Anti-counterfeiting label based on photonic crystal forward diffraction effect structural color and preparation method thereof

Abstract

The application provides a security label based on a photonic crystal forward diffraction effect structural color and a preparation method, the security label based on the photonic crystal forward diffraction effect structural color comprises a substrate layer and a security layer arranged on the substrate layer; the security layer comprises a first adhesive layer and a first photonic crystal layer, the first photonic crystal layer is pasted to the first adhesive layer and is located between the substrate layer and the first adhesive layer; the first photonic crystal layer comprises a single-layer two-dimensional photonic crystal arranged in a hexagonal lattice periodically, wherein the two-dimensional photonic crystal is polystyrene microspheres, and the particle size is 500nm-800nm. The application provides a security label based on a photonic crystal forward diffraction effect structural color, high-brightness and high-saturation structural colors generated by two-dimensional photonic crystal forward diffraction beams are used, and the security function of the apparent and hidden type is realized.

Description

Technical Field

[0001] This invention belongs to the field of anti-counterfeiting materials technology, specifically relating to an anti-counterfeiting label based on forward diffraction effect structural color. Background Technology

[0002] With the increasing prevalence of counterfeit products, developing cash anti-counterfeiting materials with physically unclonable functions has become an attractive anti-counterfeiting strategy. Among these, colloidal photonic crystals, with their optical bandgap in the visible light region, exhibit characteristics such as vibrant colors, high color saturation, and simple fabrication, making them a low-cost, difficult-to-clone, and rapidly responsive anti-counterfeiting material. In 2016, Ham et al. (Scientific Reports, Vol. 6, p. 30885) prepared a two-dimensional polystyrene (PS) microsphere array with a period of 500 nm using inkjet large initiation. They demonstrated and concealed structural colors under both illuminated and unilluminated conditions, achieving anti-counterfeiting applications on banknotes, reagent bottles, and other items. However, the generated structural colors were still not saturated or bright enough. In 2018, Wu's team (Nanoscale, Vol. 10, p. 14755) reported an anti-counterfeiting material in which uniform polystyrene particles self-assemble into a tightly packed three-dimensional face-centered cubic structure embedded in a PDMS polymer matrix. PC anti-counterfeiting patterns were prepared using a spray coating method, exhibiting different structural colors from different angles. Recently, Li et al. (Advanced Materials, Vol. 34, pp. 2107-243) proposed a quasi-three-dimensional photonic structure of a polarization-sensitive photonic crystal composite film (PCCF). This structure possesses full-space control of light, multi-path imaging, and multi-channel cryptography, enabling information methyl ether and anti-counterfeiting based on multi-dimensional control of viewing angle and polarization degree. Although many anti-counterfeiting materials are currently based on colloidal crystal structure colors, most are three-dimensional photonic crystal structures. The fabrication methods for three-dimensional photonic crystals are complex and difficult to maintain order, resulting in shortcomings in damage resistance and large-area fabrication. Furthermore, due to the strong scattering effect of multilayer structures, three-dimensional colloidal crystals are typically opaque. Existing two-dimensional photonic crystal anti-counterfeiting materials are relatively few, and they mainly generate structure colors through backdiffraction. Due to the weak scattering characteristic of the single-layer structure of two-dimensional photonic crystals, the intensity of backdiffraction light is often very weak, requiring a high-reflectivity substrate to present bright, highly saturated iridescent colors, or using a black background to improve the signal-to-noise ratio to display colors. This presents aesthetic and flexibility limitations in applications with high transparency and curved surfaces. Furthermore, the single-layer structure of two-dimensional photonic crystals has very weak adhesion to the substrate and is extremely unstable. Traditional two-dimensional photonic crystal structures have poor resistance to damage in practical applications.

[0003] Therefore, current two-dimensional photonic crystal anti-counterfeiting materials face a series of challenges. First, improving the everyday concealment, identifiability, and non-cloning properties of these materials is a crucial issue. Second, existing problems such as cumbersome preparation steps, poor device stability, and low security urgently need to be addressed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and provide an anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal. The label achieves both explicit and implicit anti-counterfeiting functions through the high brightness and high saturation structural color generated by the forward diffraction beam of a two-dimensional photonic crystal.

[0005] This invention is achieved through the following technical solution:

[0006] An anti-counterfeiting label based on the structural color of a photonic crystal forward diffraction effect includes a base layer and an anti-counterfeiting layer disposed on the base layer; the anti-counterfeiting layer includes a first adhesive layer and a first photonic crystal layer, the first photonic crystal layer being adhered to the first adhesive layer and located between the base layer and the first adhesive layer; the first photonic crystal layer includes a single-layer two-dimensional photonic crystal with a hexagonal lattice periodically arranged, wherein the two-dimensional photonic crystal is a polystyrene microsphere with a particle size of 500nm-800nm.

[0007] This invention provides an anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal. The first photonic crystal layer is formed by a single layer of two-dimensional photonic crystals arranged in a hexagonal lattice periodically, with the particle size controlled at 500nm-800nm ​​to maintain high transparency and high forward diffraction intensity. The high brightness and high saturation structural color generated by the forward diffraction beam of the two-dimensional photonic crystal realizes the visible and invisible anti-counterfeiting function. The first photonic crystal layer is encapsulated by attaching it to the substrate layer through a first adhesive layer, which is beneficial for attaching the anti-counterfeiting layer to a soft, curved surface or a hard surface.

[0008] Furthermore, the first adhesive layer is a pressure-sensitive transparent polyacrylic tape with a thickness of 40-50 μm. The use of a transparent and flexible pressure-sensitive polyacrylic tape facilitates the attachment of the first and second photonic crystal layers to complex surfaces.

[0009] Furthermore, the base layer is a transparent base layer. Using a transparent base, the anti-counterfeiting label appears colorless to the naked eye under natural light, achieving a visible yet invisible anti-counterfeiting function.

[0010] Furthermore, the first photonic crystal layer is a patterned single-layer two-dimensional photonic crystal. Through this patterned first photonic crystal layer, the pattern can be observed at specific angles during observation, improving the accuracy of anti-counterfeiting measures.

[0011] Furthermore, the first photonic crystal layer includes polystyrene microspheres with a particle size of 500nm-600nm; the anti-counterfeiting layer also includes a second adhesive layer and a second photonic crystal layer, the second adhesive layer is stacked on the first adhesive layer, the second photonic crystal layer is adhered to the second adhesive layer and located between the first adhesive layer and the second adhesive layer, and the position of the second photonic crystal layer corresponds to the position of the first photonic crystal layer; the second photonic crystal layer includes a single-layer two-dimensional photonic crystal arranged periodically in a hexagonal lattice, wherein the two-dimensional photonic crystal is polystyrene microspheres with a particle size of 700nm-800nm. The second photonic crystal layer is set on the first photonic crystal layer through the second adhesive layer. The angle with the lowest diffraction intensity in the second photonic crystal layer with a period of 700nm-800nm ​​coincides with the angle with the highest diffraction intensity in the first photonic crystal layer with a period of 500nm-600nm. The optical properties are enhanced by the non-closely packed combination of single-layer two-dimensional photonic crystals with different particle sizes. This overcomes the problem of structural color mixing and indistinguishability caused by the close packing of heterogeneous photonic crystals in the prior art. The matching of special sizes can achieve the effect of pattern decryption within a small angle range, which increases the difficulty of identifying and cloning anti-counterfeiting labels.

[0012] Furthermore, the area of ​​the second photonic crystal layer is not less than the area of ​​the first photonic crystal layer; the second adhesive layer is a polyacrylic pressure-sensitive transparent tape.

[0013] This invention also provides a method for preparing the above-mentioned anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal, comprising the following steps:

[0014] Polystyrene microspheres arranged periodically in a hexagonal lattice are prepared on a substrate. A first adhesive layer is attached to the surface of the polystyrene microspheres, and a monolayer of polystyrene microspheres is attached to one side of the first adhesive layer. The first adhesive layer is then peeled off to transfer the monolayer of polystyrene microspheres from the substrate to the first adhesive layer, resulting in a first adhesive layer with a monolayer of polystyrene attached. The side of the first adhesive layer with the monolayer of polystyrene microspheres is attached to a substrate layer, with the monolayer of polystyrene microspheres serving as the first photonic crystal layer located between the first adhesive layer and the substrate layer.

[0015] Furthermore, in the step of preparing polystyrene microspheres arranged periodically with a hexagonal lattice on a substrate, a monolayer polystyrene microsphere is prepared using a liquid-gas interface self-assembly method; the monolayer polystyrene microsphere is then transferred from the gas-liquid interface to the substrate. By preparing monolayer polystyrene microspheres using the liquid-gas interface self-assembly method and then transferring them to the substrate, monolayer polystyrene microspheres can be rapidly prepared.

[0016] This invention also provides a method for preparing the above-mentioned anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal, comprising the following steps:

[0017] Polystyrene microspheres arranged periodically in a hexagonal lattice are prepared on a substrate, wherein the particle size of the polystyrene microspheres is 500-600 nm; the polystyrene microspheres with a particle size of 500 nm-600 nm are patterned on the substrate; a first adhesive layer is attached to the surface of the polystyrene microspheres with a particle size of 500-600 nm, so that a monolayer of polystyrene microspheres with a particle size of 500-600 nm is attached to one side of the first adhesive layer; then the first adhesive layer is peeled off to transfer the monolayer polystyrene microspheres with a particle size of 500-600 nm from the substrate to the first adhesive layer, resulting in a first adhesive layer with monolayer polystyrene microspheres with a particle size of 500-600 nm attached.

[0018] Polystyrene microspheres arranged periodically in a hexagonal lattice are prepared on a substrate, wherein the particle size of the polystyrene microspheres is 700nm-800nm. A second adhesive layer is attached to the surface of the polystyrene microspheres with a particle size of 700nm-800nm, so that a monolayer of polystyrene microspheres with a particle size of 700nm-800nm ​​is attached to one side of the second adhesive layer. Then, the second adhesive layer is peeled off to transfer the monolayer polystyrene microspheres with a particle size of 700nm-800nm ​​from the substrate to the second adhesive layer, resulting in a second adhesive layer with monolayer polystyrene microspheres with a particle size of 700nm-800nm ​​attached.

[0019] One side of the second adhesive layer, to which monolayer polystyrene microspheres with a particle size of 700nm-800nm ​​are attached, is attached to the first adhesive layer. The monolayer polystyrene microspheres with a particle size of 700nm-800nm ​​serve as the second photonic crystal layer, located between the first and second adhesive layers.

[0020] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal, as described in Example 1.

[0022] Figure 2 This is a scanning electron microscope image of a two-dimensional photonic crystal with a period of 600 nm from Example 1.

[0023] Figure 3 This is a schematic diagram of the back-diffraction beam of the anti-counterfeiting label in Example 1.

[0024] Figure 4 This is a schematic diagram of the forward diffraction beam of the anti-counterfeiting label in Example 1.

[0025] Figure 5 This is a comparison diagram of the forward and backward diffraction of the anti-counterfeiting label in Example 1.

[0026] Figure 6 This is a flowchart of Example 2 for preparing anti-counterfeiting labels based on the structural color of photonic crystal forward diffraction effect.

[0027] Figure 7 This is a schematic diagram of the anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal, as described in Example 3.

[0028] Figure 8 This is the forward diffraction spectrum of the first and second photonic crystal layers in Example 3.

[0029] Figure 9 These are observation images of the anti-counterfeiting label based on the structural color of the photonic crystal forward diffraction effect in Example 3, taken at different angles.

[0030] Figure 10 This is a flowchart of Example 4 for preparing anti-counterfeiting labels based on the structural color of photonic crystal forward diffraction effect.

[0031] Figure 11 This is a scanning electron microscope image of a two-dimensional photonic crystal with a period of 800 nm, as described in Example 4. Detailed Implementation

[0032] This invention provides an anti-counterfeiting label based on the structural color of a photonic crystal forward diffraction effect, comprising a base layer and an anti-counterfeiting layer disposed on the base layer; the anti-counterfeiting layer comprises a first adhesive layer and a first photonic crystal layer, wherein the first photonic crystal layer is adhered to the first adhesive layer and is located between the base layer and the first adhesive layer; the first photonic crystal layer comprises a single-layer two-dimensional photonic crystal with a hexagonal lattice periodically arranged, wherein the two-dimensional photonic crystal is a polystyrene microsphere with a particle size of 500nm-800nm.

[0033] In the anti-counterfeiting label based on the forward diffraction effect of photonic crystals provided in this embodiment of the invention, the first photonic crystal layer is formed by a single layer of two-dimensional photonic crystals arranged in a hexagonal lattice periodically, with the particle size controlled at 500nm-800nm ​​to maintain high transparency and high forward diffraction intensity. The high brightness and high saturation structural color generated by the forward diffraction beam of the two-dimensional photonic crystal realizes the visible and invisible anti-counterfeiting function. The first photonic crystal layer is encapsulated by attaching it to the substrate layer through the first adhesive layer, which is beneficial for attaching the anti-counterfeiting layer to a soft, curved surface or a hard surface.

[0034] In this embodiment of the invention, the first photonic crystal layer is a patterned single-layer two-dimensional photonic crystal. Through the patterned first photonic crystal layer, the pattern can be observed at a specific angle during observation, thus improving the accuracy of anti-counterfeiting measures.

[0035] In this embodiment of the invention, the first photonic crystal layer includes polystyrene microspheres with a particle size of 500nm-600nm; the anti-counterfeiting layer further includes a second adhesive layer and a second photonic crystal layer, the second adhesive layer being stacked on the first adhesive layer, and the second photonic crystal layer being adhered to the second adhesive layer and located between the first and second adhesive layers, with the position of the second photonic crystal layer corresponding to the position of the first photonic crystal layer; the second photonic crystal layer...

[0036] The crystal layer comprises a single-layer two-dimensional photonic crystal arranged periodically in a hexagonal lattice, wherein the two-dimensional photonic crystal is polystyrene microspheres with a particle size of 800 nm. A second photonic crystal layer is disposed on the first photonic crystal layer through a second adhesive layer. The angle with the lowest diffraction intensity in the second photonic crystal layer with a period of 800 nm coincides with the angle with the highest diffraction intensity in the first photonic crystal layer with a period of 500 nm-600 nm. The non-close-packing combination of single-layer two-dimensional photonic crystals with different particle sizes enhances the optical properties, overcoming the problem of structural color mixing and indistinguishability caused by the close-packing of heterogeneous photonic crystals in existing technologies. The matching of special dimensions can achieve the effect of pattern decryption within a small angle range, increasing the difficulty of identification and cloning of anti-counterfeiting labels.

[0037] In this embodiment of the invention, the first adhesive layer and the second adhesive layer are polyacrylic pressure-sensitive transparent tape. The use of transparent and flexible polyacrylic pressure-sensitive transparent tape facilitates the attachment of the first and second photonic crystal layers to complex surfaces. Specifically, the thickness of the first and second adhesive layers is 40-50 μm.

[0038] The area of ​​the first adhesive layer is larger than the area of ​​the first photonic crystal layer, and the area of ​​the second adhesive layer is larger than the area of ​​the second photonic crystal layer.

[0039] In this embodiment of the invention, the base layer is a transparent base layer. Using a transparent base, the anti-counterfeiting label appears colorless to the naked eye.

[0040] This invention also provides a method for preparing the above-mentioned anti-counterfeiting label based on the forward diffraction effect structure color of a photonic crystal, comprising the following steps: preparing polystyrene microspheres arranged periodically in a hexagonal lattice on a substrate; attaching a first adhesive layer to the surface of the polystyrene microspheres, attaching a monolayer of polystyrene microspheres to one side of the first adhesive layer, and then peeling off the first adhesive layer to transfer the monolayer of polystyrene microspheres from the substrate to the first adhesive layer, thereby obtaining a first adhesive layer with a monolayer of polystyrene microspheres attached; attaching the side of the first adhesive layer with the monolayer of polystyrene microspheres attached to a substrate layer, wherein the monolayer of polystyrene microspheres serve as a first photonic crystal layer located between the first adhesive layer and the substrate layer.

[0041] In the step of preparing polystyrene microspheres arranged in a hexagonal lattice on a substrate, a monolayer polystyrene microsphere with a hexagonal lattice periodic arrangement is prepared using a liquid-gas interface self-assembly method; the monolayer polystyrene microspheres are then transferred from the gas-liquid interface to the substrate. By preparing monolayer polystyrene microspheres using the liquid-gas interface self-assembly method and then transferring them to the substrate, monolayer polystyrene microspheres can be rapidly prepared.

[0042] This invention also provides a method for preparing the above-mentioned anti-counterfeiting label based on the forward diffraction effect structure color of a photonic crystal, comprising the following steps: preparing polystyrene microspheres arranged periodically in a hexagonal lattice on a substrate, wherein the particle size of the polystyrene microspheres is 500-600 nm; adhering a first adhesive layer to the surface of the polystyrene microspheres with a particle size of 500-600 nm, so that a single layer of polystyrene microspheres with a particle size of 500-600 nm is adhered to one side of the first adhesive layer; and then peeling off the first adhesive layer to transfer the single layer of polystyrene microspheres with a particle size of 500-600 nm from the substrate to the first adhesive layer. A first adhesive layer with monolayer polystyrene microspheres with a particle size of 500-600 nm was obtained; polystyrene microspheres with a hexagonal lattice periodically arranged on a substrate were prepared, wherein the polystyrene microspheres had a particle size of 800 nm; a second adhesive layer was attached to the surface of the polystyrene microspheres with a particle size of 800 nm, so that one side of the second adhesive layer was attached with monolayer polystyrene microspheres with a particle size of 800 nm; then the second adhesive layer was peeled off to transfer the monolayer polystyrene microspheres with a particle size of 800 nm from the substrate to the second adhesive layer, thus obtaining a second adhesive layer with monolayer polystyrene microspheres with a particle size of 800 nm attached.

[0043] One side of the second adhesive layer, to which monolayer polystyrene microspheres with a particle size of 800 nm are attached, is attached to the first adhesive layer. The monolayer polystyrene microspheres with a particle size of 800 nm serve as the second photonic crystal layer, located between the first and second adhesive layers.

[0044] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the embodiments of the present invention, and not all structures.

[0045] Furthermore, the terms "first," "second," "third," etc., used in the specification and claims are only for the purpose of distinguishing the description of the same technical features and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated, nor necessarily the order of description or chronological sequence. Where appropriate, the terms are interchangeable. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0046] Similarly, the terms "fixed" and "connected" are used in the specification and claims and should not be construed as limited to a direct connection. Therefore, the expression "device A is connected to device B" should not be limited to device A being directly connected to device B in a device or system; it means that there is a path between device A and device B, which can be a path that includes other devices or tools.

[0047] Example 1

[0048] This embodiment provides an anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals. Figure 1 This is a schematic diagram of the structure of an anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals. Please refer to [link / reference]. Figure 1 The anti-counterfeiting label based on the forward diffraction effect structure color of photonic crystal includes a base layer 1 and an anti-counterfeiting layer disposed on the base layer 1; the anti-counterfeiting layer includes a first adhesive layer 3 and a first photonic crystal layer 2, the first photonic crystal layer 2 is attached to the first adhesive layer 3 and is located between the base layer 1 and the first adhesive layer 3; the first photonic crystal layer 2 includes a single-layer two-dimensional photonic crystal with a hexagonal lattice periodically arranged, wherein the two-dimensional photonic crystal is a polystyrene microsphere with a particle size of 500nm-800nm.

[0049] This embodiment provides an anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals. The first photonic crystal layer 2 is formed by a single layer of two-dimensional photonic crystals arranged in a hexagonal lattice periodically, with the particle size controlled at 500nm-800nm ​​to maintain high transparency and high forward diffraction intensity. The high brightness and high saturation structural color generated by the forward diffraction beam of the two-dimensional photonic crystal realizes the hidden anti-counterfeiting function. The first photonic crystal layer 2 is encapsulated by attaching it to the base layer 1 through the first adhesive layer 3, which is beneficial for attaching the anti-counterfeiting layer to a soft, curved surface or a hard surface.

[0050] Figure 2 This is a scanning electron microscope image of a two-dimensional photonic crystal with a period of 600 nm. Please refer to [link / reference]. Figure 2 In this embodiment, the polystyrene microspheres have a particle size of 500nm-600nm, maintaining high transparency and high forward diffraction intensity.

[0051] In this embodiment, the first photonic crystal layer 2 is a patterned single-layer two-dimensional photonic crystal. Through the patterned first photonic crystal layer 2, the pattern can be observed at a specific angle during observation, thus improving the accuracy of anti-counterfeiting measures.

[0052] In this embodiment, the first adhesive layer 3 is a polyacrylic pressure-sensitive transparent tape with a thickness of 40-50 μm. The polyacrylic pressure-sensitive tape solves the problem of two-dimensional photonic crystals being difficult to adhere to the surface, and by controlling the appropriate thickness, it achieves an invisible effect under natural light. Due to the use of polyacrylic pressure-sensitive transparent tape for encapsulation, the single-layer polystyrene microsphere structure exhibits strong adhesion and stability on the substrate layer 1. The anti-counterfeiting label is suitable for environments with mechanical abrasion and humidity, demonstrating ultra-high stability.

[0053] In this embodiment, the substrate layer 1 is a transparent substrate layer. In one implementation, the substrate layer 2 can be selected from, but is not limited to, silicon dioxide, transparent glass, and transparent plastic, with a thickness of 0.15-3 mm. The anti-counterfeiting label based on the structural color of the photonic crystal forward diffraction effect in this embodiment does not require a high-reflectivity substrate or a black background. The structural color can be displayed on the transparent substrate layer 1, while appearing transparent and colorless under natural light, making it suitable for applications with high transparency and curved surfaces.

[0054] The anti-counterfeiting label based on the forward diffraction effect of photonic crystals in this embodiment can exhibit the structural color of a two-dimensional photonic crystal when observed under emitted light at a specific angle. The diffraction wavelength is determined by the lattice constant of the periodic structure, the incident light angle, and the diffraction angle. Based on the Mie scattering effect of particles, the forward diffraction intensity of the anti-counterfeiting label in this embodiment is greater than the backward diffraction intensity.

[0055] In this embodiment, the structural color of the anti-counterfeiting label is achieved based on the forward diffraction beam 8 of a single layer of polystyrene microspheres arranged in a hexagonal lattice periodically.

[0056] Figure 3 This is a schematic diagram of the observation of the back diffraction beam of the anti-counterfeiting label. Figure 4 This is a schematic diagram of the forward diffraction beam of the anti-counterfeiting label in Example 1. Figure 5 This is a comparison diagram of the forward and backward diffraction patterns of the anti-counterfeiting label. Please refer to [link / reference]. Figure 3-5A white light source is placed on the side of the base layer 1 facing away from the anti-counterfeiting layer. An observer looks at the side of the base layer 1 closest to the anti-counterfeiting layer; it appears transparent in the absence of a light source. The anti-counterfeiting layer of the label is illuminated by a white light source at an incident angle of 30°, with a straight-line distance greater than 40cm between the white light source and the label. The observation angle of the back diffracted beam 7 is selected between 10° and 70°, the observation angle is on the same side as the white light source, and the observation distance is greater than 30cm. When observing the back diffracted beam 7, under the illumination of the white light beam 6 emitted by the white light source, a pattern can be observed, but it is blurry. Similarly, the observation angle of the forward diffracted beam 8 is selected between 10° and 70°, the observation angle is on the opposite side of the white light source, and the observation distance is greater than 30cm. Under the illumination of the white light beam 6 emitted by the white light source, a clear pattern can be observed, and the intensity of the forward diffracted beam 8 is significantly greater than that of the back diffracted beam 7. The anti-counterfeiting label provided in this embodiment is transparent under natural light. Under white light, it produces structural color through forward diffraction. The structural color is bright and saturated, and its intensity is much greater than that of backward diffraction, thus achieving visible-implicit anti-counterfeiting.

[0057] Example 2

[0058] This embodiment provides a method for preparing the anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal as described in Example 1. Figure 6 This is a flowchart of the preparation of the forward diffraction anti-counterfeiting label in Example 2. Please refer to [link / reference]. Figure 6 The method for preparing anti-counterfeiting labels based on the structural colors of photonic crystal forward diffraction effects includes the following steps:

[0059] Step S1: Prepare polystyrene microspheres arranged periodically in a hexagonal lattice on a substrate:

[0060] In this embodiment, a hexagonal lattice periodically arranged monolayer polystyrene microsphere is prepared using a liquid-gas interface self-assembly method, and then the monolayer polystyrene microsphere is transferred from the gas-liquid interface to a substrate. The specific operation is as follows:

[0061] S11: Dimensions of 3*3cm 2 After cleaning, the silicon wafer was treated with low-temperature plasma for 60 seconds to make it hydrophilic. A long glass slide (5*20cm) was partially immersed in a glass container containing 200mL of ultrapure water (400mL capacity). To reduce the surface tension gradient effect, 10μL of 10%wt SDS solution was pre-injected at the gas-liquid interface.

[0062] S12: Prepare a mixture of polystyrene microsphere nanosuspension and ethanol at a volume ratio of 1:2 to form a mixed nanosphere suspension, wherein the mass fraction of polystyrene microspheres in the polystyrene microsphere nanosuspension is 5 wt%. Different particle size specifications of polystyrene microsphere nanosuspensions are selected according to the required particle size. To ensure uniformity, the mixed nanosphere suspension is ultrasonically treated for 30 seconds. In this embodiment, 1 mL of polystyrene microsphere nanosuspension is mixed with 2 mL of ethanol to form 3 mL of mixed nanosphere suspension.

[0063] S13: Inject the mixed nanosphere suspension into the ultrapure water surface in S11 using a syringe at a rate of 0.4 μL / s. Guide the mixed nanosphere suspension to flow uniformly and continuously toward the gas-liquid interface with a glass slide at a constant tilt angle of approximately 60°. After reaching the water surface boundary, the mixed nanosphere suspension forms a hemispherical low-pressure zone and slides along the direction of the high-pressure zone, thereby gradually self-assembling into a monolayer polystyrene microsphere structure at the gas-liquid interface. After assembly, gently remove the long glass slide and let it stand for five minutes. Once there is no obvious movement or cracking, the monolayer polystyrene microsphere structure can be transferred to the substrate.

[0064] S14: Place the pretreated silicon wafer on the lifting device using tweezers and lower it at a uniform speed until it is completely immersed in the water from S13, while avoiding contact with the monolayer polystyrene microsphere structure. Adjust the position of the silicon wafer to ensure alignment between the monolayer polystyrene microsphere structure and the silicon wafer. Slowly lift the silicon wafer upward using the lifting device until it contacts the monolayer polystyrene microsphere structure, thereby transferring the monolayer polystyrene microspheres onto the silicon wafer. After the transfer is complete, remove the silicon wafer, air dry it at room temperature for 1 hour, and store it in a petri dish for later use.

[0065] Step S2: The first adhesive layer 3 is adhered to the surface of the polystyrene microspheres. A monolayer of polystyrene microspheres is then adhered to one side of the first adhesive layer 3. The first adhesive layer 3 is then peeled off to transfer the monolayer of polystyrene microspheres from the substrate to the first adhesive layer 3, resulting in a first adhesive layer 3 with a monolayer of polystyrene microspheres adhered to it. The specific operation is as follows:

[0066] The first adhesive layer 3 is placed on the monolayer polystyrene microspheres. In this embodiment, the first adhesive layer 3 is a polyacrylic pressure-sensitive transparent tape. Since the bonding force between the monolayer polystyrene microspheres and the hydrophilic silicon wafer and the hydrophobic substrate is relatively weak, when a certain pressure is applied to the polyacrylic pressure-sensitive transparent tape to press it onto the monolayer polystyrene microspheres, the monolayer polystyrene microspheres can be peeled off from the silicon wafer, so that the monolayer polystyrene microspheres are attached to the first adhesive layer 3, thus obtaining the first adhesive layer 3 with the monolayer polystyrene microspheres attached.

[0067] Step S3: Adhere the side of the first adhesive layer 3 with the monolayer polystyrene microspheres to the substrate layer 1. The monolayer polystyrene microspheres serve as the first photonic crystal layer 2, located between the first adhesive layer 3 and the substrate layer 1, to obtain an anti-counterfeiting label based on the structural color of the photonic crystal forward diffraction effect.

[0068] The first photonic crystal layer 2 can be firmly attached to the flexible or curved substrate layer 1 using the first adhesive layer 3. In this embodiment, the substrate layer 1 can be any of metal, glass or plastic.

[0069] In this embodiment, the first photonic crystal layer can be a patterned monolayer polystyrene microsphere or an unpatterned monolayer polystyrene microsphere. If the first photonic crystal layer uses patterned monolayer polystyrene microspheres, after transferring the monolayer polystyrene microspheres onto the substrate in step S14, a patterned perforated template sticker is used to attach the monolayer polystyrene microspheres, leaving the patterned monolayer polystyrene microspheres. If a clear pattern is observed under incident light, it indicates the presence of an anti-counterfeiting label. If the first photonic crystal layer uses unpatterned monolayer polystyrene microspheres, and the structural color of the first photonic crystal layer is observed under incident light, it indicates the presence of an anti-counterfeiting label.

[0070] Example 3

[0071] This embodiment provides an anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals. Figure 7 This is a schematic diagram of the structure of an anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals. Please refer to [link / reference]. Figure 7 The anti-counterfeiting label based on the forward diffraction effect structure color of photonic crystal in this embodiment includes a base layer 1 and an anti-counterfeiting layer disposed on the base layer 1; the anti-counterfeiting layer includes a first adhesive layer 3, a first photonic crystal layer 2, a second adhesive layer 5, and a second photonic crystal layer 4;

[0072] The first photonic crystal layer 2 is adhered to the first adhesive layer 3, and the first photonic crystal layer 2 is adhered to the substrate layer 1 through the first adhesive layer, and the first photonic crystal layer 2 is located between the first adhesive layer 3 and the substrate layer 1; the first photonic crystal layer 2 includes a patterned single-layer two-dimensional photonic crystal arranged periodically in a hexagonal lattice, and the two-dimensional photonic crystal is a polystyrene microsphere with a particle size of 500-600 nm;

[0073] The second adhesive layer 5 is stacked on the first adhesive layer 3, and the second photonic crystal layer 4 is attached to the second adhesive layer 5 and located between the first adhesive layer 3 and the second adhesive layer 5. The position of the second photonic crystal layer 4 corresponds to the position of the first photonic crystal layer 2. The second photonic crystal layer 4 includes a single-layer two-dimensional photonic crystal arranged periodically in a hexagonal lattice. The two-dimensional photonic crystal is a polystyrene microsphere with a particle size of 700-800 nm.

[0074] In the anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals provided in this embodiment, the first photonic crystal layer 2 is formed by a single layer of two-dimensional photonic crystals arranged in a hexagonal lattice periodically, with a controlled particle size of 500-600nm. The second photonic crystal layer 4 is set on the first photonic crystal layer 2 through a second adhesive layer 5, so that the angle with the lowest diffraction intensity in the second photonic crystal layer 4 with a period of 700-800nm ​​coincides with the angle with the highest diffraction intensity in the first photonic crystal layer 2 with a period of 500nm-600nm. The optical properties are enhanced by the non-closely packed combination of single-layer two-dimensional photonic crystals with different particle sizes, which overcomes the problem of structural color mixing and difficulty in distinguishing caused by the close packing of heterogeneous photonic crystals in the prior art. The matching of special sizes can achieve the effect of pattern decryption within a small angle range, increasing the difficulty of identification and cloning of anti-counterfeiting labels.

[0075] In this embodiment, the area of ​​the second photonic crystal layer 4 is not less than the area of ​​the first photonic crystal layer 2, and their positions correspond to each other, so that the second photonic crystal layer 4 covers the first photonic crystal layer 2.

[0076] The second adhesive layer 5 is a polyacrylic pressure-sensitive transparent tape with a thickness of 40-50μm.

[0077] The anti-counterfeiting label based on the forward diffraction effect of photonic crystals in this embodiment achieves small-angle anti-counterfeiting by matching the diffraction intensity through a double-layer photonic crystal structure. When the incident light angle is controlled between 10° and 50°, the pattern of the first photonic crystal layer 2 can be observed, proving the existence of the anti-counterfeiting label.

[0078] Figure 8 These are the forward diffraction spectra of the first photonic crystal layer 2 and the second photonic crystal layer 4 in Example 3. Please refer to [link / reference]. Figure 8 When the incident light angle is 30°, at an observation angle of approximately 45°, the second photonic crystal layer 4 of the upper layer with a particle size of 800nm ​​is between first-order and second-order diffraction, and its diffraction intensity is the weakest. Among the polystyrene microspheres with a particle size of 600nm, the light intensity is the greatest at a wavelength of 500nm and an observation angle of 45°, and the corresponding structural color is green light. The first photonic crystal layer 2 of the lower layer is in first-order diffraction, and its diffraction intensity is the strongest. Therefore, when observed at a 45° angle, when the color of the second photonic crystal layer 4 of the upper layer disappears, the color of the first photonic crystal layer 2 of the lower layer appears. Since the first photonic crystal layer 2 is patterned, the presence of an anti-counterfeiting label can be proven when the pattern is observed.

[0079] Figure 9This is an observation image of an anti-counterfeiting label based on the forward diffraction effect of photonic crystals at different angles. The first photonic crystal layer 2 is a single layer of polystyrene microspheres with a diameter of 600 nm arranged in a hexagonal lattice periodic arrangement. The second photonic crystal layer 4 is a single layer of polystyrene microspheres with a diameter of 800 nm arranged in a hexagonal lattice periodic arrangement. A white light beam 6 emitted by a white light source is incident at a 30° angle away from the normal of the anti-counterfeiting layer surface of the label. Within the range of 10°-60°, by changing the observation angle of the forward diffraction beam, it is found that the encrypted pattern "SCNU" is fully visible at an angle of 40°-45°, while other angles are completely or partially blocked. The weakest forward diffraction beam of the upper second photonic crystal layer 4 coincides with the strongest diffraction beam of the lower first photonic crystal layer 2 at about 45°, achieving the effect of small-angle anti-counterfeiting.

[0080] Example 4

[0081] This embodiment provides a method for preparing the anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal, as described in Example 3. Figure 10 This is a flowchart of the anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals in this embodiment. Please refer to [link / reference]. Figure 10 The method for preparing anti-counterfeiting labels based on the structural colors of photonic crystal forward diffraction effects includes the following steps:

[0082] Step S1: Prepare polystyrene microspheres arranged periodically in a hexagonal lattice on a substrate, wherein the polystyrene microspheres have a particle size of 500-600 nm; pattern the polystyrene microspheres with a particle size of 500 nm-600 nm on the substrate. Referring to the operations of steps S11-S14 in Example 1, prepare monolayer polystyrene microspheres with a particle size of 500-600 nm using a liquid-gas phase self-assembly method, and transfer them to a silicon wafer to obtain polystyrene microspheres with a particle size of 500-600 nm arranged periodically in a hexagonal lattice on the substrate; after transferring the monolayer polystyrene microspheres to the substrate, attach the monolayer polystyrene microspheres with a patterned hollow template sticker, leaving the patterned monolayer polystyrene microspheres, to obtain patterned monolayer polystyrene microspheres with a particle size of 500-600 nm.

[0083] Step S2: The first adhesive layer 3 is adhered to the surface of polystyrene microspheres with a particle size of 500-600nm, so that one side of the first adhesive layer 3 is adhered with a single layer of polystyrene microspheres with a particle size of 500-600nm. Then, the first adhesive layer 3 is peeled off to transfer the single layer of polystyrene microspheres with a particle size of 500-600nm from the substrate to the first adhesive layer 3, thus obtaining the first adhesive layer 3 with the single layer of polystyrene microspheres with a particle size of 500-600nm adhered.

[0084] Figure 2This is a scanning electron microscope image of a two-dimensional photonic crystal with a period of 600 nm. Please refer to [link / reference]. Figure 2 The monolayer polystyrene microspheres with a particle size of 600 nm are arranged periodically in a hexagonal lattice.

[0085] In this embodiment, the first adhesive layer 3 is a polyacrylic pressure-sensitive transparent tape.

[0086] Step S3: The side of the first adhesive layer 3 with monolayer polystyrene microspheres with a particle size of 500-600nm is attached to the substrate layer 1. The monolayer polystyrene microspheres with a particle size of 500-600nm serve as the first photonic crystal layer 2, located between the first adhesive layer 3 and the substrate layer 1.

[0087] Step S4: Prepare polystyrene microspheres arranged periodically in a hexagonal lattice on a substrate, wherein the polystyrene microspheres have a particle size of 800 nm. Referring to the operations of steps S11-S14 in Example 1, prepare monolayer polystyrene microspheres with a particle size of 800 nm using a liquid-gas phase self-assembly method, and transfer them onto a silicon wafer to obtain polystyrene microspheres with a particle size of 800 nm arranged periodically in a hexagonal lattice on a substrate. Figure 11 This is a scanning electron microscope image of a two-dimensional photonic crystal with a period of 800 nm. Please refer to [link / reference]. Figure 11 The monolayer polystyrene microspheres with a particle size of 800 nm are arranged periodically in a hexagonal lattice.

[0088] Step S5: The second adhesive layer 5 is adhered to the surface of polystyrene microspheres with a particle size of 800 nm, so that one side of the second adhesive layer 5 is covered with a single layer of polystyrene microspheres with a particle size of 800 nm. Then, the second adhesive layer 5 is peeled off, transferring the single layer of polystyrene microspheres with a particle size of 800 nm from the substrate to the second adhesive layer 5, resulting in a second adhesive layer 5 with single layer polystyrene microspheres with a particle size of 800 nm adhered to it. In this embodiment, the second adhesive layer 5 is a polyacrylic pressure-sensitive transparent tape.

[0089] Step S6: Adhere the side of the second adhesive layer 5 with monolayer polystyrene microspheres with a particle size of 700-800nm ​​to the first adhesive layer 3. The monolayer polystyrene microspheres with a particle size of 700-800nm ​​serve as the second photonic crystal layer 4, located between the first adhesive layer 3 and the second adhesive layer 5, to obtain an anti-counterfeiting label based on the structural color of the photonic crystal forward diffraction effect.

[0090] Example 5

[0091] This embodiment provides an anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals. Its structure is similar to that of Embodiment 3, with the main difference being that the particle size of the monolayer polystyrene microspheres in the first photonic crystal layer 2 is 500 nm, and the particle size of the monolayer polystyrene microspheres in the second photonic crystal layer 4 is 700 nm. By controlling the non-close packing of the two photonic crystal layers to enhance optical properties, the angle at which the diffraction intensity of the second photonic crystal layer 4 (particle size 700 nm) is lowest coincides with the angle at which the diffraction intensity of the first photonic crystal layer 2 (particle size 500 nm) is highest, achieving the effect of pattern decryption within a small angle.

[0092] Example 6

[0093] This embodiment provides an anti-counterfeiting label based on the structural color of the forward diffraction effect of photonic crystals. Its structure is similar to that of Embodiment 3, with the main difference being that the particle size of the monolayer polystyrene microspheres in the first photonic crystal layer 2 is 600 nm, and the particle size of the monolayer polystyrene microspheres in the second photonic crystal layer 4 is 800 nm. By controlling the non-close packing of the two photonic crystal layers to enhance optical properties, the angle at which the diffraction intensity of the second photonic crystal layer 4 with a particle size of 800 nm is lowest coincides with the angle at which the diffraction intensity of the first photonic crystal layer 2 with a particle size of 600 nm is highest, achieving the effect of pattern decryption within a small angle.

[0094] This invention is not limited to the above-described embodiments. If any modifications or variations to this invention do not depart from the spirit and scope of this invention, and if such modifications and variations fall within the scope of the claims and equivalent technologies of this invention, then this invention also intends to include such modifications and variations.

Claims

1. A type of anti-counterfeiting label based on structural colors of photonic crystal forward diffraction effect, characterized in that: Includes a base layer and an anti-counterfeiting layer disposed on the base layer; The anti-counterfeiting layer includes a first adhesive layer, a first photonic crystal layer, a second adhesive layer, and a second photonic crystal layer; The first photonic crystal layer is bonded to the first adhesive layer and is located between the substrate layer and the first adhesive layer; The first photonic crystal layer is a patterned monolayer two-dimensional photonic crystal; the first photonic crystal layer includes a monolayer two-dimensional photonic crystal arranged periodically in a hexagonal lattice, wherein the two-dimensional photonic crystal is a polystyrene microsphere with a particle size of 500nm-600nm; The second adhesive layer is stacked on the first adhesive layer, and the second photonic crystal layer is attached to the second adhesive layer and located between the first adhesive layer and the second adhesive layer. The position of the second photonic crystal layer corresponds to the position of the first photonic crystal layer. The second photonic crystal layer includes a single-layer two-dimensional photonic crystal arranged periodically in a hexagonal lattice, wherein the two-dimensional photonic crystal is polystyrene microspheres with a particle size of 700nm-800nm; The angle with the lowest diffraction intensity in the second photonic crystal layer with a period of 700-800nm ​​coincides with the angle with the highest diffraction intensity in the first photonic crystal layer with a period of 500nm-600nm.

2. The anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal according to claim 1, characterized in that: The first adhesive layer is a pressure-sensitive transparent polyacrylic tape with a thickness of 40-50μm.

3. The anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal according to claim 1, characterized in that: The base layer is a transparent base layer.

4. The anti-counterfeiting label based on the structural color of the forward diffraction effect of a photonic crystal according to claim 1, characterized in that: The area of ​​the second photonic crystal layer is not less than the area of ​​the first photonic crystal layer; The second adhesive layer is a pressure-sensitive transparent polyacrylic tape.

5. A method for preparing an anti-counterfeiting label based on the structural color of a photonic crystal forward diffraction effect as described in any one of claims 1-4, characterized in that, Includes the following steps: Polystyrene microspheres arranged in a hexagonal lattice periodically on a substrate were prepared, wherein the particle size of the polystyrene microspheres was 500-600 nm. Patterning polystyrene microspheres with a particle size of 500nm-600nm on a substrate; The first adhesive layer is adhered to the surface of polystyrene microspheres with a particle size of 500-600nm, so that one side of the first adhesive layer is adhered with a single layer of polystyrene microspheres with a particle size of 500-600nm. Then the first adhesive layer is peeled off to transfer the single layer of polystyrene microspheres with a particle size of 500-600nm from the substrate to the first adhesive layer, resulting in a first adhesive layer with a single layer of polystyrene microspheres with a particle size of 500-600nm adhered to it. The first adhesive layer with monolayer polystyrene microspheres with a particle size of 500-600nm attached to it is attached to the substrate layer. The monolayer polystyrene microspheres with a particle size of 500-600nm serve as the first photonic crystal layer, located between the first adhesive layer and the substrate layer. Polystyrene microspheres arranged in a hexagonal lattice periodically on a substrate were prepared, wherein the polystyrene microspheres had a particle size of 800 nm. The second adhesive layer is attached to the surface of polystyrene microspheres with a particle size of 700nm-800nm, so that one side of the second adhesive layer is attached with a single layer of polystyrene microspheres with a particle size of 700nm-800nm. Then the second adhesive layer is peeled off to transfer the single layer of polystyrene microspheres with a particle size of 700nm-800nm ​​from the substrate to the second adhesive layer, resulting in a second adhesive layer with a single layer of polystyrene microspheres with a particle size of 700nm-800nm ​​attached. One side of the second adhesive layer, to which monolayer polystyrene microspheres with a particle size of 700nm-800nm ​​are attached, is attached to the first adhesive layer. The monolayer polystyrene microspheres with a particle size of 700nm-800nm ​​serve as the second photonic crystal layer, located between the first and second adhesive layers.

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