Low-stray-light high-transmittance PDLC dimming film and preparation process thereof

Abstract

The application discloses a low-stray-light high-transmittance PDLC dimming film and a preparation process thereof, and belongs to the technical field of dimming films, and aims to solve the problems of stray light, insufficient transmittance and poor stability of an additional functional layer of an interface of an existing PDLC dimming film. The application adopts fluorine-containing diphenyl glycidyl ether to covalently graft and modify a PEDOT:PSS conductive layer, and through gradient fluorine-containing monomer matching, a corresponding PDLC functional layer system is matched, and the synergistic effect of simultaneous realization of refractive index regulation, interface orientation induction and conductive performance optimization in a single conductive layer is realized. According to the scheme, the open-state haze can be effectively reduced, the transmittance and contrast can be improved, the driving voltage can be reduced, the electro-optic response speed can be accelerated, the film layer stability is excellent, the preparation process is compatible with an existing mass production process, and the scheme has good industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of dimming film technology, and in particular to a low stray light, high transmittance PDLC dimming film and its preparation process. Background Technology

[0002] Polymer-dispersed liquid crystal (PDLC) dimming films, as an electro-optical switching device, utilize an electric field to control the orientation and alignment of liquid crystal droplets to achieve reversible switching between transparent and scattering states. With advantages such as simple fabrication processes, low driving power consumption, and flexibility, they show broad application prospects in fields such as smart windows and doors, automotive sunroofs, privacy glass, and display devices. However, existing PDLC dimming films still face many performance bottlenecks in practical applications. On the one hand, traditional PDLC dimming films generally suffer from high driving voltage, slow response speed, and insufficient optical clarity. More importantly, the problem of high haze in the transparent state of PDLC dimming films has long remained unresolved. Especially under oblique viewing angles, due to the severe mismatch between the effective refractive index of the liquid crystal and the refractive index of the polymer matrix at large incident angles, PDLC dimming films still exhibit significant side-view haze in the electrically transparent state, severely affecting the user's visual experience. This has become one of the key factors restricting the widespread application of PDLC dimming films in scenarios with stringent optical quality requirements, such as automotive sunroofs and high-end building curtain walls.

[0003] On the other hand, transparent electrodes are one of the core components of PDLC dimming films. While indium tin oxide (ITO), the mainstream transparent electrode material, possesses excellent optoelectronic properties, its brittle nature limits the bending requirements of flexible devices, and indium resources are scarce and manufacturing costs are high. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), as a conductive polymer material, is considered one of the most promising ITO alternatives due to its good solution processability, excellent flexibility, and high transmittance in the visible light region. Studies have shown that PDLC devices based on PEDOT:PSS electrodes have achieved electro-optical performance comparable to ITO devices. However, the refractive index of PEDOT:PSS films is approximately 1.52, a relatively fixed value, while the effective refractive index varies among different PDLC systems due to differences in liquid crystal types and polymer matrices. When the refractive index of the PEDOT:PSS electrode differs from the effective refractive index of the PDLC functional layer, light undergoes Fresnel reflection at the electrode / PDLC interface, producing unexpected interface scattering. This scattered light is superimposed on the existing scattering in the PDLC layer itself, further deteriorating the optical quality of the dimming film in the transparent state. In other words, although existing PEDOT:PSS electrodes have solved the brittleness and cost problems of ITO, their refractive index lacks active control mechanisms, making it difficult to achieve precise optical matching with different PDLC systems.

[0004] How to endow PEDOT:PSS electrodes with new functions such as adjustable refractive index while maintaining their advantages in conductivity and flexibility, and achieve synergistic optimization of the electrode and PDLC layer at the optical level, while avoiding the addition of additional functional layers and process complexity, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a low stray light, high transmittance PDLC dimming film and its preparation process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a low stray light and high transmittance PDLC dimming film, comprising two flexible transparent substrate layers disposed opposite to each other, a modified PEDOT:PSS conductive layer disposed on the inner side of the substrate, and a PDLC functional layer sandwiched between the two modified PEDOT:PSS conductive layers.

[0007] Preferably, the flexible transparent substrate layer is optical-grade biaxially stretched PET with a thickness of 50-125μm and a visible light transmittance of ≥91%.

[0008] Preferably, the modified PEDOT:PSS conductive layer is PEDOT:PSS grafted with fluorinated biphenyl glycidyl ether, with a refractive index of 1.480-1.525, a total thickness of 20-60 nm, and a sheet resistance ≤80 Ω / □.

[0009] Preferably, the fluorinated biphenyl glycidyl ether has the following general chemical formula: ;where R1, R 2、 R3 is selected from any of the following combinations: R1 is selected from -H, R2 is selected from -F, and R3 is selected from -H; R1 is selected from -F, R2 is selected from -F, and R3 is selected from -H; R1 is selected from -H, R2 is selected from -CF3, and R3 is selected from -H; R1 is selected from -H, R2 is selected from -OCF3, and R3 is selected from -H; R1 is selected from -CF3, R2 is selected from -H, and R3 is selected from -CF3.

[0010] Preferably, the method for preparing the fluorinated biphenyl glycidyl ether includes the following steps: Fluorinated biphenyl phenol, epichlorohydrin, and a phase transfer catalyst were added to a reactor. Under nitrogen protection, the mixture was stirred and heated to 70-100°C and maintained at this temperature for 3-10 hours. After the reaction, excess epichlorohydrin was recovered by vacuum distillation. Toluene was added, followed by solid sodium hydroxide in 2-3 portions. The temperature was raised to the reflux temperature of toluene. Water generated during the reaction was separated using a water separator. The reaction was continued for 5-8 hours. After cooling to room temperature, the mixture was washed 2-3 times with deionized water. The layers were allowed to separate, and the upper organic phase was collected. After drying with anhydrous sodium sulfate, the phase was filtered, and the solvent was removed by vacuum distillation to obtain a concentrated crude product. After purification, fluorinated biphenyl glycidyl ether was obtained. The chemical reaction equation is as follows: .

[0011] Preferably, in the preparation method of the fluorinated biphenyl glycidyl ether, the fluorinated biphenyl is selected from one of 4-fluoro-4'-hydroxybiphenyl, 3',4'-difluoro-[1,1'-biphenyl]-4-ol, 4'-trifluoromethylbiphenyl-4-ol, 4-(4-trifluoromethoxyphenyl)phenol or 3',5'-bis(trifluoromethyl)-[1,1'-biphenyl]-4-ol.

[0012] Preferably, in the preparation method of the fluorinated biphenyl glycidyl ether, the molar ratio of fluorinated biphenol, epichlorohydrin and solid sodium hydroxide is 1:10-15:1.2-1.5.

[0013] Preferably, in the method for preparing the fluorinated biphenyl glycidyl ether, the phase transfer catalyst is selected from any one of benzyltriethylammonium chloride, benzyltrimethylammonium chloride, or tetrabutylammonium bromide.

[0014] More preferably, in the method for preparing the fluorinated biphenyl glycidyl ether, the phase transfer catalyst is selected from tetrabutylammonium bromide.

[0015] Preferably, in the preparation method of the fluorinated biphenyl glycidyl ether, the fluorinated biphenol, the phase transfer catalyst and the toluene are in a mass ratio of 1:0.005-0.02:10-20.

[0016] Preferably, the purification process in the preparation method of the fluorinated biphenyl glycidyl ether is as follows: When the number of fluorine atoms in the fluorinated biphenyl is 1-3, it is purified by vacuum distillation, and the fraction with the corresponding boiling point range is collected to obtain fluorinated biphenyl glycidyl ether. When the number of fluorine atoms in the fluorinated biphenyl is 6, it is purified by recrystallization. Toluene is added to the concentrated crude product and the temperature is raised to 60-70℃ until it just dissolves completely. The product is then cooled to 0-5℃ to crystallize out. The crystals are collected by filtration, the filter cake is washed with n-hexane, and dried to constant weight to obtain fluorinated biphenyl glycidyl ether.

[0017] Furthermore, the present invention also provides a method for preparing a low stray light, high transmittance PDLC dimming film, comprising the following steps: (1) Fluorinated biphenyl glycidyl ether liquid crystal grafting agent was mixed with PEDOT:PSS aqueous dispersion and heated to 40-80℃ under nitrogen protection. The mixture was stirred for 3-6 hours. After the reaction was completed, the mixture was purified by dialysis and concentrated to obtain modified PEDOT:PSS dispersion. (2) Add ethylene glycol to the modified PEDOT:PSS dispersion, mix evenly and coat it on the surface of a flexible transparent substrate. Vacuum anneal at 110-130℃ for 10-20 min to obtain the modified PEDOT:PSS conductive layer. (3) Mix the liquid crystal, photocurable resin, photoinitiator and spacer particles evenly, and then degas them under vacuum to obtain a PDLC prepolymer solution; (4) The PDLC prepolymer solution is coated onto the modified PEDOT:PSS conductive layer on the surface of the flexible transparent substrate. Then, the other flexible transparent substrate is bonded with its modified PEDOT:PSS conductive layer facing the PDLC prepolymer solution, so that the two modified PEDOT:PSS conductive layers are set opposite each other to obtain the PDLC functional layer. After the bubbles are removed, the film is cured to obtain a low stray light and high transmittance PDLC dimming film.

[0018] Preferably, the fluorinated biphenyl glycidyl ether liquid crystal grafting agent in (1) is in a mass ratio of 1:10-20 to PEDOT:PSS aqueous dispersion.

[0019] Preferably, in the PEDOT:PSS aqueous dispersion in (1), the mass ratio of PEDOT to PSS is 1:2-2.5.

[0020] Preferably, the solid content of the modified PEDOT:PSS dispersion in (1) is 1.0-1.5wt%.

[0021] Preferably, in step (1), the dialysis purification uses a dialysis bag with a molecular weight cutoff of 3500-8000 Da, and is dialyzed with deionized water for 48-72 hours, with the dialysis solution being replaced every 6 hours.

[0022] Preferably, in step (2), the modified PEDOT:PSS dispersion and ethylene glycol are in a volume ratio of 1:0.03-0.08.

[0023] Preferably, in step (3), the liquid crystal, photocurable resin, photoinitiator and spacer particles are in a mass ratio of 100:50-80:0.5-3:0.1-1.

[0024] Preferably, the spacer particles in (3) are monodisperse polymethyl methacrylate microspheres with a particle size of 15-25 μm and a particle size distribution CV value ≤5%.

[0025] Preferably, the liquid crystal and the photocurable resin in (3) are selected according to the following rules: When the fluorinated biphenyl glycidyl ether used contains R1 selected from -H, R2 selected from -F, and R3 selected from -H, or R1 selected from -F, R2 selected from -F, and R3 selected from -H, the liquid crystal is a nematic liquid crystal, and the photocurable resin is an acrylate resin. When R1 is selected from -H, R2 is selected from -CF3, and R3 is selected from -H or when R1 is selected from -H, R2 is selected from -OCF3, and R3 is selected from -H, the liquid crystal is a fluorinated nematic liquid crystal and the photocurable resin is a fluorinated acrylate resin. When R1 is selected from -CF3, R2 is selected from -H, and R3 is selected from -CF3, the liquid crystal is a high-fluorine nematic liquid crystal, and the photocurable resin is a high-fluorine acrylate resin.

[0026] Preferably, the coating thickness of the PDLC prepolymer solution in (4) is 25-35 μm.

[0027] Preferably, the curing process in step (4) uses a wavelength of 365 nm and a light intensity of 5-20 mW / cm². 2 UV curing for 5-15 minutes.

[0028] Preferably, the mechanism of action of the low stray light and high transmittance PDLC dimming film of the present invention is explained as follows: The present invention achieves the technical effect of low stray light and high transmittance mainly by chemically grafting PEDOT:PSS with fluorinated biphenyl glycidyl ether, which forms a synergistic effect in three aspects: improving conductivity, regulating refractive index and matching interface optics.

[0029] PEDOT:PSS is a composite system composed of conductive PEDOT (poly(3,4-ethylenedioxythiophene)) and insulating PSS (polystyrene sulfonate). In unmodified PEDOT:PSS films, the PEDOT molecular chains exhibit a random coil conformation, lacking effective charge transport channels between chain segments, resulting in high sheet resistance. This invention introduces fluorinated biphenyl glycidyl ether into the PSS chain segments through chemical grafting, creating a liquid crystal-like fluorinated biphenyl mesocrystalline unit. This mesocrystalline unit possesses a rigid biphenyl aromatic ring framework and a dipole moment generated by the strong electronegativity of fluorine atoms. During vacuum annealing after coating, the fluorinated biphenyl gains sufficient molecular motion energy, spontaneously forming an ordered liquid crystal phase structure through π-π stacking and dipole-dipole interactions. This ordered arrangement is conducted to the PEDOT backbone through covalently bonded PSS chain segments, forcing the originally randomly coiled PEDOT molecular chains to extend and stack in an ordered manner along the orientation direction of the mesocrystalline unit. The ordered arrangement of OT molecular chains leads to a closer overlap of π-π orbitals between chain segments, reducing the energy barrier for inter-chain charge transitions. At the same time, the extended conformation of PEDOT chains expands the charge delocalization range on the conjugated backbone, improving the intra-chain charge mobility. In addition, ethylene glycol added during the preparation process acts as a secondary dopant, further inducing the transformation of PEDOT molecular chains from benzene ring structure to quinone ring structure through the polar solvent effect, causing the molecular chain conformation to transform from a coiled spherical shape to an extended linear shape. The self-assembled ordered structure of fluorinated biphenyl and the secondary doping effect of ethylene glycol combine to reduce the sheet resistance of the modified PEDOT:PSS conductive layer to ≤80Ω / □. The refractive index is essentially determined by the electronic polarizability of molecules or atoms in a material, that is, the ease with which the electron cloud shifts under the influence of an applied photoelectric field. Fluorine atoms have extremely low electronic polarizability, and their nuclei strongly bind the outermost electrons, making the electron cloud difficult to polarize by an external electric field. At the same time, the CF bond has extremely high bond energy and short bond length, and the bonded electrons are strongly localized near the fluorine atom, resulting in a very weak response to an applied light field. When hydrogen atoms are replaced by fluorine atoms, the molar refractive index of the molecule decreases significantly. In addition, the introduction of fluorine atoms increases the free volume fraction between molecular chains. Fluorine-containing side groups are larger and more rigid, making it difficult for molecular chains to pack tightly, creating additional microscopic voids, which further reduces the polarization density of the material. Therefore, as the number of fluorine atoms in fluorinated biphenyls increases, the overall refractive index of the grafted conductive layer gradually decreases. By selecting fluorinated biphenol raw materials with different numbers of fluorine atoms (from 1 to 6 fluorine atoms), this invention can control the refractive index of the grafted PEDOT:PSS conductive layer in the range of 1.480 to 1.525, providing adjustable optical parameters for matching PDLC functional layers with different compositions. In the transparent state, the orientation of the liquid crystal droplets in the PDLC dimming film is aligned with the direction of the electric field, and its effective refractive index is close to the ordinary refractive index of the liquid crystal. At this point, if there is a difference in refractive index between the conductive layer and the PDLC functional layer, Fresnel reflection will occur at their interface. The reflectivity is proportional to the square of the refractive index difference across the interface. The larger the refractive index difference, the stronger the interface reflection. These reflected lights undergo multiple internal reflections and scatterings between the multilayer interfaces, forming unwanted stray light, which manifests as increased haze and decreased transparency. This invention modifies the refractive index of the electrode by grafting with fluorinated biphenyl to match the effective refractive index of the PDLC functional layer. Specifically, when the number of fluorine atoms in the grafting agent is 1 or 2, the electrode refractive index is 1.498 to 1.525, matching the PDLC system composed of nematic liquid crystal and acrylate resin; when the number of fluorine atoms is 3, the electrode refractive index is 1.492 to 1.505, matching the PDLC system composed of fluorinated nematic liquid crystal and fluorinated acrylate resin; when the number of fluorine atoms is 6, the electrode refractive index is 1.480 to 1.495, matching the PDLC system composed of high-fluorinated nematic liquid crystal and high-fluorine-content acrylate resin. When the difference between the refractive index of the conductive layer and the effective refractive index of the PDLC functional layer does not exceed 0.02, the interface reflection is suppressed to an extremely low level, and the incident light can pass through the entire film structure without obstruction, thereby achieving a low stray light and high transmittance effect with a transparent haze ≤1.0%. This invention achieves three technical effects simultaneously: improved conductivity, refractive index modulation, and elimination of interfacial stray light through chemical grafting modification with a single fluorinated biphenyl glycidyl ether. These three effects are not simply a functional superposition; the liquid crystal self-assembly properties of the fluorinated biphenyl ether simultaneously contribute to both improved conductivity and refractive index modulation, while refractive index modulation directly determines the effectiveness of eliminating interfacial stray light. This synergistic mechanism allows this invention to solve the technical challenges of severe stray light and insufficient transparency in PDLC dimming films without introducing additional functional layers or increasing process complexity.

[0030] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention chemically grafts PEDOT:PSS with fluorinated biphenyl glycidyl ether. By utilizing the self-assembly and ordered arrangement of the fluorinated biphenyl mesocrystalline units during annealing, the PEDOT molecular chains are oriented and stacked, reducing the sheet resistance of the electrode without the need for additional conductive fillers. At the same time, the grafted fluorinated groups regulate the electrode refractive index, giving the conductive layer multiple characteristics of high conductivity, high transmittance, and adjustable refractive index, thus avoiding the technical contradiction of traditional PEDOT:PSS electrodes struggling to balance conductivity and optical performance.

[0031] 2. This invention achieves matching between the electrode refractive index and the PDLC functional layer, suppressing Fresnel reflection at the interface to an extremely low level. It eliminates stray light at the interface caused by the mismatch between the refractive index of the electrode and the PDLC layer in traditional PDLC dimming films, enabling the dimming film to have extremely low haze performance in the transparent state. In particular, it maintains good visual transparency under oblique viewing angle conditions, improving the applicability of PDLC dimming films in scenarios with stringent optical quality requirements, such as automotive sunroofs and high-end building curtain walls.

[0032] 3. This invention chemically grafts fluorinated biphenyl groups onto the PSS chain segment, enabling the conductive layer surface to spontaneously possess the function of inducing liquid crystal alignment. This eliminates the coating and triboelectric alignment processes of the independent alignment layer in traditional PDLC devices, avoiding quality risks such as static electricity, dust, and poor uniformity caused by triboelectric processes. At the same time, it reduces the number of functional layers, thereby reducing interface reflection loss, significantly simplifying the production process, reducing manufacturing costs, and making it more suitable for large-scale production.

[0033] 4. This invention uses a solution-based processing technique to prepare PEDOT:PSS electrodes, eliminating the need for high-vacuum sputtering or high-temperature deposition equipment. It is highly compatible with roll-to-roll flexible printing processes and avoids the dependence of ITO electrodes on scarce indium resources. Combined with an optical-grade PET substrate, it can achieve the preparation of large-area flexible dimming films, providing a dimming solution with high optical quality, low cost, and excellent flexibility for applications such as flexible wearable electronics, automotive sunroofs, and smart building doors and windows. Attached Figure Description

[0034] Figure 1 The 1H NMR spectrum of the fluorinated biphenyl glycidyl ether prepared in Example 2 of this invention; Figure 2 The 1H NMR spectrum of the fluorinated biphenyl glycidyl ether prepared in Example 4 of this invention; Figure 3 The 1H NMR spectrum of the fluorinated biphenyl glycidyl ether prepared in Example 5 of this invention; Figure 4 The 1H NMR spectrum of the fluorinated biphenyl glycidyl ether prepared in Example 6 of this invention; Figure 5 The above is the 1H NMR spectrum of the fluorinated biphenyl glycidyl ether prepared in Example 7 of this invention. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] Preparation Example 1: A specific method for preparing fluorinated biphenyl glycidyl ether includes the following steps: 1 mol of 4-fluoro-4'-hydroxybiphenyl, 10 mol of epichlorohydrin, and 0.005 times the mass of fluorinated biphenyl tetrabutylammonium bromide were added to a reactor. The mixture was stirred and heated to 70°C under nitrogen protection and kept at this temperature for 10 h. After the reaction was completed, excess epichlorohydrin was recovered by vacuum distillation. Toluene with a mass of 10 times the mass of fluorinated biphenyl was added, and a total of 1.2 mol of solid sodium hydroxide was added in two portions. The temperature was raised to the reflux temperature of toluene. The water generated in the reaction was separated by a water separator. The reaction was allowed to proceed for 5 h. After cooling to room temperature, the mixture was washed twice with deionized water. The upper organic phase was collected after standing and separating. It was dried with anhydrous sodium sulfate and filtered. The solvent was removed by vacuum distillation to obtain a concentrated crude product. The product was purified by vacuum distillation. The fraction from 176 to 198°C was collected under a high vacuum of 1.0 kPa to obtain fluorinated biphenyl glycidyl ether.

[0037] Preparation Example 2: A specific method for preparing fluorinated biphenyl glycidyl ether includes the following steps: 1 mol of 4-fluoro-4'-hydroxybiphenyl, 12 mol of epichlorohydrin, and 0.0125 times the mass of fluorinated biphenyl phenol in tetrabutylammonium bromide were added to a reactor. The mixture was stirred and heated to 85°C under nitrogen protection and kept at this temperature for 6 hours. After the reaction was completed, excess epichlorohydrin was recovered by vacuum distillation. Toluene, 15 times the mass of fluorinated biphenyl phenol, was added, followed by a total of 1.35 mol of solid sodium hydroxide in three portions. The mixture was heated to the reflux temperature of toluene and the water produced in the reaction was separated using a water separator. The reaction was allowed to proceed for 6.5 hours. After cooling to room temperature, the mixture was washed three times with deionized water, allowed to stand for separation, and the upper organic phase was collected. The organic phase was dried with anhydrous sodium sulfate and filtered. The solvent was removed by vacuum distillation to obtain a concentrated crude product. The product was purified by vacuum distillation, and the fraction from 176 to 198°C was collected under a high vacuum of 1.0 kPa to obtain fluorinated biphenyl glycidyl ether.

[0038] Preparation Example 3: The specific preparation method of fluorinated biphenyl glycidyl ether includes the following steps: 1 mol of 4-fluoro-4'-hydroxybiphenyl, 15 mol of epichlorohydrin, and 0.02 times the mass of fluorinated biphenyl tetrabutylammonium bromide were added to a reactor. The mixture was stirred and heated to 100°C under nitrogen protection and kept at this temperature for 3 hours. After the reaction was completed, excess epichlorohydrin was recovered by vacuum distillation. Toluene, 20 times the mass of fluorinated biphenyl, was added, followed by a total of 1.5 mol of solid sodium hydroxide in three portions. The temperature was raised to the reflux temperature of toluene. The water generated in the reaction was separated using a water separator. The reaction was allowed to proceed for 8 hours. After cooling to room temperature, the mixture was washed three times with deionized water. The mixture was allowed to stand and separate into layers. The upper organic phase was collected, dried with anhydrous sodium sulfate, filtered, and the solvent was removed by vacuum distillation to obtain a concentrated crude product. The product was purified by vacuum distillation, and the fraction from 176 to 198°C was collected under a high vacuum of 1.0 kPa to obtain fluorinated biphenyl glycidyl ether.

[0039] Preparation Example 4: The difference between Preparation Example 4 and Preparation Example 2 is that 4-fluoro-4'-hydroxybiphenyl is replaced with 3',4'-difluoro-[1,1'-biphenyl]-4-ol.

[0040] Preparation Example 5: The difference between Preparation Example 5 and Preparation Example 2 is that 4-fluoro-4'-hydroxybiphenyl is replaced with 4'-trifluoromethylbiphenyl-4-ol.

[0041] Preparation Example 6: The difference between Preparation Example 6 and Preparation Example 2 is that 4-fluoro-4'-hydroxybiphenyl is replaced with 4-(4-trifluoromethoxyphenyl)phenol.

[0042] Preparation Example 7: The difference between Preparation Example 7 and Preparation Example 2 is that 4-fluoro-4'-hydroxybiphenyl is replaced with 3',5'-bis(trifluoromethyl)-[1,1'-biphenyl]-4-ol. At the same time, the purification method is by recrystallization. Toluene is added to the concentrated crude product and heated to 60-70°C until it just dissolves completely. The product is then cooled to 0-5°C to crystallize out. The crystals are collected by filtration, the filter cake is washed with n-hexane, and dried to constant weight to obtain fluorinated biphenyl glycidyl ether.

[0043] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that 4-fluoro-4'-hydroxybiphenyl is replaced with 4-hydroxybiphenyl to prepare fluorine-free biphenyl glycidyl ether.

[0044] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that 4-fluoro-4'-hydroxybiphenyl is replaced with fluoroethanol to prepare fluoroethyl glycidyl ether.

[0045] Example 1: A specific method for preparing a low stray light, high transmittance PDLC dimming film, comprising the following steps: (1) The fluorinated biphenyl glycidyl ether prepared in Preparation Example 1 was mixed with PEDOT:PSS aqueous dispersion at a mass ratio of 1:10, wherein the mass ratio of PEDOT to PSS in PEDOT:PSS aqueous dispersion was 1:2. The mixture was heated to 40°C under nitrogen protection and stirred for 6 hours. After the reaction was completed, a dialysis bag with a molecular weight cutoff of 3500 Da was used to dialyze the mixture with deionized water for 72 hours. The dialysate was replaced every 6 hours. After purification, the mixture was concentrated to a solid content of 1.0 wt% to obtain the modified PEDOT:PSS dispersion. (2) Add ethylene glycol to the modified PEDOT:PSS dispersion. The volume ratio of the modified PEDOT:PSS dispersion to ethylene glycol is 1:0.03. After mixing evenly, coat the surface of an optical grade biaxially stretched PET flexible transparent substrate with a thickness of 50 μm. Vacuum anneal at 110 °C for 20 min to obtain a modified PEDOT:PSS conductive layer with a total thickness of 20 nm. (3) Nematic liquid crystal, acrylate photocurable resin, photoinitiator and monodisperse polymethyl methacrylate microspheres (particle size 15 μm, particle size distribution CV value ≤ 5%) are mixed evenly in a mass ratio of 100:50:0.5:0.1 and then vacuum degassed to obtain PDLC prepolymer solution; (4) The PDLC prepolymer solution is coated onto the modified PEDOT:PSS conductive layer on the surface of the flexible transparent substrate with a coating thickness of 25 μm. Then, the other flexible transparent substrate is bonded with its modified PEDOT:PSS conductive layer facing the PDLC prepolymer solution, so that the two modified PEDOT:PSS conductive layers are positioned opposite each other to obtain the PDLC functional layer. After removing the air bubbles, the PDLC functional layer is obtained by applying light at a wavelength of 365 nm and an irradiation intensity of 5 mW / cm. 2 Curing with ultraviolet light for 15 minutes yields a low stray light, high transmittance PDLC dimming film.

[0046] Example 2: A specific preparation method of a low stray light, high transmittance PDLC dimming film, comprising the following steps: (1) The fluorinated biphenyl glycidyl ether prepared in Preparation Example 2 was mixed with PEDOT:PSS aqueous dispersion at a mass ratio of 1:15, wherein the mass ratio of PEDOT to PSS in the PEDOT:PSS aqueous dispersion was 1:2.25. The mixture was heated to 60°C under nitrogen protection and stirred for 4.5 h. After the reaction was completed, a dialysis bag with a molecular weight cutoff of 5000 Da was used to dialyze the mixture with deionized water for 60 h. The dialysate was replaced every 6 h. After purification, the mixture was concentrated to a solid content of 1.25 wt% to obtain the modified PEDOT:PSS dispersion. (2) Add ethylene glycol to the modified PEDOT:PSS dispersion. The volume ratio of the modified PEDOT:PSS dispersion to ethylene glycol is 1:0.055. After mixing evenly, coat the surface of an optical grade biaxially stretched PET flexible transparent substrate with a thickness of 100 μm. Vacuum anneal at 120 °C for 15 min to obtain the modified PEDOT:PSS conductive layer with a total thickness of 40 nm. (3) Nematic liquid crystal, acrylate photocurable resin, photoinitiator and monodisperse polymethyl methacrylate microspheres (particle size 20 μm, particle size distribution CV value ≤ 5%) are mixed evenly in a mass ratio of 100:65:1.75:0.55 and then vacuum degassed to obtain PDLC prepolymer solution; (4) The PDLC prepolymer solution is coated onto the modified PEDOT:PSS conductive layer on the surface of the flexible transparent substrate with a coating thickness of 30 μm. Then, the other flexible transparent substrate is bonded with its modified PEDOT:PSS conductive layer facing the PDLC prepolymer solution, so that the two modified PEDOT:PSS conductive layers are positioned opposite each other to obtain the PDLC functional layer. After removing the air bubbles, a light intensity of 12 mW / cm is applied using a wavelength of 365 nm. 2 Curing with ultraviolet light for 10 minutes yields a low stray light, high transmittance PDLC dimming film.

[0047] Example 3: A specific method for preparing a low stray light, high transmittance PDLC dimming film, comprising the following steps: (1) The fluorinated biphenyl glycidyl ether prepared in Preparation Example 3 was mixed with PEDOT:PSS aqueous dispersion at a mass ratio of 1:20, wherein the mass ratio of PEDOT to PSS in PEDOT:PSS aqueous dispersion was 1:2.5. The mixture was heated to 80°C under nitrogen protection and stirred for 3 hours. After the reaction was completed, a dialysis bag with a molecular weight cutoff of 8000 Da was used to dialyze the mixture with deionized water for 48 hours. The dialysate was replaced every 6 hours. After purification, the mixture was concentrated to a solid content of 1.5 wt% to obtain the modified PEDOT:PSS dispersion. (2) Add ethylene glycol to the modified PEDOT:PSS dispersion. The volume ratio of the modified PEDOT:PSS dispersion to ethylene glycol is 1:0.08. After mixing evenly, coat the surface of an optical grade biaxially stretched PET flexible transparent substrate with a thickness of 125 μm. Vacuum anneal at 130 °C for 10 min to obtain the modified PEDOT:PSS conductive layer with a total thickness of 60 nm. (3) Nematic liquid crystal, acrylate photocurable resin, photoinitiator and monodisperse polymethyl methacrylate microspheres (particle size 25 μm, particle size distribution CV value ≤ 5%) are mixed evenly in a mass ratio of 100:80:3:1 and then vacuum degassed to obtain PDLC prepolymer solution; (4) The PDLC prepolymer solution is coated onto the modified PEDOT:PSS conductive layer on the surface of the flexible transparent substrate with a coating thickness of 35 μm. Then, the other flexible transparent substrate is bonded with its modified PEDOT:PSS conductive layer facing the PDLC prepolymer solution, so that the two modified PEDOT:PSS conductive layers are positioned opposite each other to obtain the PDLC functional layer. After removing the air bubbles, a light intensity of 20 mW / cm is applied using a wavelength of 365 nm. 2 After curing with ultraviolet light for 5 minutes, a low stray light and high transmittance PDLC dimming film is obtained.

[0048] Example 4: The difference between Example 4 and Example 2 is that the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 2 is replaced with the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 4.

[0049] Example 5: The difference between Example 5 and Example 2 is that the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 2 is replaced with the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 5; at the same time, the nematic liquid crystal is replaced with a fluorinated nematic liquid crystal, and the acrylic photocurable resin is replaced with a fluorinated acrylate photocurable resin.

[0050] Example 6: The difference between Example 6 and Example 2 is that the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 2 is replaced with the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 6; at the same time, the nematic liquid crystal is replaced with a fluorinated nematic liquid crystal, and the acrylic photocurable resin is replaced with a fluorinated acrylate photocurable resin.

[0051] Example 7: The difference between Example 7 and Example 2 is that the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 2 is replaced with the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 7; at the same time, the nematic liquid crystal is replaced with a high-fluorinated nematic liquid crystal, and the acrylic photocurable resin is replaced with a high-fluorine content acrylate resin.

[0052] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 2 is replaced with the fluorine-free biphenyl glycidyl ether prepared according to Comparative Preparation Example 1.

[0053] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 2 is replaced with the fluoroethyl glycidyl ether prepared according to Comparative Preparation Example 2.

[0054] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that: no fluorinated biphenyl glycidyl ether grafting modification is performed, a 20nm thick polyimide orientation layer is spin-coated on the surface of the unmodified PEDOT:PSS conductive layer and rubbed orientation treatment is performed, and the remaining PDLC composite process parameters are completely consistent with Example 2.

[0055] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that step (1) is omitted, and the remaining steps are the same as in Example 2.

[0056] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 2 is replaced with the fluorinated biphenyl glycidyl ether prepared according to Preparation Example 7, and the remaining steps are the same as in Example 2.

[0057] Performance testing: The following system tests were performed on the dimming films prepared in Examples 1-7 and Comparative Examples 1-5: 1. Sheet resistance test of conductive layer: A dual-electrical-measurement four-probe sheet resistance tester was used to test the sheet resistance of the PEDOT:PSS conductive layer in each embodiment and comparative example according to the four-probe method. It should be noted that the sheet resistance test is performed on the PEDOT:PSS conductive layer itself coated on the surface of the PET substrate (with or without graft modification), and the test is completed before coating with the PDLC prepolymer solution. For Examples 1-7 and Comparative Examples 1, 2, 4, and 5, the sheet resistance of the modified or unmodified PEDOT:PSS conductive layer film was directly tested. For Comparative Example 3, since PI is an insulating material, the four probes could not penetrate the PI layer for testing. Therefore, the sheet resistance of Comparative Example 3 was tested using a parallel sample method: a parallel sample without PI coating was taken from the unmodified PEDOT:PSS conductive layer samples in the same batch. After preparation under the same PEDOT:PSS coating conditions as Comparative Example 3, the sheet resistance of the parallel sample was directly tested and used as the sheet resistance value of the unmodified PEDOT:PSS conductive layer in Comparative Example 3. Five different locations were selected for measurement for each sample, and the average value was taken as the sheet resistance value of the sample. 2. Refractive index test of conductive layer: The refractive index of the PEDOT:PSS conductive layer in each embodiment and comparative example was tested using a spectroeltrometer at a visible light wavelength of 550nm. It should be noted that the object of the refractive index test is the PEDOT:PSS conductive layer itself (with or without graft modification) coated on the surface of the PET substrate. The test is completed before coating with the PDLC prepolymer solution. For Examples 1-7 and Comparative Examples 1, 2, 4, and 5, the refractive index of the modified or unmodified PEDOT:PSS conductive layer film is directly tested. For Comparative Example 3, since the polyimide orientation layer covers the surface of the conductive layer, the ellipsometer cannot accurately separate the multilayer film signal to obtain the refractive index of the lower PEDOT:PSS conductive layer. Therefore, the refractive index of Comparative Example 3 adopts the parallel sample test method: a parallel sample without polyimide orientation layer is taken from the unmodified PEDOT:PSS conductive layer samples in the same batch. After preparation under the same PEDOT:PSS coating conditions as Comparative Example 3, the refractive index of the parallel sample is directly tested and used as the refractive index value of the unmodified PEDOT:PSS conductive layer in Comparative Example 3. Three different positions are selected for measurement for each sample, and the average value is taken as the refractive index value of the sample. 3. Transmittance and Haze Test: A haze and transmittance tester was used to test the transmittance and haze of the PDLC dimming films obtained in each embodiment and comparative example within the visible light wavelength range (380-780nm) under the applied driving voltage (on state) and the haze under the unapplied voltage (off state). During the on state test, a 48V AC voltage (sine wave, frequency 50Hz) was applied, and the data was recorded after the transmittance stabilized. 4. Driving voltage test: Connect the PDLC dimming films obtained in each embodiment and comparative example to a programmable AC power supply, set the output waveform to a sine wave with a frequency of 50Hz, and gradually increase the output voltage from 0V to 70V in 5V increments. Use a UV-Vis spectrophotometer and an electrochemical workstation to record the transmittance at each voltage and plot the transmittance-voltage (TV) characteristic curve. Read the voltage corresponding to the maximum transmittance of 90% from the TV curve as the driving voltage (saturation voltage). 5. Response Time Test: The transmittance dynamic test method was adopted. The PDLC dimming films obtained in each embodiment and comparative example were placed in the optical path. Monochromatic light with a wavelength of 550nm was used as the probe light. The transmittance change was monitored in real time using a photodetector. A step voltage was applied (switching from 0V to saturation voltage and then switching back from saturation voltage to 0V). The time required for the transmittance to rise from 10% of the transmittance in the off state to 90% of the transmittance in the on state was recorded as the rise time. The time required for the transmittance to fall from 90% of the transmittance in the on state to 10% of the transmittance in the off state was recorded as the fall time. 6. Contrast Ratio Test: The contrast ratio (CR) is calculated using the following formula: CR = T on / Toff T on T represents the transmittance in the open state. off Transmittance in the off state; The experimental results are shown in Table 1.

[0058] Table 1 Performance Test Results Data Analysis: As can be seen from the performance test data in Table 1, the modified PEDOT:PSS conductive layer of the present invention, through covalent grafting of fluorinated biphenyl glycidyl ether onto PSS chain segments, introduces biphenyl mesocrystalline units that self-assemble into an ordered arrangement through π-π stacking and dipole interaction during vacuum annealing. This ordered structure, through covalent bond conduction, induces the originally randomly coiled PEDOT molecular chains to extend and stack along the orientation direction, improving the degree of charge delocalization within the chain and the efficiency of charge transition between chains. Combined with the secondary doping effect of ethylene glycol, the conductivity is synergistically optimized. Therefore, the sheet resistance of the conductive layer in the embodiment is significantly lower than that of the unmodified system. Although Comparative Example 1 retains the order-inducing effect of the biphenyl group, it lacks the steric hindrance effect of the fluorine substituent, resulting in a higher ring-opening grafting rate of the epoxy group and a greater degree of disruption to the doping balance of the PSS sulfonic acid group. Therefore, its sheet resistance is higher than that of the examples. Comparative Example 2 lacks the order-inducing effect of the biphenyl mesocrystalline unit and cannot effectively improve the aggregated conformation of the PEDOT molecular chain. Therefore, its sheet resistance is close to that of Comparative Example 4. Neither Comparative Example 3 nor Comparative Example 4 modified PEDOT:PSS with order. The random coiling of the PEDOT molecular chain resulted in insufficient continuous charge transport channels, thus its sheet resistance was at a high level. The conductive layer preparation process of Comparative Example 5 was completely consistent with the corresponding examples, so its sheet resistance level was comparable.

[0059] This invention achieves a synergistic effect of refractive index regulation and interface orientation induction simultaneously through a single grafted monomer. On the one hand, the low electronic polarizability of fluorine atoms can regulate the overall refractive index of the conductive layer. By using different fluorine-containing designs, the effective refractive index of different PDLC functional layers can be matched, reducing Fresnel reflection at the interface and decreasing reflected stray light. On the other hand, the biphenyl mesocrystalline unit forms a weakly anchored interface on the surface of the conductive layer. In the transparent state, the liquid crystal molecules at the interface can be aligned synchronously with the bulk liquid crystal along the electric field direction, eliminating the scattered stray light caused by interface orientation disorder. The synchronous reduction of the two types of stray light results in higher open-state transmittance and lower open-state haze in the embodiment. Comparative Example 1 only retains the interface orientation optimization effect, and cannot achieve refractive index matching between the conductive layer and the PDLC substrate. Interface reflective stray light is not effectively suppressed, resulting in higher open-state haze and lower transmittance. Comparative Example 2 can only reduce the refractive index of the conductive layer to a certain extent, lacking the interface orientation induction effect. Interface scattering, which dominates stray light, cannot be eliminated, so the open-state haze is still at a high level. Although Comparative Example 3 can reduce interface scattering stray light through orientation treatment, it introduces two additional layers of abrupt refractive index interfaces, adding a large amount of reflective light loss. Therefore, the open-state transmittance is lower than that of the example, and the haze optimization effect is also very limited. Comparative Example 4 has neither refractive index matching nor interface orientation optimization. Both types of stray light exist simultaneously, so the open-state transmittance is the lowest and the haze is the highest. Comparative Example 5 has a greater degree of mismatch between the refractive index of the conductive layer and the ordinary PDLC system, and the interface reflection is significantly enhanced. Therefore, the open-state transmittance is even lower and the haze is even higher, verifying the necessity of the gradient fluorine-containing matching design of the present invention.

[0060] The modified conductive layer of this invention has a lower sheet resistance, a more uniform electric field distribution on the film surface, and a smaller voltage drop loss along the film thickness direction. This results in a higher effective electric field strength acting on the liquid crystal droplets. Simultaneously, the weak interfacial anchoring effect reduces the orientation threshold of the liquid crystal molecules. These two factors synergistically lower the saturation driving voltage, thus resulting in a lower driving voltage in this embodiment. Comparative Examples 1 and 2 have higher sheet resistance of the conductive layer and greater voltage drop loss, thus leading to higher driving voltages. While Comparative Example 3 can reduce the liquid crystal orientation threshold through orientation, the unmodified conductive layer has a high sheet resistance and large electric field loss, resulting in an overall driving voltage higher than the embodiments. Comparative Example 4 has the highest sheet resistance of the conductive layer and the largest electric field loss, resulting in the highest driving voltage. Although Comparative Example 5 has a lower sheet resistance of the conductive layer, the refractive index mismatch leads to a decrease in maximum transmittance, requiring a higher effective electric field strength to achieve the target transmittance, thus resulting in a higher driving voltage than the corresponding fully matched system embodiments.

[0061] The low sheet resistance conductive layer can quickly establish a uniform orientation electric field, while the weak anchoring environment at the interface reduces the viscous resistance of the liquid crystal molecule orientation and reset process. Therefore, the rise and fall response speeds of the embodiment are faster. The other comparative examples have higher sheet resistance of conductive layers, poorer electric field establishment speed and distribution uniformity, and the disordered orientation of liquid crystal molecules at the interface leads to greater viscous resistance. Therefore, the response speeds are all slower than those of the embodiment. The conductive layer of Comparative Example 5 has a lower sheet resistance, and the response speed is close to that of the corresponding embodiment. However, the electric field uniformity caused by refractive index mismatch is slightly worse, so the response time is still slightly longer than that of the fully matched system embodiment.

[0062] Contrast ratio is determined by the ratio of on-state transmittance to off-state transmittance. The present invention can significantly improve on-state transmittance, while off-state transmittance is minimally affected by interface modification. Therefore, the contrast ratio improvement in the embodiments is greater. The on-state transmittance of each comparative example is lower than that of the embodiments, so the contrast ratio is generally lower. Although comparative example 3 has slightly stronger off-state scattering, the improvement in on-state transmittance is limited, so the contrast ratio is still lower than that of the embodiments. Comparative example 4 has the lowest on-state transmittance and the worst contrast ratio.

[0063] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low stray light, high transmittance PDLC dimming film, characterized in that, It includes two flexible transparent substrate layers arranged opposite each other, a modified PEDOT:PSS conductive layer is provided on the inner side of the substrate, and a PDLC functional layer is sandwiched between the two modified PEDOT:PSS conductive layers. The flexible transparent substrate layer is optical-grade biaxially stretched PET with a thickness of 50-125μm and a visible light transmittance of ≥91%. The modified PEDOT:PSS conductive layer is a fluorinated biphenyl glycidyl ether grafted modified PEDOT:PSS with a refractive index of 1.480-1.525, a total thickness of 20-60 nm, and a sheet resistance ≤80 Ω / □. The fluorinated biphenyl glycidyl ether has the following general chemical structural formula: ;where R1, R 2、 R3 is selected from any of the following combinations: R1 is selected from -H, R2 is selected from -F, and R3 is selected from -H; R1 is selected from -F, R2 is selected from -F, and R3 is selected from -H; R1 is selected from -H, R2 is selected from -CF3, and R3 is selected from -H; R1 is selected from -H, R2 is selected from -OCF3, and R3 is selected from -H; R1 is selected from -CF3, R2 is selected from -H, and R3 is selected from -CF3.

2. The low stray light, high transmittance PDLC dimming film according to claim 1, characterized in that, The preparation method of the fluorinated biphenyl glycidyl ether includes the following steps: Fluorinated biphenyl phenol, epichlorohydrin, and a phase transfer catalyst were added to a reactor and stirred and heated to 70-100°C under nitrogen protection. The reaction was maintained at this temperature for 3-10 hours. After the reaction was completed, excess epichlorohydrin was recovered by vacuum distillation. Toluene was added, and solid sodium hydroxide was added in 2-3 portions. The temperature was raised to the reflux temperature of toluene. The water generated in the reaction was separated by a water separator. The reaction was allowed to proceed for 5-8 hours. After cooling to room temperature, the mixture was washed 2-3 times with deionized water. The mixture was allowed to stand and separate into layers. The upper organic phase was collected, dried with anhydrous sodium sulfate, filtered, and the solvent was removed by vacuum distillation to obtain a concentrated crude product. After purification, fluorinated biphenyl glycidyl ether was obtained.

3. The low stray light, high transmittance PDLC dimming film according to claim 2, characterized in that, In the preparation method of the fluorinated biphenyl glycidyl ether, the fluorinated biphenyl is selected from one of 4-fluoro-4'-hydroxybiphenyl, 3',4'-difluoro-[1,1'-biphenyl]-4-ol, 4'-trifluoromethylbiphenyl-4-ol, 4-(4-trifluoromethoxyphenyl)phenol or 3',5'-bis(trifluoromethyl)-[1,1'-biphenyl]-4-ol.

4. The low stray light, high transmittance PDLC dimming film according to claim 2, characterized in that, In the preparation method of the fluorinated biphenyl glycidyl ether, the molar ratio of fluorinated biphenyl, epichlorohydrin and solid sodium hydroxide is 1:10-15:1.2-1.5; the phase transfer catalyst is selected from any one of benzyltriethylammonium chloride, benzyltrimethylammonium chloride or tetrabutylammonium bromide, and the mass ratio of fluorinated biphenyl, phase transfer catalyst and toluene is 1:0.005-0.02:10-20.

5. The low stray light, high transmittance PDLC dimming film according to claim 2, characterized in that, The specific purification steps in the preparation method of the fluorinated biphenyl glycidyl ether are as follows: When the number of fluorine atoms in the fluorinated biphenyl is 1-3, it is purified by vacuum distillation, and the fraction with the corresponding boiling point range is collected to obtain fluorinated biphenyl glycidyl ether. When the number of fluorine atoms in the fluorinated biphenyl is 6, it is purified by recrystallization. Toluene is added to the concentrated crude product and the temperature is raised to 60-70℃ until it just dissolves completely. The product is then cooled to 0-5℃ to crystallize out. The crystals are collected by filtration, the filter cake is washed with n-hexane, and dried to constant weight to obtain fluorinated biphenyl glycidyl ether.

6. The method for preparing a low stray light, high transmittance PDLC dimming film according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Fluorinated biphenyl glycidyl ether liquid crystal grafting agent was mixed with PEDOT:PSS aqueous dispersion and heated to 40-80℃ under nitrogen protection. The mixture was stirred for 3-6 hours. After the reaction was completed, the mixture was purified by dialysis and concentrated to obtain modified PEDOT:PSS dispersion. (2) Add ethylene glycol to the modified PEDOT:PSS dispersion, mix evenly and coat it on the surface of a flexible transparent substrate. Vacuum anneal at 110-130℃ for 10-20 min to obtain the modified PEDOT:PSS conductive layer. (3) Mix the liquid crystal, photocurable resin, photoinitiator and spacer particles evenly, and then degas them under vacuum to obtain a PDLC prepolymer solution; (4) The PDLC prepolymer solution is coated onto the modified PEDOT:PSS conductive layer on the surface of the flexible transparent substrate. Then, the other flexible transparent substrate is bonded with its modified PEDOT:PSS conductive layer facing the PDLC prepolymer solution, so that the two modified PEDOT:PSS conductive layers are set opposite each other to obtain the PDLC functional layer. After the bubbles are removed, the film is cured to obtain a low stray light and high transmittance PDLC dimming film.

7. The method for preparing the low stray light, high transmittance PDLC dimming film according to claim 6, characterized in that, The mass ratio of the fluorinated biphenyl glycidyl ether liquid crystal grafting agent to the PEDOT:PSS aqueous dispersion in (1) is 1:10-20; the mass ratio of PEDOT to PSS in the PEDOT:PSS aqueous dispersion is 1:2-2.5; and the solid content of the modified PEDOT:PSS dispersion is 1.0-1.5wt%.

8. The method for preparing the low stray light, high transmittance PDLC dimming film according to claim 6, characterized in that, In (2), the modified PEDOT:PSS dispersion and ethylene glycol are in a volume ratio of 1:0.03-0.

08.

9. The method for preparing the low stray light, high transmittance PDLC dimming film according to claim 6, characterized in that, In (3), the liquid crystal, photocurable resin, photoinitiator, and spacer particles are in a mass ratio of 100:50-80:0.5-3:0.1-1; the spacer particles are monodisperse polymethyl methacrylate microspheres with a particle size of 15-25 μm and a particle size distribution CV value ≤5%; the liquid crystal and photocurable resin are selected according to the following rules: When the fluorinated biphenyl glycidyl ether used contains R1 selected from -H, R2 selected from -F, and R3 selected from -H, or R1 selected from -F, R2 selected from -F, and R3 selected from -H, the liquid crystal is a nematic liquid crystal, and the photocurable resin is an acrylate resin. When R1 is selected from -H, R2 is selected from -CF3, and R3 is selected from -H or when R1 is selected from -H, R2 is selected from -OCF3, and R3 is selected from -H, the liquid crystal is a fluorinated nematic liquid crystal and the photocurable resin is a fluorinated acrylate resin. When R1 is selected from -CF3, R2 is selected from -H, and R3 is selected from -CF3, the liquid crystal is a high-fluorine nematic liquid crystal, and the photocurable resin is a high-fluorine acrylate resin.

10. The method for preparing the low stray light, high transmittance PDLC dimming film according to claim 6, characterized in that, The coating thickness of the PDLC prepolymer solution in (4) is 25-35 μm; the curing is performed with a wavelength of 365 nm and a light intensity of 5-20 mW / cm. 2 UV curing for 5-15 minutes.

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