Multi-layer composite film giving consideration to light transmission, infrared stealth and electromagnetic shielding and preparation method of multi-layer composite film

Abstract

The invention relates to a multi-layer composite film giving consideration to light transmission, infrared stealth and electromagnetic shielding and a preparation method of the multi-layer composite film, and belongs to the technical field of preparation of electromagnetic shielding materials. The preparation method of the multi-layer composite film comprises the following steps: firstly, coprecipitating to obtain indium tin oxide (ITO) nanoparticles, preparing ITO / PVB, silver nanowire / PVB dispersion liquid and a polyvinyl alcohol (PVA) aqueous solution, and sequentially spin-coating the ITO / PVB dispersion liquid and the PVA aqueous solution on a polyethylene glycol terephthalate (PET) substrate. And coating the silver nanowire / PVB dispersion liquid by adopting a Mayer bar coating method, and finally packaging by using polydimethylsiloxane (PDMS) to obtain the silver nanowire / PVB composite material. According to the preparation method of the multi-layer composite flexible film considering light transmission, infrared stealth and electromagnetic shielding, a conductive network is formed by utilizing silver nanowires, and a layered structure is constructed and designed through PDMS so as to optimize EMI shielding performance and mechanical performance of the film. The ITO nanoparticles are added into the film, so that the film has good light transmission and high infrared barrier property.

Description

Technical Field

[0001] The invention relates to a multilayer composite film having light transmittance, infrared stealth and electromagnetic shielding and a preparation method thereof, belonging to the technical field of electromagnetic shielding material preparation. Background Art

[0002] Silver nanowires are considered to be the best material for preparing flexible transparent electromagnetic interference shielding films due to their excellent aspect ratio and good conductivity. Wang et al. used a simple rod coating method to embed the AgNWs layer into gelatin. By controlling the concentration of AgNWs in the AgNWs layer, a flexible film with a visible light transmittance of 72% and an electromagnetic interference shielding efficiency of 37.7 dB was obtained. (Reference [1]: Wang, GH; Hao, LL; Zhang, XD; Tan, SJ; Zhou, M.; Gu, WH; Ji, GB Flexible and transparent silver nanowires / biopolymer film for high-efficient electromagnetic interference shielding [J]. Colloid Interface Sci. 2022, 607: 89–99.) Jung et al. used transparent flexible polydimethylsiloxane (PDMS) as a substrate and transferred the AgNWs layer deposited on the Teflon filter to the substrate by vacuum filtration and transfer method. The electromagnetic interference shielding material has both efficient electromagnetic shielding performance and transparent and stretchable properties. (Reference [2]: Jung, J.; Lee, H.; Ha, I.; Cho, H.; Kim, KK; Kwon, J.; Won, P.; Hong, S.; Ko, SH Highly stretchable and transparent electromagnetic interference shielding film based on silver nanowire percolation network for wearable electronics applications [J]. ACS Appl. Mater. Interfaces. 2017, 9 (51): 44609–44616.). However, integrating electromagnetic interference shielding, near-infrared shielding, and visible light transmittance into AgNWs materials remains a huge challenge. In addition, indium tin oxide (ITO) has excellent visible light transmittance and effective infrared blocking properties and is an effective transparent infrared shielding material. However, due to its inherent mechanical brittleness, ITO cannot meet the potential applications of flexible electronics. Fine structural design and composites with other materials provide a feasible way to optimize mechanical and electromagnetic interference shielding properties, promoting the application of next-generation smart electronic devices. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing a multilayer composite film that takes into account light transmittance, infrared stealth and electromagnetic shielding. The prepared multilayer composite film has excellent electromagnetic interference shielding performance, excellent near-infrared shielding performance and high light transmittance.

[0004] The present invention also provides a multi-layer composite film which is prepared by the above-mentioned preparation method and has the characteristics of light transmittance, infrared stealth and electromagnetic shielding.

[0005] In order to achieve the above objectives, the technical solution adopted by the multi-layer composite film of the present invention is:

[0006] A method for preparing a multilayer composite film that takes into account light transmission, infrared stealth and electromagnetic shielding, comprising the following steps: preparing indium tin oxide (ITO) nanoparticles by a coprecipitation method, and preparing ITO / PVB, silver nanowire (AgNWs) / PVB dispersions and PVA aqueous solutions, and sequentially coating the ITO / PVB dispersion and the PVA aqueous solution on a polyethylene terephthalate (PET) substrate by a spin coating method. The number of AgNWs layers, the gap distance of the PDMS framework and the arrangement of AgNWs films with different deposition amounts are designed, and the AgNWs / PVB dispersion is coated by a Mayer bar coating method, and finally encapsulated with polydimethylsiloxane (PDMS).

[0007] The preparation method of the multilayer composite film of the present invention uses silver nanowires to form a conductive network to obtain electromagnetic shielding performance through simple layer-by-layer coating, and constructs a layered structure designed by PDMS to optimize the EMI shielding performance and mechanical properties of the film. By adding ITO nanoparticles to the film, it has good light transmittance and high infrared barrier properties. The process is simple and stable. By designing the multilayer structure of material components such as the number of AgNWs layers, the gap distance of the PDMS construction frame, and the arrangement of AgNWs films with different deposition amounts, ITO and AgNWs are combined to prepare a multifunctional compatible flexible composite film with high light transmittance, strong EMI shielding and good thermal insulation performance.

[0008] Preferably, the preparation of indium tin oxide nanoparticles includes the following steps: First, InCl3·4H2O and SnCl4·5H2O are added to 200 mL of deionized water in a mass ratio of 9:1, and magnetic stirring is used to completely dissolve them. Then, an ammonia solution is slowly added dropwise until the pH value of the mixed solution is about 8. The solution is stirred in a 60°C water bath for 2 hours, taken out after complete reaction, and aged at room temperature for 1 hour. The precipitate is collected from the bottom of the beaker and centrifuged and washed several times. After vacuum drying, an ITO precursor is obtained. The dried ITO precursor is heat treated at 650°C for 2 hours to obtain blue ITO nanoparticles.

[0009] Preferably, the preparation of ITO / PVB, AgNWs / PVB dispersion and PVA aqueous solution includes the following steps: adding KH-570 and ITO nanoparticles to ethanol at a mass ratio of 1:20 and ultrasonicating for 30 minutes to obtain an ethanol dispersion in which ITO nanoparticles are uniformly dispersed, and adding PVB to the ethanol solution at a mass ratio of 1:10, stirring for 2 hours, to obtain a fully mixed and uniform ITO / PVB dispersion. For AgNWs / PVB dispersion, first prepare 50 mg / mL PVB / ethanol solution, then mix 5 mg / mL AgNWs / ethanol dispersion with the prepared PVB / ethanol solution at a volume ratio of 7:1 to obtain AgNWs / PVB dispersion. When preparing the PVA aqueous solution, first mix PVA with deionized water at a mass ratio of 1:10, completely dissolve at 95°C, and obtain a transparent PVA aqueous solution.

[0010] Preferably, polyethylene terephthalate (PET) with a smooth surface and stable performance is selected as the substrate material. The PET substrate is cleaned in an ethanol solution by ultrasonic cleaning for 15 minutes. The clean PET substrate is spin-coated with an ITO / PVB dispersion and dried at 35° C. for 30 minutes to obtain a bottom layer.

[0011] Preferably, in order to avoid damage to the bottom layer by the ethanol solution in the AgNWs / PVB dispersion system, a PVA protective layer insoluble in ethanol is spin-coated on the ITO layer. After drying, the AgNWs / PVB dispersion is dripped onto one side of the film and quickly coated with a Mayer rod to evenly distribute it on the surface of the film. Among them, the content of AgNWs in the film can vary with the increase in the number of coating times. After the AgNWs layer is dried, the PDMS sealant is poured in and dried overnight at 40°C to solidify. A multilayer transparent film is obtained. The number of coated AgNWs layers is 1-6 layers, preferably 6 layers.

[0012] Preferably, frames of different thicknesses are prepared using PDMS. The AgNWs film deposited six times is divided into two equal parts and distributed on both sides of the frames of different thicknesses. A double-layer structure sample is prepared. The gap distance is 1-6 mm, preferably 2-6 mm, preferably 2-6 mm.

[0013] Preferably, under the premise of the total gap distance and the total deposition amount being unchanged, the method for preparing the three-layer structure sample is similar to the method for preparing the double-layer structure. According to the different arrangement modes and different deposition amounts of AgNWs films, they are named TIA, 1 / 2 / 3 ,TIA 1 / 3 / 2 ,TIA 2 / 1 / 3 ,TIA 2 / 3 / 1 ,TIA 3 / 1 / 2 ,TIA 3 / 2 / 1 , preferably TIA 1 / 3 / 2 ,TIA2 / 1 / 3 .

[0014] The technical solution adopted by the multi-layer composite film of the present invention that takes into account light transmission, infrared stealth and electromagnetic shielding is:

[0015] A graphene composite flexible wave-absorbing plate produced by the above-mentioned method for producing the graphene composite flexible wave-absorbing plate.

[0016] The preparation method of the multilayer composite film of the present invention uses silver nanowires to form a conductive network to obtain electromagnetic shielding performance through simple layer-by-layer coating, and constructs a layered structure designed by PDMS to optimize the EMI shielding performance and mechanical properties of the film. By adding ITO nanoparticles to the film, it has good light transmittance and high infrared barrier properties. By designing the multilayer structure of material components such as the number of AgNWs layers, the gap distance of the PDMS frame, and the arrangement of AgNWs films with different deposition amounts, ITO and AgNWs are combined to prepare a multifunctional compatible flexible composite film with high light transmittance, strong EMI shielding and good thermal insulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a SEM image of the composite membrane before and after coating with PDMS in Example 1 of the present invention, wherein: Figure 1 The red dashed box in (f) indicates the AgNW layer;

[0018] Figure 2 Schematic diagram of the double-layer composite film prepared in Example 2 of the present invention and SE R ,SE A ,R,and A values, where Figure 2 (a) The gray transparent part is the IA film, the blue part is the frame, and the two are combined to form a double-layer structure. The yellow dotted box represents AgNWs;

[0019] Figure 3 The A / (A+R) of the three-layer composite film prepared in Example 3 of the present invention varies with the arrangement of different AgNWs deposited films and the transmittance in the range of 200-2500nm, wherein Figure 3 (a) TIA 1 / 2 / 3 、TIA 1 / 3 / 2 、TIA 2 / 1 / 3 、TIA 2 / 3 / 1 、TIA 3 / 1 / 2 、TIA 3 / 2 / 1 The A / (A+R) values ​​are 46.3%, 46.5%, 32.9%, 31.7%, 13.5% and 14.1% respectively. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0021] Example 1

[0022] The method for preparing the multilayer composite film of this embodiment comprises the following steps:

[0023] 1) Preparation of indium tin oxide nanoparticles.

[0024] 2) Preparation of ITO / PVB, AgNWs / PVB dispersions and PVA aqueous solutions.

[0025] 3) Select polyethylene terephthalate (PET) with a smooth surface and stable performance as the substrate material. Spin-coat the clean PET substrate with ITO / PVB dispersion and dry it at 35°C for 30 minutes to obtain the bottom layer. Apply PVA as a protective layer. Then use a Mayer rod to evenly distribute the AgNWs / PVB dispersion on the film surface and dry it to obtain the AgNWs / PVB film.

[0026] 4) After the AgNWs layer was dried, the PDMS sealant was poured in and dried overnight at 40°C to solidify. A multilayer transparent film was obtained.

[0027] The composite membrane before PDMS coating obtained in Example 3) was subjected to SEM test, and the obtained SEM image is shown in Figure 1 (ac), it can be seen that the AgNWs are randomly distributed on the substrate and cross-overlap each other. Due to the capillary force generated by the rapid evaporation of ethanol in the slurry during the AgNWs coating process, it can be observed that the AgNWs have a slight deformation at the intersection where the wires have good contact with each other, which improves the contact between the AgNWs. The composite film coated with PDMS obtained in Example 4) was subjected to SEM testing, and the resulting SEM image is shown in Figure 1 (df), by Figure 1 (d) It can be seen from the SEM image after coating the PDMS layer that the surface is smooth and crack-free, providing good protection for the AgNW layer. Figure 1 As shown in (e, f), the successful construction of the four-layer structure can be clearly seen. The flatness of the cross-section layer also shows that the layers are evenly coated. The close bonding between the layers also provides good encapsulation of the AgNW layer.

[0028] Example 2

[0029] The method for preparing the multilayer composite film of this embodiment comprises the following steps:

[0030] 1) Preparation of indium tin oxide nanoparticles.

[0031] 2) Preparation of ITO / PVB, AgNWs / PVB dispersions and PVA aqueous solutions.

[0032] 3) Choose polyethylene terephthalate (PET) with a smooth surface and stable performance as the substrate material. Spin-coat the clean PET substrate with ITO / PVB dispersion and dry it at 35°C for 30 minutes to obtain the bottom layer. Apply PVA as a protective layer. Then use a Mayer rod to evenly distribute the AgNWs / PVB dispersion on the film surface. Apply 6 layers of AgNWs / PVB.

[0033] 4) Using PDMS as a sealant, the AgNWs film deposited six times was divided into two equal parts and distributed in a thickness of DIA d＝6mm on both sides of the frame and dried at 40°C overnight to cure.

[0034] For this embodiment 4), a schematic diagram of a double-layer structure constructed by PDMS is obtained as follows Figure 2 (a) shows; SE of the obtained double-layer composite film R ,SE A ,R,and A values ​​are as follows Figure 2 As shown in (b), the results show that compared with the single-layer film, the R and SER of the double-layer structure are reduced to a certain extent. And as the gap distance increases, both maintain a stable trend. SE A It shows a gradually increasing trend, indicating that the increase in EMI SE at this time mainly comes from the increase in absorption loss.

[0035] Example 3

[0036] The method for preparing the multilayer composite film of this embodiment comprises the following steps:

[0037] 1) Preparation of indium tin oxide nanoparticles.

[0038] 2) Preparation of ITO / PVB, AgNWs / PVB dispersions and PVA aqueous solutions.

[0039] 3) Choose polyethylene terephthalate (PET) with a smooth surface and stable performance as the substrate material. Spin-coat the clean PET substrate with ITO / PVB dispersion and dry it at 35°C for 30 minutes to obtain the bottom layer. Apply PVA as a protective layer. Then use a Mayer rod to evenly distribute the AgNWs / PVB dispersion on the film surface. Apply 6 layers of AgNWs / PVB.

[0040] 4) Using PDMS as a sealant, the AgNWs film deposited six times was divided into three equal parts, with a gap thickness of 3 mm and a total gap thickness of 6 mm. The arrangement of the AgNWs films with different deposition amounts was TIA. 1 / 2 / 3 .

[0041] The A / (A+R) of the three-layer composite film constructed by PDMS in Example 4) varies with the arrangement of the AgNWs deposited films, such as Figure 3 As shown in (a), it can be seen that with the decrease of AgNWs content in the electromagnetic wave incident layer, the A value and SE A / SE TOTAL The increase indicates that the reduction of the surface AgNWs content provides convenience for electromagnetic wave incident, and achieves high absorption efficiency on the basis of high EMI shielding efficiency. The transmittance of the three-layer composite film constructed by PDMS in the range of 200-2500nm is as follows Figure 3 As shown in (b), it can be seen that the shielding effect of ITO on near-infrared light is mainly achieved through ITO, so without changing the ITO content, the film often has a consistent transmittance in the near-infrared light range. In the range of 1500-2500nm, the shielding efficiency of near-infrared light is 96.2%.

[0042] As can be seen from the above embodiments, the present invention provides a multilayer composite film that takes into account light transmittance, infrared stealth and electromagnetic shielding, uses silver nanowires to form a conductive network to obtain electromagnetic shielding performance, and constructs a layered structure designed by PDMS to optimize the EMI shielding performance and mechanical properties of the film. By adding ITO nanoparticles to the film, it has good light transmittance and high infrared barrier properties. By designing the multilayer structure of material components such as the number of AgNWs layers, the gap distance of the PDMS construction frame, and the arrangement of AgNWs films with different deposition amounts, ITO and AgNWs are combined to prepare a multifunctional compatible flexible composite film with high light transmittance, strong EMI shielding and good thermal insulation performance.

[0043] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a multilayer composite film that takes into account light transmission, infrared stealth and electromagnetic shielding, characterized in that: The following steps are involved: Indium tin oxide (ITO) nanoparticles were prepared by coprecipitation, and ITO / PVB, silver nanowire (silver nanowire) / PVB dispersion and PVA aqueous solution were prepared. The ITO / PVB dispersion and PVA aqueous solution were sequentially coated on a polyethylene terephthalate (PET) substrate by spin coating. The number of silver nanowire layers, the gap distance of the PDMS framework and the arrangement of silver nanowire films with different deposition amounts were designed, and the silver nanowire / PVB dispersion was coated by Mayer bar coating, and finally encapsulated with polydimethylsiloxane (PDMS).

2. The method for preparing a multilayer composite film having light transmission, infrared stealth and electromagnetic shielding properties according to claim 1, characterized in that: The preparation of indium tin oxide nanoparticles includes the following steps: First, InCl3·4H2O and SnCl4·5H2O were added to 200 mL of deionized water in a mass ratio of 9:1, and magnetic stirring was used to completely dissolve them. Then, an ammonia solution was slowly added dropwise until the pH value of the mixed solution was about 8. The solution was stirred in a 60°C water bath for 2 hours, and after it was completely reacted, it was taken out and aged at room temperature for 1 hour. The precipitate was collected from the bottom of the beaker and washed by centrifugation several times. After vacuum drying, an ITO precursor was obtained. The dried ITO precursor was heat treated at 650°C for 2 hours to obtain blue ITO nanoparticles.

3. The method for preparing a multilayer composite film having light transmission, infrared stealth and electromagnetic shielding properties according to claim 1, characterized in that: The preparation of ITO / PVB, silver nanowire / PVB dispersion and PVA aqueous solution includes the following steps: KH-570 and ITO nanoparticles are added to ethanol at a mass ratio of 1:20 and ultrasonicated for 30 minutes to obtain an ethanol dispersion in which ITO nanoparticles are uniformly dispersed, and PVB is added to the ethanol solution at a mass ratio of 1:10, stirred for 2 hours, and a fully mixed and uniform ITO / PVB dispersion is obtained. For silver nanowire / PVB dispersion, 50 mg / mL PVB / ethanol solution is first prepared, and then 5 mg / mL silver nanowire / ethanol dispersion is mixed with the prepared PVB / ethanol solution at a volume ratio of 7:1 to obtain a silver nanowire / PVB dispersion. When preparing the PVA aqueous solution, PVA and deionized water are first mixed at a mass ratio of 1:10, and all are dissolved at 95°C to obtain a transparent PVA aqueous solution.

4. The method for preparing a multilayer composite film having light transmission, infrared stealth and electromagnetic shielding properties according to claim 1, characterized in that: Polyethylene terephthalate (PET) with a smooth surface and stable performance was selected as the substrate material. The PET substrate was ultrasonically cleaned in an ethanol solution for 15 minutes. The clean PET substrate was spin-coated with ITO / PVB dispersion and dried at 35°C for 30 minutes to obtain the bottom layer.

5. The method for preparing a multilayer composite film having light transmittance, infrared stealth and electromagnetic shielding according to claim 1, characterized in that: In order to avoid damage to the bottom layer by the ethanol solution in the silver nanowire / PVB dispersion system, a PVA protective layer that is insoluble in ethanol was spin-coated on the ITO layer. After drying, the silver nanowire / PVB dispersion was dripped onto one side of the film and quickly coated with a Mayer rod to evenly distribute it on the film surface. Among them, the content of silver nanowires in the film can change with the increase in the number of coating times. After the silver nanowire layer is dried, the PDMS sealant is poured and dried at 40°C overnight to cure. A multilayer transparent film was obtained. According to the number of silver nanowire layers coated, these layers are named IA-1, IA-2, IA-3, IA-4, IA-5 and IA-6 in sequence.

6. The method for preparing a multilayer composite film having both light transmission, infrared stealth and electromagnetic shielding according to any one of claims 1 to 5, characterized in that: Frames of different thicknesses were prepared using PDMS. The silver nanowire film deposited six times was divided into two equal parts and distributed on both sides of the frames of different thicknesses. The double-layer structure samples were prepared. According to the gap distance, they were named DIA d＝1mm ,DIA d＝2mm ,DIA d＝3mm ,DIA d＝6mm .

7. The method for preparing a multilayer composite film having both light transmission, infrared stealth and electromagnetic shielding according to any one of claims 1 to 5, characterized in that: Under the premise that the total gap distance and total deposition amount remain unchanged, the method for preparing the three-layer structure sample is similar to that for the two-layer structure. According to the different arrangement and different deposition amount of silver nanowire films, they are named TIA, 1 / 2 / 3 ,TIA 1 / 3 / 2 ,TIA 2 / 1 / 3 ,TIA 2 / 3 / 1 ,TIA 3 / 1 / 2 ,TIA 3 / 2 / 1 .

Images