Ultraviolet light color-changing high-low temperature film and preparation method thereof

Abstract

This invention provides a UV-chromatic high-low temperature film and its preparation method. The high-low temperature film comprises five functional layers stacked sequentially: a photochromic surface layer, a photochromic enhancement intermediate layer, an interface bonding layer, a high-temperature support layer, and a hot-melt adhesive layer. The photochromic surface layer is composed of UV-curable waterborne polyurethane resin, a colorant, and modified UV photochromic powder. The photochromic enhancement intermediate layer is composed of chemically resistant waterborne polyurethane resin and modified UV photochromic powder. The interface bonding layer is composed of thermally crosslinked waterborne polyurethane resin and a crosslinking agent. The high-temperature support layer is composed of polyether-type high-transparency thermoplastic polyurethane material. The hot-melt adhesive layer is composed of thermoplastic polyurethane hot-melt adhesive. This invention, through a unique multi-layer functional layer structure design and material modification process, achieves a stable and uniform UV-chromatic effect over a wide temperature range, while significantly improving interlayer bonding strength and weather resistance.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to an ultraviolet light color-changing high and low temperature film and its preparation method. Background Technology

[0002] Ultraviolet (UV) photochromic materials, as functional materials with unique optical properties, have gained widespread attention and application in various fields in recent years. When exposed to UV light of a specific wavelength, the molecular structure of these materials undergoes a reversible change, resulting in color characteristics different from those under normal lighting conditions. When the UV light source disappears, the material reverts to its original color state. This unique property makes UV photochromic materials valuable for applications in clothing and textiles, outdoor advertising, product anti-counterfeiting packaging, automotive decorative films, and building decoration materials.

[0003] Currently, most UV-sensitive color-changing materials on the market exist in thin film form. Their basic preparation method involves directly dispersing photochromic powder within a polymer matrix to form a composite film. However, in practical applications, these traditional photochromic films have gradually revealed several technical defects and limitations. Firstly, they suffer from poor environmental adaptability. Ordinary photochromic films are prone to softening and deformation at high temperatures, leading to a significant decrease or even failure of their color-changing performance. At low temperatures, they may experience embrittlement and cracking, making it difficult to maintain stable performance over a wide temperature range.

[0004] Secondly, there's the issue of uniformity in color-changing effect. Due to poor dispersion of the photochromic powder in the resin matrix, agglomeration easily occurs, leading to inconsistent color depths in different areas of the film, resulting in color differences and spots, severely impacting the product's visual appeal and aesthetics. Thirdly, there are defects in the film structure design. A single-layered photochromic film often cannot meet multiple performance requirements simultaneously, exhibiting insufficient adhesion when bonded to different substrates. This can easily lead to delamination, peeling, and other quality problems during use, shortening the product's lifespan.

[0005] To address these technical challenges, existing technologies have proposed several improvement schemes. For example, selecting specific types of polyurethane resin as the carrier material aims to improve the temperature resistance of the membrane; or adding various dispersants and additives can improve the uniformity of the distribution of photochromic powder in the matrix. Other solutions propose multilayer membrane structures, attempting to balance various material performance indicators by setting different functional layers. However, these improvement schemes still have significant shortcomings. For instance, simply changing the resin type can improve temperature resistance to some extent, but often at the expense of material flexibility and processability; and ordinary multilayer structure designs often neglect the compatibility and interfacial bonding strength between layers, leading to interfacial delamination due to the mismatch in thermal expansion coefficients of the layers during temperature changes.

[0006] Furthermore, existing technologies have failed to effectively address key technical challenges such as powder agglomeration and sedimentation in the matrix, directly affecting the uniformity and stability of the color-changing effect. At the same time, existing preparation processes are often complex and costly, which also limits the widespread application of these materials.

[0007] Therefore, it is necessary to design an ultraviolet light color-changing high and low temperature film and its preparation method. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, an ultraviolet light color-changing high and low temperature film and its preparation method are provided.

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

[0010] An ultraviolet light-changing high and low temperature film, comprising five functional layers stacked sequentially: a light-changing surface layer, a light-changing enhancement intermediate layer, an interface bonding layer, a high-temperature support layer, and a hot-melt adhesive layer.

[0011] The photochromic surface layer is composed of UV-curable waterborne polyurethane resin, colorant, and modified ultraviolet photochromic powder; the photochromic reinforced intermediate layer is composed of chemically resistant waterborne polyurethane resin and modified ultraviolet photochromic powder; the interface bonding layer is composed of thermally crosslinked waterborne polyurethane resin and crosslinking agent; the high-temperature support layer is composed of polyether-type high-transparency thermoplastic polyurethane material; and the hot melt adhesive layer is composed of thermoplastic polyurethane hot melt adhesive.

[0012] Preferably, the mass fractions of each component in the photochromic surface layer are: 60-90 parts of UV-curable waterborne polyurethane resin, 2-8 parts of colorant, and 8-18 parts of modified ultraviolet photochromic powder.

[0013] Preferably, the mass fractions of each component in the photochromic enhancement intermediate layer are: 70-110 parts of chemically resistant waterborne polyurethane resin and 6-12 parts of modified ultraviolet photochromic powder.

[0014] Preferably, the mass fractions of each component in the interface bonding layer are: 75-105 parts of thermally crosslinked waterborne polyurethane resin and 2-7 parts of crosslinking agent.

[0015] Preferably, the polyether-type high-transparency thermoplastic polyurethane material used in the high-temperature support layer has a melting point of 155-165℃ and a heat distortion temperature of 150-160℃.

[0016] Preferably, the thermoplastic polyurethane hot melt adhesive used in the hot melt adhesive layer has a melting point of 115-125°C and a Shore hardness of 90-98A.

[0017] Preferably, the preparation method of the modified ultraviolet photochromic powder includes the following steps: adding ultraviolet photochromic powder to an organic solvent to form a suspension, then adding a silane coupling agent and a dispersing agent, stirring continuously at a temperature of 55-75°C for 1.5-2.5 hours, and simultaneously performing ultrasonic treatment during the stirring process, with an ultrasonic frequency of 25-45kHz and an ultrasonic treatment time of 30-60 minutes.

[0018] Preferably, the dispersing agent is polyvinylpyrrolidone, and its addition amount is 0.5-3% of the mass of the UV photochromic powder.

[0019] Preferably, the UV-curable waterborne polyurethane resin is a toughened modified polyurethane resin, and the preparation steps of the UV-curable waterborne polyurethane resin include: melt blending polyurethane resin and nano silica in a twin-screw extruder, wherein the amount of nano silica added is 3-8% of the mass of polyurethane resin, the blending temperature is controlled at 160-190℃, and the screw speed is 200-400 rpm.

[0020] This invention also provides a method for preparing an ultraviolet-sensitive color-changing high and low temperature film, the method comprising the following steps:

[0021] Step 1: Preparation of photochromic surface layer slurry: Mix UV-curable waterborne polyurethane resin, colorant and modified ultraviolet photochromic powder, and stir at 65-85℃ until homogeneous to obtain photochromic surface layer slurry;

[0022] Step 2: Preparation of photo-modified intermediate layer slurry: Chemical-resistant waterborne polyurethane resin and modified ultraviolet photomodified powder are mixed in proportion and stirred at 70-95℃ until homogeneous to obtain photo-modified intermediate layer slurry.

[0023] Step 3: Preparation of interface bonding layer slurry: Mix the thermal crosslinking waterborne polyurethane resin and crosslinking agent in proportion, and stir at 75-105℃ until uniform to obtain interface bonding layer slurry.

[0024] Step 4: Forming a multi-layer structure: The above three slurries are sequentially coated on the release film to form a pre-formed structure consisting of a photochromic surface layer, a photochromic enhancement intermediate layer, and an interface bonding layer.

[0025] Step 5: Composite high-temperature support layer: Polyether-type high-transparency thermoplastic polyurethane material is laminated onto the interface bonding layer to form a high-temperature support layer;

[0026] Step 6, Composite hot melt adhesive layer: Thermoplastic polyurethane hot melt adhesive is laminated onto the high-temperature support layer to form a hot melt adhesive layer;

[0027] Step 7: Post-processing: The composite membrane is cured at room temperature for 8-20 hours, and then cut and rolled up to obtain the final product.

[0028] Preferably, the specific steps of the composite high-temperature support layer are as follows: polyether-type high-transparency thermoplastic polyurethane material is laminated onto the interface bonding layer by melt extrusion to form a high-temperature support layer, and the extrusion temperature is controlled at 155-165℃.

[0029] Preferably, the specific steps of the composite hot melt adhesive layer are as follows: thermoplastic polyurethane hot melt adhesive is laminated onto the high-temperature support layer by hot pressing to form a hot melt adhesive layer, and the hot pressing temperature is controlled at 115-125℃.

[0030] Preferably, the curing parameters are as follows: curing for 8-20 hours in an environment with a relative humidity of 40%-60%.

[0031] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0032] 1. This invention achieves stable performance of a UV-sensitive high- and low-temperature film under a wide temperature range by employing a multi-layer functional structure design. The photochromic surface layer uses UV-curable waterborne polyurethane resin as the matrix material, combined with a specific amount of modified UV photochromic powder. This not only ensures that the film layer produces a significant color change under UV irradiation, but also imparts excellent wear resistance and weather resistance to the surface through the UV curing process. The photochromic enhancement intermediate layer uses chemical-resistant waterborne polyurethane resin, further improving the uniformity and stability of the color-changing effect and effectively avoiding performance degradation caused by environmental factors.

[0033] 2. In the interfacial bonding layer, this invention employs a thermally crosslinked waterborne polyurethane resin combined with a crosslinking agent. This combination forms a stable three-dimensional network structure, significantly enhancing the bonding force between layers. This design effectively solves the delamination problem caused by the mismatch of thermal expansion coefficients among layers in traditional multilayer films when temperatures change, ensuring the structural integrity of the film layer under alternating high and low temperature environments.

[0034] 3. The high-temperature support layer of this invention is made of polyether-type highly transparent thermoplastic polyurethane material. Its melting point and heat distortion temperature ensure that the film layer can maintain dimensional stability and mechanical strength under high-temperature conditions. At the same time, the hot melt adhesive layer uses thermoplastic polyurethane hot melt adhesive with a specific melting point and hardness, which not only ensures good adhesion to various substrates, but also avoids affecting the overall performance due to the adhesive layer being too hard or too soft.

[0035] 4. This invention significantly improves the dispersibility and compatibility of UV-sensitive powder in a resin matrix through surface modification treatment, including silane coupling agent modification and ultrasonic dispersion. This treatment effectively prevents the aggregation and sedimentation of the UV-sensitive powder, ensuring the uniformity of the color-changing effect, while also improving the interfacial bonding strength between the UV-sensitive powder and the resin matrix, thus extending the service life of the material. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the specific embodiments of this application, the sources of various main raw materials are briefly described as follows:

[0038] Chemical-resistant waterborne polyurethane resin (model UW-3039E) and thermally crosslinked waterborne polyurethane resin (model UW-1527): purchased from Ube Industries, Ltd., Japan.

[0039] Polyether-type high-transparency thermoplastic polyurethane material (model A65P4324N): purchased from Dongguan Jiurui Plastic Raw Materials Co., Ltd.

[0040] Thermoplastic polyurethane hot melt adhesive: purchased from Dongguan Bailing New Materials Co., Ltd.;

[0041] Aziridine crosslinking agent: purchased from Guangdong Enders Chemical Co., Ltd.;

[0042] Polyvinylpyrrolidone: purchased from Hubei Shixing Chemical Co., Ltd.;

[0043] UV photochromic powder: purchased from Dongguan Hongtai New Material Technology Co., Ltd.

[0044] The technical solution of this application is as follows:

[0045] An ultraviolet light-changing high and low temperature film, comprising five functional layers stacked sequentially: a light-changing surface layer, a light-changing enhancement intermediate layer, an interface bonding layer, a high-temperature support layer, and a hot-melt adhesive layer.

[0046] The photochromic surface layer is composed of UV-curable waterborne polyurethane resin, colorant, and modified ultraviolet photochromic powder; the photochromic reinforced intermediate layer is composed of chemically resistant waterborne polyurethane resin and modified ultraviolet photochromic powder; the interface bonding layer is composed of thermally crosslinked waterborne polyurethane resin and crosslinking agent; the high-temperature support layer is composed of polyether-type high-transparency thermoplastic polyurethane material; and the hot melt adhesive layer is composed of thermoplastic polyurethane hot melt adhesive.

[0047] The mass fractions of each component in the photochromic surface layer are as follows: 60-90 parts of UV-curable waterborne polyurethane resin, 2-8 parts of colorant, and 8-18 parts of modified ultraviolet photochromic powder.

[0048] The mass fractions of each component in the photochromic enhancement intermediate layer are: 70-110 parts of chemically resistant waterborne polyurethane resin and 6-12 parts of modified ultraviolet photochromic powder.

[0049] The mass fractions of each component in the interface bonding layer are: 75-105 parts of thermally crosslinked waterborne polyurethane resin and 2-7 parts of crosslinking agent.

[0050] The high-temperature support layer uses a polyether-type highly transparent thermoplastic polyurethane material with a melting point of 155-165℃ and a heat distortion temperature of 150-160℃.

[0051] The thermoplastic polyurethane hot melt adhesive used in the hot melt bonding layer has a melting point of 115-125℃ and a Shore hardness of 90-98A.

[0052] The preparation method of the modified ultraviolet photochromic powder includes the following steps: adding ultraviolet photochromic powder to an organic solvent to form a suspension, then adding a silane coupling agent and a dispersing agent, stirring continuously at a temperature of 55-75℃ for 1.5-2.5 hours, and simultaneously performing ultrasonic treatment during the stirring process, with an ultrasonic frequency of 25-45kHz and an ultrasonic treatment time of 30-60 minutes.

[0053] The dispersing agent is polyvinylpyrrolidone, and its addition amount is 0.5-3% of the mass of the ultraviolet photochromic powder.

[0054] The UV-curable waterborne polyurethane resin is a toughened and modified polyurethane resin. The preparation steps of the UV-curable waterborne polyurethane resin include: melt blending polyurethane resin and nano-silica in a twin-screw extruder, wherein the amount of nano-silica added is 3-8% of the mass of polyurethane resin, the blending temperature is controlled at 160-190℃, and the screw speed is 200-400 rpm.

[0055] This application also provides a method for preparing an ultraviolet-sensitive color-changing high and low temperature film, the method comprising the following steps:

[0056] Step 1: Preparation of photochromic surface layer slurry: Mix UV-curable waterborne polyurethane resin, colorant and modified ultraviolet photochromic powder, and stir at 65-85℃ until homogeneous to obtain photochromic surface layer slurry;

[0057] Step 2: Preparation of photo-modified intermediate layer slurry: Chemical-resistant waterborne polyurethane resin and modified ultraviolet photomodified powder are mixed in proportion and stirred at 70-95℃ until homogeneous to obtain photo-modified intermediate layer slurry.

[0058] Step 3: Preparation of interface bonding layer slurry: Mix the thermal crosslinking waterborne polyurethane resin and crosslinking agent in proportion, and stir at 75-105℃ until uniform to obtain interface bonding layer slurry.

[0059] Step 4: Forming a multi-layer structure: The above three slurries are sequentially coated on the release film to form a pre-formed structure consisting of a photochromic surface layer, a photochromic enhancement intermediate layer, and an interface bonding layer.

[0060] Step 5: Composite high-temperature support layer: Polyether-type high-transparency thermoplastic polyurethane material is laminated onto the interface bonding layer to form a high-temperature support layer;

[0061] Step 6, Composite hot melt adhesive layer: Thermoplastic polyurethane hot melt adhesive is laminated onto the high-temperature support layer to form a hot melt adhesive layer;

[0062] Step 7: Post-processing: The composite membrane is cured at room temperature for 8-20 hours, and then cut and rolled up to obtain the final product.

[0063] The specific steps of the composite high-temperature support layer are as follows: polyether-type high-transparency thermoplastic polyurethane material is laminated onto the interface bonding layer by melt extrusion to form a high-temperature support layer, and the extrusion temperature is controlled at 155-165℃.

[0064] The specific steps of the composite hot melt adhesive layer are as follows: thermoplastic polyurethane hot melt adhesive is laminated onto the high-temperature support layer by hot pressing to form a hot melt adhesive layer, and the hot pressing temperature is controlled at 115-125℃.

[0065] The curing parameters and steps are as follows: curing for 8-20 hours in an environment with a relative humidity of 40%-60%.

[0066] This invention achieves a stable and uniform ultraviolet color-changing effect under a wide temperature range through a unique multi-layer functional layer structure design and material modification process, while significantly improving the interlayer bonding strength and weather resistance.

[0067] The present invention will be described in detail below through examples and comparative examples, but the scope of protection of the present invention is not limited to these examples. Unless otherwise specified, the chemical reagents and raw materials used in the following examples and comparative examples are all conventional commercially available products.

[0068] Example 1: The preparation process of the ultraviolet-sensitive color-changing high and low temperature film in this example is as follows:

[0069] First, a photochromic topcoat slurry is prepared by mixing 90 parts of UV-curable waterborne polyurethane resin, 5 parts of colorant, and 8 parts of modified UV photochromic powder, and stirring at 85°C until homogeneous. Second, a photochromic reinforced intermediate layer slurry is prepared by mixing 110 parts of chemical-resistant waterborne polyurethane resin and 9 parts of modified UV photochromic powder, and stirring at 95°C until homogeneous. Third, an interface bonding layer slurry is prepared by mixing 75 parts of thermally crosslinked waterborne polyurethane resin and 7 parts of crosslinking agent, and stirring at 105°C until homogeneous. Finally, a multilayer structure is formed. The process involves sequentially coating the three slurries onto a release film to form a pre-formed structure consisting of a photochromic surface layer, a photochromic enhanced intermediate layer, and an interface bonding layer. Subsequently, a high-temperature support layer is laminated, where polyether-type high-transparency thermoplastic polyurethane material is melt-extruded onto the interface bonding layer at a controlled extrusion temperature of 165°C. Next, a hot-melt adhesive layer is laminated, where thermoplastic polyurethane hot melt adhesive is hot-pressed onto the high-temperature support layer at a controlled hot-press temperature of 125°C. Finally, post-treatment is performed, curing the laminated film in an environment with 50% relative humidity for 20 hours, followed by cutting and winding to obtain the final product.

[0070] The preparation of modified ultraviolet photochromic powder includes: adding ultraviolet photochromic powder to an organic solvent to form a suspension, then adding a silane coupling agent and a dispersant polyvinylpyrrolidone at a mass of 3% of the ultraviolet photochromic powder, stirring continuously at 75°C for 2.5 hours, and simultaneously performing ultrasonic treatment at a frequency of 45 kHz for 30 minutes.

[0071] The UV-curable waterborne polyurethane resin is a toughened and modified polyurethane resin. The preparation steps include: melt blending polyurethane resin and nano silica in a twin-screw extruder, wherein the amount of nano silica added is 8% of the mass of polyurethane resin, the blending temperature is controlled at 190℃, and the screw speed is 400 rpm.

[0072] In this embodiment, the chemical-resistant waterborne polyurethane resin is model UW-3039E, the thermally crosslinked waterborne polyurethane resin is model UW-1527DF, the polyether-type high-transparency thermoplastic polyurethane material is polyether-type high-transparency TPU, model A65P4324N, and the crosslinking agent is aziridine crosslinking agent.

[0073] Example 2: In this example, the similarities to Example 1 will not be repeated, and the differences are as follows:

[0074] The preparation process of the UV-sensitive high and low temperature film in this embodiment is as follows: First, a photochromic surface layer slurry is prepared by mixing 60 parts of UV-curable waterborne polyurethane resin, 8 parts of colorant, and 13 parts of modified UV photochromic powder, and stirring at 65°C until homogeneous to obtain the photochromic surface layer slurry; second, a photochromic reinforced intermediate layer slurry is prepared by mixing 70 parts of chemically resistant waterborne polyurethane resin and 12 parts of modified UV photochromic powder, and stirring at 70°C until homogeneous to obtain the photochromic reinforced intermediate layer slurry; then, an interface bonding layer slurry is prepared by mixing 105 parts of thermally crosslinked waterborne polyurethane resin and 2 parts of crosslinking agent, and stirring at 75°C until homogeneous to obtain the interface bonding layer slurry. The three slurries are applied sequentially onto the release film to form a pre-formed structure consisting of a photochromic top layer, a photochromic enhanced intermediate layer, and an interface bonding layer. A high-temperature support layer is then laminated, where polyether-type high-transparency thermoplastic polyurethane material is melt-extruded onto the interface bonding layer at a controlled extrusion temperature of 155°C. Next, a hot-melt adhesive layer is laminated, where thermoplastic polyurethane hot melt adhesive is hot-pressed onto the high-temperature support layer at a controlled hot-press temperature of 115°C. Finally, the laminated film is cured for 8 hours in an environment with a relative humidity of 60%, and then cut and wound to obtain the final product.

[0075] The preparation of modified ultraviolet photochromic powder includes: adding ultraviolet photochromic powder to an organic solvent to form a suspension, then adding a silane coupling agent and a dispersant polyvinylpyrrolidone, with the addition amount being 0.5% of the mass of the ultraviolet photochromic powder, stirring continuously at 55°C for 1.5 hours, and simultaneously performing ultrasonic treatment during the stirring process, with an ultrasonic frequency of 25kHz and an ultrasonic treatment time of 60 minutes.

[0076] The UV-curable waterborne polyurethane resin is a toughened and modified polyurethane resin. The preparation steps include: melt blending polyurethane resin and nano silica in a twin-screw extruder, wherein the amount of nano silica added is 3% of the mass of polyurethane resin, the blending temperature is controlled at 160℃, and the screw speed is 200 rpm.

[0077] Example 3: In this example, the similarities to Example 1 will not be repeated, and the differences are as follows:

[0078] The preparation process of the UV-sensitive high and low temperature film in this embodiment is as follows: First, a photochromic surface layer slurry is prepared by mixing 75 parts of UV-curable waterborne polyurethane resin, 2 parts of colorant, and 18 parts of modified UV photochromic powder, and stirring at 75°C until homogeneous to obtain the photochromic surface layer slurry; second, a photochromic reinforced intermediate layer slurry is prepared by mixing 90 parts of chemically resistant waterborne polyurethane resin and 6 parts of modified UV photochromic powder, and stirring at 82.5°C until homogeneous to obtain the photochromic reinforced intermediate layer slurry; then, an interface bonding layer slurry is prepared by mixing 90 parts of thermally crosslinked waterborne polyurethane resin and 4.5 parts of crosslinking agent, and stirring at 90°C until homogeneous to obtain the interface bonding layer slurry. The three slurries are applied sequentially onto the release film to form a pre-formed structure consisting of a photochromic surface layer, a photochromic enhanced intermediate layer, and an interface bonding layer. A high-temperature support layer is then laminated, where polyether-type high-transparency thermoplastic polyurethane material is melt-extruded onto the interface bonding layer to form the high-temperature support layer, with the extrusion temperature controlled at 160°C. Next, a hot-melt adhesive layer is laminated, where thermoplastic polyurethane hot melt adhesive is hot-pressed onto the high-temperature support layer to form the hot-melt adhesive layer, with the hot-pressing temperature controlled at 120°C. Finally, post-treatment is performed, where the laminated film is cured for 14 hours in an environment with a relative humidity of 40%, and then cut and wound to obtain the final product.

[0079] The preparation of the modified ultraviolet photochromic powder includes: adding the ultraviolet photochromic powder to an organic solvent to form a suspension, then adding a silane coupling agent and a dispersant polyvinylpyrrolidone, the amount of which is 1.75% of the mass of the ultraviolet photochromic powder, stirring continuously at 65°C for 2.0 hours, and simultaneously performing ultrasonic treatment during the stirring process, with an ultrasonic frequency of 35kHz and an ultrasonic treatment time of 45 minutes.

[0080] The UV-curable waterborne polyurethane resin is a toughened and modified polyurethane resin. The preparation steps include: melt blending polyurethane resin and nano silica in a twin-screw extruder, wherein the amount of nano silica added is 5.5% of the mass of polyurethane resin, the blending temperature is controlled at 175℃, and the screw speed is 300 rpm.

[0081] Comparative Example 1:

[0082] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0083] A single-layer structure is used instead of a multi-layer structure. Specifically, the components of the photochromic top layer, the photochromic enhancement intermediate layer, and the interface bonding layer are mixed into a single monolithic layer.

[0084] Comparative Example 2:

[0085] In this comparative example, the similarities with Example 2 will not be repeated, and the differences are as follows:

[0086] Using unmodified UV photochromic powder means omitting the modification step and directly applying the UV photochromic powder to the preparation of each layer.

[0087] Comparative Example 3:

[0088] In this comparative example, the similarities with Example 3 will not be repeated, and the differences are as follows:

[0089] Ordinary polyurethane resin is used instead of UV-curable waterborne polyurethane resin in the photochromic surface layer.

[0090] Comparative Example 4:

[0091] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0092] The high-temperature support layer uses a polyether-type, highly transparent thermoplastic polyurethane material from Lubrizol, USA, model number 5714.

[0093] Comparative Example 5:

[0094] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0095] Ultrasonic treatment is omitted in the preparation of modified ultraviolet photochromic powder; only stirring is performed.

[0096] Performance test results and analysis:

[0097] Performance evaluations of three examples and five comparative examples were conducted using general testing methods, including: UV color-changing performance testing: samples were irradiated with a UV light source, and the uniformity of color change and color-changing response time were observed; high and low temperature cycling testing: samples were alternately placed in a high-temperature chamber and a low-temperature chamber, with each cycle consisting of maintaining a high temperature of 150°C for 30 minutes and a low temperature of -40°C for 30 minutes, for a total of 100 cycles, and the appearance and performance changes of the samples were checked; peel strength testing: the peel strength between layers was measured using a universal testing machine, with the unit being N / cm; abrasion resistance testing: friction testing was conducted using an abrasion testing machine, and the number of cycles at which surface wear occurred was recorded; weathering resistance testing: samples were exposed to alternating UV light and water spray environments for 500 hours, and the color stability and physical properties were evaluated. All tests were performed according to standard procedures to ensure the comparability of results, and the specific test results are shown in Table 1.

[0098] Table 1 Analysis of test results:

[0099] As shown in Table 1, the three embodiments exhibit excellent performance in terms of color change uniformity, color change response time, appearance after high and low temperature cycling, peel strength, abrasion resistance, and weather resistance, while the comparative embodiment shows a decline in performance across different indicators. Specifically, Embodiments 1, 2, and 3 all achieve uniform color change, with color change response times between 2 and 3 seconds, no change in appearance after high and low temperature cycling, peel strength in the range of 14-15 N / cm, abrasion resistance in the range of 9500-10000 cycles, and no significant color change after weathering. This demonstrates the stable performance achieved by the multi-layer functional structure design of this invention. The photochromic surface layer uses UV-curable waterborne polyurethane resin and modified ultraviolet photochromic powder, combined with the improved dispersibility brought about by surface modification, ensuring the consistency of color change and surface durability. The photochromic reinforcement intermediate layer uses chemically resistant waterborne polyurethane resin, further enhancing the ability to resist environmental factors, which is particularly evident in the high and low temperature cycling test.

[0100] Comparative Example 1, employing a single-layer structure, resulted in uneven color change, delamination, and low peel strength, validating the necessity of multilayer structures in addressing interlayer bonding and performance balance. Comparative Example 2, using unmodified photochromic powder, exhibited powder detachment and aggregation, demonstrating the crucial role of surface modification in improving dispersibility and compatibility, thereby extending material lifespan. Comparative Example 3, using ordinary polyurethane resin, resulted in surface softening and prolonged response time, highlighting the advantages of UV-curable resins in abrasion resistance and rapid curing. In Comparative Example 4, the excessively low melting point of the high-temperature support layer caused deformation, illustrating the importance of a specific melting point range for dimensional stability under high-temperature conditions. Comparative Example 5, omitting ultrasonic treatment, led to powder aggregation and performance degradation, emphasizing the contribution of ultrasonic treatment in ensuring uniform modification effects.

[0101] Test results show that the present invention effectively solves the defects of traditional optical variable films in terms of environmental adaptability, color uniformity and interlayer bonding through multi-layer structure, material selection and process optimization, and achieves stable application under wide temperature range conditions.

[0102] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An ultraviolet light color-shifting high-low temperature film, characterized in that, The high and low temperature film comprises five functional layers stacked in sequence: a photochromic surface layer, a photochromic enhancement intermediate layer, an interface bonding layer, a high temperature support layer, and a hot melt adhesive layer. The photochromic surface layer is composed of UV-curable waterborne polyurethane resin, colorant, and modified ultraviolet photochromic powder; the photochromic reinforced intermediate layer is composed of chemically resistant waterborne polyurethane resin and modified ultraviolet photochromic powder; the interface bonding layer is composed of thermally crosslinked waterborne polyurethane resin and crosslinking agent; the high-temperature support layer is composed of polyether-type high-transparency thermoplastic polyurethane material; and the hot melt adhesive layer is composed of thermoplastic polyurethane hot melt adhesive.

2. The UV color-shifting high-low temperature film according to claim 1, wherein, The mass fractions of each component in the photochromic surface layer are: 60-90 parts of UV-curable waterborne polyurethane resin, 2-8 parts of colorant, and 8-18 parts of modified ultraviolet photochromic powder. The mass fractions of each component in the photochromic enhancement intermediate layer are: 70-110 parts of chemically resistant waterborne polyurethane resin and 6-12 parts of modified ultraviolet photochromic powder. The mass fractions of each component in the interface bonding layer are: 75-105 parts of thermally crosslinked waterborne polyurethane resin and 2-7 parts of crosslinking agent.

3. The UV color-shifting high-low temperature film according to claim 1, wherein, The polyether-type highly transparent thermoplastic polyurethane material used in the high-temperature support layer has a melting point of 155-165℃ and a heat distortion temperature of 150-160℃. The thermoplastic polyurethane hot melt adhesive used in the hot melt bonding layer has a melting point of 115-125℃ and a Shore hardness of 90-98A.

4. The ultraviolet color-shifting high-low temperature film according to claim 1, wherein, The preparation method of the modified ultraviolet photochromic powder includes the following steps: adding ultraviolet photochromic powder to an organic solvent to form a suspension, then adding a silane coupling agent and a dispersing agent, stirring continuously at a temperature of 55-75℃ for 1.5-2.5 hours, and simultaneously performing ultrasonic treatment during the stirring process, with an ultrasonic frequency of 25-45kHz and an ultrasonic treatment time of 30-60 minutes.

5. The ultraviolet-sensitive color-changing high and low temperature film according to claim 4, characterized in that, The dispersing agent is polyvinylpyrrolidone, and its addition amount is 0.5-3% of the mass of the UV photochromic powder.

6. The ultraviolet color-shifting high-low temperature film according to claim 1, wherein, The UV-curable waterborne polyurethane resin is a toughened and modified polyurethane resin. The preparation steps of the UV-curable waterborne polyurethane resin include: melt blending polyurethane resin and nano-silica in a twin-screw extruder, wherein the amount of nano-silica added is 3-8% of the mass of polyurethane resin, the blending temperature is controlled at 160-190℃, and the screw speed is 200-400 rpm.

7. A method for preparing a UV color-shifting high-low temperature film, for preparing a UV color-shifting high-low temperature film according to any one of claims 1-6, characterized in that, The method includes the following steps: Step 1: Preparation of photochromic surface layer slurry: Mix UV-curable waterborne polyurethane resin, colorant and modified ultraviolet photochromic powder, and stir at 65-85℃ until homogeneous to obtain photochromic surface layer slurry; Step 2: Preparation of photo-modified intermediate layer slurry: Chemical-resistant waterborne polyurethane resin and modified ultraviolet photomodified powder are mixed in proportion and stirred at 70-95℃ until homogeneous to obtain photo-modified intermediate layer slurry. Step 3: Preparation of interface bonding layer slurry: Mix the thermal crosslinking waterborne polyurethane resin and crosslinking agent in proportion, and stir at 75-105℃ until uniform to obtain interface bonding layer slurry. Step 4: Forming a multi-layer structure: The above three slurries are sequentially coated on the release film to form a pre-formed structure consisting of a photochromic surface layer, a photochromic enhancement intermediate layer, and an interface bonding layer. Step 5: Composite high-temperature support layer: Polyether-type high-transparency thermoplastic polyurethane material is laminated onto the interface bonding layer to form a high-temperature support layer; Step 6, Composite hot melt adhesive layer: Thermoplastic polyurethane hot melt adhesive is laminated onto the high-temperature support layer to form a hot melt adhesive layer; Step 7: Post-processing: The composite membrane is cured at room temperature for 8-20 hours, and then cut and rolled up to obtain the final product.

8. The method for preparing an ultraviolet-chromatic high and low temperature film according to claim 7, characterized in that, The specific steps of the composite high-temperature support layer are as follows: polyether-type high-transparency thermoplastic polyurethane material is laminated onto the interface bonding layer by melt extrusion to form a high-temperature support layer, and the extrusion temperature is controlled at 155-165℃.

9. The method for preparing an ultraviolet-chromatic high and low temperature film according to claim 7, characterized in that, The specific steps of the composite hot melt adhesive layer are as follows: thermoplastic polyurethane hot melt adhesive is laminated onto the high-temperature support layer by hot pressing to form a hot melt adhesive layer, and the hot pressing temperature is controlled at 115-125℃.

10. The method for preparing an ultraviolet-chromatic high and low temperature film according to claim 7, characterized in that, The curing parameters and steps are as follows: cure for 8-20 hours in an environment with a relative humidity of 40%-60%.

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