Micro-nano laminated anti-counterfeiting optical film with multimodal layer thickness distribution as well as preparation method and application of micro-nano laminated anti-counterfeiting optical film

Abstract

The invention belongs to the technical field of anti-counterfeiting optical films, and particularly relates to a micro-nano laminated anti-counterfeiting optical film with multimodal layer thickness distribution as well as a preparation method and application of the micro-nano laminated anti-counterfeiting optical film. The layer thickness multimodal distribution micro-nano laminated anti-counterfeiting optical film provided by the invention comprises a plurality of laminated film units, and the thicknesses of the plurality of film units are different; one film unit is formed by a plurality of first film layers and a plurality of second film layers which are alternately stacked; the refractive index of the first film layer is larger than that of the second film layer. The micro-nano laminated anti-counterfeiting optical film provided by the invention can develop colors through multiple reflection peaks, realizes a color gamut and a color change rule different from those of a traditional structural color material, remarkably improves the utilization efficiency of a light source, and enhances the brightness of structural colors. Therefore, the micro-nano laminated anti-counterfeiting optical film provided by the invention has important application value in anti-counterfeiting application.

Description

Technical Field

[0001] The present invention belongs to the technical field of anti-counterfeiting optical films, and specifically relates to a micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness, and a preparation method and application thereof. Background Art

[0002] Optical anti-counterfeiting technology plays a vital role in modern society and is widely used in the fields of currency, certificates, luxury goods packaging, etc. Traditional optical anti-counterfeiting technology mainly relies on technical routes such as ink printing and holographic images, which have problems such as easy duplication and single anti-counterfeiting effect, and it is difficult to meet the growing anti-counterfeiting needs.

[0003] In recent years, structural color anti-counterfeiting technology based on photonic crystals has gradually become a research hotspot. Photonic crystals are a type of material with a periodic distribution of refractive index in space. They can selectively reflect light of a specific wavelength through multi-interface interference effects, thereby presenting bright structural colors. They have broad application prospects in the field of optical anti-counterfeiting.

[0004] However, currently, due to the limitations of the color rendering rules of photonic crystals, existing photonic crystal films are also limited to a single optical anti-counterfeiting effect, which makes it difficult to meet the complex and changing anti-counterfeiting needs. Summary of the invention

[0005] The purpose of the present invention is to provide a micro-nano laminated anti-counterfeiting optical film with a multi-peak distribution of layer thickness, and a preparation method and application thereof. The micro-nano laminated anti-counterfeiting optical film with a multi-peak distribution of layer thickness provided by the present invention can display color through multiple reflection peaks to achieve a color gamut and color change law different from traditional structural color materials, while significantly improving the utilization efficiency of the light source and enhancing the brightness of the structural color.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness, comprising a plurality of laminated film units, wherein the thicknesses of the plurality of film units are different;

[0008] One membrane unit is formed by a plurality of first membrane layers and a plurality of second membrane layers alternately stacked, and the number of the first membrane layers in one membrane unit is equal to the number of the second membrane layers;

[0009] The refractive index of the first film layer in each film unit is greater than the refractive index of the second film layer;

[0010] In the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness: the first film layer and the second film layer are arranged alternately, and the total number of layers 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 of the membrane unit with the largest thickness to the membrane unit with the smallest thickness among the plurality of membrane units is greater than 1 and less than or equal to 10.

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

[0014] Preferably, the thickness of the single-layer films in the first film layer and the second film layer is independently 30 to 200 nm.

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

[0016] Preferably, the material of the first film layer further comprises a high refractive index inorganic nanofiller doped in the high refractive index optical resin, and the high refractive index inorganic nanofiller comprises 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, and the low-refractive index optical resin includes one or more of polymethyl methacrylate, polyvinylidene fluoride, 4-methylpentene polymer, cycloolefin 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, cycloolefin copolymer, polyethylene, polypropylene and polyvinyl alcohol;

[0018] Alternatively, the material of the second film layer is a polymer formed by a high-refractive-index optical resin and a polymerizable monomer, and the polymerizable monomer includes 1,4-cyclohexanedimethanol.

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

[0020] The first film layer material and the second film layer material are prepared into a multilayer sheet by using a micro-nano stacking co-extrusion method;

[0021] The multi-layer sheet is biaxially stretched to obtain the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness.

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

[0023] The present invention provides a micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness, comprising a plurality of laminated film units, the thickness of each of the plurality of film units being different; one film unit is formed by a plurality of first film layers and a plurality of second film layers alternately laminated, the number of first film layers and the number of second film layers in one film unit being equal; the refractive index of the first film layer in each film unit being greater than the refractive index of the second film layer; in the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness: 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 micro-nano laminated anti-counterfeiting optical film provided by the present invention is a one-dimensional photonic crystal film with alternately arranged film layer refractive index, having a multi-peak distribution characteristic of film layer thickness, and a plurality of film units with different thicknesses being able to form selective reflection of multi-wavelength light. The present invention realizes multi-band selective transflection by designing a plurality of film units with different thicknesses, and then realizes a color gamut and color change rule different from that of traditional structural color materials through a multi-color light mixing strategy, and at the same time significantly improves the utilization efficiency of the light source and enhances the brightness of the structural color. Therefore, the micro-nano laminated anti-counterfeiting optical film provided by the present invention has important technical value in anti-counterfeiting applications.

[0024] Furthermore, by selecting suitable materials for the first film layer and the second film layer, the obtained micro-nano laminated anti-counterfeiting optical film has efficient patterning capability and can be patterned by printing, local surface processing or hot embossing, etc. Its excellent mechanical properties and weather resistance make it have important technical value in large-scale production and anti-counterfeiting applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a high-layer distributor used in the present invention;

[0026] Figure 2 A flow chart of preparing a micro-nano laminated anti-counterfeiting optical film by a high-layer distributor route according to an embodiment of the present invention;

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

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

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

[0030] Figure 6 The multi-angle color coordinates of the micro-nano laminated anti-counterfeiting optical film prepared in Example 1 of the present invention;

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

[0032] Figure 8 The multi-angle reflectivity spectrum of the micro-nano laminated anti-counterfeiting optical film prepared in Example 2 of the present invention;

[0033] Fig. 9 The multi-angle color coordinates of the micro-nano laminated anti-counterfeiting optical film prepared in Example 2 of the present invention;

[0034] Fig.10 Schematic diagram of a patterned label of a micro-nano laminated anti-counterfeiting optical film prepared in Examples 3 to 5 of the present invention;

[0035] Fig.11 The partitioned multi-angle reflection spectrum of the micro-nano laminated anti-counterfeiting optical film prepared in Example 3 of the present invention;

[0036] Fig.12 The partitioned multi-angle color coordinates of the micro-nano laminated anti-counterfeiting optical film prepared in Example 3 of the present invention;

[0037] Fig.13 The appearance pictures of the anti-counterfeiting label at different angles prepared in Example 3 of the present invention;

[0038] Fig.14 The partitioned multi-angle reflection spectrum of the micro-nano laminated anti-counterfeiting optical film prepared in Example 4 of the present invention;

[0039] Fig.15 The partitioned multi-angle color coordinates of the micro-nano laminated anti-counterfeiting optical film prepared in Example 4 of the present invention;

[0040] Fig.16 The partitioned multi-angle reflection spectrum of the micro-nano laminated anti-counterfeiting optical film prepared in Example 5 of the present invention;

[0041] Fig.17 The partitioned multi-angle color coordinates of the micro-nano laminated anti-counterfeiting optical film prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0042] The present invention provides a micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness, comprising a plurality of laminated film units, wherein the thicknesses of the plurality of film units are different;

[0043] One membrane unit is formed by a plurality of first membrane layers and a plurality of second membrane layers alternately stacked, and the number of the first membrane layers in one membrane unit is equal to the number of the second membrane layers;

[0044] The refractive index of the first film layer in each film unit is greater than the refractive index of the second film layer;

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

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

[0047] The micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness provided by the present invention comprises a plurality of film units arranged in a stacked manner, and the thickness of the plurality of film units is different. In the present invention, the plurality of film units are capable of forming selective reflection of multi-wavelength light. In the present invention, the plurality of film units are preferably capable of forming a plurality of reflection peaks (i.e., one film unit corresponds to a reflection peak of reflected light of a specific central wavelength), and the plurality of reflection peaks are distributed in the visible light band and the infrared light band, and the infrared light band can be a near-infrared light band.

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

[0049] In the present invention, the color rendering principle of the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness is as shown in Formula 1, and the λ obtained in Formula 1 is the central wavelength of the reflection peak corresponding to the laminated structure formed by the adjacent first film layer and the second film layer 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 one film unit, n2 is the refractive index of the second film layer material in one film unit, d1 is the single layer thickness of the first film layer in one film unit, d2 is the single layer thickness of the second film layer in one film unit, θ is the incident angle, and λ is the central wavelength of light that can be selectively reflected by the stacked structure formed by the adjacent first film layer and the second film layer in one film unit. The incident angle is the angle between the incident light and the normal direction of the plane.

[0052] The reflection peaks corresponding to the stacked structure formed by the adjacent first film layer and the second film layer in one film unit overlap with each other, forming a reflection peak of a specific central wavelength corresponding to one film unit.

[0053] In the present invention, the thicknesses of the plurality of membrane units are different, and one membrane unit can obtain a reflection peak corresponding to one specific central wavelength. In the present invention, the thickness gradient of the plurality of membrane units can achieve that the maximum peak widths of the reflection peaks corresponding to the plurality of membrane units do not overlap.

[0054] In the micro-nano laminated anti-counterfeiting optical film provided by the present invention, multiple layer thickness distributions are constructed by having multiple film units with different thicknesses, and selective reflection of multi-wavelength light is achieved at the same time.

[0055] In an embodiment of the present invention, the micro-nano laminated anti-counterfeiting optical film includes two laminated film units, the thickness of the two film units are different, and the two reflection peaks corresponding to the two film units are respectively placed in the visible light band and the near-infrared light band. Under low observation angle (θ), only a single reflection peak of the visible light band participates in color development. As the observation angle increases, the reflection peak of the near-infrared light band moves toward the low band and enters the visible light band, and the two reflection peaks participate in color development together, thereby achieving a color change rule different from that of traditional structural color materials. The micro-nano laminated anti-counterfeiting optical film provided by the present invention selectively changes the film thickness of the pattern area by direct printing, local hot pressing, local surface processing and other methods, resulting in different reflection center bands corresponding to the film structure of the pattern area and the background area.

[0056] In the present invention, the thickness ratio of the thickest membrane unit to the thinnest membrane unit among the plurality of membrane units is preferably greater than 1 and less than or equal to 10, more preferably 2-8, and even more preferably 3-6.

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

[0058] In the present invention, one membrane unit is formed by a plurality of first membrane layers and a plurality of second membrane layers alternately stacked, and the number of first membrane layers and the number of second membrane layers in one membrane unit are equal. When one membrane unit contains a plurality of first membrane layers, the thickness of the first membrane layers in one membrane unit may be the same or different. When one membrane unit contains a plurality of second membrane layers, the thickness of the second membrane layers in one membrane unit may be the same or different. The thickness of the single-layer film of the first membrane layer in one membrane unit and the thickness of the single-layer film of the second membrane layer may be the same or different. The thickness of the single-layer film of the first membrane layer in any two membrane units is different, and the thickness of the single-layer film of the second membrane layer in any two membrane units is different.

[0059] The micro-nano laminated anti-counterfeiting optical film with multi-modal distribution of layer thickness provided by the present invention controls the total number and thickness of film layers of multiple film units, while controlling the thickness of the first film layer and the second film layer in each film unit. The film thickness of the micro-nano laminated anti-counterfeiting optical film with multi-modal distribution of layer thickness provided by the present invention presents multi-modal distribution characteristics, thereby achieving a color change rule different from the conventional one through multi-modal reflection mixing.

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

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

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

[0063] In the present invention, the material of the first film layer preferably also includes a high refractive index inorganic nanofiller doped in the high refractive index optical resin, and the high refractive index inorganic nanofiller preferably includes one or more of titanium dioxide, zirconium oxide, aluminum oxide and silicon nitride. The present invention can further increase the refractive index of the first film layer by doping the high refractive index inorganic nanofiller in the first film layer. The present invention has no special requirements for the mass content of the high refractive index inorganic nanofiller in the first film layer, and can be designed according to the refractive index of the first film layer.

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

[0065] Alternatively, the material of the second film layer is preferably a polymer formed by a high refractive index optical resin and a polymerized monomer, wherein the polymerized monomer preferably includes 1,4-cyclohexanedimethanol.

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

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

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

[0069] The micro-nano laminated anti-counterfeiting optical film provided by the present invention preferably further comprises a first surface layer and a second surface layer disposed on the two outermost surfaces of the plurality of film units. The first cladding layer and the second surface layer protect the plurality of film units. The present invention has no special requirements on the material and thickness of the first surface layer and the second surface layer, and the surface layer parameters of the micro-nano laminated anti-counterfeiting optical film well known to those skilled in the art can be used.

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

[0071] The first film layer material and the second film layer material are prepared into a multilayer sheet by using a micro-nano stacking co-extrusion method;

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

[0073] The present invention adopts a micro-nano lamination co-extrusion method to prepare a multilayer sheet from a first film layer material and a second film layer material. The present invention preferably pre-treats the first film layer material and the second film layer material, and the pre-treatment preferably includes drying, and the drying is preferably performed in a crystallization drying tower, and the drying time is preferably ≥10 hours.

[0074] In the present invention, the preparation flow chart of the multilayer sheet is as follows: Figure 2 The method for preparing the multilayer sheet preferably comprises the following steps: melt-extrude the first film layer material and the second film layer material respectively, and then transport them to the distribution pipeline of the high-layer distributor for high-layer distribution, and then pass through the expansion die to obtain the multilayer melt.

[0075] In the present invention, when the micro-nano laminated anti-counterfeiting optical film also includes a surface layer, the second method is replaced by: the surface layer raw material, the first film layer material and the second film layer material are melt-extruded respectively, and then transported to the distribution pipeline of the high-layer distributor for high-layer distribution, and then the multi-layer melt is obtained through the expansion die.

[0076] In the present invention, the multilayer melt is preferably prepared by using a high-layer distributor. The structural schematic diagram of the high-layer distributor is as shown in FIG. Figure 1 shown. Figure 1 Material A in the figure corresponds to the material of the first mold layer. Figure 1 The material B in the above-mentioned film corresponds to the material of the second film layer. The size of the distribution pipeline of the high-layer distributor is set according to the film layer structure of the micro-nano laminated anti-counterfeiting optical film.

[0077] In the present invention, after obtaining the multilayer melt, the present invention preferably further comprises post-processing the multilayer melt to obtain a multilayer sheet. The post-processing preferably comprises sequentially performing cooling treatment and winding and trimming treatment. The cooling treatment is preferably completed in a cooling and traction system. The winding and trimming treatment is preferably completed in a winding and trimming system.

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

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

[0080] In the present invention, the relationship between the reflection peak of the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness and the corresponding film layer 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 one film unit, n2 is the refractive index of the second film layer material in one film unit, d1 is the single layer thickness of the first film layer in one film unit, d2 is the single layer thickness of the second film layer in one film unit, θ is the incident angle, and λ is the central wavelength of light that can be selectively reflected by the stacked structure formed by the adjacent first film layer and the second film layer in one film unit. The incident angle is the angle between the incident light and the normal direction of the plane.

[0083] The present invention adjusts the refractive index and thickness of the film layer by the stretching ratio of the biaxial stretching, thereby realizing the selective reflection of light in a specific wavelength band with a central wavelength of λ.

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

[0085] In the present invention, the application preferably includes the following steps: using the micro-nano laminated anti-counterfeiting optical film as a substrate, performing surface patterning to obtain a pattern area and a background area. The present invention achieves anti-counterfeiting according to the color changes of the pattern area and the background area at different angles.

[0086] In the present invention, the surface patterning treatment is preferably performed by modifying the film thickness in a selected area on the surface of the micro-nano laminated anti-counterfeiting optical film with a multi-peak distribution of layer thickness, forming a pattern area in the selected area and a background area in the non-selected area. The patterning treatment method preferably includes direct printing, local hot pressing or local surface processing.

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

[0088] In the present invention, the local hot pressing method preferably includes: hot pressing a selected area of ​​the micro-nano laminated anti-counterfeiting optical film with a multi-peak distribution of layer thickness to obtain a pattern area, and the non-selected area forms a background area. The film thickness of the pattern area obtained after the local hot pressing becomes thinner than the film thickness of the background area, so that the low-band reflection peak of the pattern area moves out of the visible light region, and only the high-band reflection peak participates in the color development, showing the color change law of the traditional structural color.

[0089] In the present invention, the local surface processing preferably includes laser etching. The laser etching preferably includes: performing laser etching on the selected area of ​​the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness to obtain a pattern area, and the non-selected area forms a background area. The present invention preferably selectively destroys the film layer structure of the pattern area by the laser etching, and achieves different coloring rules between the pattern area and the background area by changing the film layer structure of the pattern area.

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

[0091] The present invention adopts Figure 1 The high-layer distributor device of the structure shown in FIG. Figure 2 The preparation flow chart shown is used to complete the preparation of the optical film material in the embodiment.

[0092] Example 1

[0093] This embodiment provides a micro-nano laminated anti-counterfeiting optical film with a bimodal distribution of layer thickness, and the specific preparation method is as follows:

[0094] Material selection: The high refractive index layer is made of polyethylene terephthalate (PET, denoted as material A), and the low refractive index layer is made of polyethylene terephthalate and 1,4-cyclohexanedimethanol copolymer (PETG, denoted as material B);

[0095] Preparation process:

[0096] The high and low refractive index layer materials A and B were placed in a crystallization drying tower and dried for 10 hours.

[0097] The dried material A and material B are respectively added into the extruder feeding system. After being melt-extruded by the extruder, they flow through a multi-channel high-layer distributor in the order of alternating layer stacking of the micro-nano laminated anti-counterfeiting optical film to form a multi-layer melt formed by the first film unit and the second film unit with two layer thickness distributions, each with a layer thickness distribution of 128 layers, and a total of 256 film layer structures.

[0098] The multilayer melt is cooled and rolled up to obtain a multilayer sheet with a total thickness of 635 μm; the multilayer sheet is subjected to 5×5 ratio biaxial stretching to obtain a micro-nano laminated anti-counterfeiting optical film with a total thickness of 25.4 μm and a bimodal distribution of layer thickness. The micro-nano laminated anti-counterfeiting optical film with a bimodal distribution of layer thickness prepared in this embodiment is formed by laminating a first film unit and a second film unit, and the first film unit is formed by 128 layers of PET layers and PETG layers alternately laminated; the single layer thickness of the PET layer of the first film unit is 108 nm, and the single layer thickness of the PETG layer is 121 nm, and 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.

[0099] The layer thickness sequence distribution of the micro-nano laminated anti-counterfeiting optical film with a bimodal layer thickness distribution prepared in this embodiment is as follows: Figure 3 The cross-sectional electron micrograph of the prepared sample is shown in Figure 4 The corresponding multi-angle reflectance spectrum is shown as Figure 5 As shown, the multi-angle color coordinates are Figure 6 As shown in the figure, at small incident angles, only the low-band reflection peak participates in the color development. As the incident angle increases, the high-band reflection peak blue-shifts into the visible light band, and the double reflection peaks are mixed to develop colors, forming a color change rule and color range that is different from traditional structural color materials.

[0100] Example 2

[0101] This embodiment provides a bimodal distribution micro-nano laminated anti-counterfeiting optical film, and the specific preparation method is as follows:

[0102] Material selection: The high refractive index layer is made of polyethylene terephthalate (PET, denoted as material A), and the low refractive index layer is made of polyethylene terephthalate and 1,4-cyclohexanedimethanol copolymer (PETG, denoted as material B);

[0103] Preparation process:

[0104] The high and low refractive index layer materials A and B were placed in a crystallization drying tower and dried for 10 hours.

[0105] The dried material A and material B are respectively added into the extruder feeding system. After being melt-extruded by the extruder, they flow through a multi-channel high-layer distributor in the order of alternating layer stacking of the micro-nano laminated anti-counterfeiting optical film to form a multi-layer melt formed by the first film unit and the second film unit with two layer thickness distributions, each with a layer thickness distribution of 128 layers, and a total of 256 film layer structures.

[0106] The multilayer melt is cooled and rolled up to obtain a multilayer sheet with a total thickness of 600 μm, and the multilayer sheet is subjected to 5×6 ratio biaxial stretching to obtain a micro-nano laminated anti-counterfeiting optical film with a total thickness of 20 μm and a bimodal distribution of layer thickness. The micro-nano laminated anti-counterfeiting optical film with a bimodal distribution of layer thickness prepared in this embodiment is formed by a first film unit and a second film unit layer, and the first film unit is formed by 128 layers of PET layers and PETG layers alternately laminated; the single layer thickness of the PET layer of the first film unit is 90 nm, and the single layer thickness of the PETG layer is 90 nm, and the single layer thickness of the PET layer in the second film unit is 65 nm, and the single layer thickness of the PETG layer is 65 nm.

[0107] The layer thickness sequence distribution of the micro-nano laminated anti-counterfeiting optical film with bimodal layer thickness distribution prepared in this embodiment is as follows: Figure 7 The corresponding multi-angle reflectance spectrum is shown as Figure 8 As shown, the multi-angle color coordinates are Fig. 9As shown. At small incident angles, the double reflection peaks are mixed to produce a color that is different from the color of traditional structural color materials. As the incident angle increases, the low-band reflection peak moves out of the visible light band, and only the high-band reflection peak participates in the color development.

[0108] Example 3

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

[0110] Material selection: the bimodal distribution micro-nano laminated anti-counterfeiting optical film prepared in Example 1; the equipment selected is a commercial color printer.

[0111] Preparation process:

[0112] Fig.10 Schematic diagram of a patterned label prepared with a micro-nano laminated 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 that the initial colors of the pattern area and the background area after printing are the same). In this embodiment, ordinary non-discoloring pigment ink is used for pattern filling. The substrate prepared in Example 1 is then used instead of printing paper for direct printing. Due to the initial color matching, the pattern is hidden at normal incidence. As the observation angle increases, the structural color background area shows a unique color change pattern, while the pigment color pattern area does not change color. Therefore, the pattern can be displayed at a large angle. The partitioned multi-angle reflectance spectrum of the patterned anti-counterfeiting label prepared in this embodiment is shown in FIG. Fig.11 As shown, the partitioned multi-angle color coordinate diagram is as follows Fig.12 As shown, the appearance pictures at different angles are as follows Fig.13 shown.

[0113] Example 4

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

[0115] Material selection: the bimodal distribution micro-nano laminated anti-counterfeiting optical film prepared in Example 1; the equipment selected is a patterned stamp and a pressurized heating element.

[0116] Preparation process:

[0117] Fig.10The schematic diagram of the patterned label of the micro-nano laminated anti-counterfeiting optical film prepared in the embodiment of the present invention. The substrate prepared in Example 1 is subjected to patterned local hot pressing, and the background area maintains the original layer structure and shows the special color change law described in Example 1. Due to local hot pressing, the overall layer thickness of the pattern area is thinned, and the thickness of the pattern area is reduced. The single layer thickness of the PET layer of the first mold unit in the pattern area is 78nm, and the single layer thickness of the PETG layer is 88nm. The single layer thickness of the PET layer of the second mold unit in the pattern area is 57nm, and the single layer thickness of the PETG layer is 64nm; the single layer thickness of the PET layer of the first film unit in the background area is 108nm, and the single layer thickness of the PETG layer is 121nm. The single layer thickness of the PET layer in the second film unit is 79nm, and the single layer thickness of the PETG layer is 88nm. In this embodiment, the pattern area and the background area are obtained by the method of local hot pressing, so that the low-band reflection peak of the pattern area moves out of the visible light region, and only the high-band reflection peak participates in the color development, showing the color change law of the traditional structural color.

[0118] The multi-angle reflection spectrum of the patterned anti-counterfeiting label prepared in this embodiment is as follows: Fig.14 As shown, the partitioned multi-angle color coordinate diagram is as follows Fig.15 shown.

[0119] Example 5

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

[0121] Material selection: the bimodal distribution micro-nano laminated anti-counterfeiting optical film prepared in Example 1; the equipment selected is surface laser processing equipment.

[0122] Preparation process:

[0123] Fig.10 Schematic diagram of a patterned label of a micro-nano laminated anti-counterfeiting optical film prepared according to an embodiment of the present invention. The substrate prepared in Example 1 is subjected to patterned surface processing, the background area maintains the original layer structure and exhibits the special color change law described in Example 1, and the pattern area is formed by the first film unit due to local surface processing, and the first film unit is formed by 128 layers of PET layers and PETG layers alternately laminated; the single layer thickness of the PET layer of the first film unit is 108nm, and the single layer thickness of the PETG layer is 121nm. Part of the layer structure (second film layer) of the pattern area is destroyed and eliminated, and only a single reflection peak is dominant in the color development, showing the color change law of traditional structural color materials.

[0124] The multi-angle reflection spectrum of the patterned anti-counterfeiting label prepared in this embodiment is as follows: Fig.16 As shown, the partitioned multi-angle color coordinate diagram is as follows Fig.17 shown.

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

[0126] From the above embodiments, it can be seen that the micro-nano laminated anti-counterfeiting optical film provided by the present invention is a one-dimensional photonic crystal film with an alternating arrangement of the film layer refractive index. The present invention realizes multi-band selective transflection by designing the layer thickness sequence distribution, and then breaks through the color gamut and color change law of traditional structural color materials through the multi-color light mixing strategy, while significantly improving the utilization efficiency of the light source and enhancing the brightness of the structural color. In addition, the film has efficient patterning capabilities and can be patterned by printing, local surface processing or hot embossing. Its excellent mechanical properties and weather resistance make it have important technical value in large-scale production and anti-counterfeiting applications.

[0127] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness, comprising a plurality of laminated film units, wherein the thicknesses of the plurality of film units are different; One membrane unit is formed by a plurality of first membrane layers and a plurality of second membrane layers alternately stacked, and the number of the first membrane layers in one membrane unit is equal to the number of the second membrane layers; The refractive index of the first film layer in each film unit is greater than the refractive index of the second film layer; In the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness: the first film layer and the second film layer are arranged alternately, and the total number of layers of the first film layer and the second film layer is ≥64.

2. The micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness according to claim 1, characterized in that: 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.

3. The micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness according to claim 1, characterized in that: The thickness ratio of the membrane unit with the largest thickness to the membrane unit with the smallest thickness among the plurality of membrane units is greater than 1 and less than or equal to 10.

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

5. The micro-nano laminated anti-counterfeiting optical film with multimodal layer thickness distribution according to claim 1 or 4, characterized in that: The thickness of a single film in the first film layer and the second film layer is independently 30 to 200 nm.

6. The micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness 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 naphthalate, polystyrene, polycarbonate, polyamide and polyacrylonitrile; or the high-refractive-index optical resin includes a copolymer of at least two of polyethylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyamide and polyacrylonitrile.

7. The micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness according to claim 6, characterized in that: The material of the first film layer further includes a high-refractive-index inorganic nanofiller doped in the high-refractive-index optical resin, and the high-refractive-index inorganic nanofiller includes one or more of titanium dioxide, zirconium oxide, aluminum oxide and silicon nitride.

8. The micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness 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, cycloolefin 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, cycloolefin copolymer, polyethylene, polypropylene and polyvinyl alcohol; Alternatively, the material of the second film layer is a polymer formed by a high-refractive-index optical resin and a polymerizable monomer, and the polymerizable monomer includes 1,4-cyclohexanedimethanol.

9. The method for preparing the micro-nano laminated anti-counterfeiting optical film with multimodal layer thickness distribution according to any one of claims 1 to 8, characterized in that: The following steps are involved: The first film layer material and the second film layer material are prepared into a multilayer sheet by using a micro-nano lamination co-extrusion method; The multi-layer sheet is biaxially stretched to obtain the micro-nano laminated anti-counterfeiting optical film with multi-peak distribution of layer thickness.

10. Use of the micro-nano laminated anti-counterfeiting optical film with multimodal layer thickness distribution according to any one of claims 1 to 8 or the micro-nano laminated anti-counterfeiting optical film with multimodal layer thickness distribution prepared by the preparation method according to claim 9 in anti-counterfeiting.

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