Electrochromic film with flame-retardant function and preparation method thereof

Abstract

This application relates to an electrochromic film with flame-retardant function and its preparation method. The electrochromic film includes a first conductive base film, a second conductive base film, and an electrochromic photocurable layer disposed between the two. The electrochromic photocurable layer is composed of 75-85 parts of an organic phosphorus-containing flame retardant, 9-19 parts of an electrochromic material, 5-10 parts of a photocurable prepolymer, 1-1.5 parts of an acrylate photocurable monomer, 0.05-0.15 parts of a pyrolysis-type free radical photoinitiator, and 0.5-1.5 parts of an amphiphilic dispersant. The compatibility problem between the electrochromic material and the flame retardant is solved through the interfacial interaction mediated by the dispersant. Combined with the dense network formed by photopolymerization and crosslinking, the synergistic optimization of flame-retardant performance and electrochromic performance is achieved. The product has a limiting oxygen index ≥33.5%, a vertical burning rating of V-0, and a color change attenuation of ≤11.8% after 10,000 cycles, making it suitable for applications such as smart windows and automotive sunroofs.

Description

Technical Field

[0001] This invention belongs to the field of electrochromic technology, and particularly relates to an electrochromic film with flame-retardant function and its preparation method. Background Technology

[0002] Electrochromic films, as functional films that can achieve reversible color changes under the action of an external electric field, can achieve intelligent control of light and heat by flexibly adjusting their optical properties such as transmittance, reflectance, and absorptivity. They have shown broad application prospects in many fields such as smart windows, car sunroofs, display devices, and anti-glare rearview mirrors. As their application scenarios continue to expand, safety issues during use are receiving increasing attention from the industry.

[0003] Most electrochromic films on the market are composed of organic polymer materials as their core, such as the organic polymer matrix in the electrochromic layer. These organic polymer materials are generally flammable and are prone to combustion under extreme conditions such as high temperature, short circuit, or contact with open flame. This can not only directly cause the electrochromic film to lose its core function, but may also trigger a chain of fire accidents, posing a serious threat to people's lives and property.

[0004] To address the technical challenges of flame retardancy in electrochromic films, a common approach is to add flame retardants to the single functional layer (e.g., the electrochromic layer) of the film. However, this approach has significant technical drawbacks: most flame retardants have poor compatibility with the matrix materials and functional components of the electrochromic film's functional layers. After addition, they can easily lead to phase separation and agglomeration within the functional layers, severely impacting the core electrochromic performance (such as color change response speed, cycle stability, and color / fading contrast) and key optical performance (such as visible light transmittance and haze). It is difficult to balance flame retardancy with performance, making it unsuitable for applications with high safety requirements, such as automobiles and building curtain walls.

[0005] Therefore, developing an electrochromic film that can simultaneously achieve excellent flame retardancy, stable electrochromic properties, and good optical properties, and thus synergistically optimize flame retardancy and performance, has become a pressing technical bottleneck in this field. Summary of the Invention

[0006] The purpose of this application is to solve the technical problem of poor compatibility between electrochromic materials and flame retardants.

[0007] To achieve the above objectives, this application provides an electrochromic film with flame-retardant function, comprising a first conductive base film and a second conductive base film arranged in parallel and opposite directions, and an electrochromic photocurable layer disposed between the first conductive base film and the second conductive base film. By weight, the electrochromic photocurable layer comprises the following components:

[0008] 75 to 85 parts flame retardant; 9 to 19 parts of electrochromic material; 5 to 10 parts of light-cured prepolymer; 1 to 1.5 parts of photocurable monomer; Photoinitiator 0.05 to 0.15 parts; Dispersant 0.5 to 1.5 parts; Wherein: the flame retardant is an organic phosphorus-containing compound; the surface of the electrochromic material contains active sites that interact with the polar functional groups of the dispersant at the interface; the photocurable prepolymer contains polar functional groups, which are selected from at least one of ester bonds, ether bonds, and polyurethane segments; the photocurable monomer is selected from acrylate compounds; the photoinitiator is selected from cleavage-type free radical photoinitiators containing hydrophobic groups; and the dispersant has polar and non-polar segments.

[0009] Based on the above technical solution, the synergistic effect of molecular structure matching of each component, multiple interfacial interactions, and photopolymerization reaction has led to the construction of a stable and synergistically performing multi-component system: First, organic phosphorus-containing flame retardants, as the main component, form good structural compatibility with photocurable prepolymers (containing polar functional groups such as ester bonds, ether bonds, and polyurethane segments) through ester groups, aromatic rings and other units in their molecular structure. They achieve uniform mixing at the molecular level through van der Waals forces, while providing basic flame retardant activity for the system. Secondly, the active sites such as hydroxyl groups and metal ions on the surface of the electrochromic material interact with the polar segments such as hydrogen bonds and coordination bonds of the dispersant, which firmly anchors the dispersant to the surface of the electrochromic material. Meanwhile, the non-polar segments of the dispersant can form good compatibility with flame retardants, photocurable prepolymers and acrylate photocurable monomers. This is equivalent to building a molecular bridge between the electrochromic material and other organic components, effectively solving the compatibility problem between the electrochromic material and the flame retardant and avoiding particle agglomeration. Furthermore, the photocurable prepolymer and the acrylate photocurable monomer form a crosslinking system. The low viscosity of the photocurable monomer can dilute the viscosity of the system and optimize the coating process. The acrylate double bonds it contains have excellent reaction compatibility with the active functional groups of the photocurable prepolymer. The hydrophobic pyrolysis free radical photoinitiator is uniformly dispersed in the mixed system due to the good solubility of the hydrophobic group and the organic phase in the system. Under ultraviolet irradiation, it rapidly pyrolyzes to generate free radicals, which initiate the free radical polymerization reaction between the photocurable prepolymer and the photocurable monomer, forming a three-dimensional crosslinked dense polymer network. This firmly locks all components, such as flame retardants and electrochromic materials modified with dispersants, inside the film layer, which not only prevents component migration during use but also strengthens the interfacial bonding between the components. Finally, through a complete reaction pathway of compatibility optimization, photopolymerization crosslinking, and synergistic functional component synthesis, an electrochromic film with excellent flame retardant properties, stable electrochromic properties, and good structural stability was successfully prepared.

[0010] As a further improvement of this application, the flame retardant is selected from at least one of triethyl phosphate, trihexyl phosphate, trimethyl phosphate, toluene diphenyl phosphate, tri(xyl) phosphate, triisobutyl phosphate, tri(2-chloropropyl) phosphate, diphenyl isooctyl phosphate, tri(2-chloroethyl) phosphate, diphenyl isodecanyl phosphate, triisopropylphenyl phosphate, tributoxyethyl phosphate, tri(1,3-dichloroisopropyl) phosphate, tert-butylphenyl diphenyl phosphate, phosphite, and triphenyl phosphite.

[0011] As a further improvement of this application, the active site of the electrochromic material is selected from at least one of hydroxyl groups, metal ions, unsaturated bonds, and lattice defect sites, and the interfacial interaction is at least one of hydrogen bonds, coordination bonds, and dipole-dipole interactions.

[0012] As a further improvement of this application, the electrochromic material is selected from at least one of anisotropic metal sulfide nanoparticles, hydroxyapatite nanorods, zinc oxide nanorods, titanium dioxide nanorods, iodine-containing organic-inorganic composite nanorods, tungsten oxide nanorods, and lanthanum phosphate nanorods. Preferably, the particle size of the electrochromic material is 50 nm to 200 nm.

[0013] As a further improvement of this application, the dichromatic metal sulfide is selected from at least one of the following: copper sulfide, bismuth sulfide, bismuth antimony sulfide, titanium sulfide, tungsten sulfide, zirconium sulfide, manganese sulfide, tin sulfide, bismuth iodide, bismuth bromosulfide, and bismuth chloride.

[0014] As a further improvement of this application, the dispersant is selected from at least one of hydroxyl-containing polyurethane prepolymers, polyurethane graft copolymers, polyurethane block copolymers, polyester-type polyurethanes, polyether-type polyurethanes, acrylic-modified polyurethanes, and siloxane-modified polyurethanes. Preferably, the hydroxyl-containing polyurethane prepolymer has a hydroxyl value of 50–100 mg KOH / g and a number-average molecular weight of 3000–6000.

[0015] As a further improvement of this application, the photocurable prepolymer is selected from at least one of polyurethane-modified acrylate, polyester-modified acrylate, polyether-modified acrylate, siloxane-modified acrylate, and epoxy-modified acrylate, wherein: the polyurethane-modified acrylate molecular chain contains polyurethane segments and ester bonds, the polyester-modified acrylate contains ester bonds, and the epoxy-modified acrylate contains ether bonds. Preferably, the weight-average molecular weight of the photocurable prepolymer is 8000-15000, and the acrylate functionality is 2-3.

[0016] As a further improvement of this application, the photocurable monomer is selected from 1,6-hexanediol diacrylate (HDDA), isobornyl acrylate (IBOA), isobornyl methacrylate (IBOMA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), lauryl acrylate (LA), lauryl methacrylate (LMA), ethoxylated phthalate diacrylate (OPPEA), tripropylene glycol diacrylate (TPGDA), tetrahydrofuran acrylate (THFA), neopentyl glycol diacrylate (NPGDA), pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), ethoxylated ethoxylated acrylate (EOEOEA), 2-phenoxyethyl acrylate, isotridecyl acrylate, hydroxyethyl methacrylate, and 1,4-butanediol diacrylate. The following are at least one of the following: acrylate, tricyclodecanediethanol diacrylate, ethylene glycol dimethacrylate, bis(trimethylolpropane)tetraacrylate, propoxylated glycerol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, dicyclopentenylethoxymethacrylate, acrylmorpholine, hydroxypropyl methacrylate, cyclotrimethylolpropane methyl acetal acrylate, o-phenylphenoxyethyl acrylate, ethoxylated bisphenol A dimethacrylate, 2-hydroxyethyl methacrylate phosphate, glycidyl methacrylate, N-vinylpyrrolidone, β-carboxyethyl acrylate, methoxylated polyethylene glycol monomethacrylate, polyethylene glycol diacrylate, ethoxylated bisphenol A diacrylate, 3,3,5-trimethylcyclohexyl acrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated bisphenol A dimethacrylate, methacrylamide ethyl ethylene urea, and alkyloxylated phenol acrylate.

[0017] As a further improvement of this application, the hydrophobic group of the photoinitiator is selected from at least one of aromatic rings, alkyl groups, cycloalkyl groups, etc., and the photoinitiator is selected from at least one of the following: cleavage-type free radical photoinitiators 1173, 184, TPO, TPO-L, 907, 369, 651, 819, MBF, 2959, CTX, DETX, and hydrogen-abstracting free radical photoinitiators BP, ITX, 2,4,6-trimethylbenzophenone, wherein: the chemical name of photoinitiator 1173 is 2-hydroxy-2-methyl-1-phenyl-1-propanone, the chemical name of photoinitiator 184 is 1-hydroxycyclohexylphenyl ketone, the chemical name of photoinitiator TPO is 2,4,6-trimethylbenzoyl diphenylphosphine oxide, the chemical name of photoinitiator TPO-L is ethyl 2,4,6-trimethylbenzoyl phenylphosphonate, and the chemical name of photoinitiator 907 is 2-methyl- 1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, photoinitiator 369 is chemically named 2-benzyl-2-(dimethylamino)-1-(4-morpholinylphenyl)-1-butanone, photoinitiator 651 is chemically named 2,2-dimethoxy-2-phenylacetophenone, photoinitiator 819 is chemically named phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and photoinitiator MBF is chemically named... The names of the photoinitiators are: methyl benzoylformate, BP (benzophenone), ITX (2-isopropylthioxanthraquinone), 2959 (2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone), CTX (2-chlorothioxanthion-9-one), and DETX (2,4-diethylthioxanthraquinone).

[0018] To achieve the above objectives, this application also provides a method for preparing an electrochromic film with flame-retardant function, comprising the following steps: S1. Weigh the flame retardant, electrochromic material, photocurable prepolymer, photocurable monomer, photoinitiator and dispersant according to the preset weight parts, add them to the reaction vessel, and stir thoroughly at 30℃~50℃ to obtain a mixed solution; S2. The mixed solution is degassed, and the vacuum degree during the degasing process is controlled to be -0.08 MPa to -0.1 MPa. After degasing, the temperature of the mixed solution is lowered to 25°C to 30°C, and kept at this temperature for 24 hours to obtain a stable electrochromic photocurable solution. Preferably, the viscosity of the electrochromic photocurable solution is 500 to 1500 mPa. s, 25℃; S3. The electrochromic photocurable solution is uniformly coated on one side of the first conductive base film to obtain a wet film with a thickness of 50μm to 100μm. Then, the second conductive base film is placed on the first conductive base film coated with the solution with its conductive surface facing the electrochromic photocurable solution. The composite structure after stacking is pressed by a pressure roller assembly to remove interlayer air bubbles and make each layer tightly adhered. Irradiation curing is performed to cause the electrochromic photocurable solution to undergo photopolymerization reaction and solidify into a film, resulting in an electrochromic film with flame retardant function. The total thickness of the electrochromic film is 150μm to 300μm. Preferably, in the pressing process: the pressing temperature is 25℃~30℃, the pressing pressure is 0.3MPa~0.5MPa, and the pressing rate is 0.5m / min~1m / min; in the irradiation curing process: the irradiation source is an LED ultraviolet lamp with a wavelength of 365nm~405nm and an irradiation intensity of 800mW / cm². 2 ~1200mW / cm 2 The irradiation time is 30s to 60s.

[0019] As a further improvement of this application, in step S1, the stirring rate is 250 r / min to 350 r / min, and the stirring time is 1 h to 1.5 h.

[0020] As a further improvement of this application, in step S3, the first conductive base film includes a PET base film and a conductive layer disposed on the surface of the PET base film, wherein the conductive layer is selected from any one of indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide; the second conductive base film includes a PET base film and a conductive layer disposed on the surface of the PET base film, wherein the conductive layer is selected from any one of indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide. Preferably, the thickness of the PET base film is 50 μm to 200 μm, and the thickness of the conductive layer is 100 nm to 200 nm.

[0021] The specific benefits of this application are as follows: This application provides an electrochromic film with flame-retardant function and its preparation method. The composition ratio of the electrochromic photocurable layer is precisely defined, including 75-85 parts of flame retardant, 9-19 parts of electrochromic material, 5-10 parts of photocurable prepolymer, 1-1.5 parts of photocurable monomer, 0.05-0.15 parts of photoinitiator, and 0.5-1.5 parts of dispersant. Combining the structural characteristics of each component, a synergistic unity of multiple technological advantages is achieved. I. Successfully solved the technical bottleneck of poor compatibility between flame retardants and electrochromic materials in traditional electrochromic films—organic phosphorus-containing flame retardants and photocurable prepolymers containing polar functional groups such as ester bonds and ether bonds form good structural compatibility. The dispersant, with its amphiphilic structure and interface anchoring function, anchors the active sites on the surface of the electrochromic material through hydrogen bonds, coordination bonds, etc. on one end, and forms a compatible interface with the organic components on the other end, thus building a molecular bridge between the electrochromic material, dispersant, flame retardant, and photocuring system, effectively avoiding component aggregation and phase separation; Second, it achieves synergistic optimization of flame retardant and electrochromic properties—when organic phosphorus-containing flame retardants burn, they release phosphorus oxides, which can capture combustion free radicals and catalyze char formation to form a dense flame retardant barrier, ensuring that the limiting oxygen index of the film layer is consistently higher than 33% and the vertical burning rating reaches V-0, while inhibiting smoke generation (smoke density level controlled at 39-42); while the photocurable prepolymer and acrylate monomers are polymerized by photoinitiator, forming a three-dimensional cross-linked network that firmly locks all components, ensuring the uniform distribution and structural stability of the electrochromic material. After 10,000 cycles of power-on and power-off, the color change decay is only 10.5%-11.8%, with excellent color change response and cycle stability; III. Optimized film preparation process and structural stability—the low viscosity of the photocurable monomer reduced the system viscosity (500–1500 mPa). (s, 25℃), suitable for efficient coating processes such as blade coating, the synergistic effect of pressing and irradiation curing makes the interfaces of the film layer tightly bonded, the total thickness is controlled between 150μm and 300μm, and it has both good mechanical properties and processing adaptability. Fourth, it broadens the adaptability of application scenarios. Through the synergistic design of components, the film layer simultaneously meets the requirements of flame retardant safety, stable electrochromic performance and good optical performance. It can be adapted to scenarios with high requirements for safety level and performance, such as car sunroofs, smart building curtain walls and display devices, and solves the industry pain point that traditional products cannot take into account both flame retardancy and performance. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them, and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0023] Example 1 This embodiment provides an electrochromic film with flame-retardant function and its preparation method, specifically as follows: By weight, 75 parts of triethyl phosphate flame retardant, 9 parts of copper sulfide electrochromic material with a particle size of 50 nm, 5 parts of polyurethane-modified acrylate photocurable prepolymer with a weight-average molecular weight of 8000 and an acrylate functionality of 2, 1 part of trimethylolpropane trimethacrylate photocurable monomer, 0.05 parts of 184 photoinitiator, and 0.5 parts of a hydroxyl value of 50 mg KOH / g and a number-average molecular weight of 30... A hydroxyl-containing polyurethane prepolymer dispersant of 00 was added to a reaction vessel and stirred thoroughly at 250 r / min for 1 h at 30 °C to obtain a uniformly dispersed mixed solution. The mixed solution was then degassed, with the vacuum degree controlled at -0.08 MPa and the degassed time at 30 min. After degassed, the temperature of the mixed solution was lowered to 25 °C and kept at this temperature for 24 hours to obtain a uniform and stable electrochromic photocurable solution with a viscosity of 500 mPa. s, 25℃.

[0024] The electrochromic photocurable solution is then uniformly coated onto one side of the first conductive base film using a doctor blade coating method, with a coating thickness of 50 μm. The first conductive base film comprises a 50 μm thick PET base film and a 100 nm thick indium tin oxide conductive layer disposed on the surface of the PET base film. Subsequently, a second conductive base film is placed on top of the first conductive base film coated with the solution, with its conductive surface facing the electrochromic photocurable solution. The structure, dimensions, and performance parameters of the second conductive base film are completely identical to those of the first conductive base film. The pressure roller assembly presses the laminated composite structure at a temperature of 25°C, a pressure of 0.3 MPa, and a pressing rate of 0.5 m / min to eliminate interlayer air bubbles and ensure tight adhesion between layers. Then, an LED ultraviolet lamp is used for irradiation curing. The LED ultraviolet lamp has a wavelength of 365 nm, an irradiation intensity of 800 mW / cm², and an irradiation time of 30 s, causing the electrochromic photocuring solution to undergo a photopolymerization reaction and solidify into a film, ultimately yielding an electrochromic film with flame-retardant properties and a total thickness of 150 μm.

[0025] Example 2 This embodiment provides an electrochromic film with flame-retardant function and its preparation method, specifically as follows: By weight, 85 parts of triethyl phosphate flame retardant, 19 parts of copper sulfide electrochromic material with a particle size of 200 nm, 10 parts of polyurethane-modified acrylate photocurable prepolymer with a weight-average molecular weight of 15000 and an acrylate functionality of 3, 1.5 parts of trimethylolpropane trimethacrylate photocurable monomer, 0.15 parts of 184 photoinitiator, and 1.5 parts of a hydroxyl value of 100 mg KOH / g and a number-average molecular weight of... A hydroxyl-containing polyurethane prepolymer dispersant of 6000 mg / L was added to a reaction vessel and stirred thoroughly at 350 rpm for 1.5 h at 50 °C to obtain a uniformly dispersed mixed solution. The mixed solution was then degassed, with the vacuum level controlled at -0.1 MPa and the degassed time at 30 min. After degassed, the temperature of the mixed solution was lowered to 25 °C and held at this temperature for 24 h to obtain a homogeneous and stable electrochromic photocurable solution with a viscosity of 1500 mPa. s, 25℃.

[0026] The electrochromic photocurable solution is then uniformly coated onto one side of the first conductive base film using a doctor blade coating method, with a coating thickness of 100 μm. The first conductive base film includes a 100 μm thick PET base film and a 200 nm thick indium tin oxide conductive layer disposed on the surface of the PET base film. Subsequently, a second conductive base film is placed on top of the first conductive base film coated with the solution, with its conductive surface facing the electrochromic photocurable solution. The structure, size, and performance parameters of the second conductive base film are completely identical to those of the first conductive base film. The laminated composite structure is pressed using a pressure roller assembly at a temperature of 30°C, a pressure of 0.5 MPa, and a pressing rate of 1 m / min to eliminate interlayer air bubbles and ensure tight adhesion between layers. Subsequently, an LED ultraviolet lamp is used for irradiation curing. The LED ultraviolet lamp has a wavelength of 405 nm, an irradiation intensity of 1200 mW / cm², and an irradiation time of 60 s, causing the electrochromic photocurable solution to undergo a photopolymerization reaction and solidify into a film, ultimately yielding an electrochromic film with flame-retardant properties and a total thickness of 300 μm.

[0027] Example 3 This embodiment provides an electrochromic film with flame-retardant function and its preparation method, as follows: By weight, 80 parts of triethyl phosphate flame retardant, 15 parts of copper sulfide electrochromic material with a particle size of 100 nm, 8 parts of polyurethane-modified acrylate photocurable prepolymer with a weight-average molecular weight of 15000 and an acrylate functionality of 3, 1.2 parts of trimethylolpropane trimethacrylate photocurable monomer, 0.1 parts of 184 photoinitiator, and 1 part of a hydroxyl value of 80 mg KOH / g and a number-average molecular weight of 4... A hydroxyl-containing polyurethane prepolymer dispersant of 000 was added to a reaction vessel and stirred thoroughly at 300 r / min for 1 h at 40 °C to obtain a uniformly dispersed mixed solution. The mixed solution was then degassed, with the vacuum level controlled at -0.1 MPa and the degassed time at 30 min. After degassed, the temperature of the mixed solution was lowered to 25 °C and kept at this temperature for 24 hours to obtain a uniform and stable electrochromic photocurable solution with a viscosity of 1000 mPa. s, 25℃.

[0028] The electrochromic photocurable solution is then uniformly coated onto one side of the first conductive base film using a doctor blade coating method, with a coating thickness of 80 μm. The first conductive base film comprises an 80 μm thick PET base film and a 150 nm thick indium tin oxide conductive layer disposed on the surface of the PET base film. Subsequently, a second conductive base film is placed on top of the first conductive base film coated with the solution, with its conductive surface facing the electrochromic photocurable solution. The structure, dimensions, and performance parameters of the second conductive base film are completely identical to those of the first conductive base film. The composite structure after lamination is pressed by a pressure roller assembly at a pressing temperature of 30℃, a pressing pressure of 0.5MPa, and a pressing rate of 1m / min to eliminate interlayer air bubbles and ensure tight adhesion between the layers. Then, an LED ultraviolet lamp is used for irradiation curing. The wavelength of the LED ultraviolet lamp is 365nm, the irradiation intensity is 1000mW / cm², and the irradiation time is 50s. This causes the electrochromic photocuring solution to undergo a photopolymerization reaction and solidify into a film, ultimately yielding an electrochromic film with flame-retardant properties and a total thickness of 240μm.

[0029] Comparative Example 1 The difference between this comparative example and Example 3 is that the triethyl phosphate flame retardant is 50 parts by weight, while the others remain the same.

[0030] Comparative Example 2 The difference between this comparative example and Example 3 is that the triethyl phosphate flame retardant is 100 parts by weight, while other aspects remain unchanged.

[0031] Comparative Example 3 The difference between this comparative example and Example 3 is that the weight of the copper sulfide electrochromic material is 5 parts.

[0032] Comparative Example 4 The difference between this comparative example and Example 3 is that the weight of the copper sulfide electrochromic material is 25 parts.

[0033] Comparative Example 5 The difference between this comparative example and Example 3 is that the weight of the dispersant is 0.1 parts.

[0034] Comparative Example 6 The difference between this comparative example and Example 3 is that the weight of the dispersant is 3 parts.

[0035] The flame retardant or electrochromic properties of the electrochromic films with flame retardant function prepared by different embodiments or comparative examples were tested. The flame retardant properties included limiting oxygen index, vertical burning rating, and smoke density rating. The electrochromic properties were mainly tested to determine the degree of color change attenuation of the electrochromic film after 10,000 cycles of power on and off.

[0036] The testing standards or testing procedures are as follows: 1. Flame retardant properties The limiting oxygen index (LOI) is performed according to GB / T 2406.2-2009 standard. The electrochromic film is cut into a sample with the original thickness of 100mm×10mm and placed in an oxygen index tester. The oxygen concentration of the oxygen and nitrogen mixture is adjusted, and the lowest oxygen concentration when the sample maintains combustion for 3 minutes or the combustion length reaches 50mm is measured. This is the limiting oxygen index. The vertical burning rating is tested according to GB / T 2408-2021 standard. The sample size is 125mm×13mm and the original thickness of the sample is ignited in the vertical burning tester. The burning time, dripping situation and whether the degreased cotton is ignited are recorded. The V-0, V-1 or V-2 rating is determined according to the standard. Smoke density rating (SDR) is determined according to GB / T 8627-2007 standard. It is achieved by using a smoke density tester, placing the sample under specific combustion conditions, measuring the smoke density values ​​at different time points during the combustion process, and calculating the average smoke density rating.

[0037] 2. Electrochromic properties A test system was built according to the GB / T 33893-2017 standard. The electrochromic film was connected to a DC regulated power supply, and the working voltage was set to the rated driving voltage of the device (90V~110V). Power-on and power-off cycle tests were carried out. Each cycle included 3 seconds of color development upon power-on and 3 seconds of color fading upon power-off, with a total of 10,000 cycles. The maximum transmittance difference (ΔTmax) at the beginning of the cycle and after 10,000 cycles was measured using a spectrophotometer. The color change attenuation was calculated using the formula (initial ΔTmax - post-cycle ΔTmax) / initial ΔTmax × 100%.

[0038] The test results are shown in Table 1.

[0039] Table 1

[0040] As shown in Table 1, the overall performance of Examples 1-3 is far superior to that of Comparative Examples 1 and 2: In terms of limiting oxygen index, Examples 1-3 are 33.5%, 34.9%, and 34.5% respectively, all consistently higher than 33.5%, while Comparative Example 1 is only 28.8%, significantly lower than the level of Examples 1. Although Comparative Example 2 reaches 35.2%, slightly higher than Example 3, it does not form a synergistic performance advantage. In terms of vertical combustion rating, Examples 1-3 all reach the highest V-0 rating, while Comparative Examples 1 and 2 both drop to V-1 rating, indicating a significant decline in flame retardant safety performance. In terms of smoke density rating, Examples 1-3 are controlled within a reasonable range of 32-33, while Comparative Example 1 soars to 58, indicating a significant increase in smoke release. Although Comparative Example 2 is as low as 40, combined with other performance indicators, its combustion system stability is insufficient. In terms of electrochromic performance, the color change attenuation of Examples 1-3 is only 10.5%-11.8%, with excellent cycle stability, while Comparative Example 1 rises to 15.8% and Comparative Example 2 rises to 16.3%, indicating a significant attenuation of color change performance. The reasons are as follows: Comparative Examples 1 and 2 deviated from the weight range of flame retardant (75-85 parts) defined in the claims of this application: Comparative Example 1 used only 50 parts of triethyl phosphate flame retardant, which was far below the preset range, resulting in insufficient total amount of flame retardant elements. During combustion, it could not generate enough phosphorus oxides to capture free radicals and catalyze char formation, making it difficult to form a continuous and dense flame retardant barrier. At the same time, the proportion of flame retardant as a dispersion medium was insufficient, which disrupted the compatibility balance with electrochromic materials and dispersants, causing the electrochromic materials to agglomerate, which in turn led to a significant decrease in flame retardant performance and an aggravated decay of electrochromic performance. Comparative Example 2 used 100 parts of flame retardant. The excessive flame retardant squeezed the interfacial space between the electrochromic material and the dispersant, exceeding the interfacial anchoring capacity of the dispersant, which reduced the uniformity of system dispersion. Although the limiting oxygen index was slightly improved, the vertical burning rating could not reach the V-0 standard. Moreover, the effective distribution space of the electrochromic material was squeezed, and it could not respond uniformly to the electric field during the cycle. Ultimately, the various performances could not be optimized synergistically, and the overall performance was far inferior to Examples 1-3.

[0041] The performance of Examples 1-3 is significantly better than that of Comparative Examples 3 and 4 in all aspects: Regarding the limiting oxygen index, Examples 1-3 have 33.5%, 34.9%, and 34.5% respectively, all consistently above 33%, while Comparative Example 3 has 34.3% and Comparative Example 4 has 34.4%, which, although close to Example 3, do not reach the optimal level of Example 2; Regarding the vertical combustion rating, Examples 1-3 all reach the highest V-0 rating, while Comparative Examples 3 and 4 both drop to V-1, indicating a significant decrease in flame retardant safety; Regarding the smoke density rating, Examples 1-3 are controlled in the low smoke range of 32-33, while Comparative Example 3 is 45 and Comparative Example 4 is 43. Combined with the vertical combustion rating, it can be seen that their flame retardant system lacks stability, posing a risk of incomplete local combustion during combustion; Regarding the electrochromic performance, the color change attenuation of Examples 1-3 is only 10.5%-11.8%, demonstrating excellent cycle stability, while Comparative Example 3 increases to 14.2% and Comparative Example 4 increases significantly to 17.5%, showing a significant decrease in color change performance. The reasons are as follows: Comparative Examples 3 and 4 deviate from the weight range (9 to 19 parts) of the electrochromic material defined in the claims of this application: Comparative Example 3 uses only 5 parts of copper sulfide electrochromic material, which is insufficient and results in a lack of interfacial binding sites between the material and the dispersant, leading to a decline in the dispersion stability of the system. The flame retardant exhibits localized aggregation due to a lack of sufficient anchoring points, disrupting the continuity of the flame retardant system. Simultaneously, the electrochromic material is sparsely distributed, and the overall response consistency decreases after a small number of active sites are damaged during cycling, resulting in a decrease in vertical burning rating and a decline in color-changing performance. Example 4 uses 25 parts of copper sulfide electrochromic material. The excess material exceeds the dispersion carrying capacity of the dispersant, destroying the amphiphilic structure and interfacial anchoring function of the dispersant. This leads to a sharp decrease in the compatibility between the electrochromic material and the flame retardant, resulting in stratification and agglomeration. The excessive proportion of non-flame retardant components dilutes the concentration of flame retardant elements, making it impossible to achieve the V-0 standard for vertical burning rating. Furthermore, the agglomerated electrochromic material cannot respond uniformly to the electric field, and the interfacial interaction is prone to breakage during cycling. Ultimately, this leads to a significant increase in the color change attenuation rate, and all performance aspects are inferior to those of Examples 1-3.

[0042] As shown in Table 1, the performance of Comparative Examples 5 and 6 is inferior to that of Examples 1-3 in all aspects: Regarding the limiting oxygen index, Examples 1-3 have 33.5%, 34.9%, and 34.5% respectively, all consistently above 33%, while Comparative Example 5 has only 29.5% and Comparative Example 6 has 34.0%, with Comparative Example 5 significantly lower than the examples; Regarding the vertical combustion rating, Examples 1-3 all reach the highest V-0 rating, while Comparative Examples 5 and 6 drop to V-1, indicating a significant decrease in flame retardant safety; Regarding the smoke density rating, Examples 1-3 are controlled within a reasonable range of 32-33, while Comparative Example 5 is 39 and Comparative Example 6 is 37. Combined with the vertical combustion rating, this indicates an unstable combustion system and a potential risk of incomplete local combustion; Regarding the electrochromic performance, the color change attenuation of Examples 1-3 is only 10.5%-11.8%, demonstrating excellent cycle stability, while Comparative Example 5 soars to 18.2% and Comparative Example 6 rises to 15.5%, showing a very significant attenuation of color change performance. The reasons for these performance differences are as follows: Comparative Examples 5 and 6 also deviated from the weight range of dispersant (0.5 to 1.5 parts) defined in the claims of this application: Comparative Example 5 used only 0.1 parts of hydroxyl-containing polyurethane prepolymer dispersant, which was seriously insufficient and could not exert its interfacial bridging effect due to its amphiphilic structure. It could neither effectively reduce the interfacial tension between the electrochromic material and the flame retardant, nor could it anchor the electrochromic material through polar functional groups to form stable hydrogen bonds or coordination bonds with active sites such as hydroxyl groups and metal ions on the surface of the electrochromic material. This resulted in complete incompatibility between the electrochromic material and the flame retardant, leading to layering and agglomeration. The flame retardant could not form a continuous and effective flame retardant system, and combustion was not uniform. Catalytic carbonization and free radical capture are achieved, but the electrochromic material cannot respond uniformly to the electric field due to sedimentation and agglomeration, resulting in a significant decline in both core functions. Comparative Example 6 uses 3 parts of dispersant. Excessive dispersant will form redundant molecular chains. Although it can maintain the basic compatibility of the system, the dispersant itself has no flame retardant or electrochromic function. It not only dilutes the effective concentration of the flame retardant, leading to a decrease in flame retardant and smoke suppression performance, but also hinders the effective action of the electric field on the electrochromic material. Moreover, the redundant molecular chains are prone to aging and breakage during cycling, indirectly destroying the stability of the color-changing component. Ultimately, this leads to an accelerated decline in electrochromic performance, and all performances are far inferior to those of Examples 1-3.

[0043] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0044] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrochromic film with flame-retardant function, characterized in that, The device includes a first conductive base film and a second conductive base film arranged in parallel and opposite directions, and an electrochromic photocurable layer disposed between the first conductive base film and the second conductive base film. By weight, the electrochromic photocurable layer comprises the following components: 75 to 85 parts flame retardant; 9 to 19 parts of electrochromic material; 5 to 10 parts of light-cured prepolymer; 1 to 1.5 parts of photocurable monomer; Photoinitiator 0.05 to 0.15 parts; Dispersant 0.5 to 1.5 parts; Wherein: the flame retardant is an organic phosphorus-containing compound; the surface of the electrochromic material contains active sites that interact with the polar functional groups of the dispersant at the interface; the photocurable prepolymer contains polar functional groups, which are selected from at least one of ester bonds, ether bonds, and polyurethane segments; the photocurable monomer is selected from acrylate compounds; the photoinitiator is selected from cleavage-type free radical photoinitiators containing hydrophobic groups; and the dispersant has polar and non-polar segments. The flame retardant is selected from at least one of the following: triethyl phosphate, trihexyl phosphate, trimethyl phosphate, toluene diphenyl phosphate, tri(xyl) phosphate, triisobutyl phosphate, tri(2-chloropropyl) phosphate, diphenyl isooctyl phosphate, tri(2-chloroethyl) phosphate, diphenyl isodecanyl phosphate, triisopropylphenyl phosphate, tributoxyethyl phosphate, tri(1,3-dichloroisopropyl) phosphate, tert-butylphenyl diphenyl phosphate, phosphite, and triphenyl phosphite.

2. The electrochromic film with flame-retardant function according to claim 1, characterized in that, The active sites of the electrochromic material are selected from at least one of hydroxyl groups, metal ions, unsaturated bonds, and lattice defect sites, and the interfacial interactions are at least one of hydrogen bonds, coordination bonds, and dipole-dipole interactions.

3. The electrochromic film with flame-retardant function according to claim 2, characterized in that, The electrochromic material is selected from at least one of anisotropic metal sulfide nanoparticles, hydroxyapatite nanorods, zinc oxide nanorods, titanium dioxide nanorods, iodine-containing organic-inorganic composite nanorods, tungsten oxide nanorods, and lanthanum phosphate nanorods.

4. The electrochromic film with flame-retardant function according to claim 3, characterized in that, The anisotropic metal sulfide is selected from at least one of copper sulfide, bismuth sulfide, bismuth antimony sulfide, titanium sulfide, tungsten sulfide, zirconium sulfide, manganese sulfide, tin sulfide, bismuth iodide, bismuth bromosulfide, and bismuth chloride.

5. The electrochromic film with flame-retardant function according to claim 1, characterized in that, The dispersant is selected from at least one of hydroxyl-containing polyurethane prepolymers, polyurethane graft copolymers, polyurethane block copolymers, polyester polyurethanes, polyether polyurethanes, acrylic-modified polyurethanes, and siloxane-modified polyurethanes.

6. The electrochromic film with flame-retardant function according to claim 1, characterized in that, The photocurable prepolymer is selected from at least one of polyurethane-modified acrylate, polyester-modified acrylate, polyether-modified acrylate, siloxane-modified acrylate, and epoxy-modified acrylate.

7. The electrochromic film with flame-retardant function according to claim 1, characterized in that, The photocurable monomer is selected from 1,6-hexanediol diacrylate, isobornyl acrylate, isobornyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, lauryl acrylate, lauryl methacrylate, ethoxylated phthalate diacrylate, dipropylene glycol diacrylate, tetrahydrofuran acrylate, neopentyl glycol diacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, ethoxylated ethoxyacrylate, 2-phenoxyethyl acrylate, isotridecyl acrylate, hydroxyethyl methacrylate, 1,4-butanediol diacrylate, tricyclodecanediethanol diacrylate, ethylene glycol dimethacrylate, bis(trimethylolpropane)tetraacrylate, and propoxylated glycerol triacrylate. The following are at least one of the following: ester, tri(2-hydroxyethyl)isocyanurate triacrylate, dicyclopentenylethoxymethacrylate, acrylmorpholine, hydroxypropyl methacrylate, cyclotrimethylolpropane methyl acetal acrylate, o-phenylphenoxyethyl acrylate, ethoxylated bisphenol A dimethacrylate, 2-hydroxyethyl methacrylate phosphate, glycidyl methacrylate, N-vinylpyrrolidone, β-carboxyethyl acrylate, methoxylated polyethylene glycol monomethacrylate, polyethylene glycol diacrylate, ethoxylated bisphenol A diacrylate, 3,3,5-trimethylcyclohexyl acrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated bisphenol A dimethacrylate, methacrylamide ethyl ethylene urea, and alkyloxyphenol acrylate.

8. The electrochromic film with flame-retardant function according to claim 1, characterized in that, The photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphonate, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 2-benzyl-2-(dimethylamino)-1-(4-morpholinylphenyl)-1-butanone, 2,2-dimethoxy-2-phenylacetophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, methyl benzoylformate, benzophenone, 2-isopropylthioxanthraphenone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, 2-chlorothioxanthion-9-one, and 2,4-diethylthioxanthion-9-one.

9. A method for preparing an electrochromic film with flame-retardant function according to claim 1, characterized in that, Includes the following steps: S1. Weigh the flame retardant, electrochromic material, photocurable prepolymer, photocurable monomer, photoinitiator and dispersant according to the preset weight parts, add them to the reaction vessel, and stir thoroughly at 30℃~50℃ to obtain a mixed solution; S2. The mixed solution is degassed, and the vacuum degree during the degasing process is controlled to be -0.08MPa to -0.1MPa. After degasing is completed, the temperature of the mixed solution is reduced to 25℃ to 30℃, and kept at this temperature for 24 hours to obtain an electrochromic photocurable solution. S3. The electrochromic photocurable solution is uniformly coated on one side of the first conductive base film. Then, the second conductive base film is placed on the first conductive base film coated with the solution with its conductive surface facing the electrochromic photocurable solution. The composite structure after stacking is pressed by a pressure roller assembly to remove interlayer air bubbles and make each layer fit tightly. Irradiation curing is performed to cause the electrochromic photocurable solution to undergo photopolymerization reaction and solidify into a film, thereby obtaining an electrochromic film with flame retardant function.

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