Durable multilayer reflective film and preparation method thereof

Abstract

The invention discloses a durable multilayer reflective film and a preparation method thereof. The reflective film sequentially comprises a release layer, a pressure-sensitive adhesive layer, a film base layer, a fiber skeleton layer, a reflective adhesive layer, a microporous buffer layer and a protective layer from bottom to top. The fiber skeleton layer is of a mesh structure formed by interweaving microfibers with the diameter of 1-10 microns, glass beads are mainly distributed in meshes, and the glass beads and the water-based bonding slurry jointly form a fixation structure of mechanical locking and adhesive fixation. The micropore buffer layer is located between the reflective adhesive layer and the protective layer, and communicated micropores are obtained by coating a coating containing a pore-forming agent precursor and dissolving out or thermally decomposing the pore-forming agent. The preparation method comprises the following steps: treating the surface of the base film, laying the fiber skeleton, coating the water-based bonding slurry, spreading the glass beads, curing, preparing the microporous buffer layer, covering the protective layer, coating the pressure-sensitive adhesive on the back surface, and covering the release layer. The reflective film provided by the invention has high glass bead fixation fastness, bending durability and wet reflective performance.

Description

Technical Field

[0001] This invention belongs to the field of reflective film preparation technology, specifically relating to a durable multilayer reflective film and its preparation method. Background Technology

[0002] Reflective film is a functional material that reflects incident light back to the source along its original direction. It is widely used in traffic signs, road signs, vehicle wraps, advertising signs, and safety warning signs. A typical reflective film usually consists of a thin film base layer, a beaded adhesive layer, and a protective layer. The beaded adhesive layer contains a large number of glass microspheres, which achieve high visibility at night or in low-light environments through retroreflection. With increasing traffic safety requirements and improved regulations, the application range of reflective film is constantly expanding, and the performance requirements for it are also increasing.

[0003] However, traditional reflective films face several technical challenges in practical use. First, when applied to curved substrates or subjected to temperature changes, reflective films experience bending stress. This stress acts directly on the interface between the glass beads, the adhesive layer, and the film base layer, easily leading to adhesive layer cracking and glass bead detachment, thus causing a decrease in reflectivity. This problem is particularly prominent in applications such as vehicle wrapping and curved signs, severely impacting the lifespan and safety performance of the reflective film. Second, the protective layer of traditional reflective films is typically a dense polyurethane or acrylic coating, directly covering the top of the glass beads. When the reflective film bends and deforms, stress concentration occurs at the top of the glass beads, easily causing defects such as cracking and peeling. This not only affects the appearance but also reduces the protective effect and reflective performance.

[0004] Furthermore, the reduced reflectivity of reflective films in wet or humid environments is a long-standing technical challenge in the industry. Because a continuous water film easily forms between the glass beads in traditional structures, this film significantly weakens the retroreflective effect, drastically reducing the visibility of the reflective film in humid conditions and posing a traffic safety hazard.

[0005] To address the aforementioned issues, existing technologies primarily focus on improving the adhesive layer formulation, optimizing the surface treatment of glass beads, and adjusting the material ratios of each layer. For example, adding toughening agents and crosslinking agents to the adhesive layer can enhance its flexibility and adhesive strength, or treating the glass beads with silane coupling agents can strengthen the bead-adhesive interface bond. However, these improvements essentially remain at the formulation optimization level and fail to fundamentally solve the durability problems of reflective films under bending deformation and outdoor aging conditions. When reflective films undergo long-term outdoor exposure or are attached to curved substrates, the performance improvements brought about by formulation improvements are often unsustainable, and problems such as glass bead detachment and adhesive layer cracking persist. Therefore, there is an urgent need to develop a new type of reflective film that addresses these issues from a structural design perspective to meet increasingly stringent usage requirements. Summary of the Invention

[0006] To address the technical problems of existing reflective films, such as poor bending resistance, easy glass bead detachment, and decreased wet reflectivity, this invention provides a durable multilayer reflective film and its preparation method. This invention significantly improves the bending resistance, weather resistance, and wet reflectivity of the reflective film by introducing a fiber skeleton layer within the reflective adhesive layer and a microporous buffer layer between the reflective adhesive layer and the protective layer, thereby structurally reconstructing the mechanical transmission path and fluid discharge path within the reflective film.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A durable multilayer reflective film comprises, from bottom to top: a release layer, a pressure-sensitive adhesive layer, a thin film base layer, a fiber skeleton layer, a reflective adhesive layer, a microporous buffer layer, and a protective layer.

[0008] The thickness of the film substrate is 50-200 μm. The reflective adhesive layer comprises an aqueous adhesive slurry impregnating the fiber skeleton layer and glass beads embedded therein. The fiber skeleton layer is a mesh structure formed by continuous interwoven microfibers, the microfibers having a diameter of 1-10 μm, the pore size of the mesh structure being 1.0-3.0 times the volume average particle size of the glass beads, and the areal density being 3-15 g / m². The glass beads are mainly distributed within the mesh structure. The microporous buffer layer is disposed between the reflective adhesive layer and the protective layer, with a thickness of 8-25 μm, a pore size of 0.5-4 μm, and a porosity of 25-50%.

[0009] Furthermore, the film substrate is one of PET film, PC film, PVC film, and PMMA film; the upper surface of the film substrate is treated with corona discharge or a primer coating. As the supporting structure of the entire reflective film, the film substrate needs to possess sufficient mechanical strength, dimensional stability, and weather resistance. PET film is the most commonly used reflective film substrate due to its high strength, good transparency, and excellent dimensional stability; PC film has excellent impact resistance and heat resistance; PVC film has lower cost and better processing performance; PMMA film has excellent optical transparency and weather resistance. Corona discharge or primer coating can improve the wettability and adhesion strength of the film substrate surface, enhancing its bonding with the upper structure.

[0010] Furthermore, the microporous buffer layer is made of one or more of elastic polyurethane, elastic acrylate, and elastic silicone rubber. The microporous buffer layer uses an elastic resin material with a lower modulus than the upper protective layer. When the reflective film undergoes bending deformation, the microporous buffer layer preferentially undergoes compression or tensile deformation, absorbing and dispersing the stress from the protective layer, preventing stress from directly acting on the top of the glass beads and causing the protective layer to crack or the glass beads to fall off. Elastic polyurethane has excellent resilience and abrasion resistance; elastic acrylate has good weather resistance and transparency; and elastic silicone rubber has a wide operating temperature range and excellent aging resistance.

[0011] Furthermore, the glass beads have a particle size of 40-80 μm. The selection of the glass bead particle size requires a comprehensive consideration of the balance between reflective performance and film thickness. Too small a particle size will reduce retroreflection efficiency, while too large a particle size will increase the total film thickness, affecting the flexibility and adhesion of the reflective film. A particle size range of 40-80 μm ensures good reflective performance while maintaining suitable thickness and flexibility of the reflective film.

[0012] Furthermore, the microfiber material of the fiber skeleton layer is one or more of polyester fiber, polyamide fiber, polypropylene fiber, and glass fiber. The microfibers in the fiber skeleton layer need to possess high modulus and strength to bear the main in-plane stress when the reflective film is bent or stretched, thus reducing the stress load at the interface between the adhesive layer and the glass beads. Polyester and polyamide fibers have high strength and modulus, and good compatibility with water-based adhesive slurries; polypropylene fibers have low density and good chemical resistance; glass fibers have high modulus and good dimensional stability, making them suitable for applications requiring higher durability.

[0013] Furthermore, the pore size of the mesh structure is designed to be 1.0-3.0 times the average volume diameter of the glass beads, a specific range that is of significant technical importance. When the pore size is less than 1.0 times the glass bead diameter, the glass beads cannot fall into the mesh, and the load-bearing and locking effects of the fiber skeleton layer cannot be achieved. When the pore size is greater than 3.0 times the glass bead diameter, the glass beads will directly penetrate the mesh and fall onto the substrate, similarly losing the support and positioning function of the skeleton layer. Within the range of 1.0-3.0 times, the glass beads can be partially embedded in the mesh, "locked" by the fiber grid, forming a dual fixation mechanism of mechanical locking and adhesive bonding, significantly improving the adhesion strength of the glass beads.

[0014] Furthermore, the water-based adhesive slurry is one or more of water-based polyurethane resin, water-based acrylic resin, and water-based polyurethane-acrylic composite resin. The water-based adhesive slurry is a key material for fixing the glass beads and connecting the layers, requiring good adhesive strength, flexibility, and water resistance. Water-based polyurethane resin has excellent adhesive strength and abrasion resistance; water-based acrylic resin has good weather resistance and cost advantages; water-based polyurethane-acrylic composite resin combines the advantages of both, possessing both high strength and high flexibility. Using a water-based system also has the advantages of being environmentally friendly and having low VOC emissions.

[0015] Furthermore, the protective layer is one of a transparent polyurethane coating, a transparent acrylic coating, a transparent polyurethane film, or a transparent acrylic film. The protective layer is located on the outermost layer of the reflective film, serving to protect the glass beads, improve abrasion resistance and weather resistance, while maintaining good transparency to avoid affecting reflective performance. Transparent polyurethane coatings and films possess excellent abrasion resistance and flexibility; transparent acrylic coatings and films possess good weather resistance and gloss.

[0016] Furthermore, the pressure-sensitive adhesive layer is made of one or more of acrylic pressure-sensitive adhesive, silicone pressure-sensitive adhesive, and rubber-based pressure-sensitive adhesive, with a coating amount of 25-50 g / m². The pressure-sensitive adhesive layer gives the reflective film self-adhesive properties, facilitating adhesion to various substrate surfaces. Acrylic pressure-sensitive adhesives possess excellent weather resistance, aging resistance, and adhesive strength, making them the most commonly used backing adhesive type for reflective films; silicone pressure-sensitive adhesives have excellent high-temperature resistance and peel resistance, suitable for applications requiring re-removal; rubber-based pressure-sensitive adhesives have high initial tack, suitable for bonding to rough surfaces.

[0017] Furthermore, the release layer is one of silicone release paper, silicone release film, or fluorinated release film. The release layer is used to protect the pressure-sensitive adhesive layer and prevent the pressure-sensitive adhesive from being contaminated or sticking during storage and transportation. The release layer can be removed for application during use.

[0018] Furthermore, the microporous buffer layer is prepared by coating a precursor coating containing a soluble pore-forming agent or thermally decomposable particles onto the reflective adhesive layer. During or after curing, the pore-forming agent dissolves or the particles thermally decompose to form an interconnected microporous structure. The soluble pore-forming agent is a water-soluble salt or a water-soluble sugar; the thermally decomposable particles are ammonium carbonate or azodicarbonamide. Water-soluble salts and sugars can dissolve and form micropores by washing with water after curing; ammonium carbonate decomposes into ammonia and carbon dioxide upon heating to form micropores; azodicarbonamide decomposes at a specific temperature to produce nitrogen gas, forming micropores. By controlling the type, particle size, and content of the pore-forming agent, the pore size, porosity, and pore structure of the microporous buffer layer can be controlled to obtain optimal wet reflective and buffering performance.

[0019] The present invention also provides a method for preparing the above-mentioned durable multilayer reflective film, comprising the following steps: S1. The upper surface of the film substrate is corona treated or coated with a primer to improve surface adhesion, and then a fiber skeleton layer is laid on it. The fiber skeleton layer can be prepared by non-woven fabric laying, electrospinning, meltblowing, etc. The key is to control the diameter of the microfibers and the pore size of the mesh to match the particle size of the glass beads used later.

[0020] S2. Apply a water-based adhesive slurry to the fiber skeleton layer, then sprinkle glass beads into the mesh structure, allowing them to fall into the mesh. After curing, a reflective adhesive layer is formed. After applying the water-based adhesive slurry, the slurry partially wets the fiber skeleton layer and fills the gaps in the mesh. Subsequently, the sprinkled glass beads fall into the mesh under gravity and are adhered and fixed by the slurry. After curing, a composite structure of "base layer - fiber skeleton - adhesive + beads" is formed.

[0021] S3. A precursor coating containing a pore-forming agent is applied to the reflective adhesive layer, cured, and the pore-forming agent is removed to form a microporous buffer layer. The pore-forming agent in the precursor coating is removed during or after curing, leaving a connected microporous structure. The method of removing the pore-forming agent depends on its type: water-soluble pore-forming agents are removed by washing with water, and thermally decomposable particles are removed by heating.

[0022] S4. A protective layer is laminated onto the microporous buffer layer. The protective layer can be applied by coating or lamination. Coating is suitable for coating-type protective layers, while lamination is suitable for film-type protective layers.

[0023] S5. Apply pressure-sensitive adhesive to the lower surface of the film substrate, and after drying, laminate with a release layer to obtain a durable multilayer reflective film. The pressure-sensitive adhesive layer gives the reflective film self-adhesive function, and the release layer protects the pressure-sensitive adhesive layer from contamination during storage and transportation.

[0024] Further, in step S2, the coating amount of the water-based adhesive slurry is 80-130 g / m², the amount of glass beads sprinkled is 120-180 g / m², the curing temperature is 80-110℃, and the curing time is 3-10 min. The coating amount of the water-based adhesive slurry needs to be sufficient to wet the fiber skeleton layer and fix the glass beads, but should not be too much to avoid increasing the film thickness; the amount of glass beads sprinkled determines the reflective intensity of the reflective film; the curing temperature needs to be adjusted according to the heat resistance of the film substrate, and the curing temperature should not exceed 100℃ for PVC film substrates.

[0025] Furthermore, in step S5, the coating amount of the pressure-sensitive adhesive is 25-50 g / m², the drying temperature is 60-80℃, and the drying time is 3-5 min.

[0026] Further, in step S3, the coating amount of the precursor coating is 40-60 g / m², and the content of the pore-forming agent is 15-30% of the solid mass of the precursor coating. The coating amount of the precursor coating determines the thickness of the microporous buffer layer, and the thickness needs to be controlled while ensuring sufficient buffering effect; the content of the pore-forming agent determines the porosity of the microporous buffer layer, and a content range of 15-30% corresponds to a porosity range of 25-50%.

[0027] The beneficial effects of this invention are as follows: 1. This invention constructs a dual glass bead fixation mechanism of "mechanical locking + adhesive bonding" by embedding a fiber skeleton layer inside the reflective adhesive layer. The mesh structure of the fiber skeleton layer matches the particle size of the glass beads, positioning the glass beads within the mesh to form mechanical locking. Simultaneously, the aqueous adhesive slurry wets the fiber skeleton and coats the glass beads to form adhesive fixation. Furthermore, when the reflective film is bent or stretched, the in-plane stress is preferentially borne and transmitted by the fiber skeleton, reducing the stress acting on the interface between the adhesive layer and the glass beads, which helps to reduce the risk of adhesive layer cracking and glass bead detachment.

[0028] 2. The microporous buffer layer between the reflective adhesive layer and the protective layer in this invention has a dual function: stress buffering and promoting moisture migration and escape, while reducing water film shading. The microporous buffer layer is made of elastic resin material, which preferentially deforms and gradually transfers stress when the protective layer undergoes bending deformation, thus reducing stress concentration at the top of the glass bead. Simultaneously, the interconnected microporous structure of the microporous buffer layer provides multidirectional migration and escape channels for moisture, which helps to break down the continuous water film covering the surface of the glass bead, reducing the water film's shading effect on the reflective effect, thereby improving wet reflective performance.

[0029] 3. This invention incorporates a pressure-sensitive adhesive layer and a release layer beneath the film substrate, giving the reflective film self-adhesive properties. It can be directly applied to various substrates such as traffic signs, vehicle bodies, and billboards, making construction convenient, applicable to a wide range of situations, and the preparation method is simple, easy to control, and compatible with existing reflective film production lines. The fiber skeleton layer can be prepared using solvent-free processes such as meltblowing, while the reflective adhesive layer and microporous buffer layer utilize a water-based resin system. The entire process is environmentally friendly with low VOC emissions, meeting the requirements of green manufacturing development. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements, and equivalents included within the scope of the claims. Example 1

[0031] S1: A 100μm thick PET film was selected as the base layer, and its upper surface was corona treated to achieve a surface tension of over 42 mN / m. Polypropylene microfiber nonwoven fabric was directly prepared on the treated PET film using a melt-blowing method. Polypropylene (PP) chips were heated to 230-240℃ and melt-extruded in a screw extruder. After the melt was ejected through the melt-blowing die, it was immediately dispersed and drawn into microfibers by high-temperature, high-speed airflows (temperature 240-250℃, flow rate 6000-10000 m / min) on both sides. The microfibers were deposited on the surface of the PET film. By adjusting the melt flow rate and the drawing airflow velocity, the fiber fineness and web density were controlled to obtain a fiber skeleton layer with a microfiber diameter of approximately 5μm, an areal density of 10 g / m², and a mesh pore size of approximately 120μm.

[0032] S2: Select glass beads with a particle size of 60μm (mesh / bead diameter ratio of 2.0). Dilute the waterborne polyurethane-acrylic composite resin with deionized water to a solid content of 30%, and apply the slurry to the fiber skeleton layer using a doctor blade coating method, with a coating amount of 100 g / m² (wet weight). Immediately and evenly sprinkle glass beads at a rate of 140 g / m², ensuring the glass beads fall into the mesh structure. Place the composite material in an oven and cure it at 100℃ for 5 min to obtain the reflective adhesive layer.

[0033] S3: Dilute the elastic polyurethane resin with deionized water to a solid content of 25%. Add sodium chloride powder with a particle size of 2-10 μm as a pore-forming agent, with the pore-forming agent content being 25% of the resin solid mass. Stir until homogeneous. Apply the precursor coating to the reflective adhesive layer using a doctor blade coating method, with a coating amount of 50 g / m² (wet weight). Place the composite material in an oven and cure at 90°C for 10 min. Then, immerse it in deionized water for 30 min to dissolve the sodium chloride. Rinse with deionized water and dry at 60°C to obtain a microporous buffer layer with a thickness of 18 μm, a pore size of approximately 2 μm, and a porosity of approximately 40%.

[0034] S4: Dilute the transparent polyurethane coating resin with ethyl acetate to a solid content of 25%, and apply it to the microporous buffer layer using a doctor blade coating method, with a coating amount of 40 g / m² (wet weight). Dry at 80℃ for 5 min, and then cure at 110℃ for 3 min to obtain the protective layer.

[0035] S5: Turn the composite material over, coat the lower surface of the PET film base with acrylic pressure-sensitive adhesive at a coating amount of 35 g / m², dry at 70°C for 4 min, and then laminate with silicone release paper to obtain a durable multilayer reflective film. Example 2

[0036] The reflective film was prepared according to the method of Example 1, with the following difference: The film base layer is a 75μm thick PET film, with a polyurethane primer coated on the upper surface (coating amount 5 g / m², drying at 80℃ for 2 min); the fiber skeleton layer is prepared using the same PP melt-blowing method as in Example 1, and by adjusting the melt-blowing parameters, a fiber skeleton layer with a microfiber diameter of 2μm, an areal density of 5 g / m², and a mesh size of approximately 100μm is obtained; the glass beads have a particle size of 50μm (mesh / bead diameter ratio of 2.0); the water-based adhesive slurry is water-based polyurethane resin, with a coating amount of 80 g / m²; the glass beads are spread at a rate of 120 g / m²; the microporous buffer layer has a thickness of 12μm, a pore size of approximately 1μm, and a porosity of approximately 30%; the curing temperature of the reflective adhesive layer in step S2 is 90℃, and the curing time is 8 min; the coating amount of the pressure-sensitive adhesive in step S5 is 30 g / m². Example 3

[0037] The reflective film was prepared according to the method of Example 1, with the following difference: The film substrate is a 150 μm thick PC film with a corona treatment on its upper surface. The fiber skeleton layer is prepared using the same PP melt-blowing method as in Example 1. By adjusting the melt-blowing parameters, a fiber skeleton layer with a microfiber diameter of 10 μm, an areal density of 15 g / m², and a mesh size of approximately 240 μm is obtained. The glass beads have a particle size of 80 μm (mesh / bead diameter ratio of 3.0). The water-based adhesive slurry is water-based acrylic resin with a coating amount of 130 g / m². The glass beads are spread at a rate of 180 g / m². The microporous buffer layer is made of elastic acrylate with a thickness of 25 μm, a pore size of approximately 4 μm, and a porosity of approximately 50%. The precursor coating has a coating amount of 60 g / m², and the pore-forming agent is glucose with a particle size of 5-15 μm and a content of 30%. In step S2, the reflective adhesive layer is cured at 110℃ for 4 min. In step S5, the pressure-sensitive adhesive is an organosilicon pressure-sensitive adhesive with a coating amount of 40 g / m². g / m². Example 4

[0038] The reflective film was prepared according to the method of Example 1, with the following difference: The film substrate is an 80 μm thick PVC film, with an acrylic primer coated on the upper surface (coating amount 4 g / m², drying at 60℃ for 3 min). The fiber skeleton layer is prepared using the same PP melt-blowing method as in Example 1. By adjusting the melt-blowing parameters, a fiber skeleton layer with a microfiber diameter of 3 μm, an areal density of 4 g / m², and a mesh size of approximately 50 μm is obtained. The glass beads have a particle size of 40 μm (mesh / bead diameter ratio of 1.25). In step S2, the water-based adhesive slurry coating amount is 85 g / m², the glass bead spreading amount is 125 g / m², the curing temperature is 85℃ (considering the heat resistance of PVC), and the curing time is 6 min. The microporous buffer layer has a thickness of 8 μm, a pore size of approximately 0.5 μm, and a porosity of approximately 25%. The precursor coating coating amount is 40 g / m², and the pore-forming agent is ammonium carbonate with a particle size of 1-5 μm and a content of 15%. A step-by-step curing process is adopted: first, pre-curing at 55℃ for 3 minutes... The resin is initially formed by heating for 5 minutes, then heated to 95℃ and held for 5 minutes. This allows ammonium carbonate to gradually decompose and release gas during the resin film formation process, forming a microporous structure that does not require water washing to remove. The protective layer is a 15μm thick transparent PU film, which is bonded by hot pressing (temperature 90℃, pressure 0.5 MPa, time 2 minutes). In step S5, the pressure-sensitive adhesive coating amount is 25 g / m², the drying temperature is 60℃, and the release layer is a silicone oil release film. Example 5

[0039] The reflective film was prepared according to the method of Example 1, with the following difference: The film substrate is a 120μm thick PMMA film with corona treatment on the upper surface; the glass beads have a particle size of 70μm; the microporous buffer layer is made of elastic silicone rubber with a thickness of 20μm, a pore size of about 3μm, and a porosity of about 45%; in step S5, the pressure-sensitive adhesive coating amount is 45 g / m², and the release layer is a fluorinated release film.

[0040] Comparative Example 1 The reflective film was prepared according to the method of Example 1, but the fiber skeleton layer laying step was omitted. A water-based adhesive slurry was directly coated on the corona-treated PET film substrate and glass beads were sprinkled on it. The remaining steps were the same.

[0041] Comparative Example 2 The reflective film was prepared according to the method of Example 1, but step S3 was omitted. The protective layer was directly laminated onto the reflective adhesive layer, and the remaining steps were the same.

[0042] Comparative Example 3 Traditional reflective film structure: 100μm thick PET film is selected, corona treated, water-based adhesive slurry is directly coated (coating amount 100 g / m²), glass beads are sprinkled (sprinkling amount 140 g / m²), after curing, a transparent polyurethane protective layer is directly coated, and finally pressure-sensitive adhesive is coated on the underside of the base layer and release paper is laminated.

[0043] Performance Testing and Evaluation The reflective films prepared in the examples and comparative examples were subjected to the following performance tests: 1. Retroreflection coefficient test: According to GB / T 18833-2012 "Road Traffic Reflective Film", the retroreflection coefficient tester was used to test under the conditions of an incident angle of 5° and an observation angle of 0.2°. The unit is cd / (lx·m²).

[0044] 2. 180° peel strength test: According to GB / T 2792-2014 "Test method for peel strength of adhesive tape", the peel strength between the reflective adhesive layer and the substrate was tested using an electronic tensile testing machine at 23℃ and 50% relative humidity. The peel speed was 300 mm / min, and the unit was N / 25mm.

[0045] 3. Bending resistance test: Referring to the round bar bending test method, the reflective film was cut into 150 mm × 50 mm samples and attached to a round bar with a diameter of 3.2 mm for bending test. The sample was bent 180° along the round bar, held for 5 seconds, and then unfolded. This was repeated 500 times. The retroreflection coefficient and 180° peel strength were tested before and after bending, and the retention rate was calculated.

[0046] 4. Weather resistance test: Referring to GB / T 16422.2-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamp", the sample was placed in a xenon lamp aging chamber with a black panel temperature of 65℃ and an irradiance of 0.51 W / m² (340 nm). After continuous exposure for 500 h, the retroreflection coefficient and appearance change were tested, and the retention rate was calculated.

[0047] 5. Wet reflectivity test: Spray distilled water onto the sample surface until it is completely wet, immediately test the retroreflection coefficient, compare it with the dry retroreflection coefficient, and calculate the wet retention rate.

[0048] Table 1. Results of reflective film performance tests

[0049] Test Results According to the test data in Table 1, Comparative Example 1, lacking a fiber skeleton layer, showed significantly lower retroreflection coefficient retention (70%) and peel strength retention (64%) after bending compared to Example 1 (90% and 88%). This indicates that the mechanical locking and stress reduction effects of the fiber skeleton layer effectively improve the bending resistance of the reflective film. Comparative Example 2, lacking a microporous buffer layer, showed lower performance retention rates after bending (74% and 72%) compared to Example 1, and its wet reflective performance retention rate (65%) was significantly worse. This demonstrates that the stress buffering, moisture migration and escape promotion, and water film shading functions of the microporous buffer layer play a crucial role in improving the durability and wet performance of the reflective film. Comparative Example 3, using a traditional structure, showed significantly inferior performance compared to Example 1, verifying the synergistic effect of the dual-structure design of this invention.

[0050] Examples 1-5, by adjusting parameters such as the film base material, fiber diameter, glass bead size, and layer thickness, all achieved good bending resistance and weather resistance, demonstrating the feasibility and applicability of the claimed technical solutions. Specifically, Example 5, using elastic silicone rubber as the microporous buffer layer material, exhibited the best weather resistance (94%) and wet reflectivity (83%), making it suitable for outdoor applications requiring high durability. Example 4, using a PVC film base with a correspondingly lower processing temperature, while slightly outperforming the PET base example, still significantly outperformed the comparative example, indicating that the technical solutions of this invention have good applicability to different types of film bases.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A durable multilayer reflective film, characterized in that, From bottom to top, it includes: release layer, pressure-sensitive adhesive layer, film base layer, fiber skeleton layer, reflective adhesive layer, microporous buffer layer and protective layer; The thickness of the film substrate is 50-200 μm; the reflective adhesive layer includes an aqueous adhesive slurry that wets the fiber skeleton layer and glass beads embedded therein, the fiber skeleton layer is a continuous microfiber interwoven to form a mesh structure, the diameter of the microfiber is 1-10 μm, the pore size of the mesh structure is 1.0-3.0 times the volume average particle size of the glass beads, the areal density is 3-15 g / m², and the glass beads are mainly distributed within the mesh structure; The microporous buffer layer is disposed between the reflective adhesive layer and the protective layer, with a thickness of 8-25 μm, a pore size of 0.5-4 μm, and a porosity of 25-50%.

2. The durable multilayer reflective film according to claim 1, characterized in that, The film substrate is one of PET film, PC film, PVC film, and PMMA film; the upper surface of the film substrate is treated with corona discharge or primer.

3. The durable multilayer reflective film according to claim 1, characterized in that, The microporous buffer layer is made of one or more of the following materials: elastic polyurethane, elastic acrylate, and elastic silicone rubber.

4. The durable multilayer reflective film according to claim 1, characterized in that, The glass beads have a particle size of 40-80 μm; the microfiber material of the fiber skeleton layer is one or more of polyester fiber, polyamide fiber, polypropylene fiber, and glass fiber.

5. The durable multilayer reflective film according to claim 1, characterized in that, The water-based adhesive slurry is one or more of water-based polyurethane resin, water-based acrylic resin, and water-based polyurethane-acrylic composite resin.

6. The durable multilayer reflective film according to claim 1, characterized in that, The protective layer is one of transparent polyurethane coating, transparent acrylic coating, transparent polyurethane film, and transparent acrylic film; the pressure-sensitive adhesive layer is one or more of acrylic pressure-sensitive adhesive, silicone pressure-sensitive adhesive, and rubber-type pressure-sensitive adhesive, with a coating amount of 25-50 g / m²; the release layer is one of silicone release paper, silicone release film, and fluorine release film.

7. The durable multilayer reflective film according to claim 1, characterized in that, The microporous buffer layer is prepared by coating a precursor coating containing a soluble pore-forming agent or thermally decomposable particles onto the reflective adhesive layer. During or after curing, a connected microporous structure is formed by the dissolution of the pore-forming agent or the thermal decomposition of the particles. The soluble pore-forming agent is a water-soluble salt or a water-soluble sugar. The thermally decomposable particles are ammonium carbonate or azodicarbonamide.

8. A method for preparing a durable multilayer reflective film according to any one of claims 1-7, characterized in that, Includes the following steps: S1. The upper surface of the film substrate is corona treated or coated with a primer to improve surface adhesion, and then a fiber skeleton layer is laid on it. S2. A water-based adhesive slurry is coated on the fiber skeleton layer, and glass beads are sprinkled on it so that the glass beads fall into the mesh structure. After curing, a reflective adhesive layer is formed. S3. Apply a precursor coating containing a pore-forming agent to the reflective adhesive layer, cure and remove the pore-forming agent to form a microporous buffer layer; S4. A protective layer is coated onto the microporous buffer layer; S5. Apply pressure-sensitive adhesive to the lower surface of the film substrate, dry it, and then laminate with a release layer to obtain a durable multilayer reflective film.

9. The preparation method according to claim 8, characterized in that, In step S2, the coating amount of the water-based adhesive slurry is 80-130 g / m², the spreading amount of the glass beads is 120-180 g / m², the curing temperature is 80-110℃, and the curing time is 3-10 min; in step S5, the coating amount of the pressure-sensitive adhesive is 25-50 g / m², the drying temperature is 60-80℃, and the drying time is 3-5 min.

10. The preparation method according to claim 8, characterized in that, In step S3, the coating amount of the precursor coating is 40-60 g / m², and the content of the pore-forming agent is 15-30% of the solid mass of the precursor coating.

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