A thermochromic photoionizing intermediate film and its preparation method

Abstract

This application relates to the field of film material technology, and particularly to a thermochromic photosensitive ionic intermediate film and its preparation method. The film, by weight, comprises the following components: 50-80 parts of acrylic monomers, 3-10 parts of zinc diacrylate, 0.5-5 parts of a color-changing agent, 0.5-5 parts of an infrared absorber, and 1-5 parts of a photoinitiator; wherein the acrylic monomers include acrylic acid, methacrylic acid, and butyl acrylate; the total mass of acrylic acid and methacrylic acid is 20-40% of the mass of the acrylic monomers; and the mass of butyl acrylate is 30-60% of the mass of the acrylic monomers. This application utilizes the acrylic monomers and zinc diacrylate to form an in-situ ionic crosslinking network through UV curing, and low-temperature annealing optimizes the ion clusters, avoiding high-temperature damage, thus imparting high transparency, strong adhesion, and cycle stability to the film. The process is simple and efficient, and it is suitable for intelligent dimming glass such as building curtain walls and automotive sunroofs.

Description

Technical Field

[0001] This application relates to the field of film material technology, and in particular to a thermochromic photoionizing intermediate film and its preparation method. Background Technology

[0002] Thermochromic dimming glass is a type of smart glass that can automatically adjust its light transmittance according to temperature changes. It is widely used in building curtain walls, car sunroofs, greenhouses, and other fields. Among them, laminated dimming glass has attracted widespread attention because it combines the explosion-proof performance of safety glass with the dimming function.

[0003] In existing technologies, thermochromic materials (such as spiropyrans, fluoranes, and liquid crystal microcapsules) are typically dispersed in polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) films, and then laminated with glass under high temperature and pressure. However, the confinement effect of these films on thermochromic materials is weak, leading to dye migration, aggregation, and a significant decrease in cycle life. More importantly, PVB is highly hygroscopic and prone to yellowing and delamination with long-term use; EVA has poor weather resistance, and both have limited adhesion to glass, making it difficult to meet safety glass standards. To improve adhesion performance, intermediate films based on zinc salt ionomers of ethylene-methacrylic acid copolymers have been developed in recent years. These ionomers have advantages such as high transparency, strong adhesion, and aging resistance, but their melt processing temperature is usually 160~180℃. At this temperature, most organic thermochromic materials (such as spiropyrans and fluoranes) will undergo irreversible decomposition or lose activity, limiting their application in smart glass. In addition, existing ionomer-based light-modulating films usually rely on changes in ambient temperature to drive color change, with a significant response lag. They only begin to provide shade after the indoor temperature rises in summer, and cannot achieve adaptive regulation that "the stronger the light, the faster the color change".

[0004] Therefore, there is an urgent need to develop a thermochromic photoionic intermediate film that can be cured at low temperatures, has efficient photothermal conversion self-response capability, and has good compatibility between the color-changing material and the ion crosslinking system. Summary of the Invention

[0005] To address the problems in related technologies where high processing temperatures of thermochromic photochromic films lead to easy decomposition and failure of thermochromic materials, and the dependence on ambient temperature response results in delayed color change, this application provides a thermochromic photochromic ionic intermediate film and its preparation method.

[0006] In a first aspect, this application provides a thermochromic photoionized intermediate film, wherein the film comprises, by weight parts: 50-80 parts of acrylic monomer, 3-10 parts of zinc diacrylate, 0.5-5 parts of color-changing agent, 0.5-5 parts of infrared absorber and 1-5 parts of photoinitiator; The acrylic monomers include acrylic acid, methacrylic acid, and butyl acrylate; the total mass of the acrylic acid and the methacrylic acid is 20-40% of the mass of the acrylic monomers; and the mass of the butyl acrylate is 30-60% of the mass of the acrylic monomers.

[0007] In this application, an acrylic monomer compounded from acrylic acid, methacrylic acid, and butyl acrylate is used as the main component, combined with zinc diacrylate, a color-changing agent, an infrared absorber, and a photoinitiator to form a photocurable ionic composition. This achieves an ionic intermediate film structure that can be cured at room temperature, avoiding the damage to the thermosensitive color-changing material caused by high-temperature processing. At the same time, zinc diacrylate provides a soluble zinc source, forming an interchain ionic cross-linking network with the carboxyl groups in acrylic acid and methacrylic acid. This not only endows the film with high transparency, strong glass adhesion, and good mechanical flexibility, but also avoids the compatibility problem between the alkaline environment and the color-changing agent caused by traditional zinc oxide, ensuring color-changing activity and long-term cycling stability. The introduction of the infrared absorber enables the film to have its own photothermal conversion capability, and it can automatically trigger color change under sunlight without relying on an external electric field or ambient temperature, significantly improving the sensitivity of the dimming response and ease of use.

[0008] Preferably, the molar ratio of zinc element in the zinc diacrylate to the total carboxyl groups in the acrylic acid and the methacrylic acid is 0.04~0.10:1.

[0009] In this application, the ratio of zinc to carboxyl groups is controlled within the above-mentioned range, so that the product maintains high transparency while also having excellent glass bonding strength and moderate flexibility, avoiding the increase in haze caused by excessively dense ionic crosslinking or the insufficient mechanical properties caused by excessively sparse crosslinking, thereby obtaining a thermochromic photochromic film with better overall performance.

[0010] Preferably, the acrylic monomer further includes 2-10% by mass of 1,6-hexanediol diacrylate and / or trimethylolpropane triacrylate.

[0011] In this application, the aforementioned acrylic monomers can be used as crosslinking agents to form an interpenetrating network structure with the ionic crosslinking network, significantly improving the mechanical strength, heat resistance, and dimensional stability of the film, preventing the laminated glass from flowing or deforming under high temperature exposure, and within this addition range, there will be no increase in brittleness or decrease in transparency due to excessive crosslinking, thereby ensuring high light transmittance while meeting the requirements of safety glass for drop ball impact and high temperature weather resistance.

[0012] Preferably, the color-changing agent is a spiropyran compound.

[0013] In this application, the above-mentioned color-changing agent is used to ensure color-changing activity and long-term cycling stability. Spiropyran can still work normally in neutral or weakly alkaline systems, has good compatibility with ionic cross-linking systems, and its color-changing temperature can be flexibly controlled through molecular structure to match the thermotropic heating range required for sunlight response.

[0014] Preferably, the infrared absorber is nano-tin antimony oxide particles and / or nano-indium tin oxide particles; Wherein, the primary particle size of the nano-tin antimony oxide particles is 20~80nm, and / or, the primary particle size of the nano-indium tin oxide particles is 20~80nm.

[0015] In this application, the particle size range is smaller than the visible light wavelength, and it has a high specific surface area and good dispersibility. It can efficiently absorb near-infrared light in the 700~1500nm band and convert light energy into heat energy, so that the film can be rapidly heated to the color-changing agent threshold under sunlight, realizing adaptive dimming. At the same time, it avoids the problems of sedimentation or agglomeration caused by excessively large particle size and excessive surface activity and difficulty in dispersion caused by excessively small particle size. Thus, stable and reliable photothermal conversion performance is obtained while maintaining high transparency.

[0016] Preferably, the photoinitiator is photoinitiator TPO and / or photoinitiator 819.

[0017] In this application, the absorption wavelengths of photoinitiator TPO and photoinitiator 819 are well matched with the light source, which can ensure rapid and deep curing of the film.

[0018] Secondly, this application provides a method for preparing a thermochromic photoionized intermediate film, comprising the following steps: S1. Acrylic monomers, zinc diacrylate, color changer, near-infrared absorber and photoinitiator are mixed in the dark at 20~40℃, and then dispersed by shearing to obtain a mixture; S2. After defoaming treatment, the mixture obtained in S1 is coated onto a release film to form a wet film; S3. In an inert gas atmosphere, the wet film is cured by ultraviolet irradiation with an irradiation intensity of 100~400mW / cm2 and a total energy of 1500~4000mJ / cm2 to obtain a cured film. S4. Anneal the cured film at 50~60℃ for 2~6h to obtain the thermochromic photoionized intermediate film film.

[0019] In this application, the low-temperature environment can effectively protect the activity of the color-changing agent, and the shear dispersion and defoaming ensure that the components are uniform and defect-free. The combination of ultraviolet light rapid curing and low-temperature annealing helps to maintain the high transparency, strong adhesion and stable dimming performance of the film. The process is simple and efficient and suitable for mass production.

[0020] Preferably, in S1, the rotational speed of the shear dispersion is 3000~8000 rpm, and the shear dispersion time is 20~60 minutes.

[0021] In this application, the above-mentioned scheme can fully depolymerize and uniformly disperse the infrared absorber to the nanoscale, avoiding agglomeration and sedimentation. At the same time, the dispersion temperature rise is controlled below 40°C to prevent the color-changing agent from developing color or decomposing prematurely, thereby ensuring high initial transparency of the film, uniform photothermal conversion, and consistent color-changing response.

[0022] Preferably, in S2, the curing includes: first irradiating the surface with 100~200 mW / cm2 for 2~5 seconds to set the surface, and then irradiating it with 300~400 mW / cm2 until it is completely cured.

[0023] In this application, segmented curing is beneficial for pre-shaping, reducing volume shrinkage stress and surface oxygen inhibition, and preventing film warping or cracking; then thorough curing ensures complete cross-linking of the deep layers of the film, resulting in a flat, defect-free film with excellent mechanical properties.

[0024] Preferably, in S3, the ultraviolet light wavelength is 365nm or 395nm.

[0025] In this application, the ultraviolet light source of the above wavelength is used, which can match the absorption peak of the photoinitiator and has high initiation efficiency; moreover, this wavelength has a strong ability to penetrate the adhesive layer containing nanoparticles, which can achieve deep curing, while avoiding the damage of short-wave ultraviolet light to color changers and ionomers, thus ensuring the stability of film performance.

[0026] The advantages of the technical solution of this invention compared with the prior art are as follows: 1.1. This application introduces an infrared absorber and a spiropyran-based color-changing agent to synergistically convert near-infrared energy in sunlight into heat energy, driving the film to spontaneously and rapidly change color under sunlight, thus realizing the film's adaptive dimming and overcoming the shortcomings of traditional dimming films, such as lag in response to ambient temperature and low shading efficiency.

[0027] 2.2. This application uses acrylic monomers and zinc diacrylate to form an inter-chain ionic cross-linking network in situ during ultraviolet curing, combined with low-temperature annealing to optimize the ionic cluster structure. This avoids the thermal damage to the color-changing agent and the problem of acid-base incompatibility caused by high-temperature processing, and endows the film with high transparency, strong glass adhesion and excellent cycle stability. At the same time, the preparation process is kept below 60°C throughout, which is simple, efficient and suitable for mass production. It can be widely used in the field of smart dimming glass such as building curtain walls and automotive sunroofs. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the embodiments.

[0029] In this application's embodiments, the visible light wavelength range is typically 380nm to 780nm. In this application, the film has high transmittance in this wavelength range when it is not discolored (initial visible light transmittance is not less than 85%) to ensure the transparent light-gathering effect of the glass; after discoloration, it achieves the function of dimming and shading by absorbing or scattering visible light.

[0030] In the embodiments of this application, spiropyran compounds are a typical class of organic photo / thermochromic materials, whose molecules are composed of an indoline ring and a pyran ring linked by spirocarbon atoms. At room temperature or low temperature, spiropyrans are in a closed-ring, colorless state; when heated to their color-changing temperature (usually 45~60℃), the spirocarbon-oxygen bond undergoes heterolytic cleavage, the molecule opens the ring to form a conjugated cyanine structure, thereby strongly absorbing visible light and exhibiting color (such as blue, purple, etc.); upon cooling, the ring closes again, restoring the colorless state. This process does not require the addition of external acid or alkali as a color-developing agent, thus exhibiting good chemical compatibility with the zinc ion-containing system in this application, avoiding the problem of conflict between traditional fluorane color-changing agents and alkaline environments. In this application, common spiropyran derivatives such as 1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline] are preferred.

[0031] In this embodiment, the infrared absorber refers to a nanoparticle material capable of selectively absorbing energy in the near-infrared band (700~1500 nm) of the solar spectrum and converting it into thermal energy, such as nano-antimony tin oxide (ATO) or nano-indium tin oxide (ITO). Its mechanism of action is as follows: free charge carriers in the nanoparticles generate localized surface plasmon resonance under near-infrared light excitation, converting light energy into lattice vibrational thermal energy through a non-radiative relaxation process. This thermal energy rapidly raises the internal temperature of the film above the color-changing temperature of spiropyran, thereby triggering a reversible color change in the color-changing agent.

[0032] In the embodiments of this application, 365 nm and 395 nm are common ultraviolet wavelengths with moderate ultraviolet light energy that will not damage the molecular structure of spiropyran color changer, nor will they cause premature decomposition of zinc diacrylate or severe side reactions of the ionic cross-linking network. Furthermore, the selection of this wavelength is compatible with the photoinitiator, monomer system, and functional filler.

[0033] In this application's embodiments, room temperature refers to an ambient temperature of 20℃ to 40℃. Preferably, the room temperature is 20℃ to 30℃, more preferably 25℃ ± 2℃. It should be noted that the "mixing in the dark at 20~40℃" described in S1 of this invention is a specific implementation method of operation under room temperature conditions. Unless otherwise specified, "room temperature" in each operation step of this invention refers to this temperature range.

[0034] This application provides a thermochromic photosensitive ionic intermediate film. This product is achieved by compounding acrylic monomers, zinc diacrylate, spiropyran-based color-changing agents, nano-tin antimony oxide or indium tin oxide infrared absorbers, and a photoinitiator in specific mass proportions. During ultraviolet curing, the double bonds of zinc diacrylate participate in copolymerization to form the polymer backbone. Simultaneously, its zinc ions coordinate with the carboxyl groups provided by acrylic acid and methacrylic acid, constructing an in-situ ionic cross-linking network, giving the film high transparency and strong glass adhesion. The infrared absorber efficiently converts near-infrared energy from sunlight into heat energy, rapidly raising the internal temperature of the film above the color-changing temperature of spiropyran, driving reversible ring-opening color development, thereby achieving adaptive dimming. This product solves the technical problems in related technologies where thermochromic photosensitive films decompose and fail due to excessively high processing temperatures, and where relying solely on ambient temperature response leads to shading lag and low dimming efficiency.

[0035] For the reasons mentioned above, this application provides a thermochromic photoionized intermediate film, wherein the film comprises the following components by weight: 50-80 parts of acrylic monomer, 3-10 parts of zinc diacrylate, 0.5-5 parts of color-changing agent, 0.5-5 parts of infrared absorber and 1-5 parts of photoinitiator; The acrylic monomers include acrylic acid, methacrylic acid, and butyl acrylate; the total mass of the acrylic acid and the methacrylic acid is 20-40% of the mass of the acrylic monomers; and the mass of the butyl acrylate is 30-60% of the mass of the acrylic monomers.

[0036] In this embodiment, under ultraviolet light irradiation, the photoinitiator decomposes to generate free radicals, which initiate free radical polymerization of acrylic monomers and double bonds in zinc diacrylate to form a polyacrylate backbone. At the same time, zinc ions in zinc diacrylate coordinate with side carboxylic acid groups from acrylic acid and methacrylic acid on the polymer chain to form an interchain ionic cross-linking network. The infrared absorber is uniformly dispersed in the matrix in the form of nanoparticles and does not participate in the chemical reaction. The color-changing agent is dispersed in a molecular state and undergoes reversible ring-opening color development when heated, thereby realizing the adaptive dimming function driven by photothermal conversion.

[0037] In some embodiments, the molar ratio of zinc in the zinc diacrylate to the total carboxyl groups in the acrylic acid and methacrylic acid is 0.04 to 0.10:1.

[0038] In the embodiments, zinc ions form coordination bonds with two carboxylate groups on different polymer chains, which helps to balance transparency, adhesive strength, flexibility, and cycle stability, resulting in optimal overall performance. If the proportion is too low, the crosslinking is insufficient, leading to poor mechanical properties; if the proportion is too high, the number of free carboxyl groups decreases, the adhesive force decreases, and the excessively large ion clusters lead to increased haze.

[0039] In some embodiments, the acrylic monomer further includes 2-10% by mass of 1,6-hexanediol diacrylate and / or trimethylolpropane triacrylate.

[0040] In the embodiments, the above-mentioned substances, as crosslinking agents, participate in free radical polymerization during photocuring to form covalent crosslinking points and interpenetrating network structures with ionic crosslinking networks, which can further significantly improve the mechanical strength, heat distortion temperature and creep resistance of the film.

[0041] In some embodiments, the color-changing agent is a spiropyran compound.

[0042] In the examples, spiropyran compounds (such as 1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline], etc.) are colorless in a closed-ring state at room temperature. When heated to the color-changing temperature, the CO spirocycle in the molecule breaks, forming an open-ring anthocyanin structure. The conjugated system expands, absorbing visible light and developing color. Upon cooling, the ring closes again, restoring the colorless state. It is compatible with ionic crosslinking systems, requires no separate color-developing agent, has a long cycle life, and the color-changing temperature is adjustable.

[0043] In some embodiments, the infrared absorber is nano-antimony tin oxide particles and / or nano-tin indium oxide particles; Wherein, the primary particle size of the nano-tin antimony oxide particles is 20~80nm, and / or, the primary particle size of the nano-indium tin oxide particles is 20~80nm.

[0044] In this embodiment, ATO / ITO is a transparent conductive oxide whose free carriers generate plasmon resonance absorption in the near-infrared band, converting light energy into heat energy. With a particle size of 20–80 nm, much smaller than the wavelength of visible light, it exhibits extremely low visible light scattering and maintains high transparency.

[0045] In some embodiments, the photoinitiator is photoinitiator TPO and / or photoinitiator 819.

[0046] Secondly, this application provides a method for preparing a thermochromic photoionized intermediate film, comprising the following steps: S1. Acrylic monomers, zinc diacrylate, color changer, near-infrared absorber and photoinitiator are mixed in the dark at 20~40℃, and then dispersed by shearing to obtain a mixture; S2. After defoaming treatment, the mixture obtained in S1 is coated onto a release film to form a wet film; S3. In an inert gas atmosphere, the wet film is cured by ultraviolet irradiation with an irradiation intensity of 100~400mW / cm2 and a total energy of 1500~4000mJ / cm2 to obtain a cured film. S4. Anneal the cured film at 50~60℃ for 2~6h to obtain the thermochromic photoionized intermediate film film.

[0047] In the embodiments, S1 involves low-temperature, light-shielded mixing and high-speed shear dispersion to depolymerize the nano-infrared absorber and uniformly disperse it in the monomer system, while preventing the spiropyran color-changing agent from prematurely opening its ring and developing color or decomposing due to heat; S2 involves defoaming to remove air bubbles and prevent optical defects after curing; S3 involves irradiation with ultraviolet light in an inert gas atmosphere, where the photoinitiator decomposes to generate free radicals, initiating the polymerization of double bonds in acrylic monomers and zinc diacrylate to form a polymer backbone. At the same time, nitrogen gas is used to remove oxygen to eliminate oxygen inhibition and ensure a high conversion rate of double bonds. During the polymerization process, zinc ions in zinc diacrylate coordinate with side carboxylic acid groups from acrylic acid and methacrylic acid on different polymer chains, initially forming an inter-chain ionic cross-linking network; S4 involves low-temperature annealing at 50-60°C to promote further migration and rearrangement of zinc ions, forming more regular ion clusters with carboxyl groups, while eliminating internal stress during curing, thereby obtaining a highly transparent, strongly adhesive, and stable light-modulating ionic interlayer film.

[0048] In some embodiments, in S1, the rotational speed of the shear dispersion is 3000~8000 rpm, and the shear dispersion time is 20~60 minutes.

[0049] In the embodiments, high shear force can break up the agglomerates of nano-infrared absorbers, while also facilitating the adsorption of carboxylic acid groups in the monomers onto the surface of the nanoparticles, providing steric hindrance to prevent re-agglomeration.

[0050] In some embodiments, in S2, the curing includes: first irradiating the surface with 100~200 mW / cm2 for 2~5 seconds to set the surface, and then irradiating it with 300~400 mW / cm2 until it is fully cured.

[0051] In this embodiment, the film is first irradiated with low-intensity ultraviolet light. At this time, the rate of surface free radical generation is low, and the polymerization reaction proceeds slowly, forming a preliminary cross-linked gel layer. This gel layer can effectively alleviate the internal stress caused by rapid volume shrinkage and prevent cracks or orange peel defects from appearing on the film surface. Subsequently, high-intensity ultraviolet light is used for irradiation. The gel layer that has been formed can block oxygen from diffusing into the deeper layers, thereby reducing the oxygen inhibition effect and allowing the double bonds in the uncured areas inside to polymerize deeply, further improving the overall double bond conversion rate and obtaining a smooth, defect-free cured film with excellent mechanical properties.

[0052] In some embodiments, in S3, the ultraviolet light wavelength is 365nm or 395nm.

[0053] In the embodiments, this band has a strong ability to penetrate the adhesive layer containing nano-ATO / ITO and is not easily absorbed or scattered.

[0054] The technical solutions provided in this application will be described in detail below with reference to the embodiments. Unless otherwise specified, the materials used in the embodiments and comparative examples are all commercially available conventional products. Specific Implementation

[0055] Example 1

[0056] This embodiment provides a thermochromic photoionizing intermediate film, which is prepared through the following steps: S1. Under light-protected conditions, 10.5 parts of acrylic acid, 10.5 parts of methacrylic acid, and 4.5 parts of zinc diacrylate were added and stirred at room temperature for 20 minutes to form a transparent viscous liquid. Then, 42 parts of butyl acrylate, 4.2 parts of 1,6-hexanediol diacrylate, and 2.8 parts of trimethylolpropane triacrylate were added, and stirring was continued for 10 minutes until the mixture was homogeneous. Finally, 1.5 parts of spiropyran (1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline]), 12.5 parts of nano-tin antimony oxide dispersion (20% solid content), 2.0 parts of photoinitiator TPO, and 1.0 parts of photoinitiator 819 were added. A high-speed shear disperser was turned on, the speed was set to 5000 r / min, the system temperature was kept below 40℃, and shear dispersion was carried out for 30 minutes to obtain the mixture. S2. Degas the mixture obtained in step S1 under vacuum for 30 min, and then coat the degassed material onto a PET release film with a thickness of 50 μm and single-sided corona treatment. Set the wet film thickness to 0.48 mm and the coating speed to 3 m / min. S3. Place the wet film prepared in step S2 in a protective atmosphere, control the oxygen concentration in the system to be below 0.1%, and use a light source with a wavelength of 395nm to cure the wet film in stages: first, irradiate it with an irradiation intensity of 150 mW / cm2 for 3s (wherein, the energy is set to 450 mJ / cm2) to form a gel layer on the surface of the wet film; then irradiate it with an irradiation intensity of 350 mW / cm2 until (wherein, the energy is set to 3500 mJ / cm2) the film is completely cured; after curing, peel the film off from the release film to obtain the cured film. S4. Anneal the cured film from step S3 at 60°C under vacuum for 4 hours, and then allow it to cool naturally to room temperature to obtain the thermochromic photoionized intermediate film.

[0057] Example 2

[0058] This embodiment provides a thermochromic photoionizing intermediate film, which is prepared through the following steps: S1. Under light-protected conditions, 10.5 parts of acrylic acid, 10.5 parts of methacrylic acid, and 4.5 parts of zinc diacrylate were added and stirred at room temperature for 20 minutes to form a transparent viscous liquid. Then, 42 parts of butyl acrylate, 4.2 parts of 1,6-hexanediol diacrylate, and 2.8 parts of trimethylolpropane triacrylate were added, and stirring was continued for 10 minutes until the mixture was homogeneous. Finally, 1.5 parts of spiropyran (1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline]), 12.5 parts of nano-tin antimony oxide dispersion (20% solid content), 2.0 parts of photoinitiator TPO, and 1.0 parts of photoinitiator 819 were added. A high-speed shear disperser was turned on, the speed was set to 3000 r / min, the system temperature was kept below 40°C, and shear dispersion was carried out for 60 minutes to obtain the mixture. S2. Degas the mixture obtained in step S1 under vacuum for 30 min, and then coat the degassed material onto a PET release film with a thickness of 50 μm and single-sided corona treatment. Set the wet film thickness to 0.45 mm and the coating speed to 2 m / min. S3. Place the wet film prepared in step S2 in a protective atmosphere, control the oxygen concentration in the system to be below 0.1%, and use a light source with a wavelength of 395nm to cure the wet film in stages: first, irradiate it with an irradiation intensity of 100 mW / cm2 for 5s to form a gel layer on the surface of the wet film; then irradiate it with an irradiation intensity of 300 mW / cm2 until the film is completely cured (wherein, the total energy is 3500 mJ / cm2); after curing, peel the film off from the release film to obtain the cured film. S4. Anneal the cured film from step S3 at 50°C under vacuum for 6 hours, and then allow it to cool naturally to room temperature to obtain a thermochromic photoionized intermediate film.

[0059] Example 3

[0060] This embodiment provides a thermochromic photoionizing intermediate film, which is prepared through the following steps: S1. Under light-protected conditions, 10.5 parts of acrylic acid, 10.5 parts of methacrylic acid, and 4.5 parts of zinc diacrylate were added and stirred at room temperature for 20 minutes to form a transparent viscous liquid. Then, 42 parts of butyl acrylate, 4.2 parts of 1,6-hexanediol diacrylate, and 2.8 parts of trimethylolpropane triacrylate were added, and stirring was continued for 10 minutes until the mixture was homogeneous. Finally, 1.5 parts of spiropyran (1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline]), 12.5 parts of nano-indium tin oxide dispersion (20% solid content), 2.0 parts of photoinitiator TPO, and 1.0 parts of photoinitiator 819 were added. A high-speed shear disperser was turned on, the speed was set to 8000 r / min, the system temperature was kept below 40°C, and shear dispersion was carried out for 20 minutes to obtain the mixture. S2. Degas the mixture obtained in step S1 under vacuum for 30 min, and then coat the degassed material onto a PET release film with a thickness of 50 μm and single-sided corona treatment. Set the wet film thickness to 0.55 mm and the coating speed to 4 m / min. S3. Place the wet film prepared in step S2 in a protective atmosphere, control the oxygen concentration in the system to be below 0.1%, and use a light source with a wavelength of 365nm to cure the wet film in stages: first, irradiate with an irradiation intensity of 200 mW / cm2 for 2s to form a gel layer on the surface of the wet film; then irradiate with an irradiation intensity of 400 mW / cm2 until the film is completely cured (wherein, the total energy is 2000 mJ / cm2); after curing, peel the film off from the release film to obtain the cured film; S4. Anneal the cured film from step S3 at 50°C under vacuum for 4 hours, and then allow it to cool naturally to room temperature to obtain the thermochromic photoionized intermediate film.

[0061] Example 4

[0062] This embodiment provides a thermochromic photoionizing intermediate film, which is prepared through the following steps: S1. Under light-protected conditions, 10.5 parts of acrylic acid, 10.5 parts of methacrylic acid, and 4.5 parts of zinc diacrylate were added and stirred at room temperature for 20 minutes to form a transparent viscous liquid. Then, 42 parts of butyl acrylate, 4.2 parts of 1,6-hexanediol diacrylate, and 2.8 parts of trimethylolpropane triacrylate were added, and stirring was continued for 10 minutes until the mixture was homogeneous. Finally, 1.5 parts of spiropyran (1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline]), 12.5 parts of nano-indium tin oxide dispersion (20% solid content), 2.0 parts of photoinitiator TPO, and 1.0 parts of photoinitiator 819 were added. A high-speed shear disperser was turned on, the speed was set to 6000 r / min, the system temperature was kept below 40°C, and shear dispersion was carried out for 30 minutes to obtain the mixture. S2. Degas the mixture obtained in step S1 under vacuum for 30 min, and then coat the degassed material onto a PET release film with a thickness of 50 μm and single-sided corona treatment. Set the wet film thickness to 0.48 mm and the coating speed to 3 m / min. S3. Place the wet film prepared in step S2 in a protective atmosphere, control the oxygen concentration in the system to be below 0.1%, and use a light source with a wavelength of 365nm to cure the wet film in stages: first, irradiate it with an irradiation intensity of 150 mW / cm2 for 2s to form a gel layer on the surface of the wet film; then irradiate it with an irradiation intensity of 400 mW / cm2 until the film is completely cured (wherein, the total energy is 1500 mJ / cm2); after curing, peel the film off from the release film to obtain the cured film; S4. Anneal the cured film from step S3 at 60°C under vacuum for 2 hours, and then allow it to cool naturally to room temperature to obtain the thermochromic photoionized intermediate film.

[0063] Example 5

[0064] The difference from Example 1 is that, by mass parts, the acrylic monomers are 50 parts, including 7.5 parts acrylic acid, 7.5 parts methacrylic acid, 30 parts butyl acrylate, 5 parts 1,6-hexanediol diacrylate; 3 parts zinc diacrylate; 0.5 parts spiropyran; 2.5 parts nano-tin antimony oxide dispersion; and 3.0 parts photoinitiator TPO; the preparation method is the same as in Example 1.

[0065] Example 6

[0066] The difference from Example 1 is that, by mass parts, the acrylic monomers comprise 80 parts, including 16 parts acrylic acid, 16 parts methacrylic acid, 40 parts butyl acrylate, 6 parts 1,6-hexanediol diacrylate, 2 parts trimethylolpropane triacrylate; 8 parts zinc diacrylate; 2.5 parts spiropyran; 10 parts nano-tin antimony oxide dispersion; and 8193.0 parts photoinitiator. The preparation method is the same as in Example 1.

[0067] Example 7

[0068] The difference from Example 1 is that, by mass parts, the acrylic monomers comprise 60 parts, including 9 parts acrylic acid, 9 parts methacrylic acid, 36 parts butyl acrylate, 3 parts 1,6-hexanediol diacrylate, and 3 parts trimethylolpropane triacrylate; 4.5 parts zinc diacrylate; 2.5 parts spiropyran; 10 parts nano-tin antimony oxide dispersion; 1.5 parts photoinitiator TPO; and 1.0 part photoinitiator 819. The preparation method is the same as in Example 1.

[0069] Example 8

[0070] The difference from Example 1 is that, by mass parts, the acrylic monomers comprise 70 parts, including 14 parts acrylic acid, 14 parts methacrylic acid, 35 parts butyl acrylate, 4.2 parts 1,6-hexanediol diacrylate, 2.8 parts trimethylolpropane triacrylate; 7 parts zinc diacrylate; 3 parts spiropyran; 15 parts nano-tin antimony oxide dispersion; 1.5 parts photoinitiator TPO; and 1.5 parts photoinitiator 819. The preparation method is the same as in Example 1.

[0071] Example 9

[0072] The difference from Example 1 is that, by mass parts, the acrylic monomers comprise 75 parts, including 12 parts acrylic acid, 12 parts methacrylic acid, 45 parts butyl acrylate, 4.5 parts 1,6-hexanediol diacrylate, 1.5 parts trimethylolpropane triacrylate; 6 parts zinc diacrylate; 2 parts spiropyran; 15 parts nano-tin antimony oxide dispersion; 2.0 parts photoinitiator TPO; and 1.0 part photoinitiator 819. The preparation method is the same as in Example 1.

[0073] Comparative Example 1 The difference from Example 1 is that zinc diacrylate is not added, but otherwise it is the same as Example 1.

[0074] Comparative Example 2 The difference from Example 1 is that no nano-tin antimony oxide dispersion is added; otherwise, it is the same as Example 1.

[0075] Comparative Example 3 The difference from Example 1 is that the zinc diacrylate content is reduced from 4.5 parts to 1.1 parts (molar ratio of about 0.02), otherwise it is the same as Example 1.

[0076] Comparative Example 4 The difference from Example 1 is that the zinc diacrylate content is reduced from 4.5 parts to 8.5 parts (molar ratio of about 0.15), otherwise it is the same as Example 1.

[0077] To verify whether the internal temperature of the film in this application can reach the thermochromic threshold of spiropyran under illumination, the inventors used Example 1 and Comparative Example 2 as examples and conducted temperature tests using the following method: A T-type thermocouple with a diameter of 0.2 mm was embedded in the center of the film's thickness direction, and the film was laminated with two 3 mm thick float glass pieces using conventional lamination technology to form a laminated glass specimen. The thermocouple leads were sealed and led out from the edge of the glass. A xenon lamp or solar simulator was used as the light source, with irradiance set to 800 W / m², 1000 W / m², and 1200 W / m², respectively. The spectrum conformed to the AM1.5 standard and included near-infrared components. The light source irradiated vertically from one side of the glass. During the test, the ambient temperature was recorded simultaneously, the glass surface temperature was recorded using an infrared thermal imager, and the internal temperature of the film was continuously acquired through thermocouples. The time resolution of all temperature data was not less than 1 second. Tests were conducted at ambient temperatures of 25°C, 35°C, and 45°C to simulate actual operating conditions in different seasons. In this process, the time required for the internal temperature of the film to rise from the initial room temperature to the spiropyran color change temperature and the thermal equilibrium temperature reached were recorded. The results are shown in Table 1.

[0078] Table 1

[0079] Table 1 shows that under ambient temperatures of 25℃ and light intensity of 1000W / m² and above, the internal equilibrium temperature of the film reaches above 56℃, exceeding the thermochromic threshold of spiropyran, and the heating time shortens with increasing light intensity. When the ambient temperature rises to 35℃ or 45℃, even under lower light intensity of 800W / m², the equilibrium temperature can still reach above 53℃, meeting the color change requirements. This indicates that the film of this application can effectively heat up and trigger reversible spiropyran color change under typical sunlight conditions, such as light intensity ≥800W / m² and ambient temperature ≥25℃. In contrast, the equilibrium temperature of Comparative Example 2 under the same conditions is only 29℃, far below the color change threshold. In summary, the film of this application, by introducing an infrared absorber, can efficiently convert near-infrared energy in sunlight into heat energy, enabling the internal temperature of the film to reliably reach the color change temperature of spiropyran, thereby achieving a sunlight-responsive adaptive dimming function.

[0080] The films prepared in the above examples and comparative examples were used to fabricate laminated glass specimens with dimensions of 100mm × 100mm and a glass thickness of 3mm. The samples were placed in a standard environment (23±2℃, relative humidity 50±5%) for 24 hours before testing. The following performance tests were then performed: (1) Initial visible light transmittance T0, visible light transmittance T1 after color change Refer to the relevant records in GB / T 2680-2021.

[0081] (2) Initial fog Refer to the relevant records in GB / T 2410-2008.

[0082] (3) Response time to color change A xenon arc lamp solar simulator (AM1.5 filter, irradiance 1000±50 W / m2, wavelength 300~2500nm, including near-infrared) was used as the light source. The laminated glass specimens prepared in each embodiment and comparative example were placed in the center of the optical path in a constant temperature environment chamber (25±2℃). The transmittance of visible light in the 380~780 nm range was monitored in real time using a spectrophotometer. The time (seconds) required for the transmittance to decrease from the initial transmittance (T0) to T0×20% was recorded. Three specimens were measured in each group and the average value was taken. If the target was not reached within 600 seconds, it was recorded as ">600 s".

[0083] The test results are shown in Table 2.

[0084] Table 2

[0085] As shown in Table 2, and in conjunction with Examples 1-4, the intermediate films prepared using the method of this application all exhibit excellent comprehensive performance. Among them, the film of Example 1 achieves the best balance between initial transparency, color-changing response speed, and light-changing depth. The film of Example 2 has a relatively slow response speed and a slightly shallower color-changing depth, possibly due to its lower shear dispersion speed and longer time, resulting in a slightly larger particle size of the nano-infrared absorber or a decrease in dispersion uniformity, which affects the photothermal conversion efficiency and color-changing driving rate. The film of Example 3 has the fastest response speed and the deepest color change, but the initial haze is slightly increased. This may be because the internal stress between ion clusters was not completely eliminated, resulting in slight scattering of visible light. The film of Example 4 has the highest initial transparency, but the response speed is slightly slower than that of Example 1. This may be because its total polymer crosslinking density is slightly insufficient, resulting in slightly higher activity of the color-changing agent molecules and a slightly slower ring-opening response after heating. At the same time, the shorter annealing time also prevents the ion crosslinking network from reaching its optimal arrangement.

[0086] As shown in Table 2, and in conjunction with Examples 1 and 5-9, the formulation of the intermediate film of this application ensures both rapid response and deep light adjustment while maintaining high transparency and good processability. Example 5's film has the highest initial transparency and lowest haze, but the slowest color-changing response and shallowest color-changing depth. This is because its ionic crosslinking density and covalent crosslinking density are both relatively weak, and the content of spiropyran and infrared absorbers is low, resulting in insufficient photothermal heating and a high color-changing driving threshold, making it suitable for low-light conditions or applications requiring extremely high transparency. Example 6's film has the fastest color-changing response and deepest color change, but its initial haze is slightly higher. This is because its ionic clusters and crosslinking network are relatively dense, causing slight scattering of visible light. Simultaneously, the high content of acrylic acid and methacrylic acid increases the tendency for microphase separation in the matrix. Example 7 achieves a good balance between color-changing response and transparency, suitable for general architectural lighting needs. Example 8 increased the ratio of acrylic acid and methacrylic acid, increasing the carboxyl content and enhancing adhesion. However, the higher proportion of hard monomers made the film slightly brittle. Simultaneously, the ionic crosslinking density increased accordingly, resulting in a slightly faster color change response but a slight increase in haze. Example 9, with a slightly higher proportion of butyl acrylate, achieved better flexibility, making it suitable for bonding curved glass.

[0087] As shown in Table 2, compared with Example 1, Comparative Example 1, which did not contain zinc diacrylate, showed a slight improvement in initial transparency and haze, but a slower color-changing response and a shallower color-changing depth. This is because the absence of zinc diacrylate resulted in the loss of the ionic crosslinking network formed by zinc ions and carboxyl groups in the film. The confinement effect of the polymer matrix on spiropyran molecules weakened, and the synergistic effect of the ring-opening motion of the color-changing agent molecules decreased during heating. Simultaneously, the lack of ionic crosslinking also led to a significant reduction in the adhesion strength to the glass, resulting in poorer long-term cycling stability.

[0088] As shown in Table 2, compared with Example 1, Comparative Example 2, which did not contain the nano-tin antimony oxide dispersion, had normal initial transparency and haze, but its transmittance hardly decreased after color change, and its response time was extremely long, essentially losing its dimming function. This is because without the infrared absorber, the film cannot convert the near-infrared energy in sunlight into heat energy, and the internal temperature cannot reach the color-changing threshold of spiropyran, so the color-changing agent remains in a closed-loop colorless state.

[0089] Combining Table 2, Example 1, and Comparative Examples 3 and 4, it can be seen that Comparative Example 3 reduced the amount of zinc diacrylate, resulting in a lower zinc / carboxyl molar ratio, while Comparative Example 4 increased the amount of zinc diacrylate, resulting in a higher molar ratio. Both examples showed inferior overall performance compared to Example 1. When the molar ratio is too low, there are insufficient ionic crosslinking points, resulting in a loose polymer network and excessively free movement of the color-changing agent molecules, leading to slow response, insufficient color-changing depth, and decreased cycle stability. When the molar ratio is too high, excessive zinc ions form excessively large ion clusters, scattering visible light and increasing haze and reducing initial transparency. Simultaneously, excessive crosslinking restricts molecular chain movement, causing a decline in color-changing response efficiency and adhesive strength. Therefore, when the zinc / carboxyl molar ratio is controlled within a reasonable range of 0.04 to 0.10, a superior interlayer film with high transparency, fast response, strong adhesion, and long lifespan can be obtained simultaneously.

[0090] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A thermochromic photoionizing intermediate film, characterized in that, The film, by weight, comprises the following components: 50-80 parts of acrylic monomers, 3-10 parts of zinc diacrylate, 0.5-5 parts of color changer, 0.5-5 parts of infrared absorber, and 1-5 parts of photoinitiator; The acrylic monomers include acrylic acid, methacrylic acid, and butyl acrylate; the total mass of the acrylic acid and the methacrylic acid is 20-40% of the mass of the acrylic monomers; and the mass of the butyl acrylate is 30-60% of the mass of the acrylic monomers.

2. The thermochromic photoionizing intermediate film according to claim 1, characterized in that, The molar ratio of zinc in the zinc diacrylate to the total carboxyl groups in the acrylic acid and methacrylic acid is 0.04~0.10:

1.

3. The thermochromic photoionizing intermediate film according to claim 2, characterized in that, The acrylic monomers further include 2-10% by mass of 1,6-hexanediol diacrylate and / or trimethylolpropane triacrylate.

4. The thermochromic photoionizing intermediate film according to claim 1, characterized in that, The color-changing agent is a spiropyran compound.

5. The thermochromic photoionizing intermediate film according to claim 1, characterized in that, The infrared absorber is nano-tin antimony oxide particles and / or nano-indium tin oxide particles. Wherein, the primary particle size of the nano-tin antimony oxide particles is 20~80nm, and / or, the primary particle size of the nano-indium tin oxide particles is 20~80nm.

6. The thermochromic photoionizing intermediate film according to claim 1, characterized in that, The photoinitiator is photoinitiator TPO and / or photoinitiator 819.

7. A method for preparing a thermochromic photoionizing intermediate film according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Acrylic monomers, zinc diacrylate, color changer, infrared absorber and photoinitiator are mixed at 20~40℃ in the dark, and then dispersed by shearing to obtain a mixture; S2. After defoaming treatment, the mixture obtained in S1 is coated onto a release film to form a wet film; S3. In an inert gas atmosphere, the wet film is cured by ultraviolet irradiation with an irradiation intensity of 100~400 mW / cm2 and a total energy of 1500~4000 mJ / cm2 to obtain a cured film. S4. Anneal the cured film at 50~60℃ for 2~6h to obtain the thermochromic photoionized intermediate film film.

8. The preparation method according to claim 7, characterized in that, In S1, the rotational speed of the shear dispersion is 3000~8000 rpm, and the shear dispersion time is 20~60 minutes.

9. The preparation method according to claim 7, characterized in that, In S2, the curing process includes: first irradiating the surface with 100-200 mW / cm2 for 2-5 seconds to set the surface shape, and then irradiating it with 300-400 mW / cm2 until it is fully cured.

10. The preparation method according to claim 7, characterized in that, In S3, the ultraviolet light wavelength is 365nm or 395nm.

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