A method for preparing an ultraviolet resistant film

Abstract

This invention discloses an anti-ultraviolet (UV) film and its preparation method. The composite film material includes a barrier layer, an adhesive layer, an intermediate layer, and a heat-sealing layer. The barrier layer uses high-efficiency barrier materials such as KPET and KNY, while the heat-sealing layer disperses UV-resistant particles to enhance UV protection. The intermediate layer employs a reinforced film structure such as NY or PET, and the adhesive layer ensures a stable connection between the layers. Furthermore, an ink layer and a reflective layer are introduced. Two diarylethylene films with different color-changing properties can be used, exhibiting photochromic characteristics. This not only enhances aesthetics but also improves product interactivity. After color change, the film reflects ultraviolet light, improving the UV protection of this invention while maintaining its transparency.

Description

[0001] This application is a divisional application of application number 202411899614.8, filed on December 23, 2024, entitled "An Anti-ultraviolet High-Barrier Transparent Film and Its Preparation Method Thereof", the entire text of which is incorporated herein by reference. Technical Field

[0002] This invention relates to the field of composite film technology, and in particular to an anti-ultraviolet film for food packaging. Background Technology

[0003] PrePack is a type of aseptic packaging, primarily used for dairy products. Its structure consists of a multi-layered aseptic composite film, such as a three-layer black and white film, as well as high-barrier multi-layered co-extruded films and aluminum-plastic composite films. These composite films effectively block external factors such as oxygen and moisture from affecting food quality, thus extending shelf life. To allow consumers to visually inspect the food inside, there is a growing demand for transparent food packaging. However, transparent packaging cannot block ultraviolet (UV) radiation, which can easily degrade photosensitive components like vitamins and oxidize fats, causing rancidity and spoilage, thus affecting flavor and texture. Therefore, it is necessary to design and manufacture a high-barrier transparent film that resists UV radiation. Current technology uses PET as the transparent substrate, adding UV-resistant additives to achieve UV protection. However, this approach has limited effectiveness in blocking UV light, only ensuring good blocking within the 200-360nm range. It also has poor barrier properties against water and oxygen, with an OTR ≤ 120 and a WTR ≤ 15. Summary of the Invention

[0004] The main objective of this invention is to overcome the shortcomings of the prior art and provide an anti-ultraviolet film to improve the wavelength range of ultraviolet light blocking in food packaging materials; the secondary objective is to provide an improved method for synthesizing diarylene and to obtain a diarylene film material.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: An anti-ultraviolet film, comprising, from the outside to the inside: Barrier layer, the barrier layer comprising K-modified film, AlO x Modified membranes, SiO2 modified membranes; The adhesive layer is prepared by coating and laminating a transparent, boil-resistant adhesive. Intermediate layer, wherein the intermediate layer is a functional film layer; The reflective layer is a diarylethylene film (A). The heat-sealing layer is a PP or PE film with uniformly dispersed UV-resistant particles. The bottom of the barrier layer is bonded to the intermediate layer via an adhesive layer, and the intermediate layer, the reflective layer, and the heat-sealing layer are heat-sealed together.

[0006] Furthermore, the barrier layer includes at least one of KPET, KNY, PET-AlOx, BOPP-AlOx, and PET-SiO2.

[0007] Furthermore, the intermediate layer includes at least one of NY, PET, BOPE, and MDOPE.

[0008] Furthermore, the thickness ratio of the barrier layer / adhesive layer / intermediate layer / reflective layer / heat seal layer is: (0.75~1.25) / (0.5~1) / (1.5~2) / (1.5~3) / (1.5~2).

[0009] Furthermore, the adhesive layer is one of the following: water-boiling grade adhesive, semi-high temperature cooking grade adhesive, and high temperature cooking grade adhesive.

[0010] Furthermore, an ink layer is provided between the barrier layer and the adhesive layer, the barrier layer at least partially covering the ink layer, and the ink layer is bonded to one side of the barrier layer by the adhesive layer.

[0011] Furthermore, the ink layer is a diarylethylene film (B), wherein the diarylethylene film (A) and the diarylethylene film (B) are any two of the following: red light-changing diarylethylene film, blue light-changing diarylethylene film, and violet light-changing diarylethylene film.

[0012] A method for preparing a diarylethylene membrane includes the following steps: S1, by weight, weigh 5-20 parts of diarylethene photochromic compound, 150-200 parts of ethyl acetate-water solution with a volume fraction of 75-85%, and 1-5 parts of surfactant, and stir to mix well. S2, heat the mixture obtained in S1 to 40-60 degrees Celsius and keep it at that temperature for 1-2 hours to prepare the active intermediate; S3, the active intermediate obtained in S2 is coated onto the surface of at least one of the adjacent layers and dried at 60-80 degrees Celsius.

[0013] Furthermore, diarylethene photochromic compounds include: 2,3-Bis(2,4,5-trimethyl-3-thienyl)maleic anhydride, 2,3-Bis(2,4,5-trimethyl-3-thienyl)maleimide, At least one of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene.

[0014] Furthermore, in S3, the surface of the intermediate layer and / or heat-sealing layer is pretreated, the pretreatment including: activating the intermediate layer and / or heat-sealing layer at 40~50°C.

[0015] Furthermore, the diarylethylene film has a light transmittance >95% and a haze <5%.

[0016] The advantages and beneficial effects of this invention are as follows: 1. High-efficiency barrier and UV protection: Through a specially selected barrier layer, it achieves high-efficiency barrier against external environmental factors, including oxygen and moisture. At the same time, the uniformly dispersed UV-resistant particles in the heat-sealing layer effectively resist the damage of ultraviolet rays, protecting the contents of the package from UV-induced damage.

[0017] 2. Composite Structure and Function: The functional layers are tightly bonded together through an adhesive layer, ensuring not only the overall stability of the membrane structure but also the effective superposition of the functions of each layer. The selection of the intermediate layer enhances the mechanical properties and durability of the membrane.

[0018] 3. Combining weather resistance and aesthetics: The ink layer not only provides rich visual effects for the packaging but also enhances brand recognition. Simultaneously, the tight bond between the ink layer and the barrier layer ensures the durability and weather resistance of the printed design.

[0019] 4. Intelligent color-changing function: The transparent diarylethylene film (A) and diarylethylene film (B) used in the reflective layer and ink layer have photosensitive color-changing properties, which can present different colors under ultraviolet light. When the reflective layer turns blue or purple under ultraviolet light, the surface reflects blue and purple light, which further improves the anti-ultraviolet technology effect. At the same time, the ink layer turns red without affecting the visual effect of the ink layer. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; In the picture: 1-Barrier layer, 2-Ink layer, 3-Adhesive layer, 4-Intermediate layer, 5-Reflective layer, 6-Heat-sealing layer. Detailed Implementation

[0021] OTR stands for Oxygen Transmission Rate, which refers to the rate at which oxygen permeates through a material or packaging. It is often used to measure the oxygen barrier performance of a material or packaging.

[0022] WTR stands for Water Vapor Transmission Rate, which refers to the rate at which water vapor passes through a material or packaging.

[0023] PE: Polyethylene film.

[0024] PP: Polypropylene film.

[0025] BOPE: Biaxially oriented polyethylene film.

[0026] MDOPE: Longitudinal stretched polyethylene film.

[0027] KPET: Plastic film with PET (polyethylene terephthalate) as the base material, the prefix K indicates that it is coated with high-barrier PVDC (polyvinylidene chloride) on one side.

[0028] KNY: Based on NY (polyamide, nylon), the prefix K indicates a plastic film coated with high-barrier PVDC (polyvinylidene chloride) on one side.

[0029] PET-AlOx: A plastic film with PET as the substrate, in which aluminum oxide is vacuum-deposited onto the corona-treated side of the PET film, and the other side is a non-corona-treated side.

[0030] PET-SiO2: A composite film made by adding nano-silica during the PET melting process, with PET as the substrate.

[0031] BOPP-AlO x A plastic film made of BOPP (biaxially oriented polypropylene film) as the substrate, with alumina vacuum-deposited on the corona-treated side of the BOPP and the other side being non-corona-treated. In a corresponding embodiment of the present invention, the side of the K-modified film coated with PVDC is the side away from the adhesive layer.

[0032] In a corresponding embodiment of the present invention, AlO x The corona-treated surfaces of the modified membrane are all composited with the adhesive layer.

[0033] GB / T 10004 stipulates that packaging is divided into four grades according to the operating temperature: ordinary grade (≤80℃), boiling grade (80℃ or above ~100℃), semi-high temperature retort grade (100℃ or above ~121℃), and high temperature retort grade (121℃ or above ~145℃).

[0034] Diarylethylene is a type of photochromic material that changes color under specific lighting conditions. Generally, when exposed to ultraviolet light, diarylethylene changes from a colorless or light-colored state to a darker state, such as blue, purple, or red. This color change is usually reversible, meaning that the material can revert to its original colorless or light-colored state under different lighting conditions or heat.

[0035] Barrier layer: The barrier layer can be made of K-modified film, AlO xIt consists of modified membranes and SiO2 modified membranes. These materials have high barrier properties and can effectively block oxygen, water vapor and ultraviolet rays, protecting the inner layer material from the influence of the external environment.

[0036] Adhesive Layer: The adhesive layer uses a transparent, retort-resistant adhesive to ensure a strong bond between the barrier layer and the intermediate layer. This adhesive can withstand the high temperature and pressure during the retort process while maintaining the film's transparency and not affecting the overall visual effect.

[0037] Intermediate Layer: The intermediate layer is a functional film layer, which can be a material with specific functions, such as enhancing the mechanical strength of the film, providing additional barrier properties, or increasing specific optical effects. The key point is that the intermediate layer avoids direct contact bonding between the adhesive layer and the reflective layer; instead, it is optional. This allows the reflective layer to be coated simultaneously on the intermediate layer and the heat-sealing layer, enabling the reflective layer to achieve a certain thickness and thus better reflective function. It should be understood that the ink layer can optionally add reflective effects, or conventional printing techniques can be used to achieve existing technical effects without requiring intelligent color changing. The heat-sealing bonding between the intermediate layer and the barrier layer, reflective layer, and heat-sealing layer ensures a tight connection between each layer, improving the overall performance of the film.

[0038] Reflective Layer: The reflective layer is obtained by coating and drying a solution of diarylethylene in ethyl acetate. Notably, a certain volume fraction of ethyl acetate-water solution is used to disperse the diarylethylene. This utilizes the volatile nature of ethyl acetate, facilitating subsequent coating and drying processes. Furthermore, ethyl acetate, as a less polar solvent, is combined with deionized water as a solvent, enriching the diarylethylene at the ethyl acetate-water interface. This is more conducive to the dispersion of the larger diarylethylene molecules and ensures that the reflective layer, while reflecting specific wavelengths of light, reduces potential haze under non-light conditions, thus achieving a specific color effect while maintaining transparency. The heat-sealing bonding between the reflective layer, the intermediate layer, and the heat-sealing layer ensures the stability and durability of the reflective layer's function. This invention also provides a method for preparing a diarylethylene film. Diarylethylene is dispersed in an ethyl acetate solution and a surfactant, then kept at a certain temperature and activated to form a stable active intermediate. This active intermediate is coated onto the surface of at least one of the adjacent layers, such as the intermediate layer and / or the heat-sealing layer, and dried at 60-80 degrees Celsius. The coating process ensures the uniform distribution of the active intermediates, while the drying process helps form a stable film structure. Using ethyl acetate solution in conjunction with a surfactant achieves both uniform dispersion of diarylethene and facilitates subsequent drying and removal. The most prominent function of the reflective layer structure is that it fully utilizes the reflective properties of optical films, blocking some ultraviolet light and light within a certain wavelength range of visible light through reflection. This reduces the problem of ultraviolet light penetrating subsequent film layers and irradiating food, extending packaging life. Furthermore, the more vibrant the colors exhibited by photoluminescence, the more directly it can alert sales staff or customers that the food is exposed to ultraviolet light, allowing for measures such as shielding.

[0039] Heat-sealing layer: The heat-sealing layer is a PP or PE film with uniformly dispersed UV-resistant particles, which not only provides good heat-sealing performance but also enhances the film's UV resistance. The addition of UV-resistant particles acts as a final barrier to absorb or reflect ultraviolet rays, protecting the film's internal structure from UV damage.

[0040] Ink Layer: The ink layer is a diarylethylene film (B), which, together with the diarylethylene film (A) of the reflective layer, creates a red, blue, or violet color-changing effect, increasing the film's visual appeal and functionality. The ink layer is bonded to one side of the barrier layer via an adhesive layer, ensuring the stability of the ink layer and the durability of its color. The synergistic effect of each layer ensures the excellent performance of the UV-resistant film in terms of barrier properties, transparency, retort resistance, heat-sealing performance, and UV protection, making it suitable for various applications requiring high barrier properties and UV protection.

[0041] The aforementioned UV-resistant film's structural design not only reflects the synergistic effect of each layer but also considers the influence of optical principles on transparency. The design and selection of each layer's thickness are crucial for maintaining the film's high transparency. Appropriate thickness reduces multiple reflections and scattering of light within the material, thereby improving transparency. Specifically, an excessively thick barrier layer increases light scattering and absorption, reducing transparency; while an excessively thin layer may reduce barrier performance. The adhesive layer needs to be thin enough to reduce light reflection at the interlayer interface, avoiding multiple reflections and interference, thus maintaining the film's high transparency. Simultaneously, the adhesive layer needs sufficient strength to ensure a strong bond between the layers. The thickness of the intermediate layer needs to balance functionality and transparency. An excessively thick intermediate layer may introduce additional light scattering, affecting transparency; an excessively thin layer may fail to provide sufficient functional performance. The reflective layer must be of appropriate thickness to achieve the ideal intelligent reflection effect, while also negatively impacting transparency. Similarly, UV-resistant particles in the heat-sealing layer increase light scattering, thus reducing transparency. The thickness ratio of each layer is based on optical principles, aiming to balance barrier properties, functionality, and transparency. Optimal performance is ultimately achieved by controlling the overall thickness of each layer.

[0042] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0043] Examples 1-5 describe composite preparation methods for diarylene ethylene membranes (A), wherein a certain volume fraction of ethyl acetate is used, and the balance includes acetic acid, ethanol, and water formed by the esterification reaction of acetic acid and ethanol.

[0044] Example 1 A method for preparing a diarylethylene membrane includes the following steps: S1, by weight, weigh 2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride. Mix 5 parts of ethyl acetate (75% by volume) and 200 parts of surfactant until homogeneous; S2, the mixture obtained in S1 is heated to 45 degrees Celsius and kept at that temperature for 1 hour to prepare an active intermediate; S3, the active intermediate obtained in S2 is coated onto the surface of the intermediate layer and dried at 80 degrees Celsius; an intermediate layer / reflective layer structure film is obtained.

[0045] Example 2 A method for preparing a diarylethylene membrane includes the following steps: S1, by weight, weigh 2,3-bis(2,4,5-trimethyl-3-thienyl)maleimide, 10 parts of ethyl acetate (75% by volume) and 180 parts of surfactant are mixed thoroughly. S2, the mixture obtained in S1 is heated to 60 degrees Celsius and kept at that temperature for 2 hours to prepare an active intermediate; S3: After activating the intermediate layer and heat-sealing layer at 50°C for 1 hour, the active intermediate obtained in S2 is coated onto the surface of the intermediate layer and heat-sealing layer and dried at 60°C; thus, an intermediate layer / reflective layer / heat-sealing layer structure film is obtained.

[0046] Example 3 A method for preparing a diarylethylene membrane includes the following steps: S1, by weight, weigh 20 parts of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thiophene)ethylene, 150-200 parts of ethyl acetate with a volume fraction of 85%, and 5 parts of surfactant, and stir to mix well. S2, the mixture obtained in S1 is heated to 40 degrees Celsius and kept at that temperature for 2 hours to prepare an active intermediate; S3: After activating the intermediate layer and heat-sealing layer at 60°C for 1 hour, the active intermediate obtained in S2 is coated onto the surface of the heat-sealing layer and dried at 75°C; thus, an intermediate layer / reflective layer / heat-sealing layer structure film is obtained.

[0047] Example 4 A method for preparing a diarylethylene membrane includes the following steps: S1, by weight, weigh 10 parts of 2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride, 10 parts of 2,3-bis(2,4,5-trimethyl-3-thienyl)maleimide, 150-200 parts of ethyl acetate (75% by volume), and 1-5 parts of surfactant, and stir to mix well; S2, the mixture obtained in S1 is heated to 60 degrees Celsius and kept at that temperature for 1 hour to prepare an active intermediate; S3: After activating the intermediate layer and heat-sealing layer at 50°C for 2 hours, the active intermediate obtained in S2 is coated onto the surface of the intermediate layer and heat-sealing layer and dried at 80°C; thus, an intermediate layer / reflective layer / heat-sealing layer structure film is obtained.

[0048] Example 5 A method for preparing a diarylethylene membrane includes the following steps: S1, by weight, weigh 5 parts of 2,3-bis(2,4,5-trimethyl-3-thienyl)maleimide, 10 parts of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene, 150-200 parts of ethyl acetate with a volume fraction of 75%, and 1-5 parts of surfactant, and stir to mix well; S2, the mixture obtained in S1 is heated to 60 degrees Celsius and kept at that temperature for 1.5 hours to prepare an active intermediate; S3: After activating the intermediate layer and heat-sealing layer at 45°C for 2 hours, the active intermediate obtained in S2 is coated onto the surface of the intermediate layer and / or heat-sealing layer and dried at 75°C; thus, an intermediate layer / reflective layer / heat-sealing layer structural film is obtained.

[0049] Examples 6-10 describe composite preparation methods for diarylethylene membranes (A). Example 6 The only difference from Example 1 is that: S1 also contains 20 parts of ink, and S3 is to coat the active intermediate obtained in S2 onto the surface of the barrier layer and dry it at 80 degrees Celsius; thus, a barrier layer / ink layer structure film is obtained.

[0050] Example 7 The only difference from Example 2 is that: S1 also contains 25 parts of ink, and S3 is to activate the barrier layer at 50°C for 1 hour, then coat the active intermediate obtained in S2 onto the surface of the barrier layer and dry it at 60°C; thus obtaining a barrier layer / ink layer structure film.

[0051] Example 8 The only difference from Example 3 is that: S1 also contains 30 parts of ink, and S3 is to activate the barrier layer at 60°C for 1 hour, then coat the active intermediate obtained in S2 onto the surface of the barrier layer and dry it at 75°C; thus obtaining a barrier layer / ink layer structure film.

[0052] Example 9 The only difference from Example 4 is that: S1 also contains 25 parts of ink, and S3 is to activate the barrier layer at 50°C for 2 hours, then coat the active intermediate obtained in S2 onto the surface of the barrier layer and dry it at 80°C; thus obtaining a barrier layer / ink layer structure film.

[0053] Example 10 The only difference from Example 5 is that: S1 also contains 25 parts of ink, and S3 is to activate the barrier layer at 45°C for 2 hours, then coat the active intermediate obtained in S2 onto the surface of the barrier layer and dry it at 75°C; thus, a barrier layer / ink layer structure film is obtained.

[0054] Examples 11-25 describe the structure of the UV-resistant film: The PP or PE in the heat-sealing layer of each example contains UV-resistant particles. Preferably, the UV-resistant particles are one or a combination of: hydroxybenzophenone, hydroxyphenyl-S-triazine, 2-benzotriazole, titanium dioxide, zinc oxide, polyphenols, vitamins, carotenoids, hindered phenols, and phosphites. The UV-resistant particles are blended with PP / PE, extruded and blow-molded into a film, then coated with a reflective layer and / or an intermediate layer, and hot-pressed at 50-70°C and 0.4-1 MPa. The ink layer is directly coated onto the surface of the barrier layer, dried at 60°C for at least 2 hours to set, and then bonded to the intermediate layer via an adhesive layer.

[0055] Example 11 KPET / Example 6 / Water-boiling grade adhesive layer / PET / Example 1 / PP, thicknesses are as follows: 21μm / 45μm / 20μm / 34μm / 62μm / 38μm, wherein the heat-sealing layer PP is blended and dispersed with 10% by mass of hydroxybenzophenone.

[0056] Example 12 KPET / Example 7 / Semi-high temperature retort grade adhesive layer / PET / Example 2 / PP, thicknesses are as follows: 22μm / 52μm / 10μm / 42μm / 42μm / 37μm, wherein the heat-sealing layer PP is blended and dispersed with 5% by mass of hydroxyphenyl-S-triazine.

[0057] Example 13 KPET / Example 10 / High-Temperature Retort Grade Adhesive Layer / BOPE / Example 4 / PE, thicknesses are as follows: 20μm / 37μm / 15μm / 33μm / 45μm / 38μm, wherein the heat-sealing layer PE is blended and dispersed with 5% by mass of 2-benzotriazole.

[0058] Example 14 KNY / Example 6 / Semi-high temperature retort grade adhesive layer / MDOPE / Example 2 / PP, thicknesses are as follows: The thicknesses are 17μm / 56μm / 12μm / 36μm / 53μm / 38μm, with the heat-sealing layer PP being blended and dispersed with 8% by mass of nano-titanium dioxide.

[0059] Example 15 KNY / Example 10 / High-Temperature Retorting Grade Adhesive Layer / NY / Example 3 / PE, thicknesses are as follows: 15μm / 58μm / 20μm / 32μm / 52μm / 28μm, wherein the heat-sealing layer PE is blended and dispersed with 5% by mass of 2-benzotriazole.

[0060] Example 16 KNY / Example 8 / Semi-high temperature retort grade adhesive layer / PET / Example 4 / PE, thicknesses are as follows: 25μm / 62μm / 14μm / 32μm / 49μm / 35μm, wherein the heat-sealing layer PE is blended and dispersed with 8% by mass of 2-benzotriazole.

[0061] Example 17 PET-AlO x / Example 9 / Water-boiling grade adhesive layer / BOPE / Example 3 / PP, thicknesses are as follows: 26μm / 54μm / 7μm / 32μm / 54μm / 32μm, wherein the heat-sealing layer PP is blended and dispersed with 12% by mass of nano zinc oxide.

[0062] Example 18 PET-AlO x / Example 7 / High-Temperature Retorting Grade Adhesive Layer / MDOPE / Example 4 / PP, thicknesses are as follows: 25μm / 58μm / 14μm / 32μm / 38μm / 38μm, wherein the heat-sealing layer PP is blended and dispersed with 12% by mass of carotenoids.

[0063] Example 19 PET-AlO x / Example 8 / Semi-high temperature retort grade adhesive layer / NY / Example 5 / PE, thicknesses are as follows: The thicknesses are 22μm / 53μm / 17μm / 39μm / 42μm / 29μm, with the heat-sealing layer PE being blended and dispersed with 15% by mass of nano zinc oxide.

[0064] Example 20 BOPP-AlO x / Example 10 / Water-boiling grade adhesive layer / PET / Example 5 / PE, thicknesses are as follows: 25μm / 32μm / 12μm / 33μm / 41μm / 41μm, wherein the heat-sealing layer PE is blended and dispersed with 12% by mass of vitamin B.

[0065] Example 21 BOPP-AlO x / Example 6 / High-Temperature Retorting Grade Adhesive Layer / BOPE / Example 2 / PE, thicknesses are as follows: 24μm / 30μm / 21μm / 33μm / 29μm / 32μm, wherein the heat-sealing layer PE is blended and dispersed with 10% sodium phosphite by mass.

[0066] Example 22 BOPP-AlOx / Example 9 / Semi-high temperature retort grade adhesive layer / NY / Example 3 / PP, thicknesses are as follows: 25μm / 56μm / 16μm / 33μm / 39μm / 39μm, wherein the heat-sealing layer PP is blended and dispersed with 10% by mass of hindered phenol.

[0067] Example 23 PET-SiO2 / Example 10 / Water-boiling grade adhesive layer / MDOPE / Example 1 / PP, thicknesses are as follows: 23μm / 38μm / 16μm / 37μm / 42μm / 35μm, wherein the heat-sealing layer PP is blended and dispersed with 10% by mass of hindered phenol.

[0068] Example 24 PET-SiO2 / Example 9 / Water-boiling grade adhesive layer / NY / Example 2 / PE, thicknesses are as follows: 17μm / 32μm / 25μm / 30μm / 34μm / 33μm, wherein the heat-sealing layer PE is blended and dispersed with 8% by mass of nano zinc oxide.

[0069] Example 25 PET-SiO2 / Example 8 / High-Temperature Retort Grade Adhesive Layer / MDOPE / Example 5 / PE, thicknesses are as follows: The thicknesses are 16μm / 32μm / 12μm / 41μm / 57μm / 33μm, with the heat-sealing layer PE being blended and dispersed with 8% by mass of nano-titanium dioxide.

[0070] Under standard atmospheric pressure and at 25°C, the composite film materials of Examples 11-25 were tested for oxygen permeability and water vapor permeability according to GB / T19789-2021 "Test of Oxygen Permeability of Plastic Films and Sheets for Packaging Materials - Coulometric Method" and GB / T1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Method for Weight Gain and Loss". A haze meter was used for haze testing in a dark room. After each example was irradiated with 1500 lumens of light for 2 hours, a reflectance meter was used to measure the reflectance of the ink / reflective layer, avoiding the ink layer. The test results are shown in Table 1, where OTR is expressed in cm. 3 / (m 2 (×24h×0.1MPa), WTR unit is g / m 2 ×24h.

[0071] Table 1 The printing quality was visually inspected, with the absence of obvious (visible) defects as the standard. The results were all considered acceptable.

[0072] The UV wavelength absorption tests of each embodiment in Table 1 were conducted using GB / T19394-2003. The results showed that all ultraviolet rays in the range of 300~400nm were completely blocked. The test results are shown in Table 2, and the values ​​in Table 2 are percentages.

[0073] Table 2 In sequence, the use of high-temperature retort-grade adhesive layers, semi-high-temperature retort-grade adhesive layers, and water-boiling-grade adhesive layers can achieve barrier effects of OTR≤0.5, WTR≤0.5; OTR≤2, WTR≤2; and OTR≤10, WTR≤5, respectively. Regarding UV resistance, Examples 1-15 all achieve complete blocking of UV light below 400nm. The modified barrier layer can also further improve oil resistance, acid and alkali resistance, radiation resistance, and abrasion resistance. When the reflective layer is exposed to light, it can reflect the specific light rays corresponding to the color change of the reflective layer, reducing the adverse effects of different light rays on the contents, especially food. When the color change type of the ink layer and the reflective layer is different, it can make the printed text or patterns more eye-catching.

[0074] The same haze reflectance test was performed on Examples 1 to 10, and the results are shown in Table 3. Similarly, the ultraviolet wavelength absorption test at 300-400nm was performed, and the results are shown in Table 4. The values ​​in Table 4 are percentages.

[0075] Table 3 Table 4 It is worth noting that the color-changing transparency referred to in this invention refers to a color structure similar to, for example, copper sulfate solution, which has the property of being transparent (meaning that light other than the color represented by the reflective layer can pass through).

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical 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. A method for preparing an anti-ultraviolet film, characterized in that, Includes the following steps: S1, weigh 5-20 parts of diarylethene photochromic compound, 150-200 parts of ethyl acetate-water solution, and 1-5 parts of surfactant by weight and mix well; S2, heat the mixture obtained in S1 to 40-60 degrees Celsius and keep it at that temperature for 1-2 hours to prepare the active intermediate; S3, the active intermediate obtained in S2 is coated onto the surface of at least one of the adjacent layers and dried at 60-80 degrees Celsius.

2. The method for preparing the anti-ultraviolet film according to claim 1, characterized in that: The diarylethylene photochromic compound includes: 2,3-Bis(2,4,5-trimethyl-3-thienyl)maleic anhydride, 2,3-Bis(2,4,5-trimethyl-3-thienyl)maleimide, At least one of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene.

3. The method for preparing the anti-ultraviolet film according to claim 1, characterized in that: In step S3, the surface of at least one of the adjacent layers of the diarylethylene membrane is activated by heat treatment at 40~50°C for more than 1 hour.

4. The method for preparing the anti-ultraviolet film according to any one of claims 1-3, characterized in that: The diarylethylene film has a light transmittance of >95% and a haze of <5%.

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