogen peroxide solution is added to terminate the reaction, 50.0-100.0 parts of 10.0 wt% hydrochloric acid solution is used to remove metal ions, centrifugal collection is performed and washing is performed with deionized water until neutral, and finally vacuum drying is performed at 60.0-80.0°C for 8.0-16.0 h to obtain the GO / ITO composite filler.

[0017] Further, the preparation method of the ITO nanorod is as follows: 10.0-15.0 parts of indium chloride trihydrate and 1.0-3.0 parts of tin tetrachloride pentahydrate are added into a beaker with a mechanical stirrer in a molar ratio of indium to tin of 90:10-95:5, 200.0-300.0 parts of deionized water is added, and stirring is performed at room temperature at a stirring rate of 300.0-500.0 rpm for 30.0-60.0 min until complete dissolution to form a precursor solution, then 2.0-5.0 parts of polyvinylpyrrolidone with a molecular weight of 30,000-40,000 is added as a morphology control agent, and stirring is continued for 15.0-30.0 min to fully dissolve it, then the pH value of the solution is slowly adjusted to 8.5-9.5 with an ammonia solution with a concentration of 2-5.0 wt% until white precipitates appear, then stirring is continued for 30.0-60.0 min to fully form the precipitates, then the reaction mixture is transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, the filling degree is controlled to be 70.0-80.0%, and the hydrothermal reaction is performed at a reaction temperature of 160.0-200.0°C for 8.0-12.0 h, then natural cooling is performed to room temperature, centrifugal separation is performed at a rotation speed of 8,000.0-12,000.0 rpm for 10.0-20.0 min to collect the precipitates, the precipitates are washed with deionized water for 3 times and anhydrous ethanol for 2 times to remove reaction by-products and residual organic matter, centrifugal separation is performed after each washing, and finally drying is performed at a temperature of 80.0-120.0°C for 12.0-24.0 h to obtain the ITO nanorod.

[0018] Further, the ITO nanorod has a diameter of 15-25 nm and a length of 100-200 nm, and the loading amount of the graphene oxide is 5-15% of the mass of the ITO.

[0019] Further, the content of the surface-modified GO / ITO composite filler in the functional shielding layer is 3.0-8.0 wt%, and 0.20-0.35 wt% of 2,6-di-tert-butyl-4-methylphenol antioxidant and 0.1-0.2 wt% of polydimethylsiloxane leveling agent are further added to the matrix film-forming solution.

[0020] Further, the mass ratio of polycarbonate to polyetherimide in the substrate layer is 60-70:30-40, and 0.5-1.0 wt% of dibutyl phthalate plasticizer and 0.3-0.4 wt% of sodium dodecylbenzenesulfonate antistatic agent are added.

[0021] The application adopts the design of constructing a multi-layer composite structure based on a surface modified GO / ITO composite filler, and is mainly used for enhancing the electromagnetic shielding performance and mechanical strength performance of a transparent film. The GO / ITO composite filler is formed by compounding ITO nanorods with graphene oxide, and is surface modified by sodium benzoate, so that the dispersibility and interface compatibility of the GO / ITO composite filler in a polyethylene terephthalate matrix are significantly improved, and the interface bonding strength between the filler and the matrix is further enhanced. The sodium benzoate not only serves as a surface modifier to improve the stability of the filler, but also promotes the crystallization of the polyethylene terephthalate in the interface region, so that the interface layer presents an ordered structure, and the matrix away from the interface remains in an amorphous state, realizing the synergistic mechanism of strong interface bonding and plastic matching, thereby effectively improving the stress buffering capacity and structural integrity of the film under external force. The ITO nanorods in the GO / ITO composite filler itself has good conductivity, and the graphene oxide provides a sheet structure, which is helpful to form a continuous conductive network, and forms a multi-path electromagnetic wave attenuation mechanism in the shielding layer; at the same time, the high specific surface area of the graphene oxide improves the scattering and absorption capacity of electromagnetic radiation, and the synergistic effect of the two significantly enhances the electromagnetic shielding effect of the composite system. In the dispersion process of the composite filler, sodium dodecyl sulfate as an auxiliary dispersant cooperates with ultrasonic treatment, effectively reduces the agglomeration tendency of the filler, ensures the uniform distribution of the filler in the polyethylene terephthalate film forming solution, and enhances the structural stability of the entire shielding layer. In the design of the base layer, the blending ratio of polycarbonate and polyetherimide is optimized, and the polycarbonate and polyetherimide have good toughness and heat resistance, and are supplemented by dibutyl phthalate plasticizer and sodium dodecyl benzene sulfonate antistatic agent, so as to improve the processing performance and antistatic ability of the film, and provide stable support for the functional shielding layer. Finally, by constructing a multi-layer transparent film system composed of a functional shielding filler reinforced intermediate layer, a base layer with superior structural strength and a protective layer with environmental resistance, the electromagnetic shielding performance and mechanical performance are realized on the basis of ensuring optical transparency, and the synergistic effect of the multi-component material system in the aspects of structural design, interface regulation and performance composition is embodied.

[0022] The application further discloses a preparation method of the electromagnetic field shielding transparent film.

[0023] S1. Preparation of the substrate layer: polycarbonate 60.0~70.0 parts and polyetherimide 30.0~40.0 parts were mixed in a mass ratio, dibutyl phthalate plasticizer 0.5~1.0 parts and sodium dodecyl benzene sulfonate antistatic agent 0.3~0.4 parts were added, and then melt blended in a twin-screw extruder at a processing temperature of 280.0~320.0°C and a screw speed of 100.0~200.0 rpm for 10.0~20.0 min, and then a substrate layer film was prepared by flow casting at a roll temperature of 150.0~180.0°C and a pulling speed of 5.0~15.0 m / min;

[0024] S2. Preparation of the functional shielding layer film solution: polyethylene terephthalate 10.0~15.0 parts was dissolved in a mixed solvent of trifluoroacetic acid and dichloromethane in a volume ratio of 1:1 80.0~120.0 parts, and then stirred at room temperature at a stirring speed of 200.0~400.0 rpm for 4.0~8.0 h until completely dissolved to form a PET film solution, then surface modified GO / ITO composite filler, 2,6-di-tert-butyl-4-methylphenol antioxidant and polydimethylsiloxane leveling agent were added to the solution, and then ultrasonically dispersed at an ultrasonic power of 200.0~400.0 W for 30.0~60.0 min, and then stirred at a stirring speed of 150.0~300.0 rpm for 2.0~4.0 h to obtain a uniform functional shielding layer film solution;

[0025] S3. Functional shielding layer coating and curing: the functional shielding layer film solution prepared in step S2 was coated on the surface of the substrate layer prepared in step S1 by using a doctor blade coating method, the coating speed was 2.0~8.0 m / min, and the wet film thickness was controlled to be 8.0~20.0 μm, then pre-dried at a temperature of 50.0~80.0°C for 5.0~15.0 min to remove most of the solvent, and then cured by multi-stage temperature control to form a functional shielding layer;

[0026] S4. Protective layer coating: fluorinated ethylene propylene copolymer 5.0~10.0 parts was dissolved in a mixed solvent of methyl ethyl ketone and isopropyl alcohol in a volume ratio of 3:1 80.0~120.0 parts to form a protective layer solution, and then the solution was coated on the surface of the functional shielding layer by using a gravure coating method, the coating speed was 5.0~12.0 m / min, and the wet film thickness was controlled to be 2.0~15.0 μm, then dried at a temperature of 80.0~120.0°C for 10.0~30.0 min to obtain a protective layer;

[0027] S5. Post-curing and finishing: the prepared three-layer composite film is heat-pressed and cured in a heat press at a temperature of 80.0-100.0 °C and a pressure of 0.1-0.3 MPa for 10.0-20.0 min to enhance the interfacial bonding between the layers, and then stretched and shaped under a tension of 50.0-150.0 N / m, cooled to room temperature, and then laser-cut to obtain a transparent electromagnetic shielding multilayer film product of a specified size.

[0028] Further, the detailed process of the multi-stage temperature-controlled curing in step S3 is as follows: PET crystallization treatment is performed at a temperature of 120.0-140.0 °C for 10.0-20.0 min to activate the nucleation of sodium benzoate, and then the temperature is lowered to 60.0-80.0 °C for final curing for 20.0-40.0 min.

[0029] The application adopts a multi-step construction multi-layer composite coating and curing process to prepare a method mainly used to realize the overall improvement of transparent film in electromagnetic shielding performance, mechanical properties and structural stability. First, in the preparation process of the base layer, by blending polycarbonate and polyetherimide according to a certain mass ratio, and adding dibutyl phthalate plasticizer and sodium dodecyl benzene sulfonate antistatic agent, a base support layer with good strength, flexibility and antistatic performance is prepared under the process conditions of double screw extrusion and casting molding, which provides a solid foundation for the stable adhesion of the subsequent functional layer and the mechanical stability of the overall film. Subsequently, by dissolving polyethylene terephthalate in a mixed solvent of trifluoroacetic acid and dichloromethane, cooperating with ultrasonic dispersion and mechanical stirring, the surface modified GO / ITO composite filler, 2,6-di-tert-butyl-4-methylphenol antioxidant and polydimethylsiloxane leveling agent are fully dispersed and uniformly distributed to prepare a functional shielding layer solution with excellent film forming performance. After the solution is coated by a doctor blade, it is pre-dried at 50.0~80.0°C to remove the solvent, and then a multi-stage temperature control curing process is used to realize the film forming stability and structural compactness. In the heat treatment stage at 120.0~140.0°C, sodium benzoate induced nucleation promotes the formation of ordered structure of PET crystal, enhances the mechanical properties and interface stability of the film, and then the final curing is completed at 60.0~80.0°C to ensure the coating integrity and functional durability. After the completion of the shielding layer, a fluorinated ethylene propylene copolymer protective layer is uniformly coated on the surface by using a gravure coating process, and an outer layer barrier with excellent chemical resistance and environmental adaptability is formed after suitable temperature drying, which further improves the service stability and durability of the overall film. Finally, the multi-layer interface adhesion is enhanced by heat pressing and curing, and the size stability and surface uniformity of the film are realized by combining tension stretching treatment, and a transparent electromagnetic shielding composite film product with excellent processability and applicability is obtained by laser cutting. The whole process realizes systematic optimization in structure design, material synergy, interface control and film forming stability, which ensures the feasibility and application value of the prepared film in high-performance electronic devices.

[0030] (3)Beneficial technical effects

[0031] 1. The application has significant application value by designing the multi-layer structure and surface modified composite filler, which takes into account the transparency, shielding and strength, improves the stability and protection performance of the device in complex environment.

[0032] 2. The application realizes excellent electromagnetic shielding and mechanical strength performance of the transparent film by designing the surface modified GO / ITO filler and multi-layer structure, which takes into account the processability and stability, and is suitable for efficient shielding and protection of electronic devices.

[0033] 3.The application improves the electromagnetic shielding and mechanical properties of the transparent film through multi-component synergistic design, solves the problem of considering the performance of the existing materials, and has stable process, is suitable for shielding protection of high-end electronic devices, and has significant application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Morphology diagram of ITO nanorods prepared for the application example 1.

[0035] Figure 2 XRD phase analysis diagram of GO / ITO fillers prepared for the application example 1.

[0036] Figure 3 Morphology diagram of GO / ITO fillers prepared for the application example 1.

[0037] Figure 4 XRD phase analysis diagram of GO / ITO fillers prepared for the application example 1.

[0038] Figure 5 Morphology diagram of GO / ITO composite fillers and polyethylene terephthalate matrix interface prepared for the application example 1.

[0039] Figure 6 Physical diagram of the electromagnetic field shielding transparent film prepared for the application example 1.

[0040] Figure 7 Morphology diagram of ITO nanorods prepared for the application comparative example 7.

[0041] Figure 8 Morphology diagram of GO / ITO fillers prepared for the application comparative example 4.

[0042] Figure 9 Morphology diagram of GO / ITO composite fillers and polyethylene terephthalate matrix interface prepared for the application comparative example 1. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the application example clearer, the technical scheme in the application example will be described clearly and completely below by combining the drawings in the application example. Example 1

[0044] An electromagnetic field shielding transparent film, the transparent film is a multilayer structure, including a substrate layer, a functional shielding layer and a protective layer which are stacked in turn, wherein:

[0045] The substrate layer is formed by a blend of polycarbonate and polyetherimide, and the thickness is 15 μm;

[0046] The functional shielding layer is based on polyethylene terephthalate with surface modified GO / ITO composite filler dispersed therein, and the thickness of the functional shielding layer is 2.0 μm.

[0047] The surface modified GO / ITO composite filler is obtained by treating GO / ITO composite filler with sodium benzoate surface modifier.

[0048] The GO / ITO composite filler is composed of ITO nanorods and graphene oxide loaded on the surface of the nanorods.

[0049] The protective layer is selected from fluorinated ethylene propylene copolymer, and the thickness of the protective layer is 0.5 μm.

[0050] The preparation method of the surface modified GO / ITO composite filler in this embodiment is as follows: 100.0 parts of GO / ITO composite filler and 1.0 part of sodium dodecyl sulfate are added into a three-necked reaction flask equipped with a mechanical stirrer, 200.0 parts of anhydrous ethanol is added for ultrasonic dispersion, the ultrasonic power is 300.0 W, and the ultrasonic time is 30.0 min; then 50.0 parts of 0.5 wt% sodium benzoate aqueous solution is added to the dispersion liquid, and the reaction is continuously stirred at a stirring rate of 200.0 rpm at room temperature for 2.0 h; then the reaction mixture is centrifuged at a speed of 8000.0 rpm for 10.0 min to remove the supernatant; then the precipitate is washed with deionized water for 2 times to remove the unreacted sodium benzoate, and the centrifugation is performed at a speed of 6000.0 rpm for 5.0 min after each washing; finally, the obtained precipitate is vacuum dried at a temperature of 60.0°C for 12.0 h to obtain the surface modified GO / ITO composite filler.

[0051] The preparation method of the GO / ITO composite filler in this embodiment is as follows: 10.0 parts of ITO nanorods are added into 100.0 parts of 2.0 wt% γ-aminopropyl triethoxysilane anhydrous ethanol solution, and surface amination is performed at 80.0°C for 2.0 h under nitrogen protection; then the unreacted silane coupling agent is removed by centrifugal washing; then the aminated ITO nanorods are re-dispersed in 150.0 parts of deionized water, 5.0 parts of natural graphite powder is added, 30.0 parts of concentrated sulfuric acid is added dropwise under ice bath, then 2.0 parts of sodium nitrate is added, 8.0 parts of potassium permanganate is added in batches at 15.0°C, and the reaction is performed at 35.0°C for 2.0 h to oxidize and exfoliate the graphite to obtain graphene oxide and simultaneously load it on the surface of the ITO nanorods; then 10.0 parts of 30.0% hydrogen peroxide solution is added to terminate the reaction, 50.0 parts of 10.0 wt% hydrochloric acid solution is used to remove metal ions, and the product is collected by centrifugation and washed with deionized water until neutral; finally, the product is vacuum dried at 60.0°C for 8.0 h to obtain the GO / ITO composite filler.

[0052] The preparation method of the ITO nanorod of the embodiment is as follows: 11.5 parts of indium chloride trihydrate and 1.6 parts of tin tetrachloride pentahydrate are added into a beaker with a mechanical stirrer in a molar ratio of indium to tin of 92:8, 230.0 parts of deionized water is added, stirring at a stirring rate of 360.0 rpm for 39.0 min at room temperature until complete dissolution to form a precursor solution, then 2.9 parts of polyvinylpyrrolidone with a molecular weight of 33000 is added as a morphology control agent, and the stirring is continued for 18.0 min to make it fully dissolved, then the pH value of the solution is slowly adjusted to 8.8 with an ammonia solution with a concentration of 2.9 wt% until white precipitate appears, then the stirring is continued for 39.0 min to make the precipitate fully formed, then the reaction mixture is transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, the filling degree is controlled to be 73.0%, the hydrothermal reaction is carried out at a reaction temperature of 172.0°C for 9.2h, then it is naturally cooled to room temperature, centrifugal separation is carried out at a rotating speed of 9200.0 rpm for 13.0 min to collect the precipitate, and the precipitate is washed with deionized water for 3 times and anhydrous ethanol for 2 times to remove reaction byproducts and residual organic matter, centrifugal separation is carried out after each washing, and finally drying is carried out at a temperature of 92.0°C for 15.6 h to obtain the ITO nanorod.

[0053] The ITO nanorod of the embodiment has a diameter of 18 nm and a length of 130 nm, and the loading amount of the graphene oxide is 8% of the mass of the ITO.

[0054] The content of the surface-modified GO / ITO composite filler in the functional shielding layer of the embodiment in the matrix is 4.5 wt%, and 0.25 wt% of 2,6-di-tert-butyl-4-methylphenol antioxidant and 0.13 wt% of polydimethylsiloxane leveling agent are further added to the matrix film-forming solution.

[0055] The mass ratio of polycarbonate to polyetherimide in the substrate layer of the embodiment is 63:33, and 0.65 wt% of dibutyl phthalate plasticizer and 0.33 wt% of sodium dodecylbenzenesulfonate antistatic agent are added.

[0056] The preparation method of the electromagnetic field shielding transparent film of the embodiment comprises the following steps:

[0057] S1. Substrate layer preparation: polycarbonate 63.0 parts and polyetherimide 33.0 parts are mixed in a mass ratio, dibutyl phthalate plasticizer 0.65 parts and sodium dodecylbenzenesulfonate antistatic agent 0.33 parts are added, melt blending is carried out in a twin-screw extruder at a processing temperature of 292.0°C and a screw rotating speed of 130.0 rpm for 13.0 min, and then a substrate layer film is prepared by flow casting at a roll temperature of 159.0°C and a pulling speed of 8.0 m / min;

[0058] S2. Functional shielding layer film-forming solution preparation: polyethylene terephthalate 11.5 parts was dissolved in a mixed solvent of trifluoroacetic acid and dichloromethane in a volume ratio of 1:1 92.0 parts, stirred at room temperature at a stirring rate of 260.0 rpm for 5.2 h to completely dissolve to form a PET film-forming solution, then surface modified GO / ITO composite filler, 2,6-di-tert-butyl-4-methylphenol antioxidant and polydimethylsiloxane leveling agent were added to the solution, ultrasonic dispersion was carried out under the condition of ultrasonic power of 260.0 W for 39.0 min, and then stirring was carried out at a stirring rate of 195.0 rpm for 2.6 h to obtain a uniform functional shielding layer film-forming solution;

[0059] S3. Functional shielding layer coating and curing: the functional shielding layer film-forming solution prepared in step S2 was coated on the surface of the base layer prepared in step S1 by using a doctor blade coating method, the coating speed was 3.8 m / min, the wet film thickness was controlled to be 11.6 μm, then most of the solvent was removed by pre-drying at a temperature of 59.0°C for 8.0 min, and the functional shielding layer was formed by multi-stage temperature control curing; the detailed process of multi-stage temperature control curing is as follows: PET crystallization treatment is carried out at a temperature of 126.0°C for 13.0 min to activate the nucleation effect of sodium benzoate, and then the temperature is lowered to 66.0°C for final curing for 26.0 min.

[0060] S4. Protective layer coating: fluorinated ethylene propylene copolymer 6.5 parts was dissolved in a mixed solvent of methyl ethyl ketone and isopropyl alcohol in a volume ratio of 3:1 92.0 parts to form a protective layer solution, the solution was coated on the surface of the functional shielding layer by using a gravure coating method, the coating speed was 7.1 m / min, the wet film thickness was controlled to be 5.9 μm, then drying was carried out at a temperature of 92.0°C for 16.0 min to obtain a protective layer;

[0061] S5. Post-curing and finishing: the prepared three-layer composite film was heat pressed in a hot press at a temperature of 86.0°C and a pressure of 0.16 MPa for 13.0 min to enhance the interfacial bonding between the layers, then stretching and setting treatment was carried out under a tension of 80.0 N / m, and after cooling to room temperature, the transparent electromagnetic shielding multilayer film product of a specified size was obtained by laser cutting.

[0062] Figure 1 and Figure 2 ITO nanorods prepared in Example 1 of the present application have regular and uniform rod-like structure and typical crystal diffraction peaks, indicating that the crystal form is complete and the structure is stable; Figure 3 and Figure 4 It is further proved that the graphene oxide is successfully loaded on the surface of the ITO nanorods to form a GO / ITO composite filler with regular structure and tight interface, while maintaining the crystal characteristics of each component;Figure 5 It is shown that a continuous and dense interface structure is formed between the GO / ITO composite filler and the polyethylene terephthalate matrix, effectively verifying the enhancement effect of sodium benzoate surface modification and amination treatment on the interface bonding; Figure 6 The transparent film shown has uniform appearance, no obvious defects, good film forming quality and visible light transmittance.

[0063] Example 2

[0064] An electromagnetic field shielding transparent film, the transparent film is a multilayer structure, comprising a substrate layer, a functional shielding layer and a protective layer which are stacked in turn, wherein:

[0065] The substrate layer is formed by a blend of polycarbonate and polyetherimide, and has a thickness of 18 μm;

[0066] The functional shielding layer has polyethylene terephthalate as a matrix, wherein the surface modified GO / ITO composite filler is dispersed therein; the functional shielding layer has a thickness of 2.9 μm;

[0067] The surface modified GO / ITO composite filler is obtained by treating the GO / ITO composite filler with a sodium benzoate surface modifier;

[0068] The GO / ITO composite filler is composed of ITO nanorods and graphene oxide loaded on the surface of the nanorods;

[0069] The protective layer is selected from fluorinated ethylene propylene copolymer, and has a thickness of 1.6 μm.

[0070] The preparation method of the surface modified GO / ITO composite filler of the present embodiment is as follows: in parts by weight, GO / ITO composite filler 106.0 parts and sodium dodecyl sulfate 1.5 parts are added to a three-necked reaction flask equipped with a mechanical stirrer, anhydrous ethanol 230.0 parts is added for ultrasonic dispersion, the ultrasonic power is 360.0 W, the ultrasonic time is 39.0 min, then 65.0 parts of a 0.7 wt% sodium benzoate aqueous solution is added to the dispersion, continuously stirred at a stirring rate of 260.0 rpm at room temperature for a reaction time of 2.6 h, then the reaction mixture is centrifuged at a speed of 9200.0 rpm for 13.0 min to remove the supernatant, then the precipitate is washed with deionized water for 2 times to remove unreacted sodium benzoate, after each washing, it is centrifuged at a speed of 7200.0 rpm for 6.5 min, finally the obtained precipitate is vacuum dried at a temperature of 66.0°C for 15.6 h to obtain the surface modified GO / ITO composite filler.

[0071] The preparation method of the GO / ITO composite filler of this embodiment is as follows: 16.0 parts of ITO nanorods are added into 130.0 parts of a 2.0 wt% γ-aminopropyltriethoxysilane anhydrous ethanol solution, and surface amination is carried out at 86.0°C for 2.6 hours under nitrogen protection, then centrifugal washing is performed to remove unreacted silane coupling agent, then the aminated ITO nanorods are redispersed in 180.0 parts of deionized water, 8.0 parts of natural graphite powder is added, 36.0 parts of concentrated sulfuric acid is added dropwise under ice bath, then 2.9 parts of sodium nitrate is added, 10.1 parts of potassium permanganate is added in batches at 18.0°C, and the reaction is carried out at 38.0°C for 2.6 hours to oxidize and exfoliate the graphene oxide and simultaneously load it on the surface of the ITO nanorods, then 13.0 parts of 30.0% hydrogen peroxide solution is added to terminate the reaction, 65.0 parts of 10.0 wt% hydrochloric acid solution is used to remove metal ions, centrifugal collection is performed and deionized water is used for washing until neutral, and finally vacuum drying is performed at 66.0°C for 10.4 hours to obtain the GO / ITO composite filler.

[0072] The preparation method of the ITO nanorods of this embodiment is as follows: 10.0 parts of indium chloride trihydrate and 1.0 parts of tin tetrachloride pentahydrate are added into a beaker with a mechanical stirrer in a molar ratio of indium to tin of 90:10, 200.0 parts of deionized water is added, stirring is performed at room temperature at a stirring rate of 300.0 rpm for 30.0 min until complete dissolution to form a precursor solution, then 2.0 parts of polyvinylpyrrolidone with a molecular weight of 30000 is added to the precursor solution as a morphology control agent, and stirring is continued for 15.0 min to make it fully dissolved, then the pH value of the solution is slowly adjusted to 8.5 with an ammonia solution with a concentration of 2 wt% until a white precipitate appears, then stirring is continued for 30.0 min to make the precipitate fully formed, then the reaction mixture is transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, the filling degree is controlled to be 70.0%, the hydrothermal reaction is carried out at a reaction temperature of 160.0°C for 8.0h, then natural cooling is performed to room temperature, centrifugal separation is performed at a rotation speed of 8000.0 rpm for 10.0 min to collect the precipitate, the precipitate is washed with deionized water for 3 times and anhydrous ethanol for 2 times to remove reaction byproducts and residual organic matter, centrifugal separation is performed after each washing, and finally drying is performed at a temperature of 80.0°C for 12.0h to obtain the ITO nanorods.

[0073] The ITO nanorods of this embodiment have a diameter of 15 nm and a length of 100 nm, and the loading amount of graphene oxide is 5% of the mass of ITO.

[0074] The content of the surface modified GO / ITO composite filler in the functional shielding layer of this embodiment is 3.0wt%, and 0.20wt% of 2,6-di-tert-butyl-4-methylphenol antioxidant and 0.1wt% of polydimethylsiloxane leveling agent are further added to the matrix film-forming solution

[0075] The mass ratio of polycarbonate to polyetherimide in the substrate layer of this embodiment is 60:30, and 0.5wt% of dibutyl phthalate plasticizer and 0.3wt% of sodium dodecyl benzene sulfonate antistatic agent are added.

[0076] The preparation method of an electromagnetic field shielding transparent film of this embodiment comprises the following steps:

[0077] S1. Substrate layer preparation: Mix polycarbonate 60.0 parts with polyetherimide 30.0 parts in a mass ratio, add dibutyl phthalate plasticizer 0.5 parts and sodium dodecyl benzene sulfonate antistatic agent 0.3 parts, melt blend in a twin-screw extruder at a processing temperature of 280.0°C and a screw speed of 100.0 rpm for 10.0 min, then prepare a substrate layer film by flow casting at a roll temperature of 150.0°C and a pulling speed of 5.0 m / min;

[0078] S2. Functional shielding layer film-forming solution preparation: Dissolve polyethylene terephthalate 10.0 parts in a mixed solvent of trifluoroacetic acid and dichloromethane in a volume ratio of 1:1 80.0 parts, stir at a stirring speed of 200.0 rpm at room temperature for 4.0h to completely dissolve and form a PET film-forming solution, then add surface modified GO / ITO composite filler, 2,6-di-tert-butyl-4-methylphenol antioxidant and polydimethylsiloxane leveling agent to the solution, ultrasonically disperse at an ultrasonic power of 200.0 W for 30.0 min, then stir at a stirring speed of 150.0 rpm for 2.0 h to obtain a uniform functional shielding layer film-forming solution;

[0079] S3. Functional shielding layer coating and curing: The functional shielding layer film-forming solution prepared in step S2 is coated on the surface of the substrate layer prepared in step S1 by knife coating method, the coating speed is 2.0 m / min, the wet film thickness is controlled to be 8.0 μm, then pre-dry at a temperature of 50.0°C for 5.0 min to remove most of the solvent, and then perform multi-stage temperature control curing to form a functional shielding layer; the detailed process of multi-stage temperature control curing is to perform PET crystallization treatment at a temperature of 120.0°C for 10.0 min to activate the nucleation effect of sodium benzoate, and then cool to 60.0°C for final curing for 20.0 min.

[0080] S4. Protective layer coating: 5.0 parts of fluorinated ethylene propylene copolymer is dissolved in 80.0 parts of mixed solvent of methyl ethyl ketone and isopropyl alcohol with a volume ratio of 3:1 to form a protective layer solution, and the solution is coated on the surface of the functional shielding layer by gravure coating method at a coating speed of 5.0 m / min, the wet film thickness is controlled to be 2.0 μm, and then dried at a temperature of 80.0°C for 10.0 min to obtain a protective layer;

[0081] S5. Post-curing and finishing: the three-layer composite film prepared is heat-pressed and cured in a hot press at a temperature of 80.0°C and a pressure of 0.1 MPa for 10.0 min to enhance the interfacial bonding between the layers, and then stretched and shaped under a tension of 50.0 N / m, and then cooled to room temperature and cut by laser to obtain a transparent electromagnetic shielding multilayer film product with a specified size.

[0082] Example 3

[0083] A transparent electromagnetic shielding film, the transparent electromagnetic shielding film is a multilayer structure, comprising a substrate layer, a functional shielding layer and a protective layer which are sequentially stacked, wherein:

[0084] The substrate layer is formed by a blend of polycarbonate and polyetherimide, and has a thickness of 21 μm;

[0085] The functional shielding layer has polyethylene terephthalate as a matrix, and the surface modified GO / ITO composite filler is dispersed in the matrix; the functional shielding layer has a thickness of 3.8 μm;

[0086] The surface modified GO / ITO composite filler is obtained by treating the GO / ITO composite filler with a sodium benzoate surface modifier;

[0087] The GO / ITO composite filler is composed of ITO nanorods and graphene oxide loaded on the surface of the nanorods;

[0088] The protective layer is selected from fluorinated ethylene propylene copolymer, and has a thickness of 2.6 μm.

[0089] The preparation method of the surface modified GO / ITO composite filler of the present example is as follows: 112.0 parts of GO / ITO composite filler and 1.9 parts of sodium dodecyl sulfate are added into a three-necked reaction flask equipped with a mechanical stirrer, 260.0 parts of anhydrous ethanol is added for ultrasonic dispersion, the ultrasonic power is 420.0 W, the ultrasonic time is 48.0 min, then 80.0 parts of 0.8 wt% sodium benzoate aqueous solution is added to the dispersion, continuously stirring at a stirring rate of 320.0 rpm at room temperature for 3.2 h, then the reaction mixture is centrifuged at a speed of 10400.0 rpm for 16.0 min to remove the supernatant, then the precipitate is washed with deionized water for 3 times to remove unreacted sodium benzoate, centrifuged at a speed of 8400.0 rpm for 8.0 min after each washing, finally the obtained precipitate is vacuum dried at a temperature of 72.0°C for 19.2 h to obtain the surface modified GO / ITO composite filler.

[0090] The preparation method of the GO / ITO composite filler of the present example is as follows: 22.0 parts of ITO nanorods are added into 160.0 parts of 2.0 wt% γ-aminopropyl triethoxysilane anhydrous ethanol solution, surface amination is carried out at 92.0°C for 3.2 h under nitrogen protection, then centrifugal washing is carried out to remove unreacted silane coupling agent, then the aminated ITO nanorods are redispersed in 210.0 parts of deionized water, 11.0 parts of natural graphite powder is added, concentrated sulfuric acid 42.0 parts is added dropwise under ice bath, then sodium nitrate 3.8 parts is added, potassium permanganate 12.2 parts is added in batches at 21.0°C, oxidation and exfoliation of graphene oxide is carried out at 41.0°C for 3.2 h to load on the surface of ITO nanorods, then 30.0% hydrogen peroxide solution 16.0 parts is added to terminate the reaction, 10.0 wt% hydrochloric acid solution 80.0 parts is added to remove metal ions, centrifugal collection is carried out and washed with deionized water until neutral, finally vacuum drying at 72.0°C for 12.8 h to obtain the GO / ITO composite filler.

[0091] The preparation method of the ITO nanorod of the embodiment is as follows: 15.0 parts of indium chloride trihydrate and 3.0 parts of tin tetrachloride pentahydrate are added into a beaker with a mechanical stirrer in a molar ratio of indium to tin of 95:5, 300.0 parts of deionized water is added, stirring at a stirring rate of 500.0 rpm for 60.0 min at room temperature until complete dissolution to form a precursor solution, then 5.0 parts of polyvinylpyrrolidone with a molecular weight of 40000 is added as a morphology control agent, and the stirring is continued for 30.0 min to make it fully dissolved, then the pH value of the solution is slowly adjusted to 9.5 with an ammonia solution with a concentration of 5.0 wt% until white precipitate appears, then the stirring is continued for 60.0 min to make the precipitate fully formed, then the reaction mixture is transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, the filling degree is controlled to be 80.0%, the hydrothermal reaction is carried out at a reaction temperature of 200.0°C for 12.0 h, then it is naturally cooled to room temperature, centrifugal separation is carried out at a rotating speed of 12000.0 rpm for 20.0 min to collect the precipitate, and the precipitate is washed with deionized water for 3 times and anhydrous ethanol for 2 times to remove reaction byproducts and residual organic matter, centrifugal separation is carried out after each washing, and finally drying is carried out at a temperature of 120.0°C for 24.0 h to obtain ITO nanorods.

[0092] The ITO nanorod of the embodiment has a diameter of 25 nm and a length of 200 nm, and the loading amount of graphene oxide is 15% of the mass of ITO.

[0093] The content of the surface-modified GO / ITO composite filler in the functional shielding layer of the embodiment in the matrix is 8.0 wt%, and 0.35 wt% of 2,6-di-tert-butyl-4-methylphenol antioxidant and 0.2 wt% of polydimethylsiloxane leveling agent are further added to the matrix film-forming solution.

[0094] The mass ratio of polycarbonate to polyetherimide in the substrate layer of the embodiment is 70:40, and 1.0 wt% of dibutyl phthalate plasticizer and 0.4 wt% of sodium dodecylbenzenesulfonate antistatic agent are added.

[0095] The preparation method of the electromagnetic field shielding transparent film of the embodiment comprises the following steps:

[0096] S1. Substrate layer preparation: polycarbonate 70.0 parts and polyetherimide 40.0 parts are mixed in a mass ratio, dibutyl phthalate plasticizer 1.0 parts and sodium dodecylbenzenesulfonate antistatic agent 0.4 parts are added, melt blending is carried out in a twin-screw extruder at a processing temperature of 320.0°C and a screw rotating speed of 200.0 rpm for 20.0 min, and then a substrate layer film is prepared by flow casting at a roller temperature of 180.0°C and a pulling speed of 15.0 m / min;

[0097] S2. Functional shielding layer film-forming solution preparation: Dissolve 15.0 parts of polyethylene terephthalate in 120.0 parts of a mixed solvent of trifluoroacetic acid and dichloromethane in a volume ratio of 1:1, stir at a stirring rate of 400.0 rpm at room temperature for 8.0 h until complete dissolution to form a PET film-forming solution, then add surface-modified GO / ITO composite fillers, 2,6-di-tert-butyl-4-methylphenol antioxidant, and polydimethylsiloxane leveling agent to the solution, ultrasonically disperse at an ultrasonic power of 400.0 W for 60.0 min, and then stir at a stirring rate of 300.0 rpm for 4.0 h to obtain a uniform functional shielding layer film-forming solution;

[0098] S3. Functional shielding layer coating and curing: Use a doctor blade coating method to coat the functional shielding layer film-forming solution prepared in step S2 on the surface of the base layer prepared in step S1, with a coating speed of 8.0 m / min and a wet film thickness controlled at 20.0 μm, then pre-dry at a temperature of 80.0°C for 15.0 min to remove most of the solvent, and then perform multi-stage temperature-controlled curing to form a functional shielding layer; the detailed process of multi-stage temperature-controlled curing is to perform PET crystallization treatment at a temperature of 140.0°C for 20.0 min to activate the nucleation effect of sodium benzoate, and then cool to 80.0°C for final curing for 40.0 min.

[0099] S4. Protective layer coating: Dissolve 10.0 parts of fluorinated ethylene propylene copolymer in 120.0 parts of a mixed solvent of methyl ethyl ketone and isopropyl alcohol in a volume ratio of 3:1 to form a protective layer solution, use a gravure coating method to coat the solution on the surface of the functional shielding layer, with a coating speed of 12.0 m / min and a wet film thickness controlled at 15.0 μm, then dry at a temperature of 120.0°C for 30.0 min to obtain a protective layer;

[0100] S5. Post-curing and finishing: The prepared three-layer composite film is heat-pressed in a hot press at a temperature of 100.0°C and a pressure of 0.3 MPa for 20.0 min to enhance the interfacial bonding between the layers, then stretched and shaped under a tension of 150.0 N / m, and then cooled to room temperature to obtain a transparent electromagnetic shielding multilayer film product of a specified size by laser cutting.

[0101] Example 4

[0102] A transparent electromagnetic field shielding film, the transparent electromagnetic field shielding film being a multilayer structure comprising a base layer, a functional shielding layer, and a protective layer stacked in sequence, wherein:

[0103] The base layer is formed of a blend of polycarbonate and polyetherimide, and has a thickness of 25 μm;

[0104] The functional shielding layer is based on polyethylene terephthalate with surface modified GO / ITO composite filler dispersed therein, and the thickness of the functional shielding layer is 5.0 μm.

[0105] The surface modified GO / ITO composite filler is obtained by treating GO / ITO composite filler with sodium benzoate surface modifier.

[0106] The GO / ITO composite filler is composed of ITO nanorods and graphene oxide loaded on the surface of the nanorods.

[0107] The protective layer is selected from fluorinated ethylene propylene copolymer, and the thickness of the protective layer is 4.0 μm.

[0108] The preparation method of the surface modified GO / ITO composite filler in this embodiment is as follows: 120.0 parts of GO / ITO composite filler and 2.5 parts of sodium dodecyl sulfate are added into a three-necked reaction flask equipped with a mechanical stirrer, 300.0 parts of anhydrous ethanol is added for ultrasonic dispersion, the ultrasonic power is 500.0 W, and the ultrasonic time is 60.0 min, then 100.0 parts of 1.0 wt% sodium benzoate aqueous solution is added to the dispersion liquid, and the reaction is continuously stirred at room temperature at a stirring rate of 400.0 rpm for 4.0 h, then the reaction mixture is centrifuged at a speed of 12000.0 rpm for 20.0 min to remove the supernatant, then the precipitate is washed with deionized water for 3 times to remove the unreacted sodium benzoate, and the centrifugal speed is 10000.0 rpm for 10.0 min after each washing, finally the obtained precipitate is vacuum dried at a temperature of 80.0°C for 24.0 h to obtain the surface modified GO / ITO composite filler.

[0109] The preparation method of the GO / ITO composite filler in this embodiment is as follows: 30.0 parts of ITO nanorods are added into 200.0 parts of 2.0 wt% γ-aminopropyl triethoxysilane anhydrous ethanol solution, and surface amination is carried out at 100.0°C for 4.0 h under nitrogen protection, then the unreacted silane coupling agent is removed by centrifugal washing, then the aminated ITO nanorods are re-dispersed in 250.0 parts of deionized water, 15.0 parts of natural graphite powder is added, 50.0 parts of concentrated sulfuric acid is added dropwise under ice bath, then 5.0 parts of sodium nitrate is added, 15.0 parts of potassium permanganate is added in batches at 25.0°C, and the reaction is carried out at 45.0°C for 4.0 h to oxidize and exfoliate the graphite to form graphene oxide and simultaneously load it on the surface of the ITO nanorods, then 20.0 parts of 30.0% hydrogen peroxide solution is added to terminate the reaction, 100.0 parts of 10.0 wt% hydrochloric acid solution is used to remove metal ions, and the product is collected by centrifugal washing until it is neutral, finally the product is vacuum dried at 80.0°C for 16.0 h to obtain the GO / ITO composite filler.

[0110] The preparation method of the ITO nanorod of the embodiment is as follows: 13.0 parts of indium chloride trihydrate and 2.2 parts of tin tetrachloride pentahydrate are added into a beaker with a mechanical stirrer in a molar ratio of indium to tin of 93:7, 260.0 parts of deionized water is added, stirring is carried out at room temperature at a stirring rate of 420.0 rpm for 48.0 min until complete dissolution to form a precursor solution, then 3.8 parts of polyvinylpyrrolidone with a molecular weight of 36000 is added as a morphology control agent, and the stirring is continued for 21.0 min to make it fully dissolved, then the pH value of the solution is slowly adjusted to 9.1 with an ammonia water solution with a concentration of 3.8 wt% until white precipitate appears, then the stirring is continued for 48.0 min to make the precipitate fully formed, then the reaction mixture is transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, the filling degree is controlled to be 76.0%, the hydrothermal reaction is carried out at a reaction temperature of 184.0°C for 10.4 h, then it is naturally cooled to room temperature, centrifugal separation is carried out at a rotating speed of 10400.0 rpm for 16.0 min to collect the precipitate, and the precipitate is washed with deionized water for 3 times and anhydrous ethanol for 2 times to remove reaction byproducts and residual organic matter, centrifugal separation is carried out after each washing, and finally drying is carried out at a temperature of 104.0°C for 19.2 h to obtain the ITO nanorod.

[0111] The ITO nanorod of the embodiment has a diameter of 21 nm and a length of 160 nm, and the loading amount of graphene oxide is 11% of the mass of ITO.

[0112] The content of the surface-modified GO / ITO composite filler in the functional shielding layer of the embodiment in the matrix is 6.0 wt%, and 0.29 wt% of 2,6-di-tert-butyl-4-methylphenol antioxidant and 0.16 wt% of polydimethylsiloxane leveling agent are further added in the matrix film-forming solution.

[0113] The mass ratio of polycarbonate to polyetherimide in the substrate layer of the embodiment is 66:36, and 0.8 wt% of dibutyl phthalate plasticizer and 0.36 wt% of sodium dodecylbenzenesulfonate antistatic agent are added.

[0114] The preparation method of the electromagnetic field shielding transparent film of the embodiment comprises the following steps:

[0115] S1. Substrate layer preparation: polycarbonate 66.0 parts and polyetherimide 36.0 parts are mixed in a mass ratio, dibutyl phthalate plasticizer 0.8 parts and sodium dodecylbenzenesulfonate antistatic agent 0.36 parts are added, melt blending is carried out in a twin-screw extruder at a processing temperature of 304.0°C and a screw rotating speed of 160.0 rpm for 16.0 min, and then a substrate layer film is prepared by flow casting at a roll temperature of 168.0°C and a pulling speed of 11.0 m / min.

[0116] S2. Functional shielding layer film-forming solution preparation: polyethylene terephthalate 13.0 parts was dissolved in a mixed solvent of trifluoroacetic acid and dichloromethane with a volume ratio of 1:1 104.0 parts, stirred at room temperature at a stirring rate of 320.0 rpm for 6.4 h to completely dissolve to form a PET film-forming solution, then surface modified GO / ITO composite filler, 2,6-di-tert-butyl-4-methylphenol antioxidant and polydimethylsiloxane leveling agent were added to the solution, ultrasonic dispersion was carried out under the condition of ultrasonic power of 320.0 W for 48.0 min, and then uniform functional shielding layer film-forming solution was obtained by stirring at a stirring rate of 240.0 rpm for 3.2 h;

[0117] S3. Functional shielding layer coating and curing: the functional shielding layer film-forming solution prepared in step S2 was coated on the surface of the base layer prepared in step S1 by using a doctor blade coating method, the coating speed was 5.6 m / min, the wet film thickness was controlled to be 15.2 μm, then pre-drying was carried out at a temperature of 68.0°C for 11.0 min to remove most of the solvent, and the functional shielding layer was formed by multi-stage temperature control curing; the detailed process of multi-stage temperature control curing was as follows: PET crystallization treatment was carried out at a temperature of 132.0°C for 16.0 min to activate the nucleation effect of sodium benzoate, and then the temperature was lowered to 72.0°C for final curing for 32.0 min.

[0118] S4. Protective layer coating: fluorinated ethylene propylene copolymer 8.0 parts was dissolved in a mixed solvent of methyl ethyl ketone and isopropyl alcohol with a volume ratio of 3:1 104.0 parts to form a protective layer solution, the solution was coated on the surface of the functional shielding layer by using a gravure coating method, the coating speed was 9.2 m / min, the wet film thickness was controlled to be 9.8 μm, then drying was carried out at a temperature of 104.0°C for 22.0 min to obtain the protective layer;

[0119] S5. Post-curing and finishing: the prepared three-layer composite film was heat pressed in a hot press at a temperature of 92.0°C and a pressure of 0.22 MPa for 16.0 min to enhance the interfacial bonding between the layers, then stretching and setting treatment was carried out under a tension of 110.0 N / m, and after cooling to room temperature, the transparent electromagnetic shielding multilayer film product with a specified size was obtained by laser cutting.

[0120] Comparative Example 1

[0121] The same as Example 1, except that the sodium benzoate surface modifier in the surface modified GO / ITO composite filler was replaced by sodium dodecyl sulfonate surface modifier, and other preparation conditions and parameters were unchanged.

[0122] Figure 7The morphology of the interface between the GO / ITO composite filler without sodium benzoate modification and the polyethylene terephthalate (PET) matrix can be clearly observed. The interface region does not form a nanocrystalline structure, the interface layer is amorphous and lacks ordered arrangement, indicating that effective crystallization of PET at the filler interface cannot be induced under this condition.

[0123] Comparative Example 2

[0124] The same as Example 1, except that the content of the surface-modified GO / ITO composite filler in the functional shielding layer in the matrix is 1.5 wt%.

[0125] Comparative Example 3

[0126] The same as Example 1, except that the mass ratio of polycarbonate to polyetherimide in the substrate layer is 80:20.

[0127] Comparative Example 4

[0128] The same as Example 1, except that the surface of the ITO nanorod is not treated with γ-aminopropyl triethoxysilane during the preparation of the GO / ITO composite filler, and the graphene oxide is directly loaded.

[0129] Comparative Example 5

[0130] The same as Example 1, except that 2,6-di-tert-butyl-4-methylphenol antioxidant and polydimethylsiloxane leveling agent are not added to the functional shielding layer film-forming solution.

[0131] Comparative Example 6

[0132] The same as Example 1, except that polyvinyl chloride is used instead of fluorinated ethylene propylene copolymer as the protective layer material, and the thickness of the protective layer remains unchanged.

[0133] Comparative Example 7

[0134] The same as Example 1, except that polyvinylpyrrolidone is not used as a morphology control agent during the preparation of the ITO nanorod, resulting in irregular morphology of the obtained ITO nanorod.

[0135] Figure 8 The ITO nanorod prepared without a morphology control agent has a clear irregular structure, uneven particle size distribution, and difficulty in forming a rod-like morphology. In some areas, even agglomeration occurs. This morphology defect directly affects the dispersibility and conductive network construction ability in the subsequent compounding process, further weakening its role in electromagnetic shielding function. In contrast, in Example 1 of the present application, polyvinylpyrrolidone is used as a morphology control agent, successfully inducing the formation of ITO nanorods with uniform size and high aspect ratio, providing a structural basis for constructing efficient conductive paths.

[0136] Comparative Example 8

[0137] The same as Example 1, except that the functional shielding layer thickness is 8.0 pm.

[0138] Figure 9 The morphology of GO / ITO composite filler without amino treatment is shown. It can be observed that the loading effect of graphene oxide on the ITO surface is poor, the interface is not tightly combined, and even the detachment or uneven coating of GO appears in some areas. This interface instability not only affects the dispersion state of the composite filler in the polyester matrix, but also reduces the compatibility between the matrix and the filler, ultimately leading to the decline of electromagnetic shielding efficiency and mechanical properties. In the present application, the loading capacity of GO on the surface of ITO is significantly enhanced by introducing g-aminopropyl triethoxysilane for amino modification, a stable organic-inorganic interface is constructed, and the structural integrity of the composite filler is effectively improved.

[0139] Comparative Example 9

[0140] The same as Example 1, except that the PET crystallization treatment temperature in the multi-stage temperature control curing process of the functional shielding layer is 110.0 °C.

[0141] Comparative Example 10

[0142] The same as Example 1, except that the PET crystallization treatment temperature in the multi-stage temperature control curing process of the functional shielding layer is 160.0 °C.

[0143] Performance test:

[0144] Electromagnetic shielding efficiency (EMI SE) test: The test object is the overall multilayer transparent film. A vector network analyzer (VNA) is combined with a coaxial transmission line method to test the electromagnetic shielding efficiency of the sample in the frequency range of 30 MHz-3 GHz according to ASTM D4935 standard. The sample needs to be cut into a circular piece with a diameter of 33 mm and placed in a coaxial test fixture. Record the reflection loss (SE-R), absorption loss (SE-A) and total shielding efficiency (SE-T), and compare the electromagnetic shielding performance of samples with different filler contents.

[0145] Optical transparency test: The test object is the overall multilayer transparent film. Use a UV-visible spectrophotometer to measure the light transmittance and haze of the sample in the visible light range (400-800 nm) according to ASTM D1003 standard. At the same time, use a color difference meter to measure the CIE Lab color difference parameters and yellowing index (YI) of the transparent film to evaluate the optical clarity of the film.

[0146] Mechanical property test: The overall multilayer transparent film of the test object was tested. According to the ASTM D882 standard, the tensile strength, Young's modulus and elongation at break of the sample were tested by using a universal material testing machine. The sample was cut into a strip of 10 mm x 100 mm, and the tensile rate was set to 5 mm / min. At the same time, the cyclic loading-unloading test was carried out to evaluate the elastic recovery performance of the material.

[0147] Interlayer bonding strength test: The interface bonding of the multilayer film of the test object was tested. The bonding strength between the base layer and the functional shielding layer, and between the functional shielding layer and the protective layer was evaluated by using T-type peeling test (ASTM D1876) and cross-cut test (ASTM D3359). The peeling rate was set to 300 mm / min, and the average peeling strength was recorded.

[0148] The properties of the transparent films of Examples 1-4 and Comparative Examples 1-10 are summarized in Table 1. The type of modifier directly affects the interfacial bonding ability between the filler and the matrix. If the interfacial interaction is weakened, it will lead to a simultaneous decrease in shielding performance and mechanical properties. Insufficient filler content will make it difficult to form a conductive network in the functional layer, significantly reducing the electromagnetic shielding efficiency, but at the same time the optical transparency may be slightly improved. Imbalance of the polycarbonate and polyetherimide ratio in the base will weaken the toughness and strength of the overall structure, affecting the mechanical stability of the film in application. If the GO / ITO composite filler is not subjected to amination treatment, its dispersibility and interfacial compatibility will decrease, resulting in a double attenuation of shielding efficiency and mechanical properties. If the antioxidant and leveling agent are missing in the functional layer, although the influence on shielding performance is small, it will lead to a significant decrease in optical performance, manifested as a decrease in light transmittance and an increase in haze. If the protective layer material is replaced from fluorinated ethylene propylene copolymer to polyvinyl chloride, the interfacial bonding ability of the layers will weaken, affecting the stability of the overall structure and the electromagnetic shielding continuity. If the ITO nanorod does not use a morphology control agent during preparation, it is easy to form irregular structures, and the conductive network is not uniform, which will further reduce its electromagnetic shielding ability. If the thickness of the functional shielding layer is too large, it can improve the shielding efficiency, but it will significantly sacrifice the visible light transmittance, affecting the optical application performance of the film. If the PET crystallization treatment temperature is too low, it will lead to insufficient crystallization, and the internal structure of the material will be loose, which will further reduce the shielding and mechanical properties. If the temperature is too high, it may make the structure too dense or thermally degrade, resulting in overall performance deterioration. Therefore, the ratio of components, interface treatment and process parameters in the multilayer structure need to be precisely controlled to maximize the performance synergy.

[0149] Table 1 Performance summary of transparent films of Examples 1-4 and Comparative Examples 1-10

[0150]

[0151] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformation made under the concept of the present application, by using the content of the present application specification and drawings, should be covered in the protection scope of the claims of the present application.

Claims

1. A transparent thin film for electromagnetic field shielding, characterized in that, The transparent film has a multi-layer structure, comprising a base layer, a functional shielding layer, and a protective layer stacked sequentially, wherein: The base layer is formed of a blend of polycarbonate and polyetherimide, with a thickness of 15~25μm; The functional shielding layer uses polyethylene terephthalate as a matrix, in which surface-modified GO / ITO composite filler is dispersed; the thickness of the functional shielding layer is 2.0~5.0μm; The surface-modified GO / ITO composite filler is obtained by treating GO / ITO composite filler with sodium benzoate surface modifier; The GO / ITO composite filler is composed of ITO nanorods and graphene oxide supported on the surface of the nanorods. The protective layer is selected from fluorinated ethylene propylene copolymer and has a thickness of 0.5~4.0μm; The preparation method of the surface-modified GO / ITO composite filler is as follows: 100.0-120.0 parts by weight of GO / ITO composite filler and 1.0-2.5 parts by weight of sodium dodecyl sulfate are added to a three-necked reaction flask equipped with a mechanical stirrer. 200.0-300.0 parts by weight of anhydrous ethanol are added for ultrasonic dispersion at a power of 300.0-500.0 W for 30.0-60.0 min. Then, 50.0-100.0 parts by weight of a 0.5-1.0 wt% sodium benzoate aqueous solution are added to the dispersion. The mixture is continuously stirred at a stirring rate of 200.0-400.0 rpm at room temperature for 2.0-4.0 h. The reaction mixture is then centrifuged at a speed of 8000.0-12000.0 rpm for 10.0-20.0 parts. Remove the supernatant by 1 minute, then wash the precipitate 2-3 times with deionized water to remove unreacted sodium benzoate. After each wash, centrifuge at 6000.0-10000.0 rpm for 5.0-10.0 minutes. Finally, vacuum dry the obtained precipitate at 60.0-80.0°C for 12.0-24.0 hours to obtain the surface-modified GO / ITO composite filler.

2. The transparent thin film for electromagnetic field shielding as described in claim 1, characterized in that, The preparation method of the GO / ITO composite filler is as follows: 10.0-30.0 parts by weight of ITO nanorods are added to 100.0-200.0 parts of a 2.0 wt% γ-aminopropyltriethoxysilane anhydrous ethanol solution. The mixture is reacted at 80.0-100.0°C for 2.0-4.0 h under nitrogen protection for surface amination. Unreacted silane coupling agent is then removed by centrifugation and washing. The amination-treated ITO nanorods are then redispersed in 150.0-250.0 parts of deionized water, and 5.0-15.0 parts of natural graphite powder are added. 30.0-50.0 parts of concentrated sulfuric acid are added dropwise under ice bath conditions, followed by 2.0-5.0 parts of sodium nitrate. 8.0-15.0 parts of potassium permanganate are added in batches at 15.0-25.0°C, and the mixture is reacted at 35.0-45.0°C for 2.0-4.0 h. The graphite was oxidized and exfoliated to generate graphene oxide, which was then simultaneously loaded onto the surface of ITO nanorods. The reaction was then terminated by adding 10.0-20.0 parts of 30.0% hydrogen peroxide solution. Metal ions were removed by adding 50.0-100.0 parts of 10.0 wt% hydrochloric acid solution. The mixture was collected by centrifugation and washed with deionized water until neutral. Finally, it was vacuum dried at 60.0-80.0°C for 8.0-16.0 h to obtain the GO / ITO composite filler.

3. The transparent thin film for electromagnetic field shielding as described in claim 1, characterized in that, The preparation method of the ITO nanorods is as follows: 10.0-15.0 parts by weight of indium chloride trihydrate and 1.0-3.0 parts by weight of tin tetrachloride pentahydrate are added to a beaker equipped with a mechanical stirrer at an indium-tin molar ratio of 90:10-95:

5. 200.0-300.0 parts by weight of deionized water are added, and the mixture is stirred at 300.0-500.0 rpm for 30.0-60.0 min at room temperature until completely dissolved to form a precursor solution. Then, 2.0-5.0 parts by weight of polyvinylpyrrolidone (PVP) with a molecular weight of 30,000-40,000 is added to the precursor solution as a morphology control agent. Stirring is continued for 15.0-30.0 min to ensure complete dissolution. Next, the pH of the solution is slowly adjusted to 8.5-9.5 using a 2-5.0 wt% ammonia solution until a white precipitate appears. Stirring is then continued for 30.0-60.0 min. After allowing the precipitate to fully form, the reaction mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene (PTFE) and the filling degree was controlled at 70.0–80.0%. The hydrothermal reaction was carried out at a reaction temperature of 160.0–200.0°C for 8.0–12.0 h. The mixture was then allowed to cool naturally to room temperature. The precipitate was collected by centrifugation at 8000.0–12000.0 rpm for 10.0–20.0 min. The precipitate was washed three times with deionized water and twice with anhydrous ethanol to remove reaction byproducts and residual organic matter. After each washing, the mixture was centrifuged. Finally, the precipitate was dried at 80.0–120.0°C for 12.0–24.0 h to obtain ITO nanorods.

4. The transparent thin film for electromagnetic field shielding as described in claim 1, characterized in that, The ITO nanorods have a diameter of 15-25 nm and a length of 100-200 nm, and the graphene oxide loading is 5-15% of the ITO mass.

5. The transparent thin film for electromagnetic field shielding as described in claim 1, characterized in that, The surface-modified GO / ITO composite filler in the functional shielding layer contains 3.0~8.0 wt% of the matrix, and the matrix film-forming solution also contains 0.20~0.35 wt% of 2,6-di-tert-butyl-4-methylphenol antioxidant and 0.1~0.2 wt% of polydimethylsiloxane leveling agent.

6. The transparent thin film for electromagnetic field shielding as described in claim 1, characterized in that, The base layer has a polycarbonate to polyetherimide mass ratio of 60~70:30~40, and contains 0.5~1.0wt% dibutyl phthalate plasticizer and 0.3~0.4wt% sodium dodecylbenzenesulfonate antistatic agent.

7. A method for preparing a transparent thin film for electromagnetic field shielding as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Preparation of the base layer: 60.0-70.0 parts of polycarbonate and 30.0-40.0 parts of polyetherimide are mixed in a mass ratio, and 0.5-1.0 parts of dibutyl phthalate plasticizer and 0.3-0.4 parts of sodium dodecylbenzenesulfonate antistatic agent are added. The mixture is melt-blended in a twin-screw extruder at a processing temperature of 280.0-320.0°C and a screw speed of 100.0-200.0 rpm for 10.0-20.0 min. Then, the base layer film is obtained by casting at a roller temperature of 150.0-180.0°C and a traction speed of 5.0-15.0 m / min. S2. Preparation of functional shielding layer film-forming solution: 10.0-15.0 parts of polyethylene terephthalate were dissolved in 80.0-120.0 parts of a mixed solvent of trifluoroacetic acid and dichloromethane in a volume ratio of 1:

1. The solution was stirred at 200.0-400.0 rpm for 4.0-8.0 h at room temperature until completely dissolved to form a PET film-forming solution. Then, surface-modified GO / ITO composite filler, 2,6-di-tert-butyl-4-methylphenol antioxidant and polydimethylsiloxane leveling agent were added to the solution. The solution was ultrasonically dispersed at an ultrasonic power of 200.0-400.0 W for 30.0-60.0 min. Then, the solution was stirred at 150.0-300.0 rpm for 2.0-4.0 h to obtain a uniform functional shielding layer film-forming solution. S3. Functional shielding layer coating and curing: The functional shielding layer film-forming solution prepared in step S2 is coated onto the surface of the substrate layer prepared in step S1 using a doctor blade coating method. The coating speed is 2.0~8.0 m / min, and the wet film thickness is controlled at 8.0~20.0 μm. Then, it is pre-dried at a temperature of 50.0~80.0°C for 5.0~15.0 min to remove most of the solvent. The functional shielding layer is formed by multi-stage temperature-controlled curing. S4. Protective layer coating: Dissolve 5.0-10.0 parts of fluorinated ethylene propylene copolymer in 80.0-120.0 parts of a mixed solvent of methyl ethyl ketone and isopropanol in a volume ratio of 3:1 to form a protective layer solution. Coat the solution onto the surface of the functional shielding layer using a gravure coating method at a coating speed of 5.0-12.0 m / min and a wet film thickness of 2.0-15.0 μm. Then dry at a temperature of 80.0-120.0°C for 10.0-30.0 min to obtain the protective layer. S5. Post-curing and finishing: The obtained three-layer composite film is hot-pressed and cured in a hot press at a temperature of 80.0~100.0°C and a pressure of 0.1~0.3 MPa for 10.0~20.0 min to enhance the interfacial bonding between the layers. Then, it is stretched and shaped under a tension of 50.0~150.0 N / m. After cooling to room temperature, it is laser-cut to obtain transparent electromagnetic shielding multilayer film products of the specified dimensions.

8. The method for preparing a transparent thin film for electromagnetic field shielding as described in claim 7, characterized in that, The detailed process of multi-stage temperature-controlled curing in step S3 is as follows: PET crystallization is performed at a temperature of 120.0~140.0°C for 10.0~20.0 min to activate the nucleation of sodium benzoate, and then the temperature is lowered to 60.0~80.0°C for final curing for 20.0~40.0 min.

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