A micro-nano layering anti-counterfeiting optical film with layer thickness multi-peak distribution and a preparation method and application thereof

Abstract

The present application belongs to the technical field of anti-counterfeiting optical film, and particularly relates to a micro-nano layer-stacked anti-counterfeiting optical film with layer thickness multi-peak distribution and a preparation method and application thereof. The micro-nano layer-stacked anti-counterfeiting optical film with layer thickness multi-peak distribution provided by the present application comprises a plurality of film units arranged in layers, and the thicknesses of the plurality of film units are different; one film unit is formed by alternately arranging a plurality of first film layers and a plurality of second film layers; the refractive index of the first film layer is greater than the refractive index of the second film layer. The micro-nano layer-stacked anti-counterfeiting optical film provided by the present application can realize color display through multiple reflection peaks, realize a color gamut and a color change law different from traditional structural color materials, significantly improve the utilization efficiency of light sources, and enhance the brightness of structural colors. Therefore, the micro-nano layer-stacked anti-counterfeiting optical film provided by the present application has important application value in anti-counterfeiting applications.

Description

Technical Field

[0001] This invention belongs to the field of anti-counterfeiting optical film technology, specifically relating to a micro-nano laminated anti-counterfeiting optical film with multi-peak thickness distribution, its preparation method, and its application. Background Technology

[0002] Optical anti-counterfeiting technology plays a crucial role in modern society, with widespread applications in currency, certificates, and luxury goods packaging. Traditional optical anti-counterfeiting technologies mainly rely on ink printing and holographic imaging, which suffer from problems such as ease of replication and limited anti-counterfeiting effectiveness, making it difficult to meet the ever-increasing demands for anti-counterfeiting solutions.

[0003] In recent years, structural color anti-counterfeiting technology based on photonic crystals has gradually become a research hotspot. Photonic crystals are materials with a spatially periodic distribution of refractive index, which can selectively reflect light of specific wavelengths through multi-interface interference effects, thus exhibiting bright structural colors, and have broad application prospects in the field of optical anti-counterfeiting.

[0004] However, due to the limitations of the color development rules of photonic crystals, existing photonic crystal thin films are currently limited to a single optical anti-counterfeiting effect, which is difficult to meet the complex and ever-changing anti-counterfeiting requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution, its preparation method, and its application. The micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution provided by this invention can achieve color gamut and color change rules that are different from traditional structural color materials through multi-reflection peak color development. At the same time, it significantly improves the utilization efficiency of light source and enhances the brightness of structural color.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides a micro-nano stacked anti-counterfeiting optical film with multi-peak thickness distribution, comprising multiple film units stacked together, each film unit having a different thickness;

[0008] A membrane unit is formed by alternatingly stacked first membrane layers and second membrane layers, wherein the number of first membrane layers and the number of second membrane layers in a membrane unit are equal;

[0009] In each membrane unit, the refractive index of the first membrane layer is greater than the refractive index of the second membrane layer;

[0010] In the micro-nano stacked anti-counterfeiting optical film with multi-peak thickness distribution: the first film layer and the second film layer are alternately arranged, and the total number of the first film layer and the second film layer is ≥64.

[0011] Preferably, the multiple reflection peaks of the reflected light formed by the multiple film units are distributed in the visible light band and the infrared light band.

[0012] Preferably, the thickness ratio between the thickest membrane unit and the thinnest membrane unit among the multiple membrane units is greater than 1 and less than or equal to 10.

[0013] Preferably, the total number of layers in the first and second films is 64 to 2048.

[0014] Preferably, the thickness of the monolayer in the first and second film layers is independently 30 to 200 nm.

[0015] Preferably, the material of the first film layer includes a high-refractive-index optical resin, which includes one or more of polyethylene terephthalate, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyacrylonitrile; or the high-refractive-index optical resin includes a copolymer of at least two of polyethylene terephthalate, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyacrylonitrile.

[0016] Preferably, the material of the first film layer further includes high-refractive-index inorganic nanofillers doped in the high-refractive-index optical resin, wherein the high-refractive-index inorganic nanofillers include one or more of titanium dioxide, zirconium oxide, aluminum oxide and silicon nitride.

[0017] Preferably, the material of the second film layer includes a low-refractive-index optical resin, which includes one or more of polymethyl methacrylate, polyvinylidene fluoride, 4-methylpentene polymer, cyclic olefin copolymer, polyethylene, polypropylene and polyvinyl alcohol, or the low-refractive-index optical resin includes a copolymer of at least two of polymethyl methacrylate, polyvinylidene fluoride, 4-methylpentene polymer, cyclic olefin copolymer, polyethylene, polypropylene and polyvinyl alcohol;

[0018] Alternatively, the material of the second film layer is a polymer formed from a high-refractive-index optical resin and a polymeric monomer, wherein the polymeric monomer includes 1,4-cyclohexanediethanol.

[0019] This invention provides a method for preparing the micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution as described in the above technical solution, comprising the following steps:

[0020] A multilayer sheet was prepared by using a micro-nano layered co-extrusion method to fabricate a first film layer material and a second film layer material;

[0021] The multilayer sheet is biaxially stretched to obtain a micro-nano stacked anti-counterfeiting optical film with a multi-peak thickness distribution.

[0022] The present invention provides the application of the micro-nano laminated anti-counterfeiting optical film with multi-peak thickness distribution as described in the above technical solution or the micro-nano laminated anti-counterfeiting optical film with multi-peak thickness distribution prepared by the preparation method described in the above technical solution in anti-counterfeiting.

[0023] This invention provides a micro / nano-layered anti-counterfeiting optical film with a multi-peak thickness distribution, comprising multiple film units stacked together, each with a different thickness. Each film unit is formed by alternating layers of first and second films, with the number of first and second films equal in number. In each film unit, the refractive index of the first film layer is greater than that of the second film layer. In this multi-peak thickness distribution micro / nano-layered anti-counterfeiting optical film, the first and second films are alternately arranged, and the total number of first and second films is ≥64. The micro / nano-layered anti-counterfeiting optical film provided by this invention is a one-dimensional photonic crystal thin film with alternating refractive indices. It exhibits a multi-peak thickness distribution, and the multiple film units with varying thicknesses enable selective reflection of multi-wavelength light. By designing multiple film units with different thicknesses, this invention achieves multi-band selective transmission and reflection, and further utilizes a multi-color mixing strategy to achieve a color gamut and color-changing pattern different from traditional structural color materials. Simultaneously, it significantly improves the utilization efficiency of the light source and enhances the brightness of the structural color. Therefore, the micro-nano stacked anti-counterfeiting optical film provided by this invention has significant technical value in anti-counterfeiting applications.

[0024] Furthermore, by selecting suitable materials for the first and second film layers, the present invention yields a micro / nano-layered anti-counterfeiting optical film with highly efficient patterning capabilities, enabling patterned construction through printing, local surface processing, or hot stamping. Its excellent mechanical properties and weather resistance make it of significant technical value in large-scale production and anti-counterfeiting applications. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the high-level number distributor used in this invention;

[0026] Figure 2 This is a flowchart illustrating the fabrication process of a micro / nano-layered anti-counterfeiting optical film using a high-level number distributor according to an embodiment of the present invention.

[0027] Figure 3 The thickness sequence distribution diagram of the micro / nano-layered anti-counterfeiting optical film prepared in Example 1 of the present invention;

[0028] Figure 4 This is a cross-sectional electron microscope image of the micro / nano-layered anti-counterfeiting optical film prepared in Example 1 of the present invention;

[0029] Figure 5 The multi-angle reflectance spectrum of the micro-nano stacked anti-counterfeiting optical film prepared in Example 1 of the present invention;

[0030] Figure 6 Multi-angle color coordinates for the preparation of micro / nano-layered anti-counterfeiting optical films in Example 1 of this invention;

[0031] Figure 7 The thickness sequence distribution diagram of the micro / nano-layered anti-counterfeiting optical film prepared in Example 2 of the present invention;

[0032] Figure 8 Multi-angle reflectance spectrum of micro / nano-layered anti-counterfeiting optical film prepared in Example 2 of the present invention;

[0033] Figure 9 Multi-angle color coordinates for the preparation of micro / nano-layered anti-counterfeiting optical films in Example 2 of this invention;

[0034] Figure 10 This is a schematic diagram of the patterned labels prepared by the micro-nano stacked anti-counterfeiting optical film in Examples 3-5 of the present invention;

[0035] Figure 11 The partitioned multi-angle reflectance spectrum of the micro / nano-layered anti-counterfeiting optical film prepared in Example 3 of the present invention;

[0036] Figure 12 The partitioned multi-angle color coordinates for preparing the micro / nano-layered anti-counterfeiting optical film in Example 3 of this invention;

[0037] Figure 13 Images of the anti-counterfeiting label from different angles were prepared for Example 3 of the present invention;

[0038] Figure 14 The partitioned multi-angle reflectance spectrum of the micro / nano-layered anti-counterfeiting optical film prepared in Example 4 of the present invention;

[0039] Figure 15 The partitioned multi-angle color coordinates for preparing the micro / nano-layered anti-counterfeiting optical film in Example 4 of this invention;

[0040] Figure 16 The partitioned multi-angle reflectance spectrum of the micro / nano-layered anti-counterfeiting optical film prepared in Example 5 of the present invention;

[0041] Figure 17 The partitioned multi-angle color coordinates for preparing the micro / nano-layered anti-counterfeiting optical film in Example 5 of this invention. Detailed Implementation

[0042] The present invention provides a micro-nano stacked anti-counterfeiting optical film with multi-peak thickness distribution, comprising multiple film units stacked together, each film unit having a different thickness;

[0043] A membrane unit is formed by alternatingly stacked first membrane layers and second membrane layers, wherein the number of first membrane layers and the number of second membrane layers in a membrane unit are equal;

[0044] In each membrane unit, the refractive index of the first membrane layer is greater than the refractive index of the second membrane layer;

[0045] In the micro-nano stacked anti-counterfeiting optical film with multi-peak thickness distribution: the first film layer and the second film layer are alternately arranged, and the total number of the first film layer and the second film layer is ≥64.

[0046] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0047] The micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution provided by this invention comprises multiple film units stacked together, each with a different thickness. In this invention, the multiple film units are capable of selectively reflecting multiple wavelengths of light. Preferably, the multiple film units are capable of forming multiple reflection peaks (i.e., one film unit corresponds to a reflection peak of a specific center wavelength), and these multiple reflection peaks are distributed in the visible light band and the infrared light band, wherein the infrared light band can be the near-infrared light band.

[0048] The color rendering principle of the micro-nano stacked anti-counterfeiting optical film with multi-peak thickness distribution provided by the present invention is called structural color. It has the inherent characteristic that the reflection center wavelength shifts to a lower wavelength band as the θ angle increases, and the center wavelength has a strict correspondence with the film refractive index and layer thickness.

[0049] In this invention, the color development principle of the micro-nano stacked anti-counterfeiting optical film with multi-peak layer thickness distribution is as shown in Formula 1. The λ obtained from Formula 1 is the center wavelength of the reflection peak corresponding to the stacked structure formed by adjacent first and second film layers in one film unit.

[0050] λ=2(n1d1cosθ+n2d2cosθ) formula 1;

[0051] In Formula 1: n1 is the refractive index of the first film layer material in a single film unit, n2 is the refractive index of the second film layer material in a single film unit, d1 is the single-layer thickness of the first film layer in a single film unit, d2 is the single-layer thickness of the second film layer in a single film unit, θ is the angle of incidence, and λ is the center wavelength of light selectively reflected by the stacked structure formed by adjacent first and second film layers in a single film unit. The angle of incidence is the angle between the incident ray and the normal direction of the plane.

[0052] The reflection peaks corresponding to the stacked structures formed by adjacent first and second film layers in a single film unit overlap, forming a reflection peak of a specific center wavelength corresponding to a single film unit.

[0053] In this invention, the thicknesses of the multiple film units are different, and each film unit can obtain a reflection peak corresponding to a specific center wavelength. In this invention, the thickness gradient of the multiple film units ensures that the maximum peak widths of the reflection peaks corresponding to the multiple film units do not overlap.

[0054] The micro-nano stacked anti-counterfeiting optical film provided by the present invention constructs multiple layer thickness distributions by having multiple film units with different thicknesses, thereby achieving selective reflection of multiple wavelengths of light.

[0055] In an embodiment of the present invention, the micro-nano stacked anti-counterfeiting optical film comprises two stacked film units with different thicknesses. The two reflection peaks corresponding to the two film units are respectively located in the visible light band and the near-infrared light band. Under low observation angle (θ) conditions, only a single reflection peak in the visible light band participates in color development. As the observation angle increases, the reflection peak in the near-infrared light band moves to a lower band and enters the visible light band, where both reflection peaks participate in color development, thus achieving a color-changing pattern different from traditional structural color materials. The micro-nano stacked anti-counterfeiting optical film provided by the present invention selectively changes the film thickness of the pattern area through methods such as direct printing, local hot pressing, and local surface processing, resulting in different reflection center bands corresponding to the film structure of the pattern area and the background area.

[0056] In this invention, the thickness ratio of the membrane unit with the largest thickness to the membrane unit with the smallest thickness among the multiple membrane units is preferably greater than 1 and less than or equal to 10, more preferably 2 to 8, and even more preferably 3 to 6.

[0057] The present invention controls the thickness ratio of the thickest membrane unit to the thinnest membrane unit among multiple membrane units to be preferably 2 to 8, and more preferably 3 to 6. This can further avoid the problem that when the thickness ratio of the membrane units is too small, the maximum width of the reflection peaks of the two membrane units, although the center wavelengths corresponding to the two specific reflection peaks are different, will still merge.

[0058] In this invention, a membrane unit is formed by alternatingly stacked first membrane layers and second membrane layers, wherein the number of first membrane layers and the number of second membrane layers in a membrane unit are equal. When a membrane unit contains multiple first membrane layers, the thickness of the first membrane layers in a membrane unit can be the same or different. When a membrane unit contains multiple second membrane layers, the thickness of the second membrane layers in a membrane unit can be the same or different. The thickness of a single layer of the first membrane layer and the thickness of a single layer of the second membrane layer in a membrane unit can be the same or different. The thickness of a single layer of the first membrane layer in any two membrane units is different, and the thickness of a single layer of the second membrane layer in any two membrane units is different.

[0059] The micro-nano laminated anti-counterfeiting optical film with multi-peak thickness distribution provided by this invention controls the total number and thickness of multiple film units, and simultaneously controls the thickness of the first and second film layers in each film unit. This enables the film layer thickness of the micro-nano laminated anti-counterfeiting optical film with multi-peak thickness distribution to exhibit a multi-peak distribution characteristic, thereby achieving an unconventional color-changing pattern through multi-peak reflection and color mixing.

[0060] In this invention, the refractive index of the first film layer is greater than that of the second film layer. In the multi-peak thickness distribution of the micro / nano laminated anti-counterfeiting optical film: the first and second film layers are alternately arranged, and the total number of the first and second film layers is ≥64, preferably 64–2048 layers, more preferably 128–1024 layers, and even more preferably 256–1024 layers. The thickness of a single layer of the first film layer is preferably 30–200 nm, more preferably 50–150 nm. The thickness of a single layer of the second film layer is preferably 30–200 nm, more preferably 50–150 nm.

[0061] In this invention, the material of the first film layer preferably includes a high refractive index optical resin, which preferably includes one or more of polyethylene terephthalate, polyethylene terephthalate, polystyrene, polycarbonate, polyamide and polyacrylonitrile.

[0062] In this invention, when the high-refractive-index optical resin preferably includes multiples selected from polyethylene terephthalate (PET), polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyacrylonitrile, the material of the first film layer can be a combination of the aforementioned high-refractive-index optical resins. Alternatively, the high-refractive-index optical resin preferably includes a copolymer of at least two of polyethylene terephthalate, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyacrylonitrile.

[0063] In this invention, the material of the first film layer preferably further includes high-refractive-index inorganic nanofillers doped in the high-refractive-index optical resin. The high-refractive-index inorganic nanofillers preferably include one or more of titanium dioxide, zirconium oxide, aluminum oxide, and silicon nitride. By doping the first film layer with high-refractive-index inorganic nanofillers, this invention can further improve the refractive index of the first film layer. This invention does not have special requirements on the mass content of the high-refractive-index inorganic nanofillers in the first film layer; it can be designed according to the refractive index of the first film layer.

[0064] In this invention, the material of the second film layer preferably comprises a low-refractive-index optical resin, which includes one or more of polymethyl methacrylate, polyvinylidene fluoride, 4-methylpentene polymer, cyclic olefin copolymer, polyethylene, polypropylene, and polyvinyl alcohol. Alternatively, the low-refractive-index optical resin preferably comprises a copolymer of at least two of polymethyl methacrylate, polyvinylidene fluoride, 4-methylpentene polymer, cyclic olefin copolymer, polyethylene, polypropylene, and polyvinyl alcohol.

[0065] Alternatively, the material of the second film layer is preferably a polymer formed from a high-refractive-index optical resin and a polymeric monomer. The polymeric monomer preferably includes 1,4-cyclohexanediethanol.

[0066] In an embodiment of the present invention, the material of the second film layer is polyethylene terephthalate copolymer with 1,4-cyclohexanediethanol (PETG).

[0067] In this invention, the surface or interior of the second film layer may have a porous structure. The method for obtaining the porous structure preferably includes etching. In this invention, the porous structure is preferably filled with a low-refractive-index medium, which preferably includes a gaseous medium or a liquid medium. The gaseous medium is preferably air, and the liquid medium is preferably a solution. There are no special requirements for the type of low-refractive-index medium used in this invention; it can be designed according to the refractive index of the second film layer.

[0068] In this invention, the refractive index of the second film layer is preferably reduced by stretching-induced phase separation. The stretching can induce molecular chain orientation crystallization and regulate the bulk control strategy of the charge density of the system to anisotropically control the refractive index of the film layer.

[0069] The micro / nano-layered anti-counterfeiting optical film provided by the present invention preferably further includes a first surface layer and a second surface layer disposed on the outermost two surfaces of the plurality of film units. The first cladding layer and the second surface layer serve to protect the plurality of film units. The present invention does not have special requirements for the material and thickness of the first surface layer and the second surface layer, and the surface parameters of micro / nano-layered anti-counterfeiting optical films well known to those skilled in the art can be used for design.

[0070] This invention provides a method for preparing the micro / nano-layered anti-counterfeiting optical film described in the above technical solution, comprising the following steps:

[0071] A multilayer sheet was prepared by using a micro-nano layered co-extrusion method to fabricate a first film layer material and a second film layer material;

[0072] The multilayer sheet is biaxially stretched to obtain the micro-nano stacked anti-counterfeiting optical film.

[0073] This invention employs a micro-nano layered co-extrusion method to prepare a multilayer sheet from a first film layer material and a second film layer material. Preferably, the first and second film layer materials undergo pretreatment, which preferably includes drying. The drying is preferably carried out in a crystallization drying tower, and the drying time is preferably ≥10 hours.

[0074] In this invention, the fabrication process of the multilayer sheet is as follows: Figure 2 As shown. The preferred method for preparing the multilayer sheet includes the following steps: melting and extruding the first film layer material and the second film layer material respectively, then conveying them to the distribution pipe of the high layer number distributor for high layer number distribution, and then obtaining the multilayer melt through the flaring die.

[0075] In this invention, when the micro-nano stacked anti-counterfeiting optical film also includes a surface layer, the second method is replaced by: melting and extruding the surface layer raw material, the first film layer material and the second film layer material respectively, then conveying them to the distribution pipe of the high layer number distributor for high layer number distribution, and then obtaining the multilayer melt through the flaring die.

[0076] In this invention, the multilayer melt is preferably prepared using a multilayer number distributor, and a schematic diagram of the multilayer number distributor is shown below. Figure 1 As shown. Figure 1 Material A in the text corresponds to the material of the first mold layer. Figure 1 Material B in the diagram corresponds to the material of the second film layer. The dimensions of the distribution channels of the high-layer distributor are set according to the film layer structure of the micro / nano-layered anti-counterfeiting optical film.

[0077] In this invention, after obtaining the multilayer melt, the invention preferably further includes post-processing the multilayer melt to obtain a multilayer sheet. The post-processing preferably includes sequential cooling and winding / trimming. The cooling is preferably performed in a cooling traction system. The winding / trimming is preferably performed in a winding / trimming system.

[0078] After obtaining the multilayer sheet, the present invention performs biaxial stretching on the multilayer sheet to obtain the micro-nano stacked anti-counterfeiting optical film.

[0079] In this invention, the stretching ratio of the biaxial stretching is determined based on the film thickness corresponding to the reflection peak of the target material (micro-nano laminated anti-counterfeiting optical film with multi-peak thickness distribution) and the film thickness in the multilayer sheet.

[0080] In this invention, the relationship between the reflection peak of the micro-nano stacked anti-counterfeiting optical film with multi-peak thickness distribution and the corresponding film thickness is determined according to Formula 1.

[0081] λ=2(n1d1cosθ+n2d2cosθ) formula 1;

[0082] In Formula 1: n1 is the refractive index of the first film layer material in a single film unit, n2 is the refractive index of the second film layer material in a single film unit, d1 is the single-layer thickness of the first film layer in a single film unit, d2 is the single-layer thickness of the second film layer in a single film unit, θ is the angle of incidence, and λ is the center wavelength of light selectively reflected by the stacked structure formed by adjacent first and second film layers in a single film unit. The angle of incidence is the angle between the incident ray and the normal direction of the plane.

[0083] This invention achieves selective reflection of light in a specific wavelength band with a center wavelength of λ by adjusting the refractive index and thickness of the film layer through the stretching ratio of the biaxial stretching.

[0084] This invention provides the application of the micro-nano stacked anti-counterfeiting optical film described in the above technical solution or the micro-nano stacked anti-counterfeiting optical film prepared by the preparation method described in the above technical solution in anti-counterfeiting.

[0085] In this invention, the application preferably includes the following steps: using the micro / nano-layered anti-counterfeiting optical film as a substrate, performing surface patterning treatment to obtain a pattern area and a background area. This invention achieves anti-counterfeiting based on the color changes of the pattern area and background area at different angles.

[0086] In this invention, the surface patterning process is preferably performed by modifying the film thickness within a selected area on the surface of the micro / nano-layered anti-counterfeiting optical film with a multi-peak thickness distribution, forming a patterned area in the selected area and a background area in the non-selected area. The patterning process preferably includes direct printing, localized hot pressing, or localized surface processing.

[0087] In this invention, the direct printing preferably includes: printing on a selected area of ​​the micro / nano-layered anti-counterfeiting optical film with a multi-peak thickness distribution to obtain a pattern area, thereby changing the film structure and thickness of the pattern area by printing the pattern. In this invention, the ink used for direct printing is a common non-color-changing ink. Before direct printing, this invention preferably performs color matching and pattern filling on the normal incident color coordinates, selecting the pigment ink used for direct printing through color matching and pattern filling to ensure that the initial color of the pattern area is the same as the background area after printing.

[0088] In this invention, the local hot-pressing method preferably includes: hot-pressing a selected area of ​​the multi-peak distributed micro / nano-layered anti-counterfeiting optical film to obtain a patterned area, while the non-selected area forms a background area. After local hot-pressing, the film thickness of the patterned area and the background area become thinner, causing the low-band reflection peak of the patterned area to shift out of the visible light region, with only the high-band reflection peak participating in color development, exhibiting the color-changing pattern of traditional structural colors.

[0089] In this invention, the local surface processing preferably includes laser etching. The laser etching preferably includes: performing laser etching on selected areas of the multi-peak thickness distribution of the micro / nano-layered anti-counterfeiting optical film to obtain a patterned area, while non-selected areas form a background area. Preferably, this invention selectively destroys the film structure of the patterned area through laser etching, thereby altering the film structure of the patterned area and achieving different color development patterns between the patterned area and the background area.

[0090] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0091] This invention adopts Figure 1 The high-level number distributor device with the structure shown is, according to Figure 2 The flowchart shown completes the preparation of the optical film material in the example.

[0092] Example 1

[0093] This embodiment provides a micro / nano-layered anti-counterfeiting optical film with a bimodal thickness distribution. The specific preparation method is as follows:

[0094] Material selection: The high refractive index layer is selected from polyethylene terephthalate (PET, denoted as material A), and the low refractive index layer is selected from polyethylene terephthalate copolymer with 1,4-cyclohexanediethanol (PETG, denoted as material B).

[0095] Preparation process:

[0096] Materials A and B, with high and low refractive index layers, were placed in a crystallization drying tower and dried for 10 hours.

[0097] After drying, materials A and B are added to the extruder feeding system. After being melted and extruded by the extruder, they flow through a multi-channel high-layer distributor in the alternating stacking sequence of the micro-nano laminated anti-counterfeiting optical film, forming two multilayer melts with different layer thicknesses, consisting of the first and second film units, with a total of 256 film layers, each with 128 layers.

[0098] A multilayer sheet with a total thickness of 635 μm was obtained by cooling and winding the multilayer melt. The multilayer sheet was then biaxially stretched at a 5×5 ratio to prepare a micro / nano-layered anti-counterfeiting optical film with a total thickness of 25.4 μm and a bimodal thickness distribution. The micro / nano-layered anti-counterfeiting optical film with a bimodal thickness distribution prepared in this embodiment is formed by stacking a first film unit and a second film unit. The first film unit is formed by 128 alternately stacked PET and PETG layers. The single-layer thickness of the PET layer in the first film unit is 108 nm, and the single-layer thickness of the PETG layer is 121 nm. In the second film unit, the single-layer thickness of the PET layer is 79 nm, and the single-layer thickness of the PETG layer is 88 nm.

[0099] The thickness sequence distribution of the micro / nano-layered anti-counterfeiting optical film with a bimodal thickness distribution prepared in this embodiment is as follows: Figure 3 As shown, the cross-sectional electron microscope image of the prepared sample is as follows. Figure 4 As shown, the corresponding multi-angle reflectance spectrum is as follows: Figure 5 As shown, multi-angle color coordinates are as follows Figure 6 As shown, at small incident angles, only the low-band reflection peaks participate in color rendering. As the incident angle increases, the high-band reflection peaks blue-shift into the visible light band, and the dual reflection peaks mix to form colors, resulting in a color change pattern and color gamut that differs from traditional structural color materials.

[0100] Example 2

[0101] This embodiment provides a bimodal distributed micro / nano-layered anti-counterfeiting optical film, the specific preparation method of which is as follows:

[0102] Material selection: The high refractive index layer is selected from polyethylene terephthalate (PET, denoted as material A), and the low refractive index layer is selected from polyethylene terephthalate copolymer with 1,4-cyclohexanediethanol (PETG, denoted as material B).

[0103] Preparation process:

[0104] Materials A and B, with high and low refractive index layers, were placed in a crystallization drying tower and dried for 10 hours.

[0105] After drying, materials A and B are added to the extruder feeding system. After being melted and extruded by the extruder, they flow through a multi-channel high-layer distributor in the alternating stacking sequence of the micro-nano laminated anti-counterfeiting optical film, forming two multilayer melts with different layer thicknesses, consisting of the first and second film units, with a total of 256 film layers, each with 128 layers.

[0106] A multilayer sheet with a total thickness of 600 μm was obtained by cooling and winding the multilayer melt. This sheet was then biaxially stretched at a ratio of 5×6 to prepare a micro / nano-layered anti-counterfeiting optical film with a total thickness of 20 μm and a bimodal thickness distribution. The micro / nano-layered anti-counterfeiting optical film with a bimodal thickness distribution prepared in this embodiment is formed by a first film unit and a second film unit layer. The first film unit is formed by 128 alternately stacked PET and PETG layers. The single-layer thickness of the PET layer in the first film unit is 90 nm, and the single-layer thickness of the PETG layer is 90 nm. In the second film unit, the single-layer thickness of the PET layer is 65 nm, and the single-layer thickness of the PETG layer is 65 nm.

[0107] The thickness sequence distribution of the micro / nano-layered anti-counterfeiting optical film with a bimodal thickness distribution prepared in this embodiment is as follows: Figure 7 As shown, the corresponding multi-angle reflectance spectrum is as follows: Figure 8 As shown, multi-angle color coordinates are as follows Figure 9As shown, at small incident angles, the dual reflection peaks mix to form colors, resulting in a color rendering effect different from that of traditional structural color materials. As the incident angle increases, the low-band reflection peaks shift out of the visible light band, and only the high-band reflection peaks participate in color rendering.

[0108] Example 3

[0109] A direct printing patterning method using the bimodal distribution micro / nano-layered anti-counterfeiting optical film prepared in Example 1 as a substrate.

[0110] Material selection: Bimodal distribution micro / nano-layered anti-counterfeiting optical film prepared in Example 1; Equipment selection: Commercial color printer.

[0111] Preparation process:

[0112] Figure 10 This is a schematic diagram of a patterned label prepared using a micro / nano-layered anti-counterfeiting optical film according to an embodiment of the present invention. Color matching and pattern filling are performed on the normal incident color coordinates (ensuring the initial color of the pattern area and background area is the same after printing). In this embodiment, ordinary non-color-changing pigment ink is used for pattern filling. Then, the substrate prepared in Example 1 is used directly for printing instead of printing paper. Due to the initial color matching, the pattern is hidden under normal incidence. As the viewing angle increases, the structural color background area exhibits a unique color-changing pattern, while the pigment color pattern area remains unchanged. Therefore, the pattern can be displayed at large angles. The multi-angle reflectance spectrum of the patterned anti-counterfeiting label prepared in this embodiment is as follows: Figure 11 As shown, the multi-angle color coordinate diagram of the partition is as follows: Figure 12 As shown, images of the appearance from different angles are as follows: Figure 13 As shown.

[0113] Example 4

[0114] A method for local quantitative hot pressing patterning using the bimodal distribution micro / nano-layered anti-counterfeiting optical film prepared in Example 1 as a substrate.

[0115] Material selection: Bimodal distribution micro / nano-layered anti-counterfeiting optical film prepared in Example 1; Equipment selection: patterned stamp and pressure heating element.

[0116] Preparation process:

[0117] Figure 10This is a schematic diagram of a patterned label for fabricating a micro / nano-layered anti-counterfeiting optical film according to an embodiment of the present invention. The substrate prepared in Example 1 is subjected to patterned local hot pressing. The background area retains its original layer structure and exhibits the special color-changing pattern described in Example 1. Due to local hot pressing, the overall layer thickness of the patterned area is reduced, resulting in a decrease in the patterned area thickness. The single-layer thickness of the PET layer in the first module unit of the patterned area is 78 nm, and the single-layer thickness of the PETG layer is 88 nm. The single-layer thickness of the PET layer in the second module unit of the patterned area is 57 nm, and the single-layer thickness of the PETG layer is 64 nm. In the background area, the single-layer thickness of the PET layer in the first film unit is 108 nm, and the single-layer thickness of the PETG layer is 121 nm. The single-layer thickness of the PET layer in the second film unit is 79 nm, and the single-layer thickness of the PETG layer is 88 nm. This embodiment obtains the patterned area and background area through local hot pressing, causing the low-band reflection peak of the patterned area to shift out of the visible light region, with only the high-band reflection peak participating in color development, exhibiting the color-changing pattern of traditional structural colors.

[0118] The patterned anti-counterfeiting label prepared in this embodiment has a multi-angle reflectance spectrum of partitions, as shown in the example. Figure 14 As shown, the multi-angle color coordinate diagram of the partition is as follows: Figure 15 As shown.

[0119] Example 5

[0120] A method for local surface patterning using the bimodal distribution micro / nano-layered anti-counterfeiting optical film prepared in Example 1 as a substrate.

[0121] Material selection: Bimodal distribution micro / nano-layered anti-counterfeiting optical film prepared in Example 1; Equipment selection: surface laser processing equipment.

[0122] Preparation process:

[0123] Figure 10 This is a schematic diagram of a patterned label prepared using a micro / nano-layered anti-counterfeiting optical film according to an embodiment of the present invention. The substrate prepared in Example 1 undergoes patterned surface processing. The background area retains its original layer structure and exhibits the special color-changing behavior described in Example 1. Due to localized surface processing, the patterned area is formed by a first film unit, which consists of 128 alternately stacked PET and PETG layers. The single-layer thickness of the PET layer in the first film unit is 108 nm, and the single-layer thickness of the PETG layer is 121 nm. Partial layer structure (second film layer) in the patterned area is destroyed or eliminated, with only a single reflection peak dominating color development, exhibiting the color-changing behavior of traditional structural color materials.

[0124] The patterned anti-counterfeiting label prepared in this embodiment has a multi-angle reflectance spectrum of partitions, as shown in the example. Figure 16 As shown, the multi-angle color coordinate diagram of the partition is as follows: Figure 17 As shown.

[0125] In the patterned anti-counterfeiting label products prepared in the above embodiments 3, 4, and 5 of the present invention, the color display rules of the pattern area and the background area can be interchanged.

[0126] As can be seen from the above embodiments, the micro-nano layered anti-counterfeiting optical film provided by the present invention is a one-dimensional photonic crystal thin film with alternating refractive indices of the film layers. The present invention achieves selective transmission and reflection across multiple passbands by designing a layer thickness sequence distribution, and further breaks through the color gamut and color-changing rules of traditional structural color materials through a multi-color light mixing strategy. Simultaneously, it significantly improves the utilization efficiency of the light source and enhances the brightness of the structural color. Furthermore, this thin film possesses highly efficient patterning capabilities, enabling patterned construction through printing, local surface processing, or hot stamping. Its excellent mechanical properties and weather resistance make it of significant technical value in large-scale production and anti-counterfeiting applications.

[0127] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution, comprising multiple film units stacked together, wherein the thickness of each film unit is different; A membrane unit is formed by alternatingly stacked first membrane layers and second membrane layers. The number of first membrane layers and the number of second membrane layers in a membrane unit are equal. A membrane unit contains multiple first membrane layers and multiple second membrane layers. In each membrane unit, the refractive index of the first membrane layer is greater than the refractive index of the second membrane layer; In the micro-nano stacked anti-counterfeiting optical film with multi-peak thickness distribution: the first film layer and the second film layer are alternately arranged, and the total number of the first film layer and the second film layer is ≥64; the thickness ratio of the film unit with the largest thickness and the film unit with the smallest thickness among the multiple film units is greater than 1 and less than or equal to 10; the multiple film units can form selective reflection of multi-wavelength light, the multiple film units can form multiple reflection peaks, and one film unit corresponds to forming a reflection peak of a specific center wavelength of reflected light.

2. The micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution according to claim 1, characterized in that, The multiple reflection peaks of the reflected light formed by the multiple membrane units are distributed in the visible light band and the infrared light band.

3. The micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution according to claim 1, characterized in that, The total number of layers in the first and second films is 64 to 2048.

4. The micro / nano laminated anti-counterfeiting optical film with multi-peak thickness distribution according to claim 1 or 3, characterized in that, The thickness of the monolayer in the first and second film layers is independently 30~200nm.

5. The micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution according to claim 1, characterized in that, The material of the first film layer includes a high-refractive-index optical resin, which includes one or more of polyethylene terephthalate, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyacrylonitrile; or the high-refractive-index optical resin includes a copolymer of at least two of polyethylene terephthalate, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyacrylonitrile.

6. The micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution according to claim 5, characterized in that, The material of the first film layer also includes high-refractive-index inorganic nanofillers doped in the high-refractive-index optical resin, wherein the high-refractive-index inorganic nanofillers include one or more of titanium dioxide, zirconium oxide, aluminum oxide and silicon nitride.

7. The micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution according to claim 1, characterized in that, The material of the second film layer includes a low-refractive-index optical resin, which includes one or more of polymethyl methacrylate, polyvinylidene fluoride, 4-methylpentene polymer, cyclic olefin copolymer, polyethylene, polypropylene and polyvinyl alcohol, or the low-refractive-index optical resin includes a copolymer of at least two of polymethyl methacrylate, polyvinylidene fluoride, 4-methylpentene polymer, cyclic olefin copolymer, polyethylene, polypropylene and polyvinyl alcohol; Alternatively, the material of the second film layer is a polymer formed from a high-refractive-index optical resin and a polymeric monomer, wherein the polymeric monomer includes 1,4-cyclohexanediethanol.

8. The method for preparing the micro / nano-layered anti-counterfeiting optical film with multi-peak thickness distribution according to any one of claims 1 to 7, characterized in that, Includes the following steps: A multilayer sheet was prepared by using a micro-nano layered co-extrusion method to fabricate a first film layer material and a second film layer material; The multilayer sheet is biaxially stretched to obtain a micro-nano stacked anti-counterfeiting optical film with a multi-peak thickness distribution.

9. The application of the micro / nano laminated anti-counterfeiting optical film with multi-peak layer thickness distribution as described in any one of claims 1 to 7, or the micro / nano laminated anti-counterfeiting optical film with multi-peak layer thickness distribution prepared by the preparation method described in claim 8, in anti-counterfeiting.

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