Wetting response structural color anti-counterfeiting film based on planar defect layer and preparation method thereof

Abstract

The present invention relates to a wetting response structural color anti-counterfeiting film based on a planar defect layer and a preparation method thereof, belonging to the technical field of structural color films, wherein the anti-counterfeiting film comprises an anti-opal film that changes color in response to wetting and an anti-opal film containing planar defects; the preparation method comprises preparing an anti-opal film containing planar defects at the bottom layer of the anti-counterfeiting film; preparing an anti-opal film that changes color in response to wetting at the top layer of a composite anti-counterfeiting film; fixing the anti-opal film that changes color in response to wetting on the anti-opal film containing planar defects with an uncured filling material to obtain a double-layer composite anti-counterfeiting film with a wetting response structural color based on a planar defect layer. The anti-counterfeiting film of the present invention is easy to replicate, has good repeatability and color durability, is environmentally friendly, and has great advantages and potential in the preparation and application fields of anti-counterfeiting labels.

Description

Technical Field

[0001] The invention relates to a wetting response structural color anti-counterfeiting film based on a planar defect layer and a preparation method thereof, belonging to the technical field of structural color films. Background Art

[0002] In daily industrial production, chemical dyes are often used to dye handicrafts. This kind of color is called chemical color. The chemical color dyeing process is cumbersome and energy-intensive, and it will produce a large amount of wastewater and pollutants, seriously polluting the environment. Structural color is the color reflected by regulating the light field through micro-nano structures. Structural color materials use the photonic bandgap effect of the photonic crystal structure periodically arranged on the surface or inside of the object to prevent some bands of light from propagating inside the object, thereby achieving the purpose of displaying color. When the light selectively reflected by the photonic bandgap effect generated by the photonic crystal falls within the visible light region, structural color can be achieved. Compared with chemical colors, structural colors have the advantages of high brightness, high saturation, not easy to fade, and environmental protection. Changes in the material or structure of the photonic crystal caused by the stimulus response given by the outside world will play a regulatory role in the structural color. In terms of materials, when the internal gaps of photonic crystals are filled with materials of different refractive indices, the change in the effective refractive index of the material will cause the reflection peak corresponding to the photonic bandgap to redshift or blueshift; in terms of structure, the lattice constant of the photonic crystal will change under the stimulation of special reagents, causing the internal array to expand or contract, or the periodic structure to change. Under the combined effect of the two stimulus responses, the material manifests as a change in structural color on a macro scale. Based on this, the design of stimulus-responsive photonic crystal structural color materials provides ideas and methods for realizing new anti-counterfeiting films.

[0003] With the emergence of counterfeit and shoddy products, the market demand for new anti-counterfeiting technologies that are quick to respond, easy to prepare, and difficult to copy is becoming more and more urgent. Wetting-responsive photonic crystal films have always received attention and research at home and abroad. How to prepare photonic crystal anti-counterfeiting films that are quick to respond, easy to prepare, low-cost, difficult to copy, and environmentally friendly will become the main direction of future new anti-counterfeiting technology research.

[0004] Patent CN110766119A provides a method for preparing a physically unclonable structural color anti-counterfeiting label with multiple anti-counterfeiting modes, which uses the color matching between the structural color optical surface layer and the white middle layer to achieve the hiding of the structural color surface layer pattern; after the middle layer becomes transparent in water, the exposed black background bottom layer increases the saturation of the structural color, and the structural color surface layer pattern appears, achieving an anti-counterfeiting mode that is visible to the naked eye and spectrally recognizable. However, the patent has the following limitations: the number of microsphere layers cannot be easily controlled by the spin coating method and the spray coating method, and the prepared film is difficult to replicate due to the randomness of the arrangement of monodisperse colloidal particles in the disordered optical structure. Summary of the invention

[0005] The purpose of the present invention is to provide a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer and a preparation method thereof. By introducing photon localization, a narrow photon passband appears in the reflection spectrum of the photonic crystal. The dual anti-counterfeiting performance makes the inverse opal film have good anti-counterfeiting performance, and the stability of the filling material ensures the repeatability of the film's anti-counterfeiting ability.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises a wetting-responsive color-changing inverse opal film and an inverse opal film containing planar defects.

[0008] A further improvement of the technical solution of the present invention is that the wetting responsive color-changing inverse opal film comprises an inverse opal structure of filling material and a transparent layer of filling material; the inverse opal film containing planar defects comprises a planar defect structure filled with silica gel and a filling material film doped with carbon black.

[0009] A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises the following steps:

[0010] Step 1: preparing an inverse opal film having planar defects as the bottom layer of the anti-counterfeiting film;

[0011] Step 2: preparing an inverse opal film with a wetting-responsive color-changing top layer of the composite anti-counterfeiting film;

[0012] Step 3: Fix the wetting responsive color-changing inverse opal film prepared in step 2 on the inverse opal film containing planar defects prepared in step 1 using uncured filling material to prepare a wetting responsive structural color double-layer composite anti-counterfeiting film based on a planar defect layer.

[0013] A further improvement of the technical solution of the present invention is that the step 1 specifically includes the following steps:

[0014] Step 1.1: vertically immerse the substrate ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively into a 2-7 wt.% monodisperse nanosphere suspension, and uniformly pull it at a speed of 0.8 μm / s to deposit and form the first layer of opal structure;

[0015] Step 1.2: Soak the substrate on which the first layer of opal structure is deposited in a 0.2 wt.% polydiallyldimethylammonium chloride solution for 20 min;

[0016] Step 1.3: Place the substrate treated in step 1.2 in a culture dish filled with deionized water at an angle so that the substrate is completely immersed. Use a microsyringe to drop a suspension of monodisperse nanospheres with different particle sizes in step 1.1 and ethanol or n-butanol onto the air / water interface in small amounts and multiple times to form a single-layer microsphere array. Use a pipette to drain the deionized water. As the liquid level drops, the formed single-layer microsphere array is transferred to the substrate.

[0017] Step 1.4: After the surface of the substrate obtained in step 1.3 is dried, the substrate is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out;

[0018] Step 1.5: Coat the filler material with carbon black added onto the opal structure prepared in step 1.4. After the filler material is solidified, peel off the film from the substrate and etch it in a strong alkaline solution for 48 h to prepare an inverse opal structure containing planar defects.

[0019] Step 1.6: Use silica gel to fill the pores of the inverse opal structure containing planar defects prepared in step 1.5 to obtain an inverse opal film containing planar defects.

[0020] The further improvement of the technical solution of the present invention lies in that the monodisperse nanospheres are one of silicon dioxide, titanium dioxide, zinc oxide, polystyrene, polymethyl methacrylate and cadmium sulfide nanospheres; and the substrate is one of a glass slide, a silicon wafer and a polyethylene sheet.

[0021] A further improvement of the technical solution of the present invention is that the volume of the ethanol is greater than the volume of n-butanol.

[0022] A further improvement of the technical solution of the present invention is that the filling material in step 1.5 is one of epoxy resin, polyvinyl alcohol and polymethyl methacrylate.

[0023] A further improvement of the technical solution of the present invention is that the step 2 specifically includes the following steps:

[0024] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, select microspheres of appropriate particle size according to the spectrum to prepare the film, so that the structural color of the prepared film has a similar reflection peak; vertically immerse the substrate that has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 minutes respectively in a 2-7 wt.% monodisperse nano-microsphere suspension, and uniformly pull it at a speed of 0.8 μm / s to deposit and form an opal structure;

[0025] Step 2.2: The filling material is evenly coated on the opal structure prepared in step 2.1. After the filling material is solidified, the film is peeled off from the substrate and placed in a strong alkaline solution for etching for 48 hours to prepare a wetting-responsive color-changing inverse opal film; the filling material is one of epoxy resin, polyvinyl alcohol and polymethyl methacrylate.

[0026] Due to the adoption of the above technical solution, the technical effects achieved by the present invention are as follows:

[0027] The present invention prepares a composite structure anti-counterfeiting film composed of an anti-opal film that changes color in response to wetting and an anti-opal film containing planar defects. Since the reflection peaks of the top anti-opal film and the bottom anti-opal film containing planar defects are similar, the bottom film pattern is hidden. When the surface of the composite film is wetted with an ethanol reagent, the top anti-opal structure will collapse and lose its structural color due to the capillary force generated by the evaporation of ethanol on the surface, while the bottom structure is protected by the filling of silica gel and the structural color remains unchanged, and the bottom pattern is displayed through the wetting effect of ethanol. The combined action of ethanol and deionized water can restore the collapsed anti-opal structure of the top layer, and the bottom pattern is hidden again after the structural color is restored, thereby achieving repeatable anti-counterfeiting of the film.

[0028] Since the bottom film of the present invention introduces a planar defect structure, the photon passband generated in the photon band gap brings a special spectral reflection peak, so that the film obtains a special double-peak curve under the measurement of the spectrometer. Since the color of the structural color film containing planar defects is similar to that of the structural color film without the introduction of the planar defect layer under the naked eye, the composite film has the dual anti-counterfeiting properties of wetting response and spectral double peaks. This composite structure anti-counterfeiting film is easy to replicate and prepare, has good repeatability and color durability, a more stable structure, an obvious wetting response effect, and is environmentally friendly. It has great advantages and potential in the preparation and application of anti-counterfeiting labels. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the wetting response structural color anti-counterfeiting film based on the planar defect layer of the present invention;

[0030] Figure 2 The anti-counterfeiting film prepared in Example 1 of the present invention is a physical picture at different angles;

[0031] Figure 3 is a cross-sectional view of an inverse opal film containing planar defects according to Example 1 of the present invention;

[0032] Figure 4 This is a wetting effect diagram of the inverse opal film that changes color in response to wetting according to Example 1 of the present invention;

[0033] Figure 5The reflection spectra of the top layer and bottom layer of the anti-counterfeiting film of Example 1 of the present invention are shown;

[0034] Figure 6 This is a test diagram of the pattern cycle performance of the wetting response color-changing inverse opal film according to Example 1 of the present invention;

[0035] Figure 7 This is a comparison chart of the reflectance spectra of comparative example 1 of the present invention and an opal film without a planar defect structure;

[0036] Figure 8 This is a color comparison diagram of the anti-counterfeiting film of Example 1 of the present invention and the actual object of Comparative Example 2;

[0037] Fig. 9 A comparison diagram of the reflection spectra of Example 1 of the present invention and Comparative Example 2.

[0038] Among them, 1. Inverse opal structure of filling material, 2. Transparent layer of filling material, 3. Planar defect structure filled with silica gel, 4. Film of filling material doped with carbon black. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0040] A wetting-responsive structural color anti-counterfeiting film based on a planar defect layer, such as Figure 1 As shown, the anti-counterfeiting film is, from top to bottom, an inverse opal film that changes color in response to wetting and an inverse opal film containing planar defects; the inverse opal film that changes color in response to wetting includes an inverse opal structure 1 of a filling material and a transparent layer 2 of a filling material, and the inverse opal film containing planar defects includes a planar defect structure 3 filled with silica gel and a filling material film 4 doped with carbon black.

[0041] A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises the following steps:

[0042] Step 1: Preparation of an anti-counterfeiting film with planar defects as the bottom layer of the inverse opal film

[0043] Step 1.1: The substrate ultrasonically cleaned with hydrogen peroxide, deionized water and ethanol for 10 min respectively is vertically immersed in a 2-7 wt.% monodisperse nanosphere suspension, and uniformly pulled at a speed of 0.8 μm / s to deposit and form a first layer of opal structure. The monodisperse nanosphere is one of silicon dioxide (SiO2), titanium dioxide (TiO2), zinc oxide (ZnO), polystyrene (PS), polymethyl methacrylate (PMMA) and cadmium sulfide (CdS) nanospheres; the substrate is one of a glass slide, a silicon wafer and a polyethylene (PE) sheet.

[0044] Step 1.2: The substrate with the first layer of opal structure deposited was immersed in a 0.2 wt.% polydiallyldimethylammonium chloride (PDDA) solution for 20 min to make its surface positively charged to facilitate the adsorption of negatively charged nanospheres.

[0045] Step 1.3: Tilt the substrate treated in step 1.2 into a culture dish filled with deionized water so that the substrate is completely immersed. Use a microsyringe to drop a suspension of monodisperse nanospheres with different particle sizes from step 1.1 and ethanol or n-butanol (the volume of ethanol is greater than that of n-butanol) onto the air / water interface in small amounts and multiple times to form a single-layer microsphere array. Use a pipette to drain the deionized water. As the liquid level drops, the formed single-layer microsphere array is transferred to the substrate.

[0046] Step 1.4: After the substrate surface obtained in step 1.3 is dried, it is placed under the same pulling conditions as the first layer of opal structure to pull out an opal structure with the same thickness as the first layer of opal structure. The introduction of the monolayer microsphere array in step 1.3 destroys the periodicity of the photonic crystal, produces a photon localization phenomenon, and realizes the preparation of an opal structure with planar defects.

[0047] Step 1.5: Apply a filler material with carbon black added to the opal structure prepared in step 1.4, peel off the film from the substrate after the filler material is solidified, and etch it in a strong alkaline solution for 48 hours to prepare an inverse opal structure containing planar defects. The filler material is one of epoxy resin (EP), polyvinyl alcohol (PVA), and polymethyl methacrylate (PMMA).

[0048] Step 1.6: In order to form a double-layer color-developing structure and prevent the underlying structure from being destroyed by the filling of subsequent materials, silica gel is used to fill the pores of the inverse opal structure containing planar defects prepared in step 1.5 to obtain an inverse opal film containing planar defects.

[0049] Step 2: Preparation of the inverse opal film with wetting response color change on the top layer of the composite anti-counterfeiting film

[0050] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, and select microspheres of appropriate particle size to prepare the film according to the spectrum, so that the structural color of the prepared film has a similar reflection peak. The substrate that has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 minutes is vertically immersed in a 2-7 wt.% monodisperse nano-microsphere suspension, and is uniformly pulled at a speed of 0.8μm / s to deposit and form an opal structure.

[0051] Step 2.2: uniformly apply the filling material to the opal structure prepared in step 2.1, peel off the film from the substrate after the filling material is solidified, and etch it in a strong alkaline solution for 48 hours to prepare a wetting responsive color-changing inverse opal film. The filling material is one of epoxy resin, polyvinyl alcohol, and polymethyl methacrylate.

[0052] Step 3: Preparation of double-layer composite anti-counterfeiting film

[0053] The wetting responsive color-changing inverse opal film prepared in step 2 is fixed on the inverse opal film containing planar defects prepared in step 1 with uncured filling material to prepare a wetting responsive structural color double-layer composite anti-counterfeiting film based on a planar defect layer.

[0054] Example 1

[0055] A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises the following steps:

[0056] Step 1: Preparation of an anti-counterfeiting film with planar defects as the bottom layer of the inverse opal film

[0057] Step 1.1: Vertically immerse a glass slide that has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively into a 7wt.% monodisperse SiO2 microsphere suspension with a particle size of 200 nm, and pull it up at a constant speed of 0.8 μm / s to deposit and form the first layer of opal structure.

[0058] Step 1.2: The glass slide with the first layer of opal structure deposited was immersed in a 0.2 wt.% (PDDA) solution for 20 min to make its surface positively charged to facilitate the adsorption of negatively charged SiO2 microspheres.

[0059] Step 1.3: Tilt the glass slide treated in step 1.2 into a petri dish filled with deionized water so that the glass slide is completely immersed. Use a micro-syringe to drop a suspension of monodispersed SiO2 microspheres with a particle size of 230 nm and ethanol and n-butanol onto the air / water interface in small amounts and multiple times, where the volume ratio of ethanol to n-butanol is 7:3. Use a pipette to drain the deionized water, and as the liquid level drops, the formed single-layer microsphere array is transferred to the glass slide.

[0060] Step 1.4: After the surface of the glass slide prepared in step 1.3 is dried, it is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out.

[0061] Step 1.5: Coat the epoxy resin with carbon black added onto the opal structure prepared above, peel off the film from the substrate after the epoxy resin is cured, and etch the film in a 10 wt.% NaOH solution for 48 h to prepare an inverse opal structure containing planar defects.

[0062] Step 1.6: In order to form a double-layer color-developing structure and prevent the underlying structure from being destroyed by the subsequent filling of materials, silica gel is used to fill the pores of the prepared inverse opal structure containing planar defects to obtain an inverse opal film containing planar defects.

[0063] Step 2: Preparation of the inverse opal film with wetting response color change on the top layer of the composite anti-counterfeiting film

[0064] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, and select SiO2 microspheres with a particle size of 200 nm according to the spectrum so that the structural color of the prepared film has a similar reflection peak. The substrate, which has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively, is vertically immersed in a 7 wt.% monodisperse SiO2 microsphere suspension and uniformly pulled at a speed of 0.8 μm / s to deposit and form an opal structure.

[0065] Step 2.2: Evenly coat the epoxy resin on the opal structure prepared in step 2.1. After the epoxy resin is cured, peel the film off the substrate and etch it in a 10 wt.% NaOH solution for 48 h to prepare a wetting-responsive color-changing inverse opal film.

[0066] Step 3: Preparation of double-layer composite anti-counterfeiting film

[0067] The wettability-responsive color-changing inverse opal film was fixed on the inverse opal film containing planar defects with uncured epoxy resin to prepare a double-layer composite anti-counterfeiting film. Figure 2 shown.

[0068] The structure of the double-layer composite anti-counterfeiting film includes: an epoxy resin inverse opal structure, an epoxy resin transparent layer, a planar defect structure filled with silicone and an epoxy resin film doped with carbon black. The epoxy resin inverse opal structure and the epoxy resin transparent layer constitute an inverse opal film that changes color in response to wetting, and the planar defect structure filled with silicone and the epoxy resin film doped with carbon black constitute an inverse opal film containing planar defects.

[0069] Example 2

[0070] A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises the following steps:

[0071] Step 1: Preparation of an anti-counterfeiting film with planar defects as the bottom layer of the inverse opal film

[0072] Step 1.1: The PE sheet ultrasonically cleaned with hydrogen peroxide, deionized water and ethanol for 10 min respectively was vertically immersed in a 5wt.% monodisperse TiO2 microsphere suspension with a particle size of 200 nm, and was uniformly pulled up at a speed of 0.8 μm / s to deposit and form the first layer of opal structure.

[0073] Step 1.2: Soak the PE sheet with the first layer of opal structure deposited in a 0.2 wt.% (PDDA) solution for 20 min to make its surface positively charged to facilitate the adsorption of negatively charged TiO2 microspheres.

[0074] Step 1.3: Tilt the PE sheet treated in step 1.2 into a petri dish filled with deionized water so that the PE sheet is completely immersed, and use a microsyringe to drip a suspension of monodispersed TiO2 microspheres with a particle size of 230 nm and ethanol and n-butanol onto the air / water interface in small amounts and multiple times, where the volume ratio of ethanol to n-butanol is 7:3. Use a pipette to drain the deionized water, and as the liquid level drops, the formed single-layer microsphere array is transferred to the PE sheet.

[0075] Step 1.4: After the surface of the PE sheet prepared in step 1.3 is dried, it is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out.

[0076] Step 1.5: Coat the epoxy resin with carbon black added onto the opal structure prepared above, peel off the film from the substrate after the epoxy resin is cured, and etch the film in a 10 wt.% NaOH solution for 48 h to prepare an inverse opal structure containing planar defects.

[0077] Step 1.6: In order to form a double-layer color-developing structure and prevent the underlying structure from being destroyed by the subsequent filling of materials, silica gel is used to fill the pores of the prepared inverse opal structure containing planar defects to obtain an inverse opal film containing planar defects.

[0078] Step 2: Preparation of the inverse opal film with wetting response color change on the top layer of the composite anti-counterfeiting film

[0079] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, and select TiO2 microspheres with a particle size of 200 nm according to the spectrum so that the structural color of the prepared film has a similar reflection peak. The substrate, which has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively, is vertically immersed in a 5 wt.% monodispersed TiO2 microsphere suspension and pulled at a uniform speed of 0.8 μm / s to deposit and form an opal structure.

[0080] Step 2.2: Evenly coat the epoxy resin on the opal structure prepared in step 2.1. After the epoxy resin is cured, peel the film off the substrate and etch it in a 10 wt.% NaOH solution for 48 h to prepare a wetting-responsive color-changing inverse opal film.

[0081] Step 3: Preparation of double-layer composite anti-counterfeiting film

[0082] The wetting responsive color-changing inverse opal film is fixed on an inverse opal film containing planar defects by using uncured epoxy resin to prepare a double-layer composite anti-counterfeiting film.

[0083] Example 3

[0084] Step 1: Preparation of an anti-counterfeiting film with planar defects as the bottom layer of the inverse opal film

[0085] Step 1.1: A glass slide that had been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively was vertically immersed in a 3wt.% suspension of monodisperse PS microspheres with a particle size of 200 nm, and was uniformly pulled up at a speed of 0.8 μm / s to deposit and form the first layer of opal structure.

[0086] Step 1.2: The glass slide with the first layer of opal structure deposited was immersed in a 0.2 wt.% (PDDA) solution for 20 min to make its surface positively charged to facilitate the adsorption of negatively charged PS microspheres.

[0087] Step 1.3: Tilt the glass slide treated in step 1.2 into a petri dish filled with deionized water so that the glass slide is completely immersed. Use a microsyringe to drop a suspension of monodisperse PS microspheres with a particle size of 230 nm and ethanol and n-butanol onto the air / water interface in small amounts and multiple times, where the volume ratio of ethanol to n-butanol is 2: 1. Use a pipette to drain the deionized water, and as the liquid level drops, the formed single-layer microsphere array is transferred to the glass slide.

[0088] Step 1.4: After the surface of the glass slide prepared in step 1.3 is dried, it is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out.

[0089] Step 1.5: PMMA with carbon black added is coated on the opal structure prepared above. After the PMMA is solidified, the film is peeled off from the substrate and the film is etched in a 10 wt.% NaOH solution for 48 h to prepare an inverse opal structure containing planar defects.

[0090] Step 1.6: In order to form a double-layer color-developing structure and prevent the underlying structure from being destroyed by the subsequent filling of materials, silica gel is used to fill the pores of the prepared inverse opal structure containing planar defects to obtain an inverse opal film containing planar defects.

[0091] Step 2: Preparation of the inverse opal film with wetting response color change on the top layer of the composite anti-counterfeiting film

[0092] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, and select PS microspheres with a particle size of 200 nm according to the spectrum so that the structural color of the prepared film has a similar reflection peak. The substrate, which was ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively, was vertically immersed in a 3 wt.% monodisperse PS microsphere suspension and pulled at a uniform speed of 0.8 μm / s to deposit and form an opal structure.

[0093] Step 2.2: Evenly coat PMMA onto the opal structure prepared in step 2.1. After PMMA solidifies, peel the film off the substrate and etch it in a 10 wt.% NaOH solution for 48 h to prepare a wetting-responsive color-changing inverse opal film.

[0094] Step 3: Preparation of double-layer composite anti-counterfeiting film

[0095] The wetting responsive color-changing inverse opal film is fixed on the inverse opal film containing planar defects by using uncured PMMA to prepare a double-layer composite anti-counterfeiting film.

[0096] Example 4

[0097] A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises the following steps:

[0098] Step 1: Preparation of an anti-counterfeiting film with planar defects as the bottom layer of the inverse opal film

[0099] Step 1.1: A silicon wafer ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively was vertically immersed in a 7wt.% monodisperse ZnO microsphere suspension with a particle size of 200 nm, and was uniformly pulled up at a speed of 0.8 μm / s to deposit and form the first layer of opal structure.

[0100] Step 1.2: Soak the silicon wafer with the first layer of opal structure deposited in a 0.2 wt.% (PDDA) solution for 20 min to make its surface positively charged to facilitate the adsorption of negatively charged ZnO microspheres.

[0101] Step 1.3: Tilt the silicon wafer processed in step 1.2 into a petri dish filled with deionized water so that the silicon wafer is completely immersed, and use a micro-syringe to drip a suspension of monodispersed ZnO microspheres with a particle size of 230 nm and ethanol and n-butanol onto the air / water interface in small amounts and multiple times, where the volume ratio of ethanol to n-butanol is 7:3. Use a pipette to drain the deionized water, and as the liquid level drops, the formed single-layer microsphere array is transferred to the silicon wafer.

[0102] Step 1.4: After the surface of the silicon wafer prepared in step 1.3 is dried, it is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out.

[0103] Step 1.5: Coat the PVA with carbon black added onto the opal structure prepared above, peel off the film from the substrate after the PVA solidifies, and etch the film in a 10 wt.% NaOH solution for 48 h to prepare an inverse opal structure containing planar defects.

[0104] Step 1.6: In order to form a double-layer color-developing structure and prevent the underlying structure from being destroyed by the subsequent filling of materials, silica gel is used to fill the pores of the prepared inverse opal structure containing planar defects to obtain an inverse opal film containing planar defects.

[0105] Step 2: Preparation of the inverse opal film with wetting response color change on the top layer of the composite anti-counterfeiting film

[0106] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, and select ZnO microspheres with a particle size of 200 nm according to the spectrum so that the structural color of the prepared film has a similar reflection peak. The substrate, which has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively, is vertically immersed in a 2-7 wt.% monodisperse ZnO microsphere suspension and pulled at a uniform speed of 0.8 μm / s to deposit and form an opal structure.

[0107] Step 2.2: PVA is evenly coated on the opal structure prepared in step 2.1. After the PVA is solidified, the film substrate is peeled off and placed in a 10 wt.% NaOH solution for etching for 48 h to prepare a wetting-responsive color-changing inverse opal film.

[0108] Step 3: Preparation of double-layer composite anti-counterfeiting film

[0109] The wetting responsive color-changing inverse opal film was fixed on the inverse opal film containing planar defects by using uncured PVA to prepare a double-layer composite anti-counterfeiting film.

[0110] Example 5

[0111] A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises the following steps:

[0112] Step 1: Preparation of an anti-counterfeiting film with planar defects as the bottom layer of the inverse opal film

[0113] Step 1.1: A glass slide that had been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 min respectively was vertically immersed in a 5wt.% suspension of monodisperse PMMA microspheres with a particle size of 200 nm, and was uniformly pulled up at a speed of 0.8 μm / s to deposit and form the first layer of opal structure.

[0114] Step 1.2: The glass slide with the first layer of opal structure deposited was immersed in a 0.2 wt.% (PDDA) solution for 20 min to make its surface positively charged to facilitate the adsorption of negatively charged PMMA microspheres.

[0115] Step 1.3: Tilt the glass slide treated in step 1.2 into a petri dish filled with deionized water so that the glass slide is completely immersed. Use a microsyringe to drip a suspension of monodisperse PMMA microspheres with a particle size of 230 nm and ethanol and n-butanol onto the air / water interface in small amounts and multiple times, where the volume ratio of ethanol to n-butanol is 2: 1. Use a pipette to drain the deionized water, and as the liquid level drops, the formed single-layer microsphere array is transferred to the glass slide.

[0116] Step 1.4: After the surface of the glass slide prepared in step 1.3 is dried, it is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out.

[0117] Step 1.5: Coat the epoxy resin with carbon black added onto the opal structure prepared above, peel off the film from the substrate after the epoxy resin is cured, and etch the film in a 10 wt.% NaOH solution for 48 h to prepare an inverse opal structure containing planar defects.

[0118] Step 1.6: In order to form a double-layer color-developing structure and prevent the underlying structure from being destroyed by the subsequent filling of materials, silica gel is used to fill the pores of the prepared inverse opal structure containing planar defects to obtain an inverse opal film containing planar defects.

[0119] Step 2: Preparation of the inverse opal film with wetting response color change on the top layer of the composite anti-counterfeiting film

[0120] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, and select PMMA microspheres with a particle size of 200 nm according to the spectrum so that the structural color of the prepared film has a similar reflection peak. The substrate, which has been ultrasonically cleaned for 10 min with hydrogen peroxide, deionized water, and ethanol, is vertically immersed in a 2-7 wt.% monodisperse PMMA microsphere suspension, and is uniformly pulled at a speed of 0.8 μm / s to deposit and form an opal structure.

[0121] Step 2.2: Evenly coat the epoxy resin onto the opal structure prepared in step 2.1. After the epoxy resin is cured, peel off the film substrate and etch it in a 10 wt.% NaOH solution for 48 h to prepare a wetting-responsive color-changing inverse opal film.

[0122] Step 3: Preparation of double-layer composite anti-counterfeiting film

[0123] The wetting responsive color-changing inverse opal film is fixed on an inverse opal film containing planar defects by using uncured epoxy resin to prepare a double-layer composite anti-counterfeiting film.

[0124] Example 6

[0125] A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer comprises the following steps:

[0126] Step 1: Preparation of an anti-counterfeiting film with planar defects as the bottom layer of the inverse opal film

[0127] Step 1.1: The PE sheet ultrasonically cleaned with hydrogen peroxide, deionized water and ethanol for 10 min respectively was vertically immersed in a 3wt.% monodisperse CdS microsphere suspension with a particle size of 200 nm, and was uniformly pulled up at a speed of 0.8 μm / s to deposit and form the first layer of opal structure.

[0128] Step 1.2: Soak the PE sheet with the first layer of opal structure deposited in a 0.2 wt.% (PDDA) solution for 20 min to make its surface positively charged to facilitate the adsorption of negatively charged CdS microspheres.

[0129] Step 1.3: Tilt the PE sheet treated in step 1.2 into a petri dish filled with deionized water so that the PE sheet is completely immersed, and use a micro-syringe to drip a suspension of monodispersed CdS microspheres with a particle size of 230 nm and ethanol and n-butanol onto the air / water interface in small amounts and multiple times, where the volume ratio of ethanol to n-butanol is 7:3. Use a pipette to drain the deionized water, and as the liquid level drops, the formed single-layer microsphere array is transferred to the PE sheet.

[0130] Step 1.4: After the surface of the PE sheet prepared in step 1.3 is dried, it is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out.

[0131] Step 1.5: Coat the epoxy resin with carbon black added onto the opal structure prepared above, peel off the film from the substrate after the epoxy resin is cured, and etch the film in a 10 wt.% NaOH solution for 48 h to prepare an inverse opal structure containing planar defects.

[0132] Step 1.6: In order to form a double-layer color-developing structure and prevent the underlying structure from being destroyed by the subsequent filling of materials, silica gel is used to fill the pores of the prepared inverse opal structure containing planar defects to obtain an inverse opal film containing planar defects.

[0133] Step 2: Preparation of the inverse opal film with wetting response color change on the top layer of the composite anti-counterfeiting film

[0134] Step 2.1: Test the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, and select CdS microspheres with a particle size of 200 nm according to the spectrum so that the structural color of the prepared film has a similar reflection peak. Vertically immerse the substrate that has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 minutes in a 2-7 wt.% monodisperse CdS microsphere suspension, and pull it at a uniform speed of 0.8μm / s to deposit and form an opal structure.

[0135] Step 2.2: Evenly coat the epoxy resin on the opal structure prepared in step 2.1. After the epoxy resin is cured, peel the film off the substrate and etch it in a 10 wt.% NaOH solution for 48 h to prepare a wetting-responsive color-changing inverse opal film.

[0136] Step 3: Preparation of double-layer composite anti-counterfeiting film

[0137] The wetting responsive color-changing inverse opal film is fixed on an inverse opal film containing planar defects by using uncured epoxy resin to prepare a double-layer composite anti-counterfeiting film.

[0138] Comparative Example 1

[0139] A method for preparing a thin film containing planar defects comprises the following steps:

[0140] Step 1: Vertically immerse the glass slide that has been ultrasonically cleaned with hydrogen peroxide, deionized water, and ethanol for 10 minutes respectively into a 7 wt.% monodisperse SiO2 microsphere suspension with a particle size of 200 nm, and pull it up at a uniform speed of 0.8 μm / s to deposit the first layer of opal on the ultrasonically cleaned glass slide.

[0141] Step 2: Soak the glass slide with the opal structure in 0.2 wt.% PDDA solution for 20 min to make it positively charged and better adsorb the negatively charged SiO2 microspheres.

[0142] Step 3: Tilt the treated glass slide into a petri dish filled with deionized water, and use a syringe to drip a mixed solution of monodisperse SiO2 microspheres with a particle size of 230 nm onto the air / water interface multiple times. After the single-layer colloidal crystal array is assembled on the air / water interface, drain the deionized water with a pipette, and as the liquid level drops, the single-layer array is transferred to the glass slide.

[0143] Step 4: After the surface of the glass slide is dry, place it under the same pulling conditions as the first layer of opal, pull out an opal array with the same thickness as the first layer, peel off the film from the glass slide, and prepare an opal structure array containing planar defects.

[0144] Comparative Example 2

[0145] A method for preparing a silica gel-filled epoxy resin inverse opal structural color film comprises the following steps:

[0146] Step 1: The substrate ultrasonically cleaned with hydrogen peroxide, deionized water and ethanol for 10 min respectively was vertically immersed in a 7wt.% monodisperse SiO2 microsphere suspension with a particle size of 250nm, and was uniformly pulled up at a speed of 0.8μm / s to deposit and form an opal structure.

[0147] Step 2: Evenly coat the epoxy resin onto the opal structure prepared in step 2.1. After the epoxy resin is cured, peel the film off the substrate and etch it in a 10 wt.% NaOH solution for 48 h to prepare an epoxy resin inverse opal film.

[0148] Step 3: Evenly drop silica gel on the epoxy resin inverse opal film to obtain a silica gel-filled epoxy resin inverse opal structural color film.

[0149] Evaluate the performance of anti-counterfeiting films:

[0150] (1) The cross section of the inverse opal film containing planar defects in the bottom layer of the anti-counterfeiting film of Example 1 was subjected to gold spraying treatment and the morphology was observed under a field emission scanning electron microscope. The results are as follows: Figure 3As shown. The cross section of the epoxy resin "sandwich" structure was selected for analysis. The film used monodisperse SiO2 microspheres with a particle size of 200 nm as the pulling layer, monodisperse SiO2 microspheres with a particle size of 230 nm as the planar defect layer, and the gaps were filled with epoxy resin. Before the first pulling, the glass slide was ultrasonically cleaned, and the surface was smooth and flat, and the arrangement of the lower layer of microspheres was good. Because the structure is inevitably destroyed when transferring the monolayer structure, after the transfer, the surface of the protein structure will not be as flat as the surface of the pulling layer, and there will be unevenness. Some of the microspheres will not be too densely arranged, which is shown in the scanning electron microscope image. The concentration of SiO2 microspheres in the suspension was the same for the two pulling times, so the number of layers for the two pulling times was the same, and the defect layer was located at the center of the cross section.

[0151] (2) The display / hiding performance of the composite anti-counterfeiting film prepared in Example 1 was tested. Figure 4 As shown in the figure, after wiping the composite anti-counterfeiting film with ethanol, the top structural color of the film disappears instantly, showing the bottom structural color pattern with bright colors. This is because as the ethanol evaporates, the structure of the top wetting response color-changing inverse opal film collapses under the action of surface tension, making the top film transparent. The bottom inverse opal film with defects cannot be destroyed by ethanol due to the filling of silica gel and maintains the original structural color pattern. After wiping with ethanol, the colloidal array can show iridescent colors at different angles under the reflection model. The rapid display of hidden bottom patterns and bright iridescent structural colors indicates the potential application of multilayer colloidal arrays in anti-counterfeiting and information encryption. The bottom reflection spectrum peak of the composite film is the same as that of the top layer. At the same time, the stop band divides the reflection peak into two small peaks, improving its own performance. The other is the arrangement characteristics. The upper layer is an inverse opal array prepared by a single pull-up, and the bottom layer is a long-range ordered and highly crystallized inverse opal array containing planar defects prepared by the pull-up self-assembly method. During the information encryption process, the incident light is reflected by the colloidal array on the top, and the similar structural colors displayed on the top and bottom layers cannot be easily identified by the naked eye, so that the pattern of the bottom layer is hidden by the structural color of the top layer.

[0152] (3) An inverse opal film with the same structural color is prepared on the upper layer of the inverse opal film structure containing planar defects to cover the lower pattern. In the composite structure film, the structural color of the top film can be displayed and hidden by responding to ethanol. Compared with the single-layer structure film, on the one hand, it can increase the anti-counterfeiting performance of the composite structure, and on the other hand, it can protect the underlying pattern from being destroyed by external stimuli. The reflection spectrum effect of the upper and lower structure films is as follows Figure 5As shown in the figure, the reflection intensity and color of the structural color generated by the upper pattern can effectively cover the underlying pattern. In addition, the strong mechanical stability of the wettability photonic crystal composite film containing planar defects is crucial for anti-counterfeiting and information encryption in practical applications. The present invention subjected the composite structure film to 20 cycles of repeated ethanol wiping to display / hide the underlying pattern, as shown in the figure. Figure 6 As shown in the figure, the spectral reflection peak changes from 558 nm to 535 nm before and after the cycle, and the peak moves by 23 nm, but it can still hide the underlying pattern well, indicating that the photonic crystal film has good information encryption reversibility.

[0153] (4) Comparing the structural color film of comparative example 1 with the opal structural color film without defect structure, the reflection spectrum is as follows: Figure 7 As shown. The reflection peak positions of the two are roughly the same, which makes the structural colors produced by the two difficult to distinguish under the naked eye, but the planar defect structure in comparative example 1 makes its reflection peak have an obvious double peak structure, which reflects the particularity of the planar defect structure in the spectrum and provides ideas for the subsequent anti-counterfeiting of composite films. However, the opal structure is easy to fall off during the wetting response process, and the color repeatability is poor. Figure 8 The optical photos of Example 2 and Example 1 show that the film structure colors are similar and difficult to distinguish with the naked eye. Fig. 9 As shown, the reflection peaks of Example 1 and Comparative Example 2 are similar, but the spectrum of Example 1 shows a double peak structure due to the planar defect structure. This phenomenon provides a second inspection method for the anti-counterfeiting of the composite film.

[0154] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

Claims

1. A wetting-responsive structural color anti-counterfeiting film based on a planar defect layer, characterized in that: Including wetting-responsive color-changing inverse opal films and inverse opal films containing planar defects; The following steps are involved: Step 1: preparing an inverse opal film having planar defects as the bottom layer of the anti-counterfeiting film; The step 1 specifically comprises the following steps: Step 1.1: vertically immerse the substrate ultrasonically cleaned with hydrogen peroxide, deionized water and ethanol for 10 minutes respectively into a 2-7 wt.% monodisperse nanosphere suspension, and uniformly pull it at a speed of 0.8 μm / s to deposit and form the first layer of opal structure; Step 1.2: Soak the substrate on which the first layer of opal structure is deposited in a 0.2 wt.% polydiallyldimethylammonium chloride solution for 20 min; Step 1.3: Place the substrate treated in step 1.2 in a culture dish filled with deionized water at an angle so that the substrate is completely immersed. Use a microsyringe to drop a suspension of monodisperse nanospheres with different particle sizes in step 1.1 and ethanol or n-butanol onto the air / water interface in small amounts and multiple times to form a single-layer microsphere array. Use a pipette to drain the deionized water. As the liquid level drops, the formed single-layer microsphere array is transferred to the substrate. Step 1.4: After the surface of the substrate obtained in step 1.3 is dried, the substrate is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out; Step 1.5: coating a filler material with carbon black added onto the opal structure prepared in step 1.4, peeling off the film from the substrate after the filler material solidifies, and etching it in a strong alkaline solution for 48 hours to prepare an inverse opal structure containing planar defects; Step 1.6: Filling the pores of the inverse opal structure containing planar defects prepared in step 1.5 with silica gel to obtain an inverse opal film containing planar defects; Step 2: preparing an inverse opal film with a wetting-responsive color-changing top layer of the composite anti-counterfeiting film; Step 3: Fix the wetting responsive color-changing inverse opal film prepared in step 2 on the inverse opal film containing planar defects prepared in step 1 using uncured filling material to prepare a wetting responsive structural color double-layer composite anti-counterfeiting film based on a planar defect layer.

2. The wetting-responsive structural color anti-counterfeiting film based on a planar defect layer according to claim 1, characterized in that: The wetting responsive color-changing inverse opal film comprises a filling material inverse opal structure (1) and a filling material transparent layer (2); the inverse opal film containing planar defects comprises a silica gel-filled planar defect structure (3) and a filling material film (4) doped with carbon black.

3. A method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer according to claim 1 or 2, characterized in that: The following steps are involved: Step 1: preparing an inverse opal film having planar defects as the bottom layer of the anti-counterfeiting film; The step 1 specifically comprises the following steps: Step 1.1: vertically immerse the substrate ultrasonically cleaned with hydrogen peroxide, deionized water and ethanol for 10 minutes respectively into a 2-7 wt.% monodisperse nanosphere suspension, and uniformly pull it at a speed of 0.8 μm / s to deposit and form the first layer of opal structure; Step 1.2: Soak the substrate on which the first layer of opal structure is deposited in a 0.2 wt.% polydiallyldimethylammonium chloride solution for 20 min; Step 1.3: Place the substrate treated in step 1.2 in a culture dish filled with deionized water at an angle so that the substrate is completely immersed. Use a microsyringe to drop a suspension of monodisperse nanospheres with different particle sizes in step 1.1 and ethanol or n-butanol onto the air / water interface in small amounts and multiple times to form a single-layer microsphere array. Use a pipette to drain the deionized water. As the liquid level drops, the formed single-layer microsphere array is transferred to the substrate. Step 1.4: After the surface of the substrate obtained in step 1.3 is dried, the substrate is placed under the same pulling conditions as those for preparing the first layer of opal structure, and an opal structure having the same thickness as the first layer of opal structure is pulled out; Step 1.5: coating a filler material with carbon black added onto the opal structure prepared in step 1.4, peeling off the film from the substrate after the filler material solidifies, and etching it in a strong alkaline solution for 48 hours to prepare an inverse opal structure containing planar defects; Step 1.6: Filling the pores of the inverse opal structure containing planar defects prepared in step 1.5 with silica gel to obtain an inverse opal film containing planar defects; Step 2: preparing an inverse opal film with a wetting-responsive color-changing top layer of the composite anti-counterfeiting film; Step 3: Fix the wetting responsive color-changing inverse opal film prepared in step 2 on the inverse opal film containing planar defects prepared in step 1 using uncured filling material to prepare a wetting responsive structural color double-layer composite anti-counterfeiting film based on a planar defect layer.

4. The method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer according to claim 3, characterized in that: The monodisperse nano-microspheres are one of silicon dioxide, titanium dioxide, zinc oxide, polystyrene, polymethyl methacrylate and cadmium sulfide nano-microspheres; and the substrate is one of a glass slide, a silicon sheet and a polyethylene sheet.

5. The method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer according to claim 3, characterized in that: The volume of the ethanol is greater than that of n-butanol.

6. The method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer according to claim 3, characterized in that: The filling material in step 1.5 is one of epoxy resin, polyvinyl alcohol and polymethyl methacrylate.

7. The method for preparing a wetting-responsive structural color anti-counterfeiting film based on a planar defect layer according to claim 3, characterized in that: The step 2 specifically includes the following steps: Step 2.1: testing the reflection peak spectrum of the inverse opal film containing planar defects prepared in step 1, selecting microspheres of appropriate particle size to prepare the film according to the spectrum, so that the structural color of the prepared film has a similar reflection peak; vertically immersing the substrate that has been ultrasonically cleaned for 10 minutes with hydrogen peroxide, deionized water, and ethanol respectively into a 2-7wt.% monodisperse nano-microsphere suspension, and uniformly pulling at a speed of 0.8μm / s to deposit and form an opal structure; Step 2.2: uniformly apply the filling material onto the opal structure prepared in step 2.1, peel off the film from the substrate after the filling material solidifies, and etch it in a strong alkaline solution for 48 hours to prepare a wetting-responsive color-changing inverse opal film; the filling material is one of epoxy resin, polyvinyl alcohol and polymethyl methacrylate.

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