Multifunctional composite variable light film and preparation method thereof

Abstract

The invention belongs to the technical field of variable optical films, discloses a multifunctional composite variable optical film and a preparation method thereof, and aims at solving the problems that an existing variable optical film is single in function, unstable in optical performance, poor in flexibility and bending resistance and low in process precision. The preparation method comprises the following steps: pre-treating the base material: sequentially carrying out plasma cleaning on the PET base material and sputtering the ITO conductive layer, sequentially carrying out ultrasonic cleaning on the glass substrate and preparing the YAG powder enhancement layer; the coating of the functional layer is that the surface of the ITO layer of the PET-ITO composite base material is coated with a PDLC layer and an electrochromic layer, and the surface of the YAG layer of the YAG-glass composite base material is coated with a temperature-sensitive layer; the compounding and curing are as follows: firstly laminating after aligning and compounding, and then carrying out UV segmented curing. The light transmittance of the product can be adjusted by 5-95% in an electric field, and the infrared reflectivity is gt; and after the ITO layer is bent for 1000 times and the bending radius is 5mm, the resistance change rate is less than or equal to 10%, so that the ITO film is suitable for a sunshade film for a vehicle and an intelligent window of a building.

Description

Technical Field

[0001] This invention relates to the field of variable light film technology, specifically to a multifunctional composite variable light film that combines active dimming, automatic temperature-sensitive control, and high flexibility, and its preparation method. It is particularly suitable for scenarios with high requirements for optical performance and environmental adaptability, such as automotive smart sunshade films and building smart glass windows. Background Technology

[0002] With the development of intelligent transportation and green building industries, variable light films, due to their ability to dynamically adjust light transmittance, have become a core material for improving user experience and energy efficiency. However, existing variable light film technology still has the following core shortcomings, making it difficult to meet the needs of multi-scenario applications:

[0003] 1. Limited functionality and lack of synergy: Most products rely solely on polymer dispersed liquid crystal (PDLC) layers to achieve electric field dimming (transmittance adjustment), and cannot respond to ambient temperature to automatically control infrared blocking. They require additional heat insulation films, which increases film thickness, costs, and interlayer compatibility.

[0004] 2. Unstable optical performance: The PDLC layer is prone to large fluctuations in refractive index (n value) in the visible light region (±0.05) due to liquid crystal aggregation. The off-state extinction coefficient (k value) is highly wavelength dependent (k=0.3 at 400nm and k=0.1 at 700nm), resulting in poor uniformity of light blocking. The on-state k value is relatively high (>0.05), resulting in more visible light absorption and difficulty in achieving a transmittance of over 90%.

[0005] 3. Poor flexibility and bending resistance: Indium tin oxide (ITO) conductive layer is a brittle material. ITO layers prepared by traditional processes are prone to cracking after bending (radius <10mm), and the sheet resistance change rate is >30%, which cannot be adapted to flexible scenarios such as curved glass in automobiles.

[0006] 4. Low process precision and poor consistency: PDLC layers are mostly coated with a doctor blade, and the size deviation of liquid crystal droplets is >15%, which leads to fluctuations in optical performance between batches; ultraviolet (UV) curing is mostly single-stage control, which can easily cause liquid crystal prepolymerization and affect the dimming response speed.

[0007] Therefore, developing a multifunctional composite variable light film that combines functional coupling, material synergy, and precise processing has become a key requirement for addressing the pain points of existing technologies. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing variable light films, such as single function, unstable optical performance, poor flexibility, and low process precision, and to provide a multifunctional composite variable light film and its preparation method that features: ① active light modulation via electric field (5%~95% transmittance) + automatic temperature control with temperature sensitivity (>70% infrared blocking); ② stable optical performance (on-state n≈1.5, k≤0.02, off-state k stable≈0.8); ③ ITO layer bending resistance (sheet resistance change ≤10% after 1000 bends); ④ high process precision (liquid crystal droplet deviation <8%).

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] A method for preparing a multifunctional composite variable light film, comprising:

[0011] S1: Substrate pretreatment; the PET substrate is sequentially subjected to plasma cleaning and indium tin oxide (ITO) conductive layer sputtering to obtain PET-ITO composite substrate; the glass substrate is sequentially subjected to ultrasonic cleaning and yttrium aluminum garnet (YAG) powder reinforcement layer preparation to obtain YAG-glass composite substrate;

[0012] S2: Functional layer coating; On the surface of the ITO conductive layer of the PET-ITO composite substrate, a polymer dispersed liquid crystal (PDLC) layer and an electrochromic layer are sequentially coated; On the surface of the YAG powder reinforcement layer of the YAG-glass composite substrate, a temperature-sensitive layer is coated to obtain a substrate containing a functional layer.

[0013] S3: Composite and curing; Align and composite a PET-ITO composite substrate coated with a PDLC layer and an electrochromic layer with a YAG-glass composite substrate coated with a thermosensitive layer. First, perform lamination, and then perform UV segmented curing to obtain a multifunctional composite variable light film.

[0014] According to a specific embodiment, in step S1 of the multifunctional composite variable light film preparation method provided by the present invention, the plasma cleaning uses argon (Ar) gas, the cleaning power is 80W~120W, and the cleaning time is 1min~3min; the ITO sputtering power is 2.5kW~3.5kW, the substrate temperature is 70℃~90℃, and the oxygen-argon volume ratio is 1:18~1:22.

[0015] According to a specific embodiment, in step S1 of the multifunctional composite variable light film preparation method provided by the present invention, the ultrasonic cleaning uses a mixture of ethanol and acetone (volume ratio 1:1) for 15 min to 25 min; the YAG powder reinforcement layer is prepared by spraying a YAG dispersion, the solid content of the YAG dispersion is 8 wt% to 12 wt%, and the drying temperature after spraying is 110℃ to 130℃; the particle size of the YAG powder is 0.3 μm to 1.2 μm, and the doping amount in the reinforcement layer is 1.2 wt% to 1.8 wt%.

[0016] According to a specific embodiment, in step S2 of the multifunctional composite variable light film preparation method provided by the present invention, the coating process of the PDLC layer is microgravure coating with a screen ruling of 180 LPI to 220 LPI and a coating speed of 1.2 m / min to 1.8 m / min; the PDLC layer contains nematic liquid crystal and acrylic resin matrix, the mass ratio of the nematic liquid crystal is 25% to 30%, and vanadium dioxide@silicon dioxide (VO2@SiO2) core-shell particles are added, the particle size of the VO2@SiO2 core-shell particles is 180 nm to 220 nm.

[0017] According to a specific embodiment, in step S2 of the multifunctional composite variable light film preparation method provided by the present invention, the coating process of the electrochromic layer is slit extrusion coating, the slit width is 80μm~120μm, and the coating pressure is 0.15MPa~0.25MPa; the electrochromic layer includes a tungsten trioxide / nickel oxide (WO3 / NiO) composite oxide and an ion conductor layer, the thickness of the WO3 / NiO composite oxide is 70nm~90nm, and the ion conductor layer is a lithium perchlorate-propylene carbonate (LiClO4-PC) electrolyte.

[0018] According to a specific embodiment, in step S2 of the multifunctional composite variable light film preparation method provided by the present invention, the coating process of the temperature-sensitive layer is spin coating, the spin coating speed is 1800rpm~2200rpm, and the spin coating time is 25s~35s; the temperature-sensitive layer is a copolymer containing azophenyl groups, the thickness is 18μm~22μm, and the phase transition temperature is 28℃~32℃.

[0019] According to a specific embodiment, in step S3 of the multifunctional composite variable light film preparation method provided by the present invention, the lamination temperature is 55℃~65℃; the UV segmented curing includes pre-curing and main curing: pre-curing is carried out in a nitrogen atmosphere, with an irradiation wavelength of 360nm~370nm, an irradiance of 45mW / cm²~55mW / cm², and a curing time of 8s~12s; the main curing has an irradiation wavelength of 390nm~400nm, an irradiance of 90mW / cm²~110mW / cm², a curing time of 25s~35s, and a photoinitiator dosage of 0.4wt%~0.6wt%.

[0020] According to a specific embodiment, in the multifunctional composite variable light film preparation method provided by the present invention, a silver nanowire mesh is further deposited on the surface of the ITO conductive layer, wherein the linewidth of the silver nanowire is ≤5μm; the sheet resistance of the ITO conductive layer is ≤50Ω / □, and the thickness is 140nm~160nm.

[0021] This invention also provides a multifunctional composite variable light film, which is prepared by the multifunctional composite variable light film preparation method provided by this invention; the variable light film has a sandwich composite structure, comprising, from the outside to the inside:

[0022] Outer layer: PET substrate and ITO conductive layer, wherein the ITO conductive layer is disposed on the inner side of the PET substrate;

[0023] Functional layer: a PDLC layer, an electrochromic layer and a thermosensitive layer are sequentially laminated, wherein the PDLC layer is bonded to the ITO conductive layer and the thermosensitive layer is bonded to the inner layer;

[0024] Inner layer: YAG powder reinforcement layer and glass substrate, wherein the YAG powder reinforcement layer is disposed on the outer side of the glass substrate and is bonded to the temperature-sensitive layer.

[0025] According to a specific embodiment, the variable light film provided by the present invention has the following optical properties: in the visible light region of 400nm~760nm, the n value in the on state (under saturation voltage) is 1.48~1.52 and the k value is ≤0.02, and the k value in the off state (under 0V) is 0.78~0.82; the transmittance adjustment range is 5%~95%, and the infrared reflectance is >70%; the sheet resistance of the ITO conductive layer is ≤50Ω / □, and the thickness is 140nm~160nm.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The multifunctional composite variable light film preparation method provided by this invention achieves integrated "lighting + heat insulation" functions without the need for additional heat insulation film by using the following technical means: "PDLC layer + electrochromic layer electric field active light modulation (5%~95% transmittance) + temperature passive temperature control of temperature-sensitive layer (azobenzene copolymer, phase change at 28~32℃) + infrared blocking synergy of VO2@SiO2 core-shell particles (180~220nm)". When applied to automotive scenarios, the temperature inside the car can be reduced by 5℃~8℃ in summer, reducing air conditioning energy consumption; when applied to building scenarios, heating / cooling energy consumption is reduced by 30%, adapting to the needs of multiple scenarios.

[0028] 2. The multifunctional composite variable light film preparation method provided by this invention relies on the following technical means: "micro-gravure coating (180~220 LPI) to control the uniformity of liquid crystal droplets in the PDLC layer (deviation <8%), matching design of the refractive index (n≈1.5) of the ITO layer and the substrate, and UV segmented curing (pre-curing 360~370 nm + main curing 390~400 nm) to avoid liquid crystal pre-polymerization". This enables the product to achieve the following in the 400~760 nm visible light region: the on-state n value is stable at 1.48~1.52, the k value is ≤0.02, the visible light absorption is reduced by more than 60%, and the light transmittance reaches 92%~97%; the off-state k value is stable at 0.78~0.82, the full-band fluctuation is ≤0.04, and the light-shielding uniformity is improved to more than 97%, thus solving the defect of large fluctuation in the optical performance of traditional products.

[0029] 3. The multifunctional composite variable light film preparation method provided by the present invention adopts the technical means of "depositing silver nanowire mesh (line width ≤ 5μm) on the surface of ITO conductive layer (140~160nm) + plasma cleaning of PET substrate (80~120W, 1~3min) to improve interlayer bonding". After 1000 bending tests (bending radius 5mm), the sheet resistance change rate of ITO layer is ≤10%, which is more than 20 percentage points higher than the traditional silver-free nanowire structure (sheet resistance change rate >30%). It can be adapted to flexible construction scenarios such as automotive curved glass (windshield, side window).

[0030] 4. The multifunctional composite variable light film preparation method provided by this invention achieves thickness deviation of each film layer ≤5%, improves the consistency of liquid crystal microdroplet size, and reduces batch-to-batch optical performance fluctuation ≤5% through the technical means of “differentiated coating process adapted to the characteristics of each functional layer (PDLC layer microgravure, electrochromic layer slit extrusion, and thermosensitive layer spin coating) + range-based control of key parameters (such as ITO sputtering power 2.5~3.5kW, YAG doping amount 1.2~1.8wt%)”. Moreover, the equipment used is conventional equipment in the field of variable light films, without special customization, and can be directly connected to industrial continuous production.

[0031] 5. The multifunctional composite variable light film preparation method provided by this invention utilizes the technical means of "YAG powder reinforcement layer (0.3~1.2μm) to improve the hardness of the glass side, VO2@SiO2 core-shell particles to inhibit liquid crystal aging, and PE film edge sealing for moisture prevention". After 5000h weather resistance test (high and low temperature cycle, humid and hot environment), the light transmittance of the product decreases by <3%, which is more than 5 percentage points higher than the traditional YAG / VO2 structure (light transmittance decrease >8%). The service life is extended to more than 8 years, reducing the later maintenance cost. Detailed Implementation

[0032] The technical solution of the present invention will be described in detail below with reference to specific experimental examples. The raw materials used in the experimental examples are all commercially available conventional products (PET substrate: thickness 100μm, light transmittance 92%; ITO target: purity 99.99%; YAG powder: particle size 0.5μm~1μm; VO2@SiO2 core-shell particles: particle size 200nm; azobenzene copolymer: phase transition temperature 30℃). The equipment used is conventional equipment in the field of variable light film (plasma cleaner, magnetron sputtering instrument, microgravure coating machine, etc.).

[0033] Experimental Example 1

[0034] Step S1: Substrate Pretreatment

[0035] PET substrate: Argon (Ar) plasma cleaning (100W, 2min) → ITO sputtering (power 3kW, substrate temperature 80℃, oxygen-argon ratio 1:20, thickness 150nm) → deposition of silver nanowire mesh (linewidth 4μm) to obtain PET-ITO composite substrate (sheet resistance 45Ω / □).

[0036] Glass substrate: ethanol / acetone mixture (1:1) ultrasonic cleaning (20 min) → spraying YAG dispersion (solid content 10 wt%, YAG doping amount 1.5 wt%) → drying at 120℃ for 30 min to obtain YAG-glass composite substrate.

[0037] Step S2: Functional layer coating

[0038] PDLC layer: microgravure coating (200 LPI screen ruling, coating speed 1.5 m / min), PDLC slurry contains 28% nematic liquid crystal + 72% acrylic resin + 0.5 wt% VO2@SiO2, thickness 50 μm;

[0039] Electrochromic layer: slit extrusion coating (slit width 100μm, pressure 0.2MPa), WO3 / NiO composite oxide thickness 80nm, LiClO4-PC electrolyte coating thickness 20μm;

[0040] Thermosensitive layer: spin-coated (2000 rpm, 30 s) azobenzene copolymer, 20 μm thick.

[0041] Step S3: Lamination and Curing

[0042] Lamination: 60℃, pressure 0.3MPa, time 10s;

[0043] UV curing: Pre-curing (nitrogen atmosphere, 365nm, 50mW / cm², 10s) → Main curing (395nm, 100mW / cm², 30s, photoinitiator 0.5wt%), to obtain the variable light film.

[0044] Experimental Example 2

[0045] Step S1: Substrate Pretreatment

[0046] PET: Argon (Ar) plasma cleaning (80W, 1min) → ITO sputtering (2.5kW, 70℃, oxygen-argon ratio 1:18, thickness 140nm) → silver nanowires (linewidth 5μm), sheet resistance 50Ω / □;

[0047] Glass: ethanol / acetone mixture (1:1) ultrasonic cleaning (15 min) → spraying YAG dispersion (solid content 8 wt%, YAG doping 1.2 wt%) → drying at 110℃ for 30 min.

[0048] Step S2: Functional layer coating

[0049] PDLC: microgravure coating (180 LPI, coating speed 1.2 m / min), PDLC slurry contains 25% nematic liquid crystal + 75% acrylic resin + 0.3 wt% VO2@SiO2, thickness 48 μm;

[0050] Electrochromic layer: slit extrusion coating (slit width 80μm, pressure 0.15MPa), WO3 / NiO composite oxide thickness 70nm, LiClO4-PC electrolyte coating thickness 18μm;

[0051] Thermosensitive layer: spin-coated (1800 rpm, 25 s) azobenzene copolymer, 18 μm thick.

[0052] Step S3: Lamination and Curing

[0053] Lamination: 55℃, pressure 0.2MPa, time 8s;

[0054] UV curing: Pre-curing (nitrogen atmosphere, 360nm, 45mW / cm², 8s) → Main curing (390nm, 90mW / cm², 25s, photoinitiator 0.4wt%).

[0055] Experimental Example 3

[0056] Step S1: Substrate Pretreatment

[0057] PET: Argon (Ar) plasma cleaning (120W, 3min) → ITO sputtering (3.5kW, 90℃, oxygen-argon ratio 1:22, thickness 160nm) → silver nanowires (linewidth 3μm), sheet resistance 40Ω / □;

[0058] Glass: ethanol / acetone mixture (1:1) ultrasonic cleaning (25 min) → spraying YAG dispersion (solid content 12 wt%, YAG doping 1.8 wt%) → drying at 130℃ for 30 min.

[0059] Step S2: Functional layer coating

[0060] PDLC: microgravure coating (220 LPI, coating speed 1.8 m / min), PDLC slurry contains 30% nematic liquid crystal + 70% acrylic resin + 0.7 wt% VO2@SiO2, thickness 52 μm;

[0061] Electrochromic layer: slit extrusion coating (slit width 120μm, pressure 0.25MPa), WO3 / NiO composite oxide thickness 90nm, LiClO4-PC electrolyte coating thickness 22μm;

[0062] Thermosensitive layer: spin-coated (2200 rpm, 35 s) azobenzene copolymer, 22 μm thick.

[0063] Step S3: Lamination and Curing

[0064] Lamination: 65℃, pressure 0.4MPa, time 12s;

[0065] UV curing: Pre-curing (nitrogen atmosphere, 370nm, 55mW / cm², 12s) → Main curing (400nm, 110mW / cm², 35s, photoinitiator 0.6wt%).

[0066] control group

[0067] The traditional PDLC variable light film is used: PET-ITO substrate (no silver nanowires) + pure PDLC layer (no VO2@SiO2) + glass substrate (no YAG layer). The preparation process is blade coating + single-stage UV curing (365nm, 80mW / cm², 40s).

[0068] Performance Testing and Result Analysis

[0069] To verify the advantages of the product of this invention, optical performance (n-value, k-value), light-tuning performance (transmittance range), flexibility (bending resistance), and heat insulation performance (infrared reflectance) were tested on Experimental Examples 1-3 and the control group. The test methods conformed to the conventional standards in the field of variable light films. The specific results are as follows:

[0070] I. Optical Performance Testing (Elliptic Polarization Spectroscopy)

[0071] Test standard: GB / T30706-2014 "Method for Determination of Refractive Index and Thickness of Thin Films for Liquid Crystal Display Devices - Elliptic Polarization Method";

[0072] Test environment: constant temperature and humidity laboratory (25±1℃, 50±5%RH), no direct sunlight;

[0073] Test instrument: Ellipsometry (accuracy ±0.001 (n), ±0.0001 (k));

[0074] Test conditions: wavelength 400nm~760nm, incident angle 70°, on state (saturation voltage 50V), off state (0V), 3 regions for each sample, 3 measurements for each region and average value.

[0075] Test results are shown in Tables 1 and 2 below.

[0076] Table 1 Optical performance test data in the on-state (50V)

[0077] Table 2 Optical performance test data in the off-state (0V)

[0078] Note: Light shading uniformity = (minimum transmittance / maximum transmittance) × 100%. The higher the value, the more uniform the light shading.

[0079] Table 3 Comparison of optical performance differences (Δn, Δk) in the switching state

[0080] Note: Contrast improvement rate = (Experimental group Δk - Control group Δk) / Control group Δk × 100%.

[0081] Results analysis:

[0082] 1. In the open state, the n value (1.48~1.53) of Experimental Examples 1-3 is closer to that of ITO / glass substrate (n≈1.5), and the reflectivity is reduced by 30%~40% compared with the control group; the k value (≤0.02) is much lower than that of the control group (0.048~0.052), the visible light absorption is reduced by more than 60%, and the light transmittance reaches 92%~97%;

[0083] 2. In the off state, the k values ​​of Experimental Examples 1-3 (0.78~0.82) were significantly higher than those of the control group (0.18~0.32), and the fluctuation across the entire visible light region was ≤0.04, the uniformity of shading reached over 97%, and the transmittance was as low as 3%~7%.

[0084] 3. The on / off state Δk reaches 0.778~0.792, which is 195%~305% higher than the control group (0.192~0.268), showing a significant contrast advantage and meeting the core requirements of "high transmittance in the on state and high shading in the off state".

[0085] II. Flexible bending resistance test (bending radius 5mm)

[0086] Test basis: GB / T2423.10-2019 Environmental testing - Part 2: Test methods - Test Fc: Vibration (sine) (bending test adaptation method);

[0087] Test environment: room temperature 25±2℃, relative humidity 50±5%;

[0088] Testing instruments: Electric bending tester (bending angle accuracy ±1°, bending speed 10 times / min), four-probe sheet resistance tester (accuracy ±1%).

[0089] Test conditions: bending angle 180°, bending times 1000 times, sheet resistance recorded every 200 times, and 3 parallel samples (50mm×100mm) prepared for each sample.

[0090] Test results are shown in Table 4 below.

[0091] Table 4. Flexible bending resistance test data

[0092] Note: Sheet resistance change rate = (Sheet resistance after 1000 bends - Initial sheet resistance) / Initial sheet resistance × 100%, a negative value indicates a decrease in sheet resistance.

[0093] Results analysis: In the control group, the sheet resistance continued to increase during bending, with an average change rate of 35.0±0.2% after 1000 bends, indicating that the conductivity of the ITO layer decreased significantly due to brittle cracking. In contrast, in Experiments 1-3, the silver nanowire mesh (3~5μm linewidth) was deposited on the surface of the ITO layer. The flexibility of the silver nanowires could buffer the bending stress, and the average sheet resistance change rate after 1000 bends was only 1.8%~5.0%, all ≤10%. Moreover, the sheet resistance increased slowly during bending, proving that the flexibility and structural stability of the composite conductive layer were significantly better than those of the traditional ITO layer.

[0094] III. Infrared blocking performance test (near-infrared region: 780nm~2500nm)

[0095] Test standard: GB / T2680-2021 "Determination of visible light transmittance, direct solar transmittance, total solar transmittance, ultraviolet transmittance and related window glass parameters of architectural glass";

[0096] Test environment: room temperature 23±1℃, relative humidity 50±3%;

[0097] Test instrument: Fourier transform infrared spectrometer (resolution 4cm⁻¹, scanning range 780nm~2500nm);

[0098] Test conditions: Five test points were taken for each sample (avoiding the edge by 10 mm), and the infrared reflectance at different wavelengths was measured and the average reflectance was calculated;

[0099] Test results are shown in Table 5 below.

[0100] Table 5 Infrared blocking performance test data

[0101] Note: Average reflectance = (reflectance of 780 nm + 1200 nm + 1500 nm + 2000 nm + 2500 nm) / 5.

[0102] Results analysis:

[0103] 1. The control group, lacking a thermosensitive layer and VO2@SiO2 core-shell particles, had an average infrared reflectance of only 44.3±0.1%, which could not effectively block near-infrared heat.

[0104] 2. Experiments 1-3 achieved an average infrared reflectivity of 71.2%~73.7%, all >70%, through the synergistic effect of "infrared reflection regulation of the thermosensitive layer (azobenzene copolymer, phase transition at 28~32℃) + selective infrared blocking of VO2@SiO2 core-shell particles (200nm)". The reflectivity was highest at 1500nm (near-infrared core heating band) (72.3%~75.0%), which specifically improved the heat insulation effect and verified the effectiveness of the functional layer synergistic design.

[0105] The scope of protection of this invention is not limited to the above experimental examples. Any solution that is implemented by adjusting the following technical features based on the core steps of the preparation method of this invention (substrate pretreatment - functional layer coating - composite curing) is within the scope of protection of this invention.

Claims

1. A method for preparing a multifunctional composite variable light film, characterized in that, Includes the following steps: S1: Substrate pretreatment; the PET substrate is subjected to plasma cleaning and ITO conductive layer sputtering in sequence to obtain PET-ITO composite substrate; the glass substrate is subjected to ultrasonic cleaning and YAG powder reinforcement layer preparation in sequence to obtain YAG-glass composite substrate. S2: Functional layer coating; On the surface of the ITO conductive layer of the PET-ITO composite substrate, a PDLC layer and an electrochromic layer are coated in sequence; On the surface of the YAG powder reinforcement layer of the YAG-glass composite substrate, a temperature-sensitive layer is coated to obtain a substrate containing a functional layer. S3: Composite and curing; Align and laminate a PET-ITO composite substrate coated with a PDLC layer and an electrochromic layer with a YAG-glass composite substrate coated with a thermosensitive layer. First, perform lamination, and then perform UV segmented curing to obtain a multifunctional composite variable light film.

2. The preparation method according to claim 1, characterized in that, In step S1, the plasma cleaning uses argon gas, with a cleaning power of 80W~120W and a cleaning time of 1min~3min; the ITO sputtering power is 2.5kW~3.5kW, the substrate temperature is 70℃~90℃, and the oxygen-argon volume ratio is 1:18~1:

22.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the ultrasonic cleaning uses a mixture of ethanol and acetone in a volume ratio of 1:1, and the cleaning time is 15 min to 25 min. The YAG powder reinforcement layer is prepared by spraying a YAG dispersion, the solid content of which is 8 wt% to 12 wt%, and the drying temperature after spraying is 110℃ to 130℃. The particle size of the YAG powder is 0.3 μm to 1.2 μm, and the doping amount in the reinforcement layer is 1.2 wt% to 1.8 wt%.

4. The preparation method according to claim 1, characterized in that, In step S2, the coating process of the PDLC layer is microgravure coating with a screen ruling of 180 LPI to 220 LPI and a coating speed of 1.2 m / min to 1.8 m / min. The PDLC layer contains nematic liquid crystal and acrylic resin matrix, with the nematic liquid crystal accounting for 25% to 30% by mass, and VO2@SiO2 core-shell particles are added, with a particle size of 180 nm to 220 nm.

5. The preparation method according to claim 1, characterized in that, In step S2, the electrochromic layer is coated by slot extrusion coating, with a slot width of 80μm~120μm and a coating pressure of 0.15MPa~0.25MPa. The electrochromic layer comprises a WO3 / NiO composite oxide and an ion conductor layer. The thickness of the WO3 / NiO composite oxide is 70nm~90nm, and the ion conductor layer is a LiClO4-PC electrolyte.

6. The preparation method according to claim 1, characterized in that, In step S2, the coating process of the temperature-sensitive layer is spin coating, with a spin coating speed of 1800 rpm to 2200 rpm and a spin coating time of 25 s to 35 s; the temperature-sensitive layer is a copolymer containing azophenyl groups, with a thickness of 18 μm to 22 μm and a phase transition temperature of 28℃ to 32℃.

7. The preparation method according to claim 1, characterized in that, In step S3, the lamination temperature is 55℃~65℃; the UV segmented curing includes pre-curing and main curing: pre-curing is carried out in a nitrogen atmosphere, with an irradiation wavelength of 360nm~370nm, an irradiance of 45mW / cm²~55mW / cm², and a curing time of 8s~12s; the main curing has an irradiation wavelength of 390nm~400nm, an irradiance of 90mW / cm²~110mW / cm², a curing time of 25s~35s, and a photoinitiator dosage of 0.4wt%~0.6wt%.

8. The preparation method according to claim 1, characterized in that, The surface of the ITO conductive layer is also deposited with a silver nanowire mesh, the linewidth of the silver nanowires being ≤5μm; the sheet resistance of the ITO conductive layer is ≤50Ω / □, and the thickness is 140nm~160nm.

9. A multifunctional composite variable light film, characterized in that, The variable light film is prepared by the method described in claim 1; the variable light film has a sandwich composite structure, comprising, from the outside to the inside: Outer layer: PET substrate and ITO conductive layer, wherein the ITO conductive layer is disposed on the inner side of the PET substrate; Functional layer: a PDLC layer, an electrochromic layer and a thermosensitive layer are sequentially laminated, wherein the PDLC layer is bonded to the ITO conductive layer and the thermosensitive layer is bonded to the inner layer; Inner layer: YAG powder reinforcement layer and glass substrate, wherein the YAG powder reinforcement layer is disposed on the outer side of the glass substrate and is bonded to the temperature-sensitive layer.

10. The variable light film according to claim 9, characterized in that, The optical performance of the variable light film meets the following requirements: in the visible light region of 400nm~760nm, the on-state n value is 1.48~1.52, the k value is ≤0.02, and the off-state k value is 0.78~0.82; the transmittance adjustment range is 5%~95%, and the infrared reflectance is >70%; the sheet resistance of the ITO conductive layer is ≤50Ω / □, and the thickness is 140nm~160nm.

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