Micro-nano structure anti-counterfeiting element prepared based on cold transfer technology and preparation method of micro-nano structure anti-counterfeiting element

Abstract

The invention provides a micro-nano structure anti-counterfeiting element prepared based on a cold transfer technology and a preparation method thereof.The micro-nano structure anti-counterfeiting element prepared based on the cold transfer technology integrates first-level anti-counterfeiting, second-level anti-counterfeiting and third-level anti-counterfeiting, the counterfeit threshold can be greatly improved through the superposition design of the third-level anti-counterfeiting, and meanwhile verification requirements of different scenes are met; wherein the embossment / rainbow laser cold transfer film belongs to first-level anti-counterfeiting, authenticity can be directly judged through naked eyes, computer-generated holographic micro-nano structure shading of the shading cold transfer film belongs to second-level anti-counterfeiting and can be verified by means of a point light source, and the moire fringe decoding grating cold transfer film belongs to third-level anti-counterfeiting and can be verified by means of a point light source. A special effect is generated under a precise processing condition and has a processing barrier, meanwhile, a primary anti-counterfeiting effect of direct identification can be generated, white light is adopted to penetrate through the grating sheet to irradiate the surface of the printing ink, a multicolor light spot array is left on the surface of the printing ink, and multiple anti-counterfeiting functions are achieved.

Description

Technical Field

[0001] This invention relates to the field of anti-counterfeiting technology, and in particular to micro-nano structure anti-counterfeiting elements prepared based on cold transfer technology and their preparation methods. Background Technology

[0002] Traditional anti-counterfeiting technologies mainly include: laser anti-counterfeiting, fluorescent anti-counterfeiting, magnetic anti-counterfeiting, thermochromic anti-counterfeiting, digital anti-counterfeiting, and texture anti-counterfeiting. Laser anti-counterfeiting is the most widely used first-generation anti-counterfeiting technology. It utilizes laser color holographic plate-making technology and embossing replication technology to achieve anti-counterfeiting. It protects the authenticity of the product through laser holographic iridescent display, generally relying on visual observation, often exhibiting effects such as horizontal stripes, light pillars, and plain surfaces. Traditional anti-counterfeiting methods such as fluorescent ink, magnetic ink, and thermochromic ink involve printing specific graphic symbols with special inks on specific parts of the product, which are then detected using specialized methods. Digital anti-counterfeiting specifically includes QR codes or RFID, using a combination of unique digital codes and physical / digital carriers. The core logic is a "one item, one code" verification mechanism, allowing consumers to verify authenticity through scanning, sensing, or online querying. Texture anti-counterfeiting uses the inherent texture characteristics of the packaging material itself as anti-counterfeiting identification marks to create labels. Each label data is photographed, numbered, archived, and stored in an anti-counterfeiting database. Consumers and managers can use the internet, mobile phones and other communication tools to retrieve photos of the labels and compare the texture features of the physical labels with the corresponding photos to confirm the authenticity of the labels.

[0003] Traditional anti-counterfeiting technologies initially played a role, but their effectiveness was limited due to their susceptibility to counterfeiting. The reasons for this are that these anti-counterfeiting technologies generally suffer from the following shortcomings: The technology is low-tech and the structural combination is easily deciphered. Conventional anti-counterfeiting materials rely on certain special technical formulas or equipment advantages, but with the development of science and technology, these advantages will no longer exist.

[0004] Anti-counterfeiting verification methods are cumbersome, difficult to verify quickly and intuitively, and result in a poor user experience. For example, texture-based anti-counterfeiting requires consumers to compare the position and color of randomly scattered fibers on each label, giving counterfeiters another opportunity.

[0005] The anti-counterfeiting measures are too simplistic, making it easy to create a single point of vulnerability, and lacking multi-level anti-counterfeiting verification.

[0006] Therefore, existing technologies need to be improved and enhanced. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention provides a micro-nano structure anti-counterfeiting element based on cold transfer technology and its preparation method, which can break through the limitations of static and visual replication of traditional anti-counterfeiting technology, and achieve multiple anti-counterfeiting through the combination of hidden graphics and invisible images with laser holographic visual relief.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The fabrication method of micro / nano structure anti-counterfeiting elements based on cold transfer technology includes: Obtain a binary image containing the text to be hidden, and input the binary image into hologram generation software, which then generates a holographic file of the binary image. The holographic file is imported into a photolithography machine. The optical system of the photolithography machine controls the laser beam to form an exposure spot. The objective lens of the photolithography machine focuses the spot onto the photoresist surface for point-by-point exposure. After development, a three-dimensional microstructure with a preset morphology is obtained, which serves as a computational holographic image. The moiré invisible image and the moiré decoding grating to be hidden are obtained. The moiré invisible image and the moiré decoding grating are respectively imported into the photolithography machine. The laser beam is controlled by the optical system to form an exposure spot. The objective lens focuses the spot onto the photoresist surface of the glass plate for point-by-point exposure. After development, the moiré invisible image and the moiré decoding grating are obtained respectively. The computational holographic version and the moiré invisible graphic version are spliced ​​together to obtain the first resin master version. The first resin master version is used as the cathode and metallic nickel is used as the anode. Under the action of electrolysis, the first metallic nickel layer is deposited on the first resin master version. The first metallic nickel layer is separated from the first resin master version to obtain the background pattern. The large pattern template is mounted on a molding device, UV varnish is applied to the first BOPP film, and the large pattern template is molded and cured to form the microstructure of the pattern template on the surface of the first BOPP film, thus obtaining a cold transfer film of the pattern. A grayscale height image containing the image to be hidden and a rainbow laser image containing the image to be hidden are obtained. The grayscale height image and the rainbow laser image are respectively imported into the lithography machine. The laser beam is controlled by the optical system to form an exposure spot. The objective lens focuses the spot onto the photoresist surface for point-by-point exposure. After development, the relief image and the rainbow laser image are obtained respectively. The relief image template and the rainbow laser image template are combined to obtain a second resin master template. The first resin master template is used as the cathode and metallic nickel is used as the anode. Under the action of electrolysis, a second metallic nickel layer is deposited on the second resin master template. The second resin master template and the second metallic nickel layer are separated to obtain a relief / rainbow laser hybrid version. The embossed / rainbow laser hybrid plate is mounted on a molding device, UV varnish is applied to the second BOPP film, and the film is molded and cured by the embossed / rainbow laser hybrid plate, so that the microstructure of the embossed / rainbow laser hybrid plate is formed on the surface of the second BOPP film, resulting in an embossed / rainbow laser cold transfer film. The moiré decoding grating pattern is mounted on a molding machine, UV varnish is applied to the third BOPP film, and the moiré decoding grating pattern is molded and cured to form the background microstructure of the moiré decoding grating pattern on the surface of the third BOPP film, thus obtaining the moiré decoding grating cold transfer film. Rainbow dot ink is prepared and coated onto the surface of a substrate. The background cold transfer film is then laminated with the rainbow dot ink and cured. The first BOPP film is then peeled off, thus transferring the background pattern structure of the background cold transfer film onto the surface of the substrate to obtain the first substrate. An embossing varnish is applied to the surface of the first substrate, the embossed / rainbow laser cold transfer film is embossed and cured onto the first substrate, and the second BOPP film is peeled off. That is, the microstructure of the embossed / rainbow laser cold transfer film is transferred onto the first substrate to obtain the second substrate. An embossing varnish is applied to the surface of the second substrate. The moiré decoding grating cold transfer film is then embossed onto the second substrate and cured. The third BOPP film is then peeled off, and the microstructure of the moiré decoding grating cold transfer film is transferred onto the second substrate to obtain the micro-nano structure anti-counterfeiting element.

[0009] Furthermore, the generation of the holographic file of the binary image by the hologram generation software includes: The hologram generation software treats the image to be hidden as composed of multiple discrete points and calculates the complex amplitude distribution of each discrete point reaching the holographic surface. The complex amplitude distributions of each discrete point on the recording surface are superimposed according to the principle of light wave superposition to generate the holographic file.

[0010] Further, the step of treating the image to be hidden as composed of multiple discrete points and calculating the complex amplitude distribution of each discrete point reaching the holographic surface includes: The surface of the image to be hidden is discretized into a set of points, where each point on the surface is used as a separate point light source; Calculate the spherical waves emitted by each of the point light sources, and trace the path of the spherical waves to obtain the diffraction pattern of each point light source.

[0011] Further, the step of superimposing the complex amplitude distributions of each discrete point on the recording plane according to the principle of light wave superposition to generate the holographic file includes: Let the spatial coordinate system of the hidden information graphic be OXYZ, and the spatial coordinate system of the computational hologram plane of the holographic file be O′X′Y′Z′. The Z-axis of the two coordinate systems are on the same straight line, and the distance between the origins of the two coordinate systems is d. The coordinates of any point q in the binary image are (xi, yi, zi), and the coordinates of any point p on the holographic surface are (xp′, yp′, zp′). Then the distance between point p and point q is:

[0012] The complex amplitude of the light wave received at point p is:

[0013] In the formula: j is the imaginary unit; wave number k = 2π / λ; λ is the wavelength of light; Aq is the amplitude of a point on the holographic plane; exp represents the exponential function, i.e., exp() = e(), e is the natural constant, e equals 2.7.

[0014] The image to be hidden is discretized into N point light sources. The superposition of the complex amplitudes of the light wave fields diffracted onto the holographic surface by each point light source is calculated using the above formula, resulting in the diffraction field Ud(xp′, yp′, zp′) of the image to be hidden.

[0015] According to the Fresnel diffraction principle, the above formula simplifies to:

[0016] Since the phase part of the above formula is used to fabricate the phase element, the formula is further simplified to:

[0017] The diffraction field Ud(xp′, yp′, 0) is then superimposed with the reference light R(xp′, yp′, 0) to obtain the complex amplitude distribution Uh(xp′, yp′, 0) of the computational hologram. The reference light is a plane wave, and the complex amplitude distribution of the reference light is as follows:

[0018] Uh(xp′,yp′,0)=Ud(xp′,yp′,0)+R(xp′,yp′,0) In the formula: A is the amplitude of the reference light; cosα and cosβ are the direction cosines of the plane wave propagation; α and β represent the angles between the parallel light and the X-axis and Y-axis, respectively; exp represents the exponential function, i.e., exp()=e(), e is the natural constant, e equals 2.7.

[0019] The complex amplitude distribution Uh(xp′, yp′, 0) is calculated, and its amplitude is normalized and mapped to the range [0, 255] to obtain the holographic file of the image to be hidden.

[0020] Further, the step of acquiring the moiré invisible image and the moiré decoding grating of the image to be hidden includes: The information of the text to be hidden is decomposed into a pattern composed of multiple periodically arranged dots or lines to obtain the information layer text of the text to be hidden. The information layer graphics are set to be based on a fundamental frequency. Composed of dot or line arrays; Adjusting the spacing between the dot matrix or linear array allows the fundamental frequency to be adjusted. to frequency The moiré pattern hidden image is obtained; Adjust the frequency and angle of the information layer graphics in the moiré invisible graphics to a constant frequency. ,make ≈ The moiré decoding grating is obtained.

[0021] Furthermore, the design parameters of the moiré decoding grating are as follows: The grating width of the moiré decoding grating Where H is the number of viewpoints and t is the width of a single pixel; Crown height of the moiré decoding grating The crown height h is 10 μm, achieved using nanoimprinting. The radius of curvature (G) and focal length (f) of the moiré decoding grating are: G = f * (n-1), where n is the refractive index of the material.

[0022] Further, obtaining the grayscale height image and the rainbow laser image of the image to be hidden includes: Obtain a planar pattern containing the text and image to be hidden, drawn using vector software; The planar pattern is imported into 3D modeling software to create an embossed structure, resulting in the grayscale height map; The color image containing the text to be hidden is imported into optical design software. The line count of the color image is adjusted to 1500-3000 lines / mm, the angle is a multi-directional grating combination (15°, 45°, or 75°), and the depth is 0.1-0.3μm to obtain the rainbow laser image of the text to be hidden.

[0023] Further, the formula for preparing the rainbow spot ink includes: 20% ZnS quantum dots, 20% coumarin, 20% IR-806, 30% acrylic resin, 8% diluent, 0.5% leveling agent, 0.5% defoaming agent, 0.5% ultraviolet absorber, and 0.5% antioxidant.

[0024] Further, an imprint varnish is coated on the surface of the second substrate, and the moiré decoding grating cold transfer film is imprinted and cured with the second substrate, and the third BOPP film is peeled off, that is, the microstructure of the moiré decoding grating cold transfer film is transferred onto the second substrate to obtain the micro-nano structure anti-counterfeiting element, including: A gravure roll is used to locally coat the imprint varnish on the surface of the second substrate, and the area coated with the imprint varnish is UV-cured after being imprinted with the moiré decoding grating cold transfer film and the second substrate; The third BOPP film is peeled off, so that the microstructure of the moiré decoding grating cold transfer film is transferred onto the second substrate to obtain the micro-nano structure anti-counterfeiting element; wherein the cells of the gravure roll are hexagonal cells, the depth of the cells is 15–20 μm, and the opening ratio of the cells is 30–40%.

[0025] A micro-nano structure anti-counterfeiting element prepared based on the cold transfer technology is obtained by using the preparation method of the micro-nano structure anti-counterfeiting element prepared based on the cold transfer technology described above. [[ID=**12]]

[0026] Compared with the prior art, the micro-nano structure optical element and its preparation method provided by the present invention have a random state distribution on the holographic surface of the entire substrate. When the image is reproduced, as the reproduction light source undergoes a spatial displacement, through the precisely designed random state distribution phase encoding holographic structure, the reproduced color image can achieve a full-range linkage response within the entire holographic area. At the same time, by changing the distance between the illumination light source and the holographic surface, the size of the image also changes synchronously. For the present invention, by transferring the background cold transfer film, the embossed / rainbow laser cold transfer film, and the moiré decoding grating cold transfer film onto the substrate, that is, through the superimposed design of three-level anti-counterfeiting, the anti-counterfeiting threshold can be greatly increased, and at the same time, the verification requirements for different scenarios can be met. " BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0028] Figure 1 This is a schematic diagram of the point source method for calculating holography in the fabrication method of micro / nano structure anti-counterfeiting elements based on cold transfer technology provided by the present invention.

[0029] Figure 2 This is a top view of the micro / nano structure anti-counterfeiting element prepared by cold transfer technology according to the present invention.

[0030] Figure 3 This is a cross-sectional view of the micro / nano structure anti-counterfeiting element prepared by cold transfer technology provided by the present invention.

[0031] Figure 4 This is a schematic diagram of the micro-nano structure moiré pattern imaging and computational holographic point light source imaging of the micro-nano structure anti-counterfeiting element based on cold transfer technology provided by the present invention.

[0032] Explanation of reference numerals in the attached diagram: Substrate-1, Microstructure background-2, Embossing / Rainbow Laser-3, Moiré Decoding Structure-4, Moiré Decoding Imaging-A, Computational Holographic Point Light Source Imaging-B. Detailed Implementation

[0033] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] In this invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may have other meanings besides indicating orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.

[0036] Furthermore, the terms “first” and “second” as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are used only to distinguish one element from another. When used herein, the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof.

[0037] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0038] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0039] The present invention provides a method for fabricating micro / nano-structured anti-counterfeiting elements based on cold transfer technology, comprising: To obtain a binary image containing the text and images to be hidden, first use drawing software (such as Adobe Illustrator or CorelDRAW) to create a black and white binary image. The binary image contains the text and images to be hidden. The binary image is composed of pure black and pure white pixels, which facilitates precise control of the phase and amplitude of light waves during subsequent holographic processing. The binary image is then input into hologram generation software. Based on the point source method and light wave superposition principle of the computational hologram generation software, a holographic file of the binary image is calculated. That is, the binary image is imported into dedicated hologram generation software (such as MATLAB or professional CGH tools), and the light wave propagation of each pixel as an independent point source is simulated using the point source method. The interference and diffraction effects of all point sources are calculated through the light wave superposition principle to generate the holographic file (such as GDSII or CGH format) containing complex wavefront information for optical reconstruction of hidden images. The holographic file is imported into a lithography machine. The optical system of the lithography machine controls the laser beam to form an exposure spot. The objective lens of the lithography machine focuses the spot onto the photoresist surface for point-by-point exposure. After development, a three-dimensional microstructure with a preset morphology is obtained, which serves as a computational holographic template. Alternatively, the holographic file is input into the lithography machine, which controls the laser beam through optical components such as a spatial light modulator to form a tiny exposure spot. The objective lens focuses the spot onto a substrate coated with photoresist. After point-by-point exposure and development, a three-dimensional microstructure (such as an relief or grating) is formed on the substrate surface, which serves as the computational holographic template for subsequent replication of diffraction effects. To obtain the moiré invisible graphic and the moiré decoding grating to be hidden, it is understood that the moiré invisible graphic (composed of specific periodic lines or patterns) and the corresponding moiré decoding grating (usually a grating structure) are designed. When the two overlap, visible moiré patterns are generated due to interference, thereby displaying the hidden information. These designs are completed through graphics software or optical design tools to ensure that the parameters of the graphic and the grating are matched. The moiré pattern hidden image and the moiré pattern decoding grating are respectively imported into the lithography machine. The optical system of the lithography machine controls the laser beam to form an exposure spot. The objective lens of the lithography machine focuses the spot onto the photoresist surface of the glass plate for point-by-point exposure and development, thereby obtaining the moiré pattern hidden image and the moiré pattern decoding grating. It can be understood that the moiré pattern and decoding grating design files are respectively imported into the lithography machine. Through the exposure and development process, corresponding microstructures (such as raised or recessed patterns) are made on the photoresist of the glass substrate, which serve as the master of the moiré pattern hidden image and the master of the decoding grating for subsequent transfer. The computational holographic image and the moiré invisible graphic image are spliced ​​together to obtain a first resin master image. Using the first resin master image as the cathode and metallic nickel as the anode, a first metallic nickel layer is deposited on the first resin master image under electrolysis. The first metallic nickel layer is then separated from the first resin master image to obtain the base pattern large image. It can be understood that by splicing the computational holographic image and the moiré invisible graphic image onto the resin master image, and depositing a nickel layer on the surface of the resin master image through an electroforming process (electrolytic nickel plating), a robust base pattern large image is formed. This image combines holographic and moiré structures, which is convenient for large-scale molding replication. The pattern template is mounted on a molding machine. A UV varnish is applied to a first BOPP film. The pattern template is then molded and cured. After the pattern template is peeled off, the pattern microstructure remains on the surface of the first BOPP film, resulting in a pattern cold transfer film. Alternatively, a nickel-based pattern template can be used in a molding machine. A UV coating is applied to the first BOPP film, and the microstructure is transferred to the coating surface through molding. After UV curing, the template is peeled off, leaving the pattern structure on the first BOPP film, forming a transferable pattern cold transfer film for subsequent bonding to substrate 1. Obtain a grayscale height map containing the text and image to be hidden, drawn using vector software, and a rainbow laser map containing the text and image to be hidden, drawn using optical design software. Specifically, the grayscale height map is drawn using vector software (such as Illustrator) (to control the depth of the 3D relief), and the rainbow laser map is designed using optical design software (such as Zemax or DiffractMOD) (to produce a color diffraction effect). Both contain the text and image to be hidden, ensuring that the optical properties are compatible with the hidden information. The grayscale height map and the rainbow laser image are imported into the lithography machine. The optical system of the lithography machine controls the laser beam to form exposure spots. The objective lens of the lithography machine focuses these spots onto the photoresist surface for point-by-point exposure. After development, the relief image template and the rainbow laser image template are obtained respectively. In other words, the grayscale height map and the rainbow laser image files are exposed and developed using the lithography machine to create the relief image template (with height variation) and the rainbow laser image template (with diffraction grating), which serve as independent image masters. The first resin master plate is obtained by combining the embossed image and the rainbow laser image. The first resin master plate is used as the cathode and nickel metal as the anode. Under electrolysis, a second nickel metal layer is gradually deposited on the second resin master plate. The second resin master plate and the second nickel metal layer are separated to obtain an embossed / rainbow laser hybrid plate. That is, the embossed / rainbow laser image is combined with the second resin master plate and electroforming is used to obtain the embossed / rainbow laser hybrid plate. The embossed / rainbow laser hybrid plate combines the three-dimensionality of embossing and the rainbow effect of laser, enhancing the complexity and visual effect of anti-counterfeiting elements. The embossed / rainbow laser hybrid plate is mounted on a molding device. UV varnish is applied to the second BOPP film. The film is then molded and cured using the embossed / rainbow laser hybrid plate. After peeling off the embossed / rainbow laser hybrid plate, the surface of the second BOPP film is formed with the microstructure of the embossed / rainbow laser hybrid plate, resulting in an embossed / rainbow laser cold transfer film. It can be understood that the second BOPP film is molded using the embossed / rainbow laser hybrid plate, and after UV curing, a microstructure combining embossing and laser is transferred to create another cold transfer film, which is used to add multiple layers of anti-counterfeiting features to the substrate 1. The moiré pattern decoding grating is mounted on a molding machine. UV varnish is applied to a third BOPP film. After molding with the moiré pattern decoding grating, the film is cured. After peeling off the moiré pattern decoding grating, the surface of the third BOPP film is formed with the microstructure of the moiré pattern decoding grating, resulting in the moiré pattern decoding grating cold transfer film. In other words, the moiré pattern decoding grating is used to mold the third BOPP film to produce the moiré pattern decoding grating cold transfer film. The grating structure on the moiré pattern decoding grating cold transfer film can interact with the invisible graphics to decode and display hidden information. Rainbow dot ink is prepared and coated onto the surface of substrate 1. The background cold transfer film is then laminated with the rainbow dot ink and cured. The first BOPP film is then peeled off, thus transferring the background pattern structure of the background cold transfer film onto the surface of substrate 1 to obtain the first substrate. It can be understood that a dot ink with a rainbow effect is prepared, coated onto substrate 1 (such as paper or plastic), the background cold transfer film is laminated, and after curing, the BOPP carrier is peeled off to transfer the microstructure background 2 of the moiré decoding grating cold transfer film onto substrate 1, forming a first substrate with holographic and moiré features. An embossing varnish is applied to the surface of the first substrate. The embossed / rainbow laser cold transfer film is then embossed and cured onto the first substrate. The second BOPP film is then peeled off, thus transferring the microstructure of the embossed / rainbow laser cold transfer film onto the first substrate to obtain the second substrate. Alternatively, varnish is applied to the first substrate, the embossed / rainbow laser cold transfer film is bonded to it, and after embossing and curing, the carrier is peeled off to transfer the embossed / rainbow laser 3, resulting in a second substrate with multiple layers of optical effects, enhancing anti-counterfeiting and aesthetics. An embossing varnish is applied to the surface of the second substrate. The moiré decoding grating cold transfer film is then embossed and cured onto the second substrate. The third BOPP film is then peeled off, thus transferring the microstructure of the moiré decoding grating cold transfer film onto the second substrate to obtain the micro-nano structure anti-counterfeiting element. Alternatively, varnish is applied to the second substrate, the decoding grating cold transfer film is bonded, and after embossing and curing, the carrier is peeled off, transferring the moiré decoding structure 4. The final product integrates computational holography, moiré invisibility, embossing, rainbow laser, and multi-layer decoding functions, forming a high-security micro-nano structure anti-counterfeiting element that can be verified for authenticity under specific conditions (such as overlap or illumination).

[0040] It should be noted that by using the film molding method, the holographic microstructure is located on the product surface, resulting in a high structural size transfer rate and clearer imaging. The film molding method also has a fast transfer speed, making it faster than the production speed of molded paper. Furthermore, the film can be reused up to 20 times, which can greatly reduce material costs.

[0041] When the product layout is such that both sides face the same direction, the graphic design uses a single image in one direction. When the product layout is such that both sides face the same direction, the front and back of the graphic need to be considered. The graphic needs to adopt a symmetrical structure and maintain double rotational symmetry, 180-degree rotational symmetry. For product surface effects where there are no image direction requirements, a random image distribution design is used.

[0042] For films with unidirectional graphic designs, the film feeding direction must be consistent with the positive direction of the substrate 1. After each production cycle, the recycled film needs to be rewound once to reverse the direction. For films with double rotational symmetry graphics, the BOPP base film does not require rewinding and can be used directly from the outermost layer. For films with random image distribution designs, the base film does not require rewinding and can be used directly from the outermost layer.

[0043] Compared with existing technologies, the micro-nano structure anti-counterfeiting element in this invention integrates level 1, level 2, and level 3 anti-counterfeiting. Through the superposition design of the three levels of anti-counterfeiting, the counterfeiting threshold can be significantly increased, while meeting the verification needs of different scenarios. Among them, the embossed / rainbow laser cold transfer film belongs to level 1 anti-counterfeiting, and its authenticity can be directly judged by the naked eye. The computational holographic micro-nano structure background of the background cold transfer film belongs to level 2 anti-counterfeiting, which can be verified with the help of a point light source. The moiré stripe decoding grating cold transfer film belongs to level 3 anti-counterfeiting. Under precise processing conditions, it produces special effects and has processing barriers, while also producing a level 1 anti-counterfeiting effect that can be directly identified. When white light is irradiated through the grating sheet to illuminate the ink surface, a multi-color light spot array is left on the ink surface, which has multiple anti-counterfeiting functions. Due to the special nature of the transfer adhesive, no adhesive residue remains on the surface of the BOPP film, and the BOPP film can be reused multiple times, which can reduce costs.

[0044] Furthermore, such as Figure 1 As shown, the holographic file generated by the hologram generation software for the binary image includes: The hologram generation software treats the image to be hidden as composed of multiple discrete points and calculates the complex amplitude distribution of each discrete point reaching the holographic surface. The complex amplitude distributions of each discrete point on the recording surface are superimposed according to the principle of light wave superposition to generate the holographic file.

[0045] Understandably, during the generation of the holographic file, the image to be hidden is first considered as a set of numerous discrete points. Each discrete point can be viewed as an independent point light source, emitting light waves that propagate outwards in the form of spherical waves. The hologram generation software precisely calculates the complex amplitude distribution generated on the holographic surface when the light waves emitted by each such discrete point light source propagate to the preset holographic recording plane (i.e., the holographic surface). The complex amplitude distribution contains both amplitude and phase information of the light wave, and is a key physical quantity describing the vibration state of the light wave at various points in space.

[0046] Subsequently, based on the principle of light wave superposition, the hologram generation software performs vector superposition of the complex amplitude distributions generated by all the discrete points on the holographic recording surface. Since light waves are electromagnetic waves and satisfy the linear superposition condition, the total complex amplitude at any point on the holographic surface is equal to the sum of the complex amplitudes generated by each point light source propagating to that point. This superposition process simulates the physical scenario where light waves emitted by these point light sources coexist in space and interfere with each other.

[0047] Finally, by digitally sampling and encoding the complex amplitude distribution formed by interference (usually containing fine structures of interference fringes) on the holographic recording surface, it is converted into a specific data format (such as a matrix containing phase and amplitude information), thereby generating an optical file that can be used to control the fabrication of microstructures by photolithography equipment, namely the holographic file, which essentially encodes the optical wavefront information corresponding to the original binary image.

[0048] Further, the step of treating the image to be hidden as composed of multiple discrete points and calculating the complex amplitude distribution of each discrete point reaching the holographic surface includes: The surface of the image to be hidden is discretized into a set of points, where each point on the surface is used as a separate point light source; Calculate the spherical waves emitted by each of the point light sources, and trace the path of the spherical waves to obtain the diffraction pattern of each point light source.

[0049] Understandably, the core steps in the computational holographic generation process first require high-precision digital discretization of the original image to be hidden. Specifically, the two-dimensional surface or three-dimensional shape containing the image to be hidden is divided into a dense set of N points according to a set resolution, where each point is independently considered as a secondary point source emitting light waves in all directions. Subsequently, the standard spherical wavefront emitted by each point source is calculated, which propagates outward in space at the speed of light from the point source location. To accurately record the interference effect of these light waves, it is necessary to track the state of each spherical wave when it reaches the preset holographic recording plane in the propagation path. This process essentially involves solving the optical path from each point source to any sampling point on the holographic surface, and calculating the phase distribution determined by the optical path difference and the amplitude value that decays with distance. This mathematically constructs the diffraction pattern with a specific bright and dark fringe structure formed by each independent point source on the holographic surface. The diffraction pattern is the basis for subsequent light wave superposition and generation of the final holographic interference file.

[0050] Further, the step of superimposing the complex amplitude distributions of each discrete point on the recording plane according to the principle of light wave superposition to generate the holographic file includes: Let the spatial coordinate system of the hidden information graphic be OXYZ, and the spatial coordinate system of the computational hologram plane of the holographic file be O′X′Y′Z′. The Z-axis of the two coordinate systems are on the same straight line, and the distance between the origins of the two coordinate systems is d. The coordinates of any point q in the binary image are (xi, yi, zi), and the coordinates of any point p on the holographic surface are (xp′, yp′, zp′). Then the distance between point p and point q is:

[0051] It is understandable that, when calculating the complex amplitude of the light wave diffracted on the target holographic plane, with the plane as the reference point and the depth coordinates of all points being 0, the complex amplitude of the light wave received at point p is:

[0052] In the formula: j is the imaginary unit; wave number k = 2π / λ; λ is the wavelength of light; Aq is the amplitude of a point on the holographic plane; exp represents the exponential function, i.e., exp() = e(), e is the natural constant, e equals 2.7.

[0053] The image to be hidden is discretized into N point light sources. The superposition of the complex amplitudes of the light wave fields diffracted onto the holographic surface by each point light source is calculated using the above formula, resulting in the diffraction field Ud(xp′, yp′, zp′) of the image to be hidden.

[0054] According to the Fresnel diffraction principle, the above formula simplifies to:

[0055] Since the phase part of the above formula is used to fabricate the phase element, the formula is further simplified to:

[0056] The diffraction field Ud(xp′, yp′, 0) is then superimposed with the reference light R(xp′, yp′, 0) to obtain the complex amplitude distribution Uh(xp′, yp′, 0) of the computational hologram. The reference light is a plane wave, and the complex amplitude distribution of the reference light is as follows:

[0057] Uh(xp′,yp′,0)=Ud(xp′,yp′,0)+R(xp′,yp′,0) In the formula: A is the amplitude of the reference light; cosα and cosβ are the direction cosines of the plane wave propagation; α and β represent the angles between the parallel light and the X-axis and Y-axis, respectively; exp represents the exponential function, i.e., exp()=e(), e is the natural constant, e equals 2.7.

[0058] The complex amplitude distribution Uh(xp′, yp′, 0) is calculated, and its amplitude is normalized and mapped to the range [0, 255] to obtain the holographic file of the image to be hidden.

[0059] Understandably, this process begins with a well-defined space: the coordinate system OXYZ carrying the hidden information and the coordinate system O'X'Y'Z' used to compute the hologram are set to share a common Z-axis, and the origins of the two coordinate systems are d apart. Under this configuration, the core of the computation lies in solving the light wave interaction between each discrete point on the hidden information and each sampling point on the hologram.

[0060] Specifically, the binary image to be hidden is discretized into N point light sources, where the coordinates of any point q are (xi, yi, zi). For any point p (xp', yp', zp') on the holographic surface, the distance r between it and point q is precisely calculated. This distance r is crucial for calculating the propagation of light waves. According to the physical model of spherical waves emitted by point light sources, the complex amplitude of the light wave received by point p from a single point light source q can be described by the formula U = (1 / r) * exp(-jkr), where j is the imaginary unit and k is the wave number (k=2π / λ, λ is the wavelength of light). This formula simultaneously includes the amplitude attenuation (1 / r) and phase delay (-jkr) caused by the distance r.

[0061] Next, according to the principle of linear superposition of light waves, the total light wave field at point p on the holographic surface, i.e., the diffraction field Ud(xp', yp', zp') of the image to be hidden, is the vector sum of the complex amplitudes generated by all N point sources at that point. To simplify this theoretically accurate but computationally intensive spherical wave model, the Fresnel diffraction approximation is usually introduced in practice. This approximation holds at a specific distance d, allowing the complex spherical wave calculation formula to be simplified to a more easily computed form. Its core is to treat the amplitude attenuation term as a constant, while the phase term is simplified to a quadratic function of the coordinates. In some cases, to create a purely phase-type hologram, the amplitude information can be further ignored, retaining only this crucial phase component, and the formula simplifies to:

[0062] This allows computational holograms to reconstruct images by modulating only the phase.

[0063] However, to generate a standard hologram suitable for photolithography, interference fringes are typically required. Therefore, the diffraction field Ud representing the object light must interfere with a reference beam. Here, a plane wave is introduced as the reference beam R, with the following complex amplitude distribution:

[0064] Where A is the amplitude of the reference beam, and α and β determine the propagation direction of the plane wave. The object beam Ud and the reference beam R are superimposed on the holographic surface to obtain the total complex amplitude distribution of the hologram: Uh(xp′,yp′,0)=Ud(xp′,yp′,0)+R(xp′,yp′,0) This superposition process mathematically simulates physical interference, and the resulting Uh contains rich interference fringe information. Finally, in order to generate a holographic file that can be used by the lithography machine, this complex amplitude distribution (usually its intensity distribution, i.e., the product of Uh and its conjugate) needs to be digitized: after calculating the interference pattern of Uh, its numerical range is normalized and quantized to the grayscale range of [0, 255]. The final grayscale image file is the holographic file that can be used to drive the lithography machine to manufacture microstructures.

[0065] Further, the step of acquiring the moiré invisible image and the moiré decoding grating of the image to be hidden includes: The information of the text to be hidden is decomposed into a pattern composed of multiple periodically arranged dots or lines to obtain the information layer text of the text to be hidden. The information layer graphics are set to be based on a fundamental frequency. Composed of dot or line arrays; Adjusting the spacing between the dot matrix or linear array allows the fundamental frequency to be adjusted. to frequency The moiré pattern hidden image is obtained; Adjust the frequency and angle of the information layer graphics in the moiré invisible graphics to a constant frequency. ,make ≈ The moiré decoding grating is obtained.

[0066] It is understandable that the core of the fabrication of the moiré hidden image and the decoding grating lies in utilizing the physical phenomenon of moiré fringes generated by minute differences in frequency or angle when two periodic structures are superimposed. First, the image information to be hidden needs to be specially structured and encoded. This process involves decomposing and redesigning what might originally be solid block-shaped image information into a pattern composed of a large number of periodically arranged tiny dots or lines. The product of this step is called the "information layer image." Initially, the information layer image is set as a regular and uniform dot or line array with a fundamental spatial frequency b; at this stage, it does not directly display the hidden information.

[0067] To hide information, the local spatial frequency needs to be altered by fine-tuning the spacing between elements in a dot or line array. Specifically, this involves adjusting the frequency of the information layer's text in different regions based on variations in brightness or shape of the information to be hidden, changing it from the base frequency. Accordingly, it changes to a new frequency. For example, in areas where the hidden text needs to be displayed (dark areas), the spacing between dots and lines is compressed (frequency is increased), while in areas where it is displayed (bright areas), the spacing is increased (frequency is decreased). After such modulation, the resulting pattern, which appears uniform but is actually modulated by information, is called "moiré invisible text." It may appear to be just a background with a slight texture, and the hidden content cannot be directly identified by the naked eye.

[0068] To reveal the hidden information, a "moiré decoding grating" needs to be created. This decoding grating itself is also a periodic structure, and its key parameter is set to a constant spatial frequency. And require Values ​​and the basic frequency of information layer graphics and text Very close but not exactly the same (i.e., satisfying) ≈ When this has a constant frequency When the decoding grating is precisely superimposed on the prepared moiré hidden image, a tiny, information-modulated frequency difference between the two will produce clearly visible low-frequency moiré fringes due to interference. The macroscopic shape of these moiré fringes restores the original image to be hidden, thus realizing the decryption and visual presentation of the information.

[0069] Furthermore, the design parameters of the moiré decoding grating are as follows: The grating width of the moiré decoding grating Where H is the number of viewing angles and t is the width of a single pixel. If the printing resolution is 1200 dpi (pixel width ≈ 21 μm), the width of the 8-view raster is L ≈ 24 μm * 8 = 192 μm; Crown height of the moiré decoding grating The crown height is 10 μm, achieved using nanoimprinting. The radius of curvature (G) and focal length (f) of the moiré decoding grating are: G = f•(n-1), where n is the refractive index of the material.

[0070] Understandably, the grating width (L) directly determines the size of the basic periodic unit of the grating. Its calculation formula is L = H × t, where H is the total number of viewing angles (i.e., the number of images that can be presented at different viewing angles), and t is the physical width of a single pixel when creating the grating.

[0071] For example, if a printing or photolithography resolution of 1200 DPI (1200 dots per inch) is used, the width p of a single pixel is approximately 21 micrometers. If designed as an 8-view grating, its total width L is approximately 21 μm multiplied by 8, or 168 micrometers. A pixel width of 24 μm corresponds to a resolution of approximately 1060 DPI, and the calculated width of the 8-view grating is approximately 192 micrometers.

[0072] Crown height (h) refers to the height of the raised portion in the microstructure of a grating. This parameter profoundly affects the diffraction efficiency and visual effect of the grating. Traditional mechanical molding processes may struggle to produce high aspect ratios due to material flow limitations, resulting in typically high crown heights. However, advanced nanoimprinting technology achieves extremely high precision and resolution, allowing crown heights to be significantly reduced to 10 micrometers or even smaller. This reduction brings multiple advantages: it not only reduces material consumption, making the grating layer thinner and flatter, but also improves the fidelity and consistency of the imprint transfer, which is crucial for creating ultra-thin security features integrated into documents or banknotes.

[0073] The relationship between radius of curvature (G) and focal length (f) primarily concerns moiré decoding gratings designed as cylindrical lens arrays. Each micro-unit of this grating is not a simple line, but a tiny convex lens. Their geometric relationship is precisely described by the formula G = f*(n - 1), where n is the refractive index of the polymer or coating material constituting the grating. The physical significance of this formula lies in its direct link between the radius of curvature (G) of the lens surface and its optical function—focal length (f). The precise radius of curvature (R) to be etched or imprinted can be calculated backwards from the desired moiré viewing distance (i.e., focal length f) and the refractive index (n) of the selected curing ink or resin. For example, to achieve a specific converging effect, using a high-refractive-index material allows for the fabrication of a lens structure with a larger radius of curvature G (i.e., flatter and easier to process) while maintaining the same focal length f. Therefore, the radius of curvature, focal length, and material refractive index together form a closely related design triangle, ensuring that the grating not only produces moiré patterns but also possesses the desired focusing and imaging optical performance.

[0074] Further, the acquisition of a grayscale height map containing the image / text to be hidden, drawn by vector software, and a rainbow laser map containing the image / text to be hidden, drawn by optical design software, includes: Obtain a planar pattern containing the text and image to be hidden, drawn using vector software; The planar pattern is imported into 3D modeling software to create an embossed structure, resulting in the grayscale height map; The color image containing the text to be hidden is imported into optical design software. The line count of the color image is adjusted to 1500-3000 lines / mm, the angle is a multi-directional grating combination (15°, 45°, or 75°), and the depth is 0.1-0.3μm to obtain the rainbow laser image of the text to be hidden.

[0075] It should be noted that the acquisition of the grayscale height map is aimed at giving the text and image to be hidden three-dimensional depth information. First, a two-dimensional planar outline containing the text and image to be hidden is drawn in vector graphics software (such as Adobe Illustrator or CorelDRAW). The advantage of vector format is that it is defined by mathematical paths, allowing for infinite scaling without distortion, ensuring the accuracy and smoothness of the text and image edges. Then, this two-dimensional vector file is imported into professional 3D modeling or relief design software (such as ArtCAM, ZBrush, or Rhino). In these software programs, the planar vector outline can be transformed into a 3D relief model with continuous undulations using tools such as "Extrude," "Emboss," and "Gradient Height," according to creative needs. Finally, this 3D model is output by the software as a grayscale height map (usually an 8-bit or 16-bit TIFF or PNG image). In this image, different grayscale values ​​do not represent colors, but rather precisely encode the height information corresponding to each pixel—pure white usually represents the highest point, pure black represents the lowest point (or vice versa), and the grayscale gradient in between corresponds to a smooth height transition. This image became the blueprint for subsequent photolithography processes, guiding the photolithography machine to carve microscopic three-dimensional structures with preset morphologies onto the photoresist.

[0076] Regarding the acquisition of the rainbow laser image: The goal of this process is to create an optical effect that displays vibrant colors as the viewing angle changes. First, a color image defining the desired color distribution is needed as the design source. This color image is then imported into professional optical design software (such as Lighten or similar tools for grating design). The core function of the software is to convert the color information in the image into a set of extremely fine microscopic grating structure parameters. This conversion is achieved by setting several key grating parameters: the line count is set in an extremely high density range of 1500 to 3000 lines / mm, ensuring that its diffraction capability can produce vivid spectral colors visible to the naked eye; the angle employs a multi-directional grating combination strategy (e.g., simultaneously setting multiple grating units at angles of 15°, 45°, and 75°), with gratings at different angles responsible for reflecting specific colors of light at different viewing angles. As the observer moves, gratings at different angles sequentially dominate the visual effect, thus producing a dynamic, color-flowing rainbow effect; simultaneously, the grating depth is precisely controlled at the submicron level of 0.1 to 0.3 micrometers. This depth is crucial for interference and diffraction efficiency; too shallow or too deep will result in insufficient color brightness or impurity. Through comprehensive calculation and optimization of these parameters by software, a rainbow laser image data file containing the image to be hidden is finally generated, which can be used for photolithography. This file defines where and what parameters of grating should be used to accurately reproduce the dynamic rainbow effect of the source color image on a macroscopic scale.

[0077] Furthermore, the formulation for preparing the rainbow speckle ink includes: 20% ZnS quantum dots, 20% coumarin, 20% IR-806, 30% acrylic resin, 8% diluent, 0.5% leveling agent, 0.5% defoamer, 0.5% UV absorber, and 0.5% antioxidant.

[0078] Further, the process involves coating the surface of the second substrate with embossing varnish, embossing the moiré decoding grating cold transfer film onto the second substrate, curing the film, peeling off the third BOPP film, and transferring the microstructure of the moiré decoding grating cold transfer film onto the second substrate to obtain the micro / nano structure anti-counterfeiting element, comprising: An anilox roller is used to locally coat and imprint varnish on the surface of the second substrate. The area coated with varnish and the moiré decoding grating cold transfer film are then imprinted onto the second substrate and cured with UV. Peel off the third BOPP film to transfer the microstructure of the moiré decoding grating cold transfer film onto the second substrate, thereby obtaining the micro-nano structure anti-counterfeiting element. The anilox roller has hexagonal cells with a depth of 15–20 μm, a cell opening ratio of 30–40%, and a cell line count of 250 LPI / 4.5 BCM.

[0079] It is understandable that applying embossing varnish to the surface of the second substrate is a crucial step in ultimately transferring and fixing the microstructure of the moiré decoding grating onto the product. This process does not involve full-coverage coating of the entire substrate surface; instead, it employs a precision anilox roller for localized coating, precisely applying ink only to specific areas where the moiré decoding grating needs to be embossed. This localized coating technique offers several advantages: it saves on expensive varnish materials, effectively avoids unclear or clump-like images due to ink overflow, and ensures the smoothness and cleanliness of the final anti-counterfeiting element surface.

[0080] After coating, the microstructure surface of the moiré decoding grating cold transfer film is precisely aligned with the coated area and pressure is applied for imprinting, allowing the varnish to fill and replicate the grating structure on the BOPP film. Subsequently, UV (ultraviolet) light is used for instant curing. The UV light causes the photosensitive resin component in the varnish to undergo a cross-linking reaction, rapidly transforming it from a liquid to a solid state, thereby permanently fixing the replicated microstructure. After curing, the third BOPP film, acting as a carrier, is peeled off like peeling off the backing paper of a sticker. The microstructure on its surface is completely and faithfully transferred and remains on the surface of the second substrate, thus obtaining the micro / nano structure anti-counterfeiting element that integrates all anti-counterfeiting functions.

[0081] In this stage, the parameter design of the anilox roller is the core of controlling the coating amount, uniformity, and final transfer quality. Its specific parameters are precisely set as follows: hexagonal cells are used, which have better ink release uniformity and stability compared to quadrilateral or rhomboid cells; the engraving depth is about 15–20 μm, which determines the total volume of ink contained in the cells and directly affects the thickness of the varnish transferred to the substrate, ensuring that there is enough varnish to perfectly replicate the micron-level grating structure without producing excess adhesive; the aperture ratio is 30–40%, which refers to the percentage of the cell opening area to the entire roller area. This parameter balances the ink carrying capacity and the smoothness of transfer and release; the line count is 250 LPI (i.e., 250 cells per inch) and the ink transfer volume is 4.5 BCM (Billion Cubic Microns per square inch). The high line count of 250 LPI ensures the fineness of the coating layer, while the ink transfer volume of 4.5 BCM works in conjunction with the depth and aperture ratio to precisely control the structural thickness and fullness of the varnish after curing per unit area, providing a crucial material basis for high-quality transfer micro-gratings.

[0082] like Figure 1 , Figure 2 and Figure 4 As shown, a micro / nano structure anti-counterfeiting element based on cold transfer technology is prepared using the above-described method for preparing micro / nano structure anti-counterfeiting elements based on cold transfer technology.

[0083] In summary, the micro / nano structure anti-counterfeiting element and method based on cold transfer technology provided by this invention integrates first-level, second-level, and third-level anti-counterfeiting measures. Through the superimposed design of these three levels of anti-counterfeiting, the counterfeiting threshold can be significantly increased, while simultaneously meeting the verification needs of different scenarios. Specifically, this invention employs a thin-film molding method, calculating the holographic microstructure to be on the product surface, resulting in a high structural size transfer rate and clearer imaging. The thin-film molding method also offers fast transfer speeds, compared to molded paper production. The embossed / rainbow laser cold transfer film is a first-level anti-counterfeiting measure, which can be directly detected by the naked eye. To determine authenticity, the computational holographic micro-nano structure of the cold transfer film is a level 2 anti-counterfeiting measure, verifiable with a point light source. The moiré fringe decoding grating cold transfer film is a level 3 anti-counterfeiting measure, producing special effects under precise processing conditions, creating processing barriers, while also providing a level 1 anti-counterfeiting effect for direct identification. White light is used to illuminate the ink surface through the grating sheet, leaving a multi-color light spot array on the ink surface, providing multiple anti-counterfeiting functions. Due to the special nature of the transfer adhesive, no adhesive residue remains on the BOPP film surface, allowing the BOPP film to be reused multiple times, reducing costs.

[0084] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the scope of protection of the present invention.

Claims

1. A method for fabricating micro / nano-structured anti-counterfeiting elements based on cold transfer technology, characterized in that, include: Obtain a binary image containing the text to be hidden, and input the binary image into hologram generation software, which then generates a holographic file of the binary image. The holographic file is imported into a photolithography machine. The optical system of the photolithography machine controls the laser beam to form an exposure spot. The objective lens of the photolithography machine focuses the spot onto the photoresist surface for point-by-point exposure. After development, a three-dimensional microstructure with a preset morphology is obtained, which serves as a computational holographic image. The moiré invisible image and the moiré decoding grating to be hidden are obtained. The moiré invisible image and the moiré decoding grating are respectively introduced into the photolithography machine. The laser beam is controlled by the optical system to form an exposure spot. The objective lens focuses the spot onto the photoresist surface of the glass plate for point-by-point exposure. After development, the moiré invisible image and the moiré decoding grating are obtained respectively. The first resin master plate is obtained by splicing the computational holographic version with the moiré invisible graphic version; Using the first resin master plate as the cathode and metallic nickel as the anode, a first metallic nickel layer is deposited on the first resin master plate under electrolysis. The first metallic nickel layer is then separated from the first resin master plate to obtain the background pattern. The large pattern template is mounted on a molding device, UV varnish is applied to the first BOPP film, and the large pattern template is molded and cured to form the microstructure of the pattern template on the surface of the first BOPP film, thus obtaining a cold transfer film of the pattern. The grayscale height image and the rainbow laser image of the image to be hidden are obtained. The grayscale height image and the rainbow laser image are imported into the lithography machine. The laser beam is controlled by the optical system to form an exposure spot. The objective lens focuses the spot onto the photoresist surface for point-by-point exposure. After development, the relief image and the rainbow laser image are obtained respectively. The relief image template and the rainbow laser image template are combined to obtain a second resin master template. The first resin master template is used as the cathode and metallic nickel is used as the anode. Under electrolysis, a second metallic nickel layer is deposited on the second resin master template. The second metallic nickel layer is separated from the second resin master template to obtain a relief / rainbow laser hybrid version. The embossed / rainbow laser hybrid plate is mounted on a molding device, UV varnish is applied to the second BOPP film, and the film is molded and cured by the embossed / rainbow laser hybrid plate, so that the microstructure of the embossed / rainbow laser hybrid plate is formed on the surface of the second BOPP film, resulting in an embossed / rainbow laser cold transfer film. The moiré decoding grating pattern is mounted on a molding device, UV varnish is applied to the third BOPP film, and the moiré decoding grating pattern is molded and cured to form the background microstructure of the moiré decoding grating pattern on the surface of the third BOPP film, thus obtaining the moiré decoding grating cold transfer film. Rainbow dot ink is prepared and coated onto the surface of a substrate. The background cold transfer film is then laminated with the rainbow dot ink and cured. The first BOPP film is then peeled off, thus transferring the background pattern structure of the background cold transfer film onto the surface of the substrate to obtain the first substrate. An embossing varnish is applied to the surface of the first substrate, the embossed / rainbow laser cold transfer film is embossed and cured onto the first substrate, and the second BOPP film is peeled off. That is, the microstructure of the embossed / rainbow laser cold transfer film is transferred onto the first substrate to obtain the second substrate. An embossing varnish is applied to the surface of the second substrate, and the moiré decoding grating cold transfer film is embossed and cured onto the second substrate. The third BOPP film is then peeled off, thus transferring the microstructure of the moiré decoding grating cold transfer film onto the second substrate to obtain the micro-nano structure anti-counterfeiting element.

2. The method for fabricating micro / nano structure anti-counterfeiting elements based on cold transfer technology according to claim 1, characterized in that, The holographic file generated by the hologram generation software for the binary image includes: The hologram generation software treats the image to be hidden as composed of multiple discrete points and calculates the complex amplitude distribution of each discrete point reaching the holographic surface. The complex amplitude distributions of each discrete point on the recording surface are superimposed according to the principle of light wave superposition to generate the holographic file.

3. The method for preparing micro / nano-structured anti-counterfeiting elements based on cold transfer technology according to claim 2, characterized in that, The step of treating the image to be hidden as composed of multiple discrete points and calculating the complex amplitude distribution of each discrete point reaching the holographic surface includes: The surface of the image to be hidden is discretized into a set of points, where each point on the surface is used as a separate point light source; Calculate the spherical waves emitted by each of the point light sources, and trace the path of the spherical waves to obtain the diffraction pattern of each point light source.

4. The method for preparing micro / nano-structured anti-counterfeiting elements based on cold transfer technology according to claim 2, characterized in that, The step of superimposing the complex amplitude distributions of each discrete point on the recording plane according to the principle of light wave superposition to generate the holographic file includes: Let the spatial coordinate system of the image to be hidden be OXYZ, and the spatial coordinate system of the holographic file's hologram plane be O′X′Y′Z′. The Z-axis of the two coordinate systems are on the same straight line, and the distance between the origins of the two coordinate systems is d. The coordinates of any point q in the binary image are (xi, yi, zi), and the coordinates of any point p on the holographic surface are (xp′, yp′, zp′). Then: The distance between point p and point q is: The complex amplitude of the light wave received at point p is: In the formula: j is the imaginary unit; wave number k = 2π / λ; λ is the wavelength of light; Aq is the amplitude of a point on the holographic plane; exp represents the exponential function, i.e., exp() = e(), e is the natural constant, e equals 2.

7. The image to be hidden is discretized into N point light sources. The superposition of the complex amplitudes of the light wave fields diffracted onto the holographic surface by each point light source is calculated using the above formula, resulting in the diffraction field Ud(xp′, yp′, zp′) of the image to be hidden. According to the Fresnel diffraction principle, the above formula simplifies to: Since the phase part of the above formula is used to fabricate the phase element, the formula is further simplified to: The diffraction field Ud(xp′, yp′, 0) is then superimposed with the reference light R(xp′, yp′, 0) to obtain the complex amplitude distribution Uh(xp′, yp′, 0) of the computational hologram. The reference light is a plane wave, and the complex amplitude distribution of the reference light is as follows: Uh(xp′,yp′,0)=Ud(xp′,yp′,0)+R(xp′,yp′,0) In the formula: A is the amplitude of the reference light; cosα and cosβ are the direction cosines of the plane wave propagation; α and β represent the angles between the parallel light and the X-axis and Y-axis, respectively; exp represents the exponential function, i.e., exp()=e(), e is the natural constant, e equals 2.

7. Calculate the complex amplitude distribution Uh(xp′, yp′, 0), and normalize its amplitude to map it to the range [0, 255] to obtain the holographic file of the image to be hidden.

5. The method for fabricating micro / nano structure anti-counterfeiting elements based on cold transfer technology according to claim 1, characterized in that, The process of acquiring the moiré invisible image and the moiré decoding grating of the image to be hidden includes: The information of the text to be hidden is decomposed into a pattern composed of multiple periodically arranged dots or lines to obtain the information layer text of the text to be hidden. The information layer graphics are set to be based on a fundamental frequency. Composed of dot or line arrays; Adjusting the spacing between the dot matrix or linear array allows the fundamental frequency to be adjusted. to frequency The moiré pattern hidden image is obtained; Adjust the frequency and angle of the information layer graphics in the moiré invisible graphics to a constant frequency. ,make ≈ The moiré decoding grating is obtained.

6. The method for fabricating micro / nano structure anti-counterfeiting elements based on cold transfer technology according to claim 5, characterized in that, Design parameters of the moiré decoding grating: The grating width of the moiré decoding grating Where H is the number of viewpoints and t is the width of a single pixel; Crown height of the moiré decoding grating The crown height h is 10 μm, achieved using nanoimprinting. The radius of curvature (G) and focal length (f) of the moiré decoding grating are: G = f * (n-1), where n is the refractive index of the material.

7. The method for fabricating micro / nano structure anti-counterfeiting elements based on cold transfer technology according to claim 1, characterized in that, The step of obtaining the grayscale height image and the rainbow laser image of the image to be hidden includes: Obtain a planar pattern containing the text and image to be hidden, drawn using vector software; The planar pattern is imported into 3D modeling software to create an embossed structure, resulting in the grayscale height map; The color image containing the text to be hidden is imported into optical design software. The line count of the color image is adjusted to 1500-3000 lines / mm, the angle is a multi-directional grating combination (15°, 45°, or 75°), and the depth is 0.1-0.3μm to obtain the rainbow laser image of the text to be hidden.

8. The method for fabricating micro / nano structure anti-counterfeiting elements based on cold transfer technology according to claim 1, characterized in that, The formulation for preparing the rainbow speckled ink includes: 20% ZnS quantum dots, 20% coumarin, 20% IR-806, 30% acrylic resin, 8% diluent, 0.5% leveling agent, 0.5% defoamer, 0.5% UV absorber, and 0.5% antioxidant.

9. The method for fabricating micro / nano structure anti-counterfeiting elements based on cold transfer technology according to claim 1, characterized in that, An embossing varnish is applied to the surface of the second substrate. The moiré decoding grating cold transfer film is then embossed onto the second substrate and cured. The third BOPP film is then peeled off, thus transferring the microstructure of the moiré decoding grating cold transfer film onto the second substrate, resulting in the micro / nano structure anti-counterfeiting element, comprising: An anilox roller is used to partially coat the second substrate with embossing varnish. The area coated with embossing varnish and the moiré decoding grating cold transfer film are then embossed with the second substrate and cured with UV. Peel off the third BOPP film to transfer the microstructure of the moiré decoding grating cold transfer film onto the second substrate, thereby obtaining the micro-nano structure anti-counterfeiting element; wherein the cells of the anilox roller are hexagonal cells with a depth of 15–20 μm and a cell opening ratio of 30–40%.

10. A micro / nano structure anti-counterfeiting element fabricated based on cold transfer technology, characterized in that, The anti-counterfeiting element is prepared using the method for preparing micro / nano structure anti-counterfeiting elements based on cold transfer technology as described in any one of claims 1-9.

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