Transparent film with laser eavesdropping prevention performance and preparation method thereof

Abstract

The invention relates to the field of optical protection materials, and provides a transparent film with laser eavesdropping prevention performance and a preparation method thereof.The transparent film is composed of surface-modified doped tungsten oxide nanosheets, amino-isocyanate bifunctional lithium niobate nanowires, urethane acrylate, an ultraviolet light absorber, a silane coupling agent, a dispersing agent and a flatting agent; the molybdenum-doped tungsten oxide nanosheets are obtained through silane coupling modification after hydrothermal synthesis, and the lithium niobate nanowires are prepared through a gradient modification process of hydrothermal synthesis-silane coupling-isocyanate grafting-phenol end capping. A modified nano material is uniformly dispersed in a resin matrix through an ultrasonic dispersion composite technology, and through blade coating forming, ultraviolet curing and constant-temperature and constant-humidity post-treatment, compared with the prior art, the scheme overcomes the problems that a traditional protective film is insufficient in optical transparency, laser eavesdropping prevention function and dynamic viscoelasticity, and is suitable for the field of high-end security and protection.

Description

Technical Field

[0001] The present invention relates to the field of optical protection materials, and particularly to a transparent film with anti-laser eavesdropping performance and a preparation method thereof. Background Art

[0002] With the upgrading of the optical window protection requirements in high-security places (such as military command centers, data centers, diplomatic institutions, etc.), transparent anti-eavesdropping materials have become a strategic technology to ensure the security of confidential information. In the scenario of laser eavesdropping, the attacker irradiates the glass surface with a modulated laser beam and analyzes the acoustic wave information by using the vibration of the reflected light. However, due to the lack of targeted protection structures, traditional glass or ordinary polymer films are difficult to effectively resist such high-precision eavesdropping means. For such transparent protection materials, the core performance requirements are the synergistic balance of two contradictory characteristics: on the one hand, it is necessary to have excellent laser scattering and absorption capabilities, and through nanostructure design, the incident laser undergoes multiple refractions, diffractions, and local field effects to achieve a signal analysis signal-to-noise ratio lower than the detector sensitivity threshold; on the other hand, it is necessary to maintain the dynamic viscoelastic balance to ensure that the material maintains a stable mechanical deformation recovery ability within a wide temperature range from -40°C to 85°C, and avoid film layer cracking or optical distortion caused by environmental stresses (such as temperature difference deformation, mechanical vibration). Provide a new generation of active defense solutions for fields such as national security and quantum communication.

[0003] Although the current research on anti-laser eavesdropping transparent films has made some progress in functional design, there are still significant defects in the synergistic realization of key performance. For example, the Chinese patent with the publication number CN115572488A discloses a new type of laser eavesdropping protection film with certain anti-laser eavesdropping performance, but the material has insufficient dynamic viscoelasticity and is prone to interface peeling under temperature difference deformation; another patent with the publication number CN220132128U discloses an anti-laser eavesdropping blocking film, which includes a scratch-resistant layer, a wear-resistant layer, a reflection layer, an absorption layer, an adhesion layer, and a protection layer arranged in sequence. After long-term use, stress relaxation occurs between the multi-layer films, and the dynamic recovery rate decays severely. Fundamentally speaking, the existing technologies mostly focus on the optimization of single functions and lack in-depth research on the correlation mechanism between anti-eavesdropping and mechanical properties: on the one hand, the high-density nano-fillers (such as metal oxides, carbon materials) introduced to achieve laser scattering are likely to cause the destruction of the matrix cross-linking network, resulting in an increase in the elastic modulus of the material and a decrease in the elongation at break; on the other hand, traditional surface modification processes (such as physical coatings, ion implantation) are difficult to regulate the filler-matrix interfacial force at the nanoscale, resulting in uneven distribution of functional units and stress concentration under dynamic loads. In addition, most studies use thermal curing or solvent film-forming processes, and the internal stress generated during the curing process further exacerbates the brittleness of the film layer, restricting its application on flexible substrates or curved structures. These defects lead to the inability of existing materials to meet the "transparent - anti - tough" integrated performance requirements in high-security scenarios, and there is an urgent need to achieve performance leap through material system innovation and preparation process breakthrough. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The object of the present invention is to provide a transparent film with anti-laser eavesdropping performance and a preparation method thereof, so as to solve the problems of insufficient anti-laser eavesdropping and dynamic viscoelastic properties of current transparent films.

[0006] (2) Technical solutions

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A transparent film with anti-laser eavesdropping performance, comprising the following raw materials in parts by weight: 6.0 - 12.0 parts of surface-modified doped tungsten oxide nanosheets, 4.0 - 8.0 parts of amino-isocyanate bifunctionalized lithium niobate nanowires, 50 - 80 parts of polyurethane acrylate, 2.0 - 4.0 parts of UV-531 ultraviolet absorber, 0.5 - 3 parts of KH-570 silane coupling agent, 1.0 - 3.0 parts of BYK-9076 dispersant, 1 - 3 parts of polyhexamethylene diisocyanate, 0.1 - 1 part of polydimethylsiloxane defoamer, 0.1 - 0.6 part of polyether-modified polydimethylsiloxane leveling agent;

[0009] The surface-modified doped tungsten oxide nanosheets are prepared by first preparing molybdenum-doped tungsten oxide nanosheets from nitric acid, sodium tungstate and ammonium heptamolybdate by a hydrothermal synthesis method, and then obtaining them through ultrasonic dispersion, silane coupling reaction, centrifugal washing and vacuum drying with 3-aminopropyltriethoxysilane in absolute ethanol;

[0010] The amino-isocyanate bifunctionalized lithium niobate nanowires are prepared by hydrothermally synthesizing lithium niobate nanowires from lithium carbonate and niobium pentoxide, followed by coupling with 3-aminopropyltriethoxysilane, catalytic grafting with isophorone diisocyanate, capping with phenol and vacuum drying to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0011] Further, the preparation method of the surface-modified doped tungsten oxide nanosheets is as follows: by weight, take 0.3 - 0.8 parts of molybdenum-doped tungsten oxide nanosheet raw materials, 100 - 150 parts of absolute ethanol, and 0.3 - 0.8 parts of 3-aminopropyltriethoxysilane. First, disperse the molybdenum-doped tungsten oxide nanosheet raw materials in absolute ethanol to form a dispersion, and use ultrasonic treatment with an ultrasonic power of 200 - 400 W for 10 - 20 min to achieve uniform dispersion; then add 3-aminopropyltriethoxysilane to the dispersion, and under nitrogen protection, stir at a stirring rate of 400 - 800 rpm at a constant temperature for 3 - 6 h, control the temperature at 50 - 70 °C, so that the silane molecules fully react with the hydroxyl groups on the surface of the nanosheets; then perform solid-liquid separation on the reaction suspension at a centrifugation rate of 10000 - 15000 rpm, discard the supernatant containing unreacted reagents and by-products, retain the precipitate and wash it repeatedly with absolute ethanol 2 - 3 times, with each centrifugation time being 5 - 10 min to remove residual impurities; finally, place the precipitate in a vacuum drying oven, set the vacuum degree at -0.08 - 0.10 MPa and the temperature at 50 - 70 °C to dry for 8 - 16 h to obtain the surface-modified doped tungsten oxide nanosheets.

[0012] Further, the average size of the surface-modified doped tungsten oxide nanosheets is 80 - 150 nm, the thickness is 4.0 - 10.0 nm, and the molybdenum doping amount is 3 - 8 at%.

[0013] Further, the preparation method of the doped tungsten oxide nanosheets is as follows: by weight, 12-15 parts by weight of a nitric acid aqueous solution with a concentration of 60-70 wt% is mixed with 40-50 parts by weight of deionized water, and stirred for 8-15 min under the condition that the magnetic stirring rate is 300-600 rpm to form an acidic medium; 0.8-1.2 parts by weight of sodium tungstate dihydrate and 0.05-0.15 parts by weight of ammonium heptamolybdate tetrahydrate are jointly dissolved in 18-22 parts by weight of deionized water, the dissolution temperature is controlled at 25-35 °C, and the mixture is gradually dropped into the aforementioned acidic medium within 10-20 min under the condition that the continuous stirring rate is 400-800 rpm. After forming a mixed suspension, continue to stir for 25-35 min; transfer the suspension to a polytetrafluoroethylene-lined autoclave, seal it, and heat it to 120-160 °C at a heating rate of 3-5 °C / min, and maintain it at a constant temperature for 6-10.0 h under the condition that the pressure is 1.0-2.0 MPa to complete the hydrothermal reaction; after the reaction system is naturally cooled to below 40 °C, solid-liquid separation is carried out at a centrifugation rate of 8000-12000 rpm. After discarding the supernatant, wash it with deionized water and absolute ethanol 3-5 times each, the amount of washing solvent used each time is 20-30 times the mass of the solid-phase product, and the centrifugation time each time is 5-10 min; finally, place the obtained precipitate in a vacuum drying oven and dry it at a vacuum degree of -0.08 to -0.10 MPa and a temperature of 55-65 °C for 10-14 h to obtain doped tungsten oxide nanosheets.

[0014] The design of the present invention using surface-modified doped tungsten oxide nanosheets is mainly used to enhance the comprehensive performance of protective materials in terms of laser eavesdropping interference and dynamic viscoelastic response. The core lies in combining doping regulation with surface modification to endow the nanosheets with excellent structural stability, interfacial compatibility, and energy response ability, and then constructing an efficient multi-scale energy transfer and dissipation mechanism in the composite system. During the preparation process, molybdenum-doped tungsten oxide nanosheets are generated through a hydrothermal reaction. The introduction of doping elements adjusts the local environment of the tungsten oxide crystal structure, enhances the response activity of the nanosheets under microscopic vibration, and simultaneously endows them with better acoustic vibration coupling ability. The nanosheets have specific sizes and thicknesses, and can form a stable microscopic deformation basis under acoustic perturbation conditions, providing structural support for dynamic viscoelasticity. Further, in the surface modification step, 3-aminopropyltriethoxysilane is introduced to react with the hydroxyl groups on the surface of the nanosheets to form a stable organic-inorganic interfacial structure. This modification not only improves the dispersibility and interfacial binding force of the nanosheets in the composite material system, but also enhances the viscoelastic response ability of the overall material through the flexible chain segments of the functional groups. Under dynamic loads or acoustic perturbations, the modified nanosheets can achieve local dissipation and deformation coordination at the nanoscale, thereby effectively exerting a damping effect and weakening the conduction effect of external excitation on the overall structure. In terms of laser eavesdropping protection, such materials can significantly interfere with the reflection stability of lasers on the glass surface and the micro-vibration transmission path induced by sound waves, making it difficult for laser eavesdropping devices to accurately capture and restore sound signals, achieving the effects of signal shielding and distortion control. The electron and lattice adjustment capabilities provided by the doping structure and the interfacial regulation capabilities brought by surface silane modification form good functional complementarity in the material system. Their mutual interaction not only improves the sensitive response of the material to periodic perturbations, but also enhances its dissipation ability for the energy conduction process, ultimately achieving effective physical interference against laser eavesdropping behavior and multi-dimensional enhancement of dynamic viscoelastic properties. Through the systematic construction of nanostructures, doping elements, and surface functionalization methods, the present invention has established a functional material strategy with high interfacial synergy and high energy responsiveness, providing a reliable material basis and technical support for practical applications under multiple acoustic safety and dynamic physical protection requirements.

[0015] Further, the preparation of the amino-isocyanate bifunctionalized lithium niobate nanowires comprises the following steps: dispersing lithium niobate nanowires in a mixed solvent of N,N-dimethylformamide and absolute ethanol at a weight fraction of 1.0 - 5.0%, where the volume fraction of ethanol is 5 - 15% and the total water content of the system is 0.05 - 0.2%. Add 3-aminopropyltriethoxysilane at a weight fraction of 0.5 - 3.0% and react under nitrogen protection at a stirring rate of 500 - 1000 rpm, a temperature of 30 - 50 °C for a reaction time of 4.0 - 8.0 h. After the reaction, centrifuge at a rate of 10000 - 15000 rpm to separate and retain the amino-functionalized lithium niobate nanowires and remove the unreacted silane and by-products. Wash repeatedly 4 - 6 times with anhydrous N,N-dimethylformamide containing 0.5 - 2.0% molecular sieve by weight to remove free silane and residual moisture. Disperse the washed product in isophorone diisocyanate solution at a weight fraction of 5.0 - 15.0%, add triphenylbismuth catalyst at a weight fraction of 0.02 - 0.06% and molecular sieve at a weight fraction of 0.1 - 0.5%. React under nitrogen protection at a stirring rate of 600 - 1200 rpm, a temperature of 60 - 80 °C for a reaction time of 1.5 - 3.0 h. After centrifugal separation, retain the modified product grafted with isocyanate groups and remove the unreacted monomers and catalyst. Perform end-capping treatment with a molar ratio of phenol to isocyanate groups of 1:0.8 - 1.2 and remove the excess phenol. Finally, dry the end-capped product at a vacuum of -0.09 to -0.1 MPa, a temperature of 40 - 60 °C for a drying time of 8 - 12 h to obtain the amino-isocyanate bifunctionalized lithium niobate nanowires.

[0016] Further, the preparation method of the lithium niobate nanowires is as follows: mix lithium carbonate at a weight fraction of 10 - 20 wt% and niobium pentoxide at a weight fraction of 10 - 25 wt%, then add water at a weight fraction of 50 - 80 wt%. Stir at 200 - 500 rpm at 40 - 80 °C for 30 - 120 min to form a homogeneous suspension. Subsequently, dropwise add polyvinylpyrrolidone at a weight fraction of 0.5 - 3 wt% and adjust the pH value to 8.0 - 11.0 with 0.05 wt% sodium hydroxide solution. Transfer the mixture to a reaction kettle and carry out hydrothermal reaction at 180 - 220 °C for 12 - 20 h. After the reaction, centrifuge at 8000 - 12000 rpm for 5 - 15 min to retain the precipitate. Wash 3 - 5 times successively with deionized water and absolute ethanol to remove the residual solvent and unreacted substances. Finally, vacuum dry at 60 - 100 °C for 6 - 12 h. Place the dried nanowires in a tubular furnace and heat at a heating rate of 2 - 5 °C / min to 600 - 650 °C, keep warm in an air atmosphere for 1 - 3 h, and then naturally cool to room temperature.

[0017] Further, the average length of the surface-modified lithium niobate nanowires is 10-20 μm, and the average diameter is 50-150 nm.

[0018] The design of the amino-isocyanate bifunctionalized lithium niobate nanowires in the present invention is mainly used to enhance laser eavesdropping and dynamic viscoelastic properties. Its technical solution gives full play to the advantages of the structural characteristics and surface chemical activity of lithium niobate nanowires. Through multi-step surface modification means, a functional material system with high interfacial reactivity and excellent mechanical adaptability is constructed. During the preparation process of the nanowires, a hydrothermal reaction combined with a high-temperature treatment process is adopted to obtain lithium niobate nanowires with uniform size and regular structure. This one-dimensional nanostructure provides a controllable deformation channel for the mechanical response of the material under external excitation, which helps to improve its stress distribution and dissipation ability in periodic vibration. Further, an amino functional group is introduced through 3-aminopropyltriethoxysilane, making the surface of the nanowires have good organic reaction activity and interfacial affinity, and undergoing chemical bonding with isophorone diisocyanate in the subsequent grafting reaction to construct a stable isocyanate group coating layer, further guiding the regulation of the intermolecular force between the nanowires and the organic system. This process not only forms a synergistic structure of flexible segments and rigid skeletons on the surface, but also effectively controls the stability and reaction closure of surface active groups through phenol capping reaction, significantly improving the dispersion stability and interfacial binding efficiency of the nanowires in the composite system. In terms of dynamic viscoelasticity, the surface-modified lithium niobate nanowires have good deformation response ability and multi-scale dissipation mechanism, and can exhibit obvious elastic energy storage and viscous energy dissipation characteristics under periodic stress, thus enhancing the overall damping ability and vibration control effect of the material. In terms of laser eavesdropping protection, the modified nanowires disrupt the stable reflection path and acoustic wave reduction mechanism relied on by laser detection through the response perturbation of acoustic micro-vibration, making it difficult for external laser detection equipment to accurately capture and analyze indoor acoustic information, and significantly improving the material's ability to suppress acoustic information leakage. In the whole design scheme, a close cooperation is formed between the structural response characteristics and surface organic functionalization of lithium niobate nanowires. The former provides a good mechanical response basis, and the latter realizes the improvement of interfacial energy dissipation and compatibility. Finally, a stable mechanical conduction and vibration control network is established in the material system, effectively realizing the interference blocking of laser eavesdropping behavior and the multi-dimensional enhancement of dynamic viscoelastic properties, providing a practical technical path for the construction of acoustic safety protection materials.

[0019] The present invention also discloses a preparation method of a transparent film with laser eavesdropping prevention performance, including the following steps:

[0020] S1. Ultrasonically treat the surface-modified doped tungsten oxide nanosheets, amino-isocyanate bifunctionalized lithium niobate nanowires, polyurethane acrylate, UV-531 ultraviolet absorber, KH-570 silane coupling agent, BYK-9076 dispersant, polyhexamethylene diisocyanate, polydimethylsiloxane defoamer, and polyether-modified polydimethylsiloxane leveling agent at a frequency of 20 - 40 kHz for 10 - 20 min. Then add them to a high-speed disperser and mix at a stirring rate of 500 - 800 rpm for 30 - 45 min with the mixing temperature controlled at 20 - 25°C. Subsequently, transfer to a planetary vacuum degassing device and degas for 15 - 30 min under a vacuum of -0.08 to -0.1 MPa while preventing sedimentation at an auxiliary stirring rate of 50 - 100 rpm. After degassing, filter the slurry through a 150 - 200 mesh sieve;

[0021] S2. Uniformly coat the filtered slurry on the surface of a clean substrate by the doctor blade method at a coating speed of 0.5 - 1.5 m / min. After coating, place the substrate in a hot air circulation drying oven and heat it to 60 - 80°C at a heating rate of 2 - 5°C / min, keep it warm and dry for 30 - 60 min with the wind speed controlled at 0.3 - 0.8 m / s. Subsequently, transfer to an ultraviolet curing device and cure it for 30 - 90 s under nitrogen protection with a UV irradiation intensity of 80 - 120 mW / cm 2 ² and a wavelength of 320 - 400 nm;

[0022] S3. Post-treatment and performance regulation: Place the cured film material in a constant temperature and humidity chamber and leave it static for 12 - 24 h at a temperature of 25 - 30°C and a relative humidity of 50% - 70% to eliminate internal stress. After post-treatment, obtain a transparent film with anti-laser eavesdropping performance.

[0023] The present invention designs a transparent film material constructed by synergistically combining surface-modified doped tungsten oxide nanosheets and amino-isocyanate bifunctionalized lithium niobate nanowires, mainly for enhancing its laser eavesdropping interference ability and dynamic viscoelastic properties. Through the organic combination of multifunctional nanomaterials and polymer matrices, a composite film layer with excellent optical transparency, structural stability, and energy dissipation ability is constructed. After being modified with 3-aminopropyltriethoxysilane on the surface, the doped tungsten oxide nanosheets exhibit good dispersibility and interfacial activity. Their sheet structure and doping characteristics contribute to interfering with the laser reflection path and signal stability. The lithium niobate nanowires form a stable interfacial structure after grafting isocyanate groups and capping treatment. Combining their polarity and one-dimensional morphology, it effectively improves the viscoelastic response and energy dissipation ability of the material under periodic excitation. Through process means such as ultrasonic dispersion, high-speed stirring, vacuum degassing, hot air drying, and ultraviolet curing, the uniform distribution of multiple components and the rapid formation of a network structure are realized. Subsequent constant temperature and humidity treatment further releases internal stress and improves the overall structural stability of the film material. The mutual cooperation of each component in terms of structural dimension and functional mechanism enables the film material to have a significant acoustic vibration suppression effect and laser reflection interference ability while maintaining transparency, thereby effectively weakening the capture and restoration of acoustic signals by laser eavesdropping devices and achieving physical shielding and blocking of acoustic information.

[0024] (3) Beneficial technical effects

[0025] 1. The present invention synergistically regulates the structure and interfacial properties of tungsten oxide nanosheets through molybdenum doping and silane modification, significantly enhancing its dissipation response and laser eavesdropping interference ability under acoustic disturbances, achieving multi-scale energy control and viscoelastic property improvement, and having excellent practical value and irreplaceability.

[0026] 2. The present invention significantly improves the damping performance and anti-laser eavesdropping ability through the synergistic effect of the structural response and organic functionalization of amino-isocyanate bifunctionalized lithium niobate nanowires, and has both interfacial stability, energy dissipation, and dynamic responsiveness, solving problems such as weak vibration control and poor information leakage protection of existing materials, and having excellent engineering application prospects.

[0027] 3. The present invention effectively improves the interference ability of the transparent film against laser eavesdropping and the dynamic viscoelastic response through the synergistic design of doped tungsten oxide nanosheets and lithium niobate nanowires. Polyurethane acrylate provides a flexible film-forming basis, UV-531 enhances weather resistance, KH-570 improves interfacial bonding, BYK-9076 promotes nanodispersion, HDI crosslinks to form a stable network, and defoamers and leveling agents optimize the film-forming quality. Each component synergistically constructs a high-performance viscoelastic and protective system, having both excellent interfacial compatibility and energy dissipation performance, solving problems such as weak signal shielding and poor structural stability of existing materials, and having good practical application prospects. Description of the drawings

[0028] Figure 1 Morphology diagram of the doped tungsten oxide nanosheets prepared in Example 1 of the present invention.

[0029] Figure 2 EDX surface scanning element distribution of the doped tungsten oxide nanosheets prepared in Example 1 of the present invention.

[0030] Figure 3 EDX surface scanning element distribution of the lithium niobate nanowires prepared in Example 1 of the present invention.

[0031] Figure 4 Morphology diagram of the lithium niobate nanowires prepared in Example 1 of the present invention.

[0032] Figure 5 XRD phase analysis diagram of the lithium niobate nanowires prepared in Example 1 of the present invention. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0034] Example 1

[0035] A transparent film with anti-laser eavesdropping performance, comprising the following raw materials in parts by weight: 6.0 parts of surface-modified doped tungsten oxide nanosheets, 4.0 parts of amino-isocyanate bifunctionalized lithium niobate nanowires, 50 parts of polyurethane acrylate, 2.0 parts of UV-531 ultraviolet absorber, 0.5 part of KH-570 silane coupling agent, 1.0 part of BYK-9076 dispersant, 1 part of polyhexamethylene diisocyanate, 0.1 part of polydimethylsiloxane defoamer, 0.1 part of polyether-modified polydimethylsiloxane leveling agent;

[0036] The surface-modified doped tungsten oxide nanosheets are prepared by first preparing molybdenum-doped tungsten oxide nanosheets from nitric acid, sodium tungstate and ammonium heptamolybdate by hydrothermal synthesis method, and obtaining them by ultrasonic dispersion, silane coupling reaction, centrifugal washing and vacuum drying with 3-aminopropyltriethoxysilane in absolute ethanol; the amino-isocyanate bifunctionalized lithium niobate nanowires are prepared by hydrothermally synthesizing lithium niobate nanowires from lithium carbonate and niobium pentoxide, coupling with 3-aminopropyltriethoxysilane, catalytic grafting with isophorone diisocyanate, capping with phenol and vacuum drying to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0037] The preparation method of the surface-modified doped tungsten oxide nanosheets in this embodiment is as follows: by weight, take 0.3 parts of molybdenum-doped tungsten oxide nanosheet raw materials, 100 parts of absolute ethanol, and 0.3 parts of 3-aminopropyltriethoxysilane. First, disperse the molybdenum-doped tungsten oxide nanosheet raw materials in absolute ethanol to form a dispersion, and use ultrasonic treatment with an ultrasonic power of 200 W for 10 min to achieve uniform dispersion; then add 3-aminopropyltriethoxysilane to the dispersion, and under nitrogen protection, stir at a stirring rate of 400 rpm at a constant temperature for 3 h, control the temperature at 50 °C, and allow the silane molecules to fully react with the hydroxyl groups on the surface of the nanosheets; then perform solid-liquid separation on the reacted suspension at a centrifugation rate of 10,000 rpm, discard the supernatant containing unreacted reagents and by-products, retain the precipitate, and wash it twice with absolute ethanol, with a centrifugation time of 5 min each time to remove residual impurities; finally, place the precipitate in a vacuum drying oven, set the vacuum degree to -0.08 MPa and the temperature to 50 °C, and dry for 8 h to obtain the surface-modified doped tungsten oxide nanosheets.

[0038] The average size of the surface-modified doped tungsten oxide nanosheets in this embodiment is 80 nm, the thickness is 4.0 nm, and the molybdenum doping amount is 3 at%.

[0039] The preparation method of the doped tungsten oxide nanosheets in this embodiment is as follows: by weight, mix 12 parts by weight of a nitric acid aqueous solution with a concentration of 60 wt% and 40 parts by weight of deionized water, and stir at a magnetic stirring rate of 300 rpm for 8 min to form an acidic medium; dissolve 0.8 parts by weight of sodium tungstate dihydrate and 0.05 parts by weight of ammonium heptamolybdate tetrahydrate in 18 parts by weight of deionized water, control the dissolution temperature at 25 °C, and dropwise inject the aforementioned acidic medium drop by drop within 10 min under a continuous stirring rate of 400 rpm to form a mixed suspension, and then continue to stir for 25 min; transfer the suspension to a polytetrafluoroethylene-lined autoclave, seal it, and heat it to 120 °C at a heating rate of 3 °C / min, and maintain it at a constant temperature for 6 h under a pressure of 1.0 MPa to complete the hydrothermal reaction; after the reaction system naturally cools to below 40 °C, perform solid-liquid separation at a centrifugation rate of 8000 rpm, discard the supernatant, and wash it 3 times with deionized water and absolute ethanol in turn, with the amount of each washing solvent being 20 times the mass of the solid-phase product, and the centrifugation time for each time being 5 min; finally, place the obtained precipitate in a vacuum drying oven, and dry it at a vacuum degree of -0.08 MPa and a temperature of 55 °C for 10 h to obtain the doped tungsten oxide nanosheets.

[0040] The amino - isocyanate bifunctionalized lithium niobate nanowires of this embodiment include the following steps: Disperse lithium niobate nanowires at a weight fraction of 5.0% in a mixed solvent of N,N - dimethylformamide and absolute ethanol, where the volume fraction of ethanol is 15% and the total water content of the system is 0.2%. Add 3 - aminopropyltriethoxysilane at a weight fraction of 3.0% and react under nitrogen protection at a stirring rate of 1000 rpm, a temperature of 50 °C for 8.0 h. After the reaction, centrifuge at a rate of 15000 rpm to separate and retain the amino - functionalized lithium niobate nanowires and remove the unreacted silane and by - products. Repeat washing 6 times with anhydrous N,N - dimethylformamide containing 2.0% molecular sieve by weight to remove free silane and residual moisture. Disperse the washed product at a weight fraction of 15.0% in an isophorone diisocyanate solution and add 0.06% triphenylbismuth catalyst by weight and 0.5% molecular sieve by weight. React under nitrogen protection at a stirring rate of 1200 rpm, a temperature of 80 °C for 3.0 h. After centrifugal separation, retain the grafted isocyanate - group - modified product and remove the unreacted monomers and catalyst. Perform end - capping treatment with a molar ratio of phenol to isocyanate groups of 1:1.2 and remove the excess phenol. Finally, dry the end - capped product at a vacuum of - 0.1 MPa, a temperature of 60 °C for 12 h to obtain the amino - isocyanate bifunctionalized lithium niobate nanowires.

[0041] The preparation method of the lithium niobate nanowires of this embodiment is as follows: Mix 20 wt% lithium carbonate and 25 wt% niobium pentoxide by weight, then add 80 wt% water. Stir at 500 rpm for 120 min at 80 °C to form a homogeneous suspension. Subsequently, drop - wise add 3 wt% polyvinylpyrrolidone and adjust the pH value to 11.0 with 0.05 wt% sodium hydroxide solution. Transfer the mixture to a reaction kettle and carry out a hydrothermal reaction at 220 °C for 20 h. After the reaction, centrifuge at 12000 rpm for 15 min to retain the precipitate. Wash it 5 times with deionized water and absolute ethanol in turn to remove the residual solvent and unreacted substances. Finally, dry it in vacuum at 100 °C for 12 h. Place the dried nanowires in a tubular furnace, heat it to 650 °C at a heating rate of 5 °C / min, keep it warm in an air atmosphere for 3 h, and then naturally cool to room temperature.

[0042] The average length of the surface - modified lithium niobate nanowires of this embodiment is 20 μm, and the average diameter is 150 nm.

[0043] The present invention also discloses a preparation method of a transparent film with anti - laser eavesdropping performance, including the following steps:

[0044] S1. Ultrasonically treat the surface-modified doped tungsten oxide nanosheets, amino-isocyanate bifunctionalized lithium niobate nanowires, polyurethane acrylate, UV-531 ultraviolet absorber, KH-570 silane coupling agent, BYK-9076 dispersant, polyhexamethylene diisocyanate, polydimethylsiloxane defoamer and polyether-modified polydimethylsiloxane leveling agent at a frequency of 40 kHz for 20 min. Then add them to a high-speed disperser and mix at a stirring rate of 800 rpm for 45 min. Control the mixing temperature at 25 °C. Subsequently, transfer them to a planetary vacuum degassing device and degas for 30 min under a vacuum of -0.1 MPa. At the same time, use an auxiliary stirring rate of 100 rpm to prevent sedimentation. After degassing, filter the slurry through a 200-mesh sieve;

[0045] S2. Uniformly coat the filtered slurry on the surface of a clean substrate by the doctor blade method at a coating speed of 1.5 m / min. After coating, place the substrate in a hot air circulation drying oven and heat it to 80 °C at a heating rate of 5 °C / min, and keep it warm and dry for 60 min. Control the wind speed at 0.8 m / s. Subsequently, transfer it to an ultraviolet curing device and cure it for 90 s under nitrogen protection with a UV irradiation intensity of 120 mW / cm2 and a wavelength of 400 nm;

[0046] S3. Post-treatment and performance regulation: Place the cured film material in a constant temperature and humidity chamber and let it stand at a temperature of 30 °C and a relative humidity of 70% for 24 h to eliminate internal stress. After post-treatment, a transparent film with anti-laser eavesdropping performance is obtained.

[0047] Figure 1 Figure 10 shows the typical morphology of the doped tungsten oxide nanosheets in Example 1 of the present invention, clearly presenting a two-dimensional sheet structure with clear edges and uniform thickness, indicating that the nanosheets are successfully synthesized and have ideal size characteristics. Figure 2 Figure 11 is the EDX surface scan of the doped tungsten oxide nanosheets. The distributions of W, O and the doped elements are uniform throughout the field of view, further proving the compositional uniformity of the material and the success of doping. Figure 3 And Figure 4 Figures 12 and 13 are respectively the EDX element distribution and morphology of the lithium niobate nanowires. The results show that the nanowires present a regular slender structure, and the distributions of elements Nb, Li, and O are consistent, indicating that the synthesized lithium niobate nanowires have good crystalline morphology and uniform dispersion. Figure 5 Figure 14 is the XRD phase analysis of the lithium niobate nanowires. Each diffraction peak highly matches the standard PDF card, and no impurity peaks are found, proving that the synthesized material has a good crystal structure and high phase purity. In summary, these characterization results fully verify the feasibility and stability of the two key nanocomposites in the present invention in terms of morphology, composition and phase control, providing a structural basis for the subsequent improvement of the composite material performance.

[0048] Example 2

[0049] A transparent film with anti-laser eavesdropping performance, comprising the following raw materials in parts by weight: 8 parts of surface-modified doped tungsten oxide nanosheets, 5 parts of amino-isocyanate bifunctionalized lithium niobate nanowires, 59 parts of polyurethane acrylate, 2.6 parts of UV-531 ultraviolet absorber, 1.3 parts of KH-570 silane coupling agent, 1.6 parts of BYK-9076 dispersant, 1.6 parts of polyhexamethylene diisocyanate, 0.4 parts of polydimethylsiloxane defoamer, and 0.3 parts of polyether-modified polydimethylsiloxane leveling agent;

[0050] The surface-modified doped tungsten oxide nanosheets are prepared by first preparing molybdenum-doped tungsten oxide nanosheets from nitric acid, sodium tungstate, and ammonium heptamolybdate by hydrothermal synthesis, and then obtaining them through ultrasonic dispersion, silane coupling reaction, centrifugal washing, and vacuum drying with 3-aminopropyltriethoxysilane in absolute ethanol; the amino-isocyanate bifunctionalized lithium niobate nanowires are prepared by hydrothermally synthesizing lithium niobate nanowires from lithium carbonate and niobium pentoxide, followed by coupling with 3-aminopropyltriethoxysilane, catalytic grafting with isophorone diisocyanate, capping with phenol, and vacuum drying to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0051] The preparation method of the surface-modified doped tungsten oxide nanosheets in this example is as follows: in parts by weight, take 0.5 part of molybdenum-doped tungsten oxide nanosheet raw material, 115 parts of absolute ethanol, and 0.5 part of 3-aminopropyltriethoxysilane. First, disperse the molybdenum-doped tungsten oxide nanosheet raw material in absolute ethanol to form a dispersion, and use ultrasonic treatment with an ultrasonic power of 260 W for 13 min to achieve uniform dispersion; then add 3-aminopropyltriethoxysilane to the dispersion, and stir at a constant temperature with a stirring rate of 520 rpm for 4 h under nitrogen protection, controlling the temperature at 56 °C to allow the silane molecules to fully react with the hydroxyl groups on the surface of the nanosheets; then perform solid-liquid separation on the reaction suspension at a centrifugation rate of 11500 rpm, discard the supernatant containing unreacted reagents and by-products, retain the precipitate, and wash it twice with absolute ethanol, with each centrifugation time of 7 min to remove residual impurities; finally, place the precipitate in a vacuum drying oven, set the vacuum degree to -0.09 MPa and the temperature to 56 °C, and dry for 10 h to obtain surface-modified doped tungsten oxide nanosheets.

[0052] The average size of the surface-modified doped tungsten oxide nanosheets in this example is 101 nm, the thickness is 5.8 nm, and the molybdenum doping amount is 4.5 at%.

[0053] The preparation method of the doped tungsten oxide nanosheets in this example is as follows: by weight, 13 parts by weight of a nitric acid aqueous solution with a concentration of 63 wt% is mixed with 43 parts by weight of deionized water, and stirred for 10 min at a magnetic stirring rate of 390 rpm to form an acidic medium; 0.9 part by weight of sodium tungstate dihydrate and 0.08 part by weight of ammonium heptamolybdate tetrahydrate are jointly dissolved in 19 parts by weight of deionized water, the dissolution temperature is controlled at 28 °C, and it is dropwise added into the aforementioned acidic medium within 13 min under a continuous stirring rate of 520 rpm to form a mixed suspension, and then stirred for another 28 min; the suspension is transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, sealed, heated to 132 °C at a heating rate of 3.6 °C / min, and kept at a constant temperature for 7.2 h under a pressure of 1.3 MPa to complete the hydrothermal reaction; after the reaction system is naturally cooled to below 40 °C, solid-liquid separation is carried out at a centrifugation rate of 9200 rpm. After discarding the supernatant, it is washed 4 times with deionized water and anhydrous ethanol respectively, the amount of each washing solvent is 23 times the mass of the solid-phase product, and the centrifugation time for each time is 7 min; finally, the obtained precipitate is placed in a vacuum drying oven and dried for 11 h under a vacuum degree of -0.09 MPa and a temperature of 58 °C to obtain doped tungsten oxide nanosheets.

[0054] The amino-isocyanate bifunctionalized lithium niobate nanowires in this example include the following steps: The lithium niobate nanowires are dispersed in a mixed solvent of N,N-dimethylformamide and anhydrous ethanol at a weight fraction of 3.4%, where the volume fraction of ethanol is 11% and the total water content of the system is 0.14%. 2.0% by weight of 3-aminopropyltriethoxysilane is added and reacted under nitrogen protection at a stirring rate of 800 rpm, a temperature of 42 °C for 6.4 h. After the reaction, separation is carried out at a centrifugation rate of 13000 rpm to retain the amino-functionalized lithium niobate nanowires and remove the unreacted silane and by-products. It is repeatedly washed 5 times with anhydrous N,N-dimethylformamide containing 1.4% by weight of molecular sieve to remove free silane and residual moisture. The washed product is dispersed in an isophorone diisocyanate solution at a weight fraction of 11.0%, and 0.04% by weight of triphenylbismuth catalyst and 0.3% by weight of molecular sieve are added. Under nitrogen protection, it is reacted at a stirring rate of 960 rpm, a temperature of 72 °C for 2.4 h. After centrifugal separation, the modified product grafted with isocyanate groups is retained and the unreacted monomers and catalysts are removed. End-capping treatment is carried out with a molar ratio of phenol to isocyanate groups of 1:1.0 and the excess phenol is removed. Finally, the end-capped product is dried at a vacuum degree of -0.09 MPa and a temperature of 52 °C for 10 h to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0055] The preparation method of the lithium niobate nanowires in this embodiment is as follows: Mix lithium carbonate with a weight fraction of 16 wt% and niobium pentoxide with a weight fraction of 19 wt%, then add water with a weight fraction of 68 wt%. Stir at 380 rpm for 84 min at 64 °C to form a homogeneous suspension. Subsequently, gradually add polyvinylpyrrolidone with a weight fraction of 2.0 wt% and adjust the pH value to 9.8 with 0.05 wt% sodium hydroxide solution. Transfer the mixture to a reaction kettle and carry out hydrothermal reaction at 204 °C for 17 h. After the reaction, centrifuge at 10400 rpm for 11 min to retain the precipitate. Wash it 4 times with deionized water and absolute ethanol in turn to remove the residual solvent and unreacted substances. Finally, dry it in vacuum at 84 °C for 10 h. Place the dried nanowires in a tube furnace and heat them to 630 °C at a heating rate of 3.8 °C / min, keep them at this temperature in an air atmosphere for 2.2 h, and then naturally cool them to room temperature.

[0056] The average length of the surface-modified lithium niobate nanowires in this embodiment is 16 μm, and the average diameter is 110 nm.

[0057] The present invention also discloses a preparation method of a transparent film with anti-laser eavesdropping performance, including the following steps:

[0058] S1. First, ultrasonically treat surface-modified doped tungsten oxide nanosheets, amino-isocyanate bifunctionalized lithium niobate nanowires, polyurethane acrylate, UV-531 ultraviolet absorber, KH-570 silane coupling agent, BYK-9076 dispersant, polyhexamethylene diisocyanate, polydimethylsiloxane defoamer, and polyether-modified polydimethylsiloxane leveling agent at a frequency of 32 kHz for 16 min. Then add them to a high-speed disperser and mix at a stirring rate of 680 rpm for 39 min. Control the mixing temperature at 23 °C. Subsequently, transfer them to a planetary vacuum degassing device and degas at a vacuum degree of -0.09 MPa for 24 min. At the same time, use an auxiliary stirring rate of 80 rpm to prevent sedimentation. After degassing, filter the slurry through a 180-mesh sieve.

[0059] S2. Uniformly coat the filtered slurry on the surface of a clean substrate by the doctor blade method at a coating speed of 1.1 m / min. After coating, place the substrate in a hot air circulation drying oven and heat it to 72 °C at a heating rate of 3.8 °C / min, keep it warm and dry for 48 min, control the wind speed at 0.6 m / s. Subsequently, transfer it to an ultraviolet curing device and cure it for 66 s under nitrogen protection with a UV irradiation intensity of 104 mW / cm2 and a wavelength of 368 nm.

[0060] S3. Post-treatment and performance regulation: Place the cured film in a constant temperature and humidity box and let it stand at a temperature of 28 °C and a relative humidity of 62% for 19 h to eliminate internal stress. After post-treatment, a transparent film with anti-laser eavesdropping performance is obtained.

[0061] Example 3

[0062] A transparent film with anti-laser eavesdropping performance, comprising the following raw materials in parts by weight: 10 parts of surface-modified doped tungsten oxide nanosheets, 6 parts of amino-isocyanate bifunctionalized lithium niobate nanowires, 68 parts of polyurethane acrylate, 3.2 parts of UV-531 ultraviolet absorber, 2.0 parts of KH-570 silane coupling agent, 2.2 parts of BYK-9076 dispersant, 2.2 parts of polyhexamethylene diisocyanate, 0.6 part of polydimethylsiloxane defoamer, and 0.4 part of polyether-modified polydimethylsiloxane leveling agent;

[0063] The surface-modified doped tungsten oxide nanosheets are prepared by first preparing molybdenum-doped tungsten oxide nanosheets from nitric acid, sodium tungstate and ammonium heptamolybdate by hydrothermal synthesis method, and then obtaining them by ultrasonic dispersion, silane coupling reaction, centrifugal washing and vacuum drying with 3-aminopropyltriethoxysilane in absolute ethanol; the amino-isocyanate bifunctionalized lithium niobate nanowires are prepared by hydrothermally synthesizing lithium niobate nanowires from lithium carbonate and niobium pentoxide, followed by coupling with 3-aminopropyltriethoxysilane, catalytic grafting with isophorone diisocyanate, phenol capping and vacuum drying to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0064] The preparation method of the surface-modified doped tungsten oxide nanosheets in this example is as follows: in parts by weight, take 0.6 part of molybdenum-doped tungsten oxide nanosheet raw material, 130 parts of absolute ethanol, and 0.6 part of 3-aminopropyltriethoxysilane. First, disperse the molybdenum-doped tungsten oxide nanosheet raw material in absolute ethanol to form a dispersion, and use ultrasonic treatment with an ultrasonic power of 320W for 16min to achieve uniform dispersion; then add 3-aminopropyltriethoxysilane to the dispersion, and stir at a constant temperature of 62°C with a stirring rate of 640rpm under nitrogen protection for 5h to allow the silane molecules to fully react with the hydroxyl groups on the surface of the nanosheets; then perform solid-liquid separation on the reaction suspension at a centrifugation rate of 13000rpm, discard the supernatant containing unreacted reagents and by-products, retain the precipitate and wash it repeatedly with absolute ethanol 3 times, with each centrifugation time of 8min to remove residual impurities; finally, place the precipitate in a vacuum drying oven, set the vacuum degree to -0.09MPa and the temperature to 62°C, and dry for 13h to obtain the surface-modified doped tungsten oxide nanosheets.

[0065] The average size of the surface-modified doped tungsten oxide nanosheets in this example is 122nm, the thickness is 7.6nm, and the molybdenum doping amount is 6at%.

[0066] The preparation method of the doped tungsten oxide nanosheets in this embodiment is as follows: by weight, 14 parts by weight of a nitric acid aqueous solution with a concentration of 66 wt% is mixed with 46 parts by weight of deionized water, and stirred for 12 min under the condition that the magnetic stirring rate is 480 rpm to form an acidic medium; 1.0 part by weight of sodium tungstate dihydrate and 0.11 part by weight of ammonium heptamolybdate tetrahydrate are jointly dissolved in 20 parts by weight of deionized water, the dissolution temperature is controlled at 31 °C, and it is dropwise added into the aforementioned acidic medium within 16 min under the condition that the continuous stirring rate is 640 rpm to form a mixed suspension, and then stirred for 31 min; the suspension is transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, sealed and heated to 144 °C at a heating rate of 4.2 °C / min, and kept at a constant temperature for 8.4 h under the condition that the pressure is 1.6 MPa to complete the hydrothermal reaction; after the reaction system is naturally cooled to below 40 °C, solid-liquid separation is carried out at a centrifugation rate of 10400 rpm. After discarding the supernatant, it is washed 4 times with deionized water and anhydrous ethanol in turn, the dosage of each washing solvent is 26 times the mass of the solid-phase product, and the centrifugation time for each time is 8 min; finally, the obtained precipitate is placed in a vacuum drying oven and dried for 12 h under the conditions of a vacuum degree of -0.09 MPa and a temperature of 61 °C to obtain doped tungsten oxide nanosheets.

[0067] The amino-isocyanate bifunctionalized lithium niobate nanowires in this embodiment include the following steps: the lithium niobate nanowires are dispersed in a mixed solvent of N,N-dimethylformamide and anhydrous ethanol at a weight fraction of 2.2%, wherein the volume fraction of ethanol is 8% and the total water content of the system is 0.09%. 1.3% by weight of 3-aminopropyltriethoxysilane is added and reacted under nitrogen protection at a stirring rate of 650 rpm, a temperature of 36 °C for 5.2 h. After the reaction, the amino-functionalized lithium niobate nanowires are separated and retained by centrifugation at a rate of 11500 rpm to remove unreacted silane and by-products, and washed 5 times repeatedly with anhydrous N,N-dimethylformamide containing 1.0% by weight of molecular sieve to remove free silane and residual moisture. The washed product is dispersed in an isophorone diisocyanate solution at a weight fraction of 8.0%, and 0.03% by weight of triphenylbismuth catalyst and 0.2% by weight of molecular sieve are added. Under nitrogen protection, it is reacted at a stirring rate of 780 rpm, a temperature of 66 °C for 1.9 h. After centrifugal separation, the modified product grafted with isocyanate groups is retained and unreacted monomers and catalysts are removed. End-capping treatment is carried out with a molar ratio of phenol to isocyanate groups of 1:0.9 and excess phenol is removed. Finally, the end-capped product is dried at a vacuum degree of -0.09 MPa and a temperature of 46 °C for 9 h to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0068] The preparation method of the lithium niobate nanowires in this embodiment is as follows: Lithium carbonate with a weight fraction of 14 wt% and niobium pentoxide with a weight fraction of 15 wt% are mixed and then added with water with a weight fraction of 59 wt%. The mixture is stirred at 290 rpm for 57 min at 52 °C to form a homogeneous suspension. Subsequently, polyvinylpyrrolidone with a weight fraction of 1.3 wt% is added dropwise, and the pH value is adjusted to 8.9 with 0.05 wt% sodium hydroxide solution. The mixture is transferred to a reaction kettle and hydrothermally reacted at 192 °C for 14 h. After the reaction, the precipitate is retained by centrifugation at 9200 rpm for 8 min. The precipitate is washed 4 times with deionized water and anhydrous ethanol in turn to remove residual solvents and unreacted substances. Finally, it is vacuum dried at 72 °C for 8 h. The dried nanowires are placed in a tube furnace and heated to 615 °C at a heating rate of 2.9 °C / min, and kept at this temperature for 1.6 h in an air atmosphere, and then naturally cooled to room temperature.

[0069] The average length of the surface-modified lithium niobate nanowires in this embodiment is 13 μm, and the average diameter is 80 nm.

[0070] The present invention also discloses a preparation method of a transparent film with anti-laser eavesdropping performance, including the following steps:

[0071] S1. First, surface-modified doped tungsten oxide nanosheets, amino-isocyanate bifunctionalized lithium niobate nanowires, polyurethane acrylate, UV-531 ultraviolet absorber, KH-570 silane coupling agent, BYK-9076 dispersant, polyhexamethylene diisocyanate, polydimethylsiloxane defoamer, and polyether-modified polydimethylsiloxane leveling agent are ultrasonically treated at a frequency of 26 kHz for 13 min, and then added to a high-speed disperser and mixed at a stirring rate of 590 rpm for 35 min. The mixing temperature is controlled at 21 °C. Subsequently, it is transferred to a planetary vacuum degassing device and degassed at a vacuum degree of -0.09 MPa for 20 min, while preventing sedimentation at an auxiliary stirring rate of 65 rpm. After degassing, the slurry is filtered through a 165-mesh sieve.

[0072] S2. The filtered slurry is uniformly coated on the surface of a clean substrate by the doctor blade method at a coating speed of 0.8 m / min. After coating, the substrate is placed in a hot air circulation drying oven and heated to 66 °C at a heating rate of 2.9 °C / min and kept warm and dried for 39 min. The wind speed is controlled at 0.5 m / s. Subsequently, it is transferred to an ultraviolet curing device and cured under nitrogen protection at a UV irradiation intensity of 92 mW / cm2 and a wavelength of 344 nm for 48 s.

[0073] S3. Post-treatment and performance regulation: The cured film material is placed in a constant temperature and humidity box and left standing at a temperature of 26 °C and a relative humidity of 56% for 16 h to eliminate internal stress. After post-treatment, a transparent film with anti-laser eavesdropping performance is obtained.

[0074] Example 4

[0075] A transparent film with anti-laser eavesdropping performance, comprising the following raw materials in parts by weight: 12.0 parts of surface-modified doped tungsten oxide nanosheets, 8.0 parts of amino-isocyanate bifunctionalized lithium niobate nanowires, 80 parts of polyurethane acrylate, 4.0 parts of UV-531 ultraviolet absorber, 3 parts of KH-570 silane coupling agent, 3.0 parts of BYK-9076 dispersant, 3 parts of polyhexamethylene diisocyanate, 1 part of polydimethylsiloxane defoamer, and 0.6 part of polyether-modified polydimethylsiloxane leveling agent;

[0076] The surface-modified doped tungsten oxide nanosheets are prepared by first preparing molybdenum-doped tungsten oxide nanosheets from nitric acid, sodium tungstate and ammonium heptamolybdate by hydrothermal synthesis method, and then obtaining them through ultrasonic dispersion, silane coupling reaction, centrifugal washing and vacuum drying with 3-aminopropyltriethoxysilane in absolute ethanol; the amino-isocyanate bifunctionalized lithium niobate nanowires are prepared by hydrothermally synthesizing lithium niobate nanowires from lithium carbonate and niobium pentoxide, followed by coupling with 3-aminopropyltriethoxysilane, catalytic grafting with isophorone diisocyanate, capping with phenol and vacuum drying to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0077] The preparation method of the surface-modified doped tungsten oxide nanosheets in this example is as follows: in parts by weight, take 0.8 part of molybdenum-doped tungsten oxide nanosheet raw material, 150 parts of absolute ethanol, and 0.8 part of 3-aminopropyltriethoxysilane. First, disperse the molybdenum-doped tungsten oxide nanosheet raw material in absolute ethanol to form a dispersion, and use ultrasonic treatment with an ultrasonic power of 400W for 20min to achieve uniform dispersion; then add 3-aminopropyltriethoxysilane to the dispersion, and stir at a constant temperature with a stirring rate of 800rpm for 6h under nitrogen protection, controlling the temperature at 70°C to allow the silane molecules to fully react with the hydroxyl groups on the surface of the nanosheets; then perform solid-liquid separation on the reaction suspension at a centrifugation rate of 15000rpm, discard the supernatant containing unreacted reagents and by-products, retain the precipitate and wash it repeatedly with absolute ethanol 3 times, with each centrifugation time of 10min to remove residual impurities; finally, place the precipitate in a vacuum drying oven, set the vacuum degree at -0.10MPa and the temperature at 70°C for drying for 16h to obtain surface-modified doped tungsten oxide nanosheets.

[0078] The average size of the surface-modified doped tungsten oxide nanosheets in this example is 150nm, the thickness is 10.0nm, and the molybdenum doping amount is 8at%.

[0079] The preparation method of the doped tungsten oxide nanosheets in this embodiment is as follows: by weight, 15 parts by weight of a nitric acid aqueous solution with a concentration of 70 wt% is mixed with 50 parts by weight of deionized water, and stirred for 15 min under a magnetic stirring rate of 600 rpm to form an acidic medium; 1.2 parts by weight of sodium tungstate dihydrate and 0.15 parts by weight of ammonium heptamolybdate tetrahydrate are jointly dissolved in 22 parts by weight of deionized water, the dissolution temperature is controlled at 35 °C, and it is dropwise added into the aforementioned acidic medium within 20 min under a continuous stirring rate of 800 rpm. After forming a mixed suspension, it is continuously stirred for 35 min; the suspension is transferred to a polytetrafluoroethylene-lined autoclave, sealed, heated to 160 °C at a heating rate of 5 °C / min, and maintained at a constant temperature for 10.0 h under a pressure of 2.0 MPa to complete the hydrothermal reaction; after the reaction system is naturally cooled to below 40 °C, solid-liquid separation is carried out at a centrifugation rate of 12,000 rpm. After discarding the supernatant, it is washed 5 times with deionized water and anhydrous ethanol in turn, the amount of washing solvent used each time is 30 times the mass of the solid-phase product, and the centrifugation time each time is 10 min; finally, the obtained precipitate is placed in a vacuum drying oven and dried at a vacuum degree of -0.10 MPa and a temperature of 65 °C for 14 h to obtain doped tungsten oxide nanosheets.

[0080] The amino-isocyanate bifunctionalized lithium niobate nanowires in this embodiment include the following steps: the lithium niobate nanowires are dispersed in a mixed solvent of N,N-dimethylformamide and anhydrous ethanol at a weight fraction of 1.0%, wherein the volume fraction of ethanol is 5% and the total water content of the system is 0.05%. 0.5 parts by weight of 3-aminopropyltriethoxysilane is added and reacted under nitrogen protection at a stirring rate of 500 rpm, a temperature of 30 °C for 4.0 h. After the reaction, the amino-functionalized lithium niobate nanowires are separated and retained by centrifugation at a rate of 10,000 rpm to remove unreacted silane and by-products, and washed 4 times repeatedly with anhydrous N,N-dimethylformamide containing 0.5 parts by weight of molecular sieve to remove free silane and residual moisture. The washed product is dispersed in an isophorone diisocyanate solution at a weight fraction of 5.0%, and 0.02 parts by weight of triphenylbismuth catalyst and 0.1 parts by weight of molecular sieve are added. Under nitrogen protection, the reaction is carried out at a stirring rate of 600 rpm, a temperature of 60 °C for 1.5 h. After centrifugal separation, the modified product grafted with isocyanate groups is retained and unreacted monomers and catalysts are removed. End-capping treatment is carried out with a molar ratio of phenol to isocyanate groups of 1:0.8 and excess phenol is removed. Finally, the end-capped product is dried at a vacuum degree of -0.09 MPa and a temperature of 40 °C for 8 h to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

[0081] The preparation method of the lithium niobate nanowires in this embodiment is as follows: Mix lithium carbonate with a weight fraction of 10 wt% and niobium pentoxide with a weight fraction of 10 wt%, then add water with a weight fraction of 50 wt%. Stir at 40 °C at 200 rpm for 30 min to form a homogeneous suspension. Subsequently, gradually add polyvinylpyrrolidone with a weight fraction of 0.5 wt% and adjust the pH value to 8.0 with a 0.05 wt% sodium hydroxide solution. Transfer the mixture to a reaction kettle and carry out a hydrothermal reaction at 180 °C for 12 h. After the reaction, centrifuge at 8000 rpm for 5 min to retain the precipitate. Wash it three times with deionized water and absolute ethanol in turn to remove the residual solvent and unreacted substances. Finally, dry it in vacuum at 60 °C for 6 h. Place the dried nanowires in a tube furnace and heat them to 600 °C at a heating rate of 2 °C / min, keep them at this temperature for 1 h in an air atmosphere, and then naturally cool to room temperature.

[0082] The average length of the surface-modified lithium niobate nanowires in this embodiment is 10 μm, and the average diameter is 50 nm.

[0083] The present invention also discloses a preparation method of a transparent film with anti-laser eavesdropping performance, including the following steps:

[0084] S1. First, ultrasonically treat the surface-modified doped tungsten oxide nanosheets, amino-isocyanate bifunctionalized lithium niobate nanowires, polyurethane acrylate, UV-531 ultraviolet absorber, KH-570 silane coupling agent, BYK-9076 dispersant, polyhexamethylene diisocyanate, polydimethylsiloxane defoamer, and polyether-modified polydimethylsiloxane leveling agent at a frequency of 20 kHz for 10 min. Then add them to a high-speed disperser and mix at a stirring rate of 500 rpm for 30 min. Control the mixing temperature at 20 °C. Subsequently, transfer them to a planetary vacuum degassing device and degas at a vacuum degree of -0.08 MPa for 15 min. At the same time, use an auxiliary stirring rate of 50 rpm to prevent sedimentation. After degassing, filter the slurry through a 150-mesh sieve.

[0085] S2. Uniformly coat the filtered slurry on the surface of a clean substrate by the doctor blade method at a coating speed of 0.5 m / min. After coating, place the substrate in a hot air circulation drying oven and heat it to 60 °C at a heating rate of 2 °C / min, keep it warm and dry for 30 min, control the wind speed at 0.3 m / s. Subsequently, transfer it to an ultraviolet curing device and cure it for 30 s under nitrogen protection with a UV irradiation intensity of 80 mW / cm2 and a wavelength of 320 nm.

[0086] S3. Post-treatment and performance regulation: Place the cured film material in a constant temperature and humidity chamber, and let it stand at a temperature of 25 °C and a relative humidity of 50% for 12 h to eliminate internal stress. After post-treatment, a transparent film with anti-laser eavesdropping performance is obtained.

[0087] Comparative Example 1

[0088] It is basically the same as Example 1, except that the dosage of surface-modified doped tungsten oxide nanosheets is 5.0 parts (lower than the lower limit of 6.0 - 12.0 parts in the claims).

[0089] Comparative Example 2

[0090] It is basically the same as Example 1, except that the dosage of amino-isocyanate bifunctionalized lithium niobate nanowires is 9.0 parts (exceeding the upper limit of 4.0 - 8.0 parts in the claims).

[0091] Comparative Example 3

[0092] It is basically the same as Example 1, except that the temperature of the silane coupling reaction of molybdenum-doped tungsten oxide nanosheets is 40 °C (lower than the range of 50 - 70 °C in the claims).

[0093] Comparative Example 4

[0094] It is basically the same as Example 1, except that the hydrothermal reaction time of lithium niobate nanowires is 8 h (lower than the lower limit of 12 - 20 h in the claims).

[0095] Comparative Example 5

[0096] It is basically the same as Example 1, except that the molybdenum doping amount of doped tungsten oxide nanosheets is 2.5 at% (lower than the lower limit of 3 - 8 at% in the claims).

[0097] Comparative Example 6

[0098] It is basically the same as Example 1, except that the UV curing irradiation intensity is 150 mW / cm2 (exceeding the upper limit of 80 - 120 mW / cm 2 in Claim 8).

[0099] Comparative Example 7

[0100] It is basically the same as Example 1, except that the calcination temperature of lithium niobate nanowires is 580 °C (lower than the lower limit of 600 - 650 °C in the claims).

[0101] Comparative Example 8

[0102] It is basically the same as Example 1, except that the catalytic grafting time of isophorone diisocyanate is 4.0 h (exceeding the upper limit of 1.5 - 3.0 h in the claims).

[0103] Comparative Example 9

[0104] It is basically the same as Example 1, except that the vacuum drying time of surface-modified tungsten oxide nanosheets is 4 h (lower than the lower limit of 8 - 16 h in the claims).

[0105] Comparative Example 10

[0106] It is basically the same as Example 1, except that the amount of polyurethane acrylate is 45 parts (lower than the lower limit of 50 - 80 parts in the claims).

[0107] Comparative Example 11

[0108] It is basically the same as Example 1, except that the diameter of the lithium niobate nanowires is 180 nm (exceeding the upper limit of 50 - 150 nm in Claim 7).

[0109] Comparative Example 12

[0110] It is basically the same as Example 1, except that the pressure during hydrothermal synthesis of tungsten oxide is 0.8 MPa (lower than the lower limit of 1.0 - 2.0 MPa in the claims).

[0111] Comparative Example 13

[0112] It is basically the same as Example 1, except that the amount of KH-570 silane coupling agent is 0.3 parts (lower than the lower limit of 0.5 - 3.0 parts in the claims).

[0113] Comparative Example 14

[0114] It is basically the same as Example 1, except that the surface-modified doped tungsten oxide nanosheets are not doped.

[0115] Comparative Example 15

[0116] It is basically the same as Example 1, except that the surface-modified doped tungsten oxide nanosheets are not surface-modified.

[0117] Comparative Example 16

[0118] It is basically the same as Example 1, except that the lithium niobate nanowires are not subjected to amino-isocyanate bifunctionalization treatment.

[0119] Performance Test:

[0120] 1. Laser Scattering Attenuation Rate Test (Verify the Core Function of Anti-Eavesdropping)

[0121] An Nd pulsed laser with a wavelength of 1064 nm (pulse width 10 ns, repetition frequency 10 Hz) was used to build a laser scattering angle distribution test system. The sample was placed in the laser incident path, and an integrating sphere detector was used to measure the scattered light intensity distribution in the range of incident angles from 5° to 85°. The integrated scattering rate (TS%) was calculated and compared with a commercial polyurethane acrylate matrix.

[0122] 2. Dynamic Viscoelastic Spectrum Analysis (Evaluate Mechanical Property Optimization)

[0123] Test was carried out in tensile mode using a dynamic mechanical analyzer (DMA Q800, TA Instruments) according to ASTM D7028-07. The frequency was set at 1 Hz, the temperature range was -30 to 120 °C (heating rate 3 °C / min), and the storage modulus (E'), loss modulus (E") and tanδ curves were measured to verify the deformation recovery ability of the material in a wide temperature range.

[0124] 3. Ultraviolet-visible-near-infrared full-band transmittance / reflection rate test

[0125] Using a PerkinElmer Lambda 1050 spectrometer, the transmittance (T%) and reflectance (R%) in the wavelength range of 250 - 2500 nm were tested according to ASTM E424-71 standard. The transmittance in the visible light region of 500 - 600 nm (target > 85%) and the reflectance in the laser bands of 1064 / 1550 nm (target > 95%) were mainly investigated.

[0126] 4. According to the ASTM D1003-13 standard test method for haze and light transmittance of transparent plastics, the total light transmittance (T T )), parallel light transmittance (T P ) and haze value (Haze%) of the sample in the visible light band (380 - 780 nm) were tested using an integrating sphere haze meter (BYK-Gardner Haze-GardPlus) under the standard light source D65. The sample was cut into a size of 100 mm × 100 mm, ensuring that the surface had no scratches and the thickness was uniform (error ≤ ±2 μm). Before testing, the surface was cleaned with ultrapure water and isopropyl alcohol and dried. Five different positions of each sample were measured and the average value was taken.

[0127] The properties of the transparent films in Examples 1-4 and Comparative Examples 1-16 are summarized in Table 1. It can be seen from Table 1 that the dosage of doped tungsten oxide nanosheets directly affects the laser scattering attenuation rate and reflectivity. Insufficient fillers will lead to a reduction in scattering centers, reducing the laser scattering efficiency and near-infrared reflection ability, but at the same time increasing the visible light transmittance and decreasing the haze. If there are too many fillers, it may lead to agglomeration, causing an increase in light scattering and a decrease in light transmittance. The addition amount of lithium niobate nanowires has a significant impact on the storage modulus and tanδ. An appropriate amount can enhance the mechanical properties of the composite material, while an excessive amount will lead to a decrease in toughness of the material due to poor dispersion, although the modulus increases, and the light transmission performance deteriorates. The molybdenum doping amount determines the plasma resonance effect of the nanosheets. Insufficient doping will severely weaken the reflectivity and scattering ability, affecting the laser protection performance. Interface treatment parameters such as the temperature of the silane coupling reaction, the dosage of the coupling agent, and the grafting time affect the bonding strength between the filler and the matrix. Insufficient temperature or dosage, too long or too short time will all lead to a decrease in the interfacial bonding force, manifested as a decrease in the storage modulus, scattering rate, and reflectivity, and at the same time an increase in tanδ, reflecting an increase in energy loss. The size and morphology of the nanostructures are also crucial. Too large particle size will lead to a decrease in scattering efficiency and poor reflection performance. The crystallization degree of the nanowires depends on the hydrothermal reaction time and the calcination temperature. If the conditions are insufficient, the crystal defects will increase, affecting its strengthening effect and optical properties. Insufficient hydrothermal synthesis pressure will affect the uniformity and crystallinity of the nanosheets, and thus affect the light scattering and reflection ability. The lack of surface modification will lead to agglomeration and poor dispersion of the nano-fillers, and thus cause serious performance degradation, including a decrease in modulus, an increase in tanδ, poor light transmittance, and a significant increase in haze. Failure to perform doping treatment will completely lose the near-infrared reflection ability of the nanosheets, while non-functionalized nanowires cannot achieve effective grafting, resulting in interface failure and affecting the optical, mechanical, and thermal properties. Too high UV curing intensity will lead to too high crosslinking density of the material. Although the modulus increases, the structure becomes brittle, manifested as an increase in tanδ. Insufficient matrix dosage will cause an incomplete network structure, significantly reducing the mechanical strength and overall uniformity, resulting in a decrease in laser scattering and reflection ability, and the light transmittance and haze are also significantly affected. In summary, the optical, mechanical, and thermal properties of the composite material highly depend on the type, content, size, doping, surface modification of the nano-fillers and their interfacial compatibility with the matrix. Any deviation of a single factor may cause a synergistic degradation of the performance.

[0128] Table 1 Summary of the properties of the transparent films in Examples 1-4 and Comparative Examples 1-16

[0129]

[0130]

[0131]

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that any equivalent structural transformation made under the concept of the present invention by using the content of the specification and drawings of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A transparent film with anti-laser eavesdropping performance, characterized in that, It includes raw materials in the following parts by weight: 6.0 - 12.0 parts of surface-modified doped tungsten oxide nanosheets, 4.0 - 8.0 parts of amino-isocyanate bifunctionalized lithium niobate nanowires, 50 - 80 parts of polyurethane acrylate, 2.0 - 4.0 parts of UV-531 ultraviolet absorber, 0.5 - 3 parts of KH-570 silane coupling agent, 1.0 - 3.0 parts of BYK-9076 dispersant, 1 - 3 parts of polyhexamethylene diisocyanate, 0.1 - 1 part of polydimethylsiloxane defoamer, and 0.1 - 0.6 part of polyether-modified polydimethylsiloxane leveling agent; The surface-modified doped tungsten oxide nanosheets are prepared by first preparing molybdenum-doped tungsten oxide nanosheets from nitric acid, sodium tungstate and ammonium heptamolybdate by hydrothermal synthesis method, and then obtaining them through ultrasonic dispersion, silane coupling reaction, centrifugal washing and vacuum drying with 3-aminopropyltriethoxysilane in absolute ethanol; The amino-isocyanate bifunctionalized lithium niobate nanowires are prepared by hydrothermally synthesizing lithium niobate nanowires from lithium carbonate and niobium pentoxide, followed by coupling with 3-aminopropyltriethoxysilane, catalytic grafting with isophorone diisocyanate, capping with phenol and vacuum drying to obtain amino-isocyanate bifunctionalized lithium niobate nanowires.

2. The transparent film with anti-laser eavesdropping performance according to claim 1, characterized in that, The preparation method of the surface-modified doped tungsten oxide nanosheets is as follows: taking 0.3 - 0.8 parts of molybdenum-doped tungsten oxide nanosheet raw materials, 100 - 150 parts of absolute ethanol, and 0.3 - 0.8 parts of 3-aminopropyltriethoxysilane by weight. First, disperse the molybdenum-doped tungsten oxide nanosheet raw materials in absolute ethanol to form a dispersion, and use ultrasonic treatment with an ultrasonic power of 200 - 400W for 10 - 20min to achieve uniform dispersion; then add 3-aminopropyltriethoxysilane to the dispersion, and stir at a constant temperature with a stirring rate of 400 - 800rpm for 3 - 6h under nitrogen protection, controlling the temperature at 50 - 70°C to allow the silane molecules to fully react with the hydroxyl groups on the surface of the nanosheets; then perform solid-liquid separation on the reaction suspension at a centrifugal rate of 10000 - 15000rpm, discard the supernatant containing unreacted reagents and by-products, retain the precipitate and wash it repeatedly with absolute ethanol 2 - 3 times, with each centrifugation time of 5 - 10min to remove residual impurities; finally, place the precipitate in a vacuum drying oven, set the vacuum degree to -0.08 - -0.10MPa and the temperature to 50 - 70°C for drying for 8 - 16h to obtain surface-modified doped tungsten oxide nanosheets.

3. The transparent film with anti-laser eavesdropping performance according to claim 1, characterized in that, The average size of the surface-modified doped tungsten oxide nanosheets is 80 - 150nm, the thickness is 4.0 - 10.0nm, and the molybdenum doping amount is 3 - 8at%.

4. The transparent film with anti-laser eavesdropping performance according to claim 2, characterized in that, The preparation method of the doped tungsten oxide nanosheets is as follows: by weight, 12 - 15 parts by weight of a nitric acid aqueous solution with a concentration of 60 - 70 wt% is mixed with 40 - 50 parts by weight of deionized water, and stirred for 8 - 15 min at a magnetic stirring rate of 300 - 600 rpm to form an acidic medium; 0.8 - 1.2 parts by weight of sodium tungstate dihydrate and 0.05 - 0.15 parts by weight of ammonium heptamolybdate tetrahydrate are jointly dissolved in 18 - 22 parts by weight of deionized water, the dissolution temperature is controlled at 25 - 35 °C, and the solution is added dropwise into the aforementioned acidic medium within 10 - 20 min under a continuous stirring rate of 400 - 800 rpm. After forming a mixed suspension, stirring is continued for 25 - 35 min; the suspension is transferred to a polytetrafluoroethylene-lined autoclave, sealed, heated to 120 - 160 °C at a heating rate of 3 - 5 °C / min, and kept at a constant temperature for 6 - 10.0 h under a pressure of 1.0 - 2.0 MPa to complete the hydrothermal reaction; after the reaction system is naturally cooled to below 40 °C, solid-liquid separation is carried out at a centrifugation rate of 8000 - 12000 rpm. After discarding the supernatant, it is washed 3 - 5 times with deionized water and anhydrous ethanol in turn, the amount of each washing solvent is 20 - 30 times the mass of the solid-phase product, and the centrifugation time for each time is 5 - 10 min; finally, the obtained precipitate is placed in a vacuum drying oven and dried for 10 - 14 h under a vacuum degree of -0.08 - -0.10 MPa and a temperature of 55 - 65 °C to obtain the doped tungsten oxide nanosheets.

5. A transparent film with anti-laser eavesdropping performance according to claim 1, characterized in that, The described amino-isocyanate bifunctionalized lithium niobate nanowires are prepared through the following steps: Dispersing lithium niobate nanowires in a mixed solvent of N,N-dimethylformamide and absolute ethanol at a weight fraction of 1.0 - 5.0%, where the volume fraction of ethanol is 5 - 15% and the total water content in the system is 0.05 - 0.2%. Adding 3-aminopropyltriethoxysilane at a weight fraction of 0.5 - 3.0% and reacting under nitrogen protection at a stirring rate of 500 - 1000 rpm, a temperature of 30 - 50 °C for a reaction time of 4.0 - 8.0 h. After the reaction, separating and retaining the amino-functionalized lithium niobate nanowires by centrifugation at a rate of 10000 - 15000 rpm to remove unreacted silane and by-products. Repeatedly washing 4 - 6 times with anhydrous N,N-dimethylformamide containing 0.5 - 2.0% molecular sieve by weight to remove free silane and residual moisture. Dispersing the washed product in isophorone diisocyanate solution at a weight fraction of 5.0 - 15.0%, adding triphenylbismuth catalyst at a weight fraction of 0.02 - 0.06% and molecular sieve at a weight fraction of 0.1 - 0.5%, and reacting under nitrogen protection at a stirring rate of 600 - 1200 rpm, a temperature of 60 - 80 °C for a reaction time of 1.5 - 3.0 h. After centrifugal separation, retaining the modified product grafted with isocyanate groups and removing unreacted monomers and catalysts. Conducting capping treatment with a molar ratio of phenol to isocyanate groups of 1:0.8 - 1.2 and removing excess phenol. Finally, drying the capped product at a vacuum degree of -0.09 - -0.1 MPa, a temperature of 40 - 60 °C for a drying time of 8 - 12 h to obtain the amino-isocyanate bifunctionalized lithium niobate nanowires.

6. The transparent film with anti-laser eavesdropping performance according to claim 5, characterized in that, The preparation method of the described lithium niobate nanowires is as follows: Mixing lithium carbonate at a weight fraction of 10 - 20 wt% and niobium pentoxide at a weight fraction of 10 - 25 wt%, then adding water at a weight fraction of 50 - 80 wt%. Stirring at 200 - 500 rpm at 40 - 80 °C for 30 - 120 min to form a homogeneous suspension. Subsequently, dropwise adding polyvinylpyrrolidone at a weight fraction of 0.5 - 3 wt% and adjusting the pH value to 8.0 - 11.0 with 0.05 wt% sodium hydroxide solution. Transferring the mixture to a reaction kettle and conducting hydrothermal reaction at 180 - 220 °C for 12 - 20 h. After the reaction, centrifuging at 8000 - 12000 rpm for 5 - 15 min to retain the precipitate, washing 3 - 5 times successively with deionized water and absolute ethanol to remove residual solvents and unreacted substances. Finally, drying in vacuum at 60 - 100 °C for 6 - 12 h. Placing the dried nanowires in a tubular furnace and heating to 600 - 650 °C at a heating rate of 2 - 5 °C / min, keeping warm in an air atmosphere for 1 - 3 h, and then naturally cooling to room temperature.

7. A transparent film with anti-laser eavesdropping performance as claimed in claim 1, characterized in that, The average length of the surface-modified lithium niobate nanowires is 10 - 20 μm, and the average diameter is 50 - 150 nm.

8. The preparation method of a transparent film with anti-laser eavesdropping performance according to claim 1, characterized in that, Comprising the following steps: S1. Ultrasonically treat the surface-modified doped tungsten oxide nanosheets, amino-isocyanate bifunctionalized lithium niobate nanowires, polyurethane acrylate, UV-531 ultraviolet absorber, KH-570 silane coupling agent, BYK-9076 dispersant, polyhexamethylene diisocyanate, polydimethylsiloxane defoamer and polyether-modified polydimethylsiloxane leveling agent at a frequency of 20 - 40 kHz for a treatment time of 10 - 20 min. Then add them to a high-speed disperser and mix at a stirring rate of 500 - 800 rpm for 30 - 45 min. Control the mixing temperature at 20 - 25 °C. Subsequently, transfer them to a planetary vacuum degassing device and degas for 15 - 30 min under a vacuum degree of -0.08 - -0.1 MPa. At the same time, prevent sedimentation with an auxiliary stirring rate of 50 - 100 rpm. After degassing, filter the slurry through a 150 - 200 mesh sieve; S2. The filtered slurry is evenly coated on the surface of a clean substrate by the doctor blade method at a coating speed of 0.5 - 1.5 m / min. After coating, the substrate is placed in a hot air circulation drying oven and heated to 60 - 80 °C at a heating rate of 2 - 5 °C / min, dried for 30 - 60 min with the wind speed controlled at 0.3 - 0.8 m / s. Subsequently, it is transferred to an ultraviolet curing device and cured for 30 - 90 s under nitrogen protection with a UV irradiation intensity of 80 - 120 mW / cm 2 , a wavelength of 320 - 400 nm; S3. Post-treatment and performance regulation: Place the cured film material in a constant temperature and humidity chamber and let it stand at a temperature of 25 - 30 °C and a relative humidity of 50% - 70% for 12 - 24 h to eliminate internal stress. After post-treatment, a transparent film with anti-laser eavesdropping performance is obtained.

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