SiO2 / CNC multi-optical characteristic composite film and layer stacking preparation method

Abstract

The invention discloses a SiO2 / CNC composite film with multiple optical characteristics and a layer stacking preparation method, a cellulose nanocrystal (CNC) substrate layer is firstly assembled, then SiO2 / PVP / RhB (rhodamine B) dispersion liquid is poured, a CNC photonic layer and a SiO2 photonic crystal layer are tightly combined by utilizing the cohesiveness and hydrophilicity of PVP, meanwhile, the fluorescence quenching of RhB is overcome, and the SiO2 / CNC composite film with multiple optical properties is obtained. The composite film presents the structural color of a CNC photon layer under natural light, presents the birefringence color of a CNC chiral nematic structure under polarized light, presents the dynamic iridescent color of SiO2 under a point light source, and can generate fluorescence color under ultraviolet excitation, and the film with multiple optical characteristics has great application potential in the fields of optical anti-counterfeiting, information encryption and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite film materials and optical anti-counterfeiting, and particularly relates to a SiO 2 / CNC multi-optical feature composite film and a layer stacking preparation method thereof. Background Art

[0002] Information anti-counterfeiting is of extremely important significance in national defense security and daily life. Among them, optical anti-counterfeiting has received extensive attention due to its easy recognition and controllability. However, single optical anti-counterfeiting technologies have limitations such as low security and easy to be cracked. Therefore, the combined application of multiple optical anti-counterfeiting technologies is particularly important to meet the need of improving anti-counterfeiting security.

[0003] SiO 2 Photonic crystals have a unique periodic structure. When light enters this structure, diffraction and interference phenomena will occur, forming structural colors. The CNC photonic structure can also form similar structural colors. By compounding the above two kinds of films, multi-optical anti-counterfeiting can be realized. However, SiO 2 and CNC are inorganic and organic substances respectively. The difference in compatibility between the two easily leads to the destruction of the self-assembled structure, and the bilayer structure cannot be tightly combined, ultimately resulting in the destruction of their respective optical characteristics. Therefore, the preparation of composite films with multi-optical characteristics still faces many challenges. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a SiO 2 / CNC multi-optical feature composite film and a layer stacking preparation method thereof, so as to solve the problems of easy deciphering of single optical anti-counterfeiting and poor binding property of SiO 2 / CNC composite films in the prior art, and prepare an optical composite film with multi-anti-counterfeiting characteristics.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A layer stacking preparation method of a SiO 2 / CNC multi-optical feature composite film includes the following steps: Step 1: Pour the CNC aqueous dispersion onto a glass mold, and obtain a CNC photonic film after drying and self-assembly; Step 2: Disperse SiO 2 microspheres in water to obtain a SiO 2 aqueous dispersion; Step 3: Disperse RhB in water to obtain a RhB aqueous dispersion; Step 4: Add PVP to the SiO 2 aqueous dispersion to obtain a PVP / SiO 2Water dispersion; PVP / SiO 2 After mixing the water dispersion and the RhB water dispersion, a SiO 2 / PVP / RhB water dispersion is obtained; Step 5: Immerse the CNC photonic film in a water bath, and pour the SiO 2 / PVP / RhB water dispersion on the immersed CNC photonic film, and obtain a SiO 2 / CNC composite film after self-assembly.

[0006] A further improvement of the present invention lies in: Preferably, in step 1, the mass fraction of the CNC water dispersion is 2%.

[0007] Preferably, in step 1, the temperature of the drying self-assembly process is 20-80°C.

[0008] Preferably, in step 2, the mixing ratio of SiO 2 microspheres and water is (0.01-0.03) g: (3-5) mL.

[0009] Preferably, in step 2, the mixing ratio of RhB and water is 0.003 g: 100 mL.

[0010] Preferably, in step 4, the mixing ratio of PVP and SiO 2 water dispersion is (0.1-0.3) g: (3-5) mL.

[0011] Preferably, in step 4, the mixing ratio of PVP / SiO 2 water dispersion and RhB water dispersion is (3-5) mL: (3-5) g.

[0012] Preferably, in step 5, the immersion temperature is 25-45°C, and the immersion time is 2-4 h.

[0013] Preferably, in step 5, the drying temperature is 20-80°C.

[0014] A SiO 2 / CNC multiple optical feature composite film prepared by the layer stacking method according to any one of the above, comprising a lower layer of CNC photonic film and an upper layer of SiO 2 photonic crystal layer; wherein the matrix in the upper SiO 2 photonic crystal layer is PVP, and SiO 2 microspheres and RhB are both dispersed in the matrix.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for constructing SiO by layer stacking 2 / Method for preparing CNC composite film. First, prepare a CNC base layer; then, pour SiO 2 / PVP / RhB dispersion liquid, and use the adhesiveness of PVP to tightly bond the two layers, while overcoming the fluorescence quenching of RhB. Through this method, SiO 2 / CNC composite film with various optical properties can be obtained. The composite film is tightly bonded, and shows the structural color of CNC under natural light, the birefringence color of CNC under polarized light, the dynamic iridescence color of SiO 2 under point light source, and emits fluorescence color under ultraviolet light excitation. Therefore, the film has multiple optical characteristics and shows great application potential in the fields of optical anti-counterfeiting, information encryption, decoration, etc.

[0016] Among them, there are physical form differences, density differences, and surface charge differences between SiO 2 and CNC, resulting in the inability of the SiO 2 layer and the CNC layer to be tightly bonded. This method improves the surface properties of CNC and SiO 2 by adding PVP. The pyrrolidone group in PVP can form hydrogen bonds with the surface hydroxyl groups of CNC and SiO 2 , enhancing the interfacial binding force between the two, and making the SiO 2 layer and the CNC layer tightly bonded. RhB is added to achieve the photoluminescence effect, but RhB will undergo solid-state quenching in solid materials because the dense stacking of molecules in solid materials will limit the conformational freedom of rhodamine molecules. The present invention utilizes the ionic groups on the surfaces of PVP and SiO 2 , and the ionic groups will form hydrogen bonds or other interactions with dye molecules, thereby blocking the interactions between dye molecules and overcoming solid-state quenching. At the same time, under ultraviolet light, RhB is excited by ultraviolet light and emits fluorescence.

[0017] Furthermore, the addition of PVP makes silica uniformly dispersed, which is beneficial to orderly assembly, and the adhesiveness of PVP makes the formed film structure tight. Layer-by-layer assembly does not destroy the self-assembly structure of CNC, nor does it affect the self-assembly structure of silica.

[0018] Furthermore, under natural light, the periodic crystal structure inside CNC will interfere and diffract with light, and the structural color of SiO 2 will be hidden, so that only the specific structural color of CNC is presented.

[0019] Furthermore, under polarized light, the self-assembled CNC presents a chiral nematic phase structure. This helical structure will cause the material to be anisotropic, making light with different polarization directions propagate at different speeds to generate a phase difference, and then generating color changes to form birefringence.

[0020] Furthermore, under point light source, SiO 2 The color presentation depends on PVP. The addition of PVP increases the SiO 2 The transparency of the layer (similar refractive index), polydisperse SiO 2 Form a uniform dielectric layer with PVP, SiO 2 The microspheres are arranged alternately to form different photonic band gaps, which appear iridescent under a point light source. At the same time, due to the strong light from the point light source, the structural color of CNC will be hidden. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The SiO prepared in Example 1 of the present invention 2 Cross-sectional SEM image of / CNC composite film.

[0022] Figure 2 This is an optical photograph of the CNC photonic film prepared in Example 2 of the present invention.

[0023] Figure 3 This is a POM image of the CNC photonic film prepared in Example 3 of the present invention.

[0024] Figure 4 This is a 2D image of the ultra-depth microscope of the CNC photonic film prepared in Example 4 of the present invention.

[0025] Figure 5 The SiO prepared in Example 5 of the present invention 2 Optical photographs of / CNC composite films under different lighting conditions.

[0026] Figure 6 The SiO prepared in Example 6 of the present invention 2 POM image of / CNC composite film.

[0027] Figure 7 The SiO prepared in Example 7 of the present invention 2 Ultra-depth-of-field microscopic 2D image of / CNC composite film.

[0028] Figure 8 The SiO prepared in Example 8 of the present invention 2 Optical photographs of / CNC composite films under different lighting conditions. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings: To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art with respect to the present invention. In case of conflict, the definition in this specification shall prevail.

[0030] In this article, unless otherwise specified, "comprising", "including", "containing", "having" or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0031] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0032] The following embodiments use conventional instruments and equipment in the art. The experimental methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0033] The present invention discloses a method for constructing a SiO 2 / CNC composite film by a layer stacking method. The preparation method specifically includes the following steps: (1) Pour 3 - 5 g of CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in a drying oven at 20 - 80 °C for evaporation-induced self-assembly to obtain a CNC photonic film.

[0034] (2) Add 3 - 5 mL of deionized water and 0.01 - 0.03 g of SiO 2 microspheres into a beaker and stir evenly to obtain a SiO 2 aqueous dispersion, wherein the particle size range of the SiO 2 microspheres is 450 - 650 nm.

[0035] (3) Add 100 ml of deionized water and 0.003 g of RhB into a beaker and stir evenly to obtain a RhB aqueous dispersion.

[0036] (4) Add 0.1 - 0.3 g of PVP into 3 - 5 mL of SiO 2 aqueous dispersion, and then add 3 - 5 g of RhB aqueous dispersion. After ultrasonic dispersion for 30 - 40 min, SiO 2 / PVP / RhB aqueous dispersion is obtained.

[0037] (5) Place the CNC photon film in a water bath at 25 - 45 °C, soak it in deionized water for 2 - 4 h. After taking it out, pour SiO 2 / PVP / RhB aqueous dispersion, and place it in an oven at 20 - 80 °C for self-assembly to obtain SiO 2 / CNC composite film.

[0038] For the preparation method of the SiO 2 / CNC composite film of the present invention, by utilizing the adhesiveness and hydrophilicity of PVP, the CNC base layer and SiO 2 photon crystal layer are tightly combined. At the same time, both SiO 2 and PVP can overcome the solid-state quenching of RhB. By utilizing the fluorescence characteristics of RhB, the fluorescence characteristics of the film are increased, and a SiO 2 / CNC composite film with multiple optical characteristics is obtained. This composite film presents the structural color of CNC under natural light, the birefringence color of CNC under polarized light, the dynamic iridescence color of SiO 2 under a point light source, and generates fluorescence color under ultraviolet light excitation. It has multiple optical characteristics and has great application potential in the fields of optical anti-counterfeiting, information encryption, and decoration.

[0039] The present invention also discloses a SiO 2 / CNC multiple optical characteristic composite film. This film includes a CNC photon film in the lower layer and a SiO 2 photon crystal layer in the upper layer. After pouring the dispersion liquid in the upper layer of the film, as the solvent evaporates, SiO 2 is fixed in the PVP matrix, and RhB is evenly dispersed in the film.

[0040] Example 1 (1) Pour 4 g of CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in an oven at 30 °C for evaporation-induced self-assembly to obtain a CNC photon film.

[0041] (2) Add 4 ml of deionized water and 0.012 g of SiO 2 into a beaker, stir evenly to obtain SiO 2 aqueous dispersion.

[0042] (3) Add 100 ml of deionized water and 0.003 g of RhB into a beaker, and stir evenly to obtain a RhB aqueous dispersion.

[0043] (4) Add 0.12 g of PVP into 4 ml of SiO 2 aqueous dispersion, and then add 4 g of RhB aqueous dispersion, and ultrasonically disperse for 30 min to obtain SiO 2 / PVP / RhB aqueous dispersion.

[0044] (5) Place the CNC photonic film in a water bath at 40 °C, soak it in deionized water for 2 h, take it out and pour SiO 2 / PVP / RhB aqueous dispersion, and place it in an oven at 40 °C for self-assembly to obtain SiO 2 / CNC composite film.

[0045] Figure 1 is the cross-sectional SEM image of the SiO 2 / CNC composite film prepared in this example. It can be seen from the figure that the composite film has an obvious layered structure. The upper layer is the crystalline layer formed by PVP-coated SiO 2 , and the lower layer is the crystalline layer formed by PVP-coated CNC.

[0046] Example 2 (1) Pour 3 g of CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in an oven at 40 °C for evaporation-induced self-assembly to obtain a CNC photonic film.

[0047] (2) Add 3 ml of deionized water and 0.01 g of SiO 2 into a beaker, and stir evenly to obtain SiO 2 aqueous dispersion.

[0048] (3) Add 100 ml of deionized water and 0.003 g of RhB into a beaker, and stir evenly to obtain a RhB aqueous dispersion.

[0049] (4) Add 0.1 g of PVP into 3 ml of SiO 2 aqueous dispersion, and then add 5 g of RhB aqueous dispersion, and ultrasonically disperse for 30 min to obtain SiO 2 / PVP / RhB aqueous dispersion.

[0050] (5) Place the CNC photonic film in a water bath at 30 °C, soak it in deionized water for 3 h, take it out and pour SiO 2 / PVP / RhB aqueous dispersion, and place it in an oven at 40 °C for self-assembly to obtain SiO 2 / CNC composite film.

[0051] Figure 2 This is an optical photograph of the CNC photonic film prepared in this example. As can be seen from the figure, there is no obvious coffee ring phenomenon in this film, and it has high gloss and surface flatness.

[0052] Example 3 (1) Pour 5 g of the CNC aqueous dispersion (the mass fraction of CNC is 2%) onto a glass mold, and place it in a drying oven at 30 °C for evaporation-induced self-assembly to obtain a CNC photonic film.

[0053] (2) Add 5 ml of deionized water and 0.015 g of SiO 2 to a beaker, and stir evenly to obtain a SiO 2 aqueous dispersion.

[0054] (3) Add 100 ml of deionized water and 0.003 g of RhB to a beaker, and stir evenly to obtain a RhB aqueous dispersion.

[0055] (4) Add 0.15 g of PVP to 4 ml of the SiO 2 aqueous dispersion, and add 3 g of the RhB aqueous dispersion, and ultrasonically disperse for 30 min to obtain a SiO 2 / PVP / RhB aqueous dispersion.

[0056] (5) Place the CNC photonic film in a water bath at 30 °C, soak it in deionized water for 2 h, take it out, pour the SiO 2 / PVP / RhB aqueous dispersion on it, and place it in a drying oven at 30 °C for self-assembly to obtain a SiO 2 / CNC composite film.

[0057] Figure 3 This is the POM diagram of the CNC photonic film prepared in this example. As can be seen from the figure, this film has an obvious birefringence phenomenon, indicating that the chiral nematic phase structure of CNC is not destroyed.

[0058] Example 4 (1) Pour 4 g of the CNC aqueous dispersion (the mass fraction of CNC is 2%) onto a glass mold, and place it in a drying oven at 30 °C for evaporation-induced self-assembly to obtain a CNC photonic film.

[0059] (2) Add 5 ml of deionized water and 0.015 g of SiO 2 to a beaker, and stir evenly to obtain a SiO 2 aqueous dispersion.

[0060] (3) Add 100 ml of deionized water and 0.003 g of RhB to a beaker, and stir evenly to obtain a RhB aqueous dispersion.

[0061] (4) Add 0.15 g of PVP to 5 ml of SiO 2 aqueous dispersion, and add 3 g of RhB aqueous dispersion. Ultrasonically disperse for 40 min to obtain SiO 2 / PVP / RhB aqueous dispersion.

[0062] (5) Place the CNC photonic film in a 40 °C water bath, soak it in deionized water for 1 h, take it out and pour SiO 2 / PVP / RhB aqueous dispersion, and place it in a 30 °C drying oven for self-assembly to obtain SiO 2 / CNC composite film.

[0063] Figure 4 is the 2D super-depth-of-field microscope image of the CNC photonic film prepared in this example. As can be seen from the figure, the film exhibits obvious birefringent iridescence and fingerprint texture. Example 5 (1) Pour 4 g of CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in a 60 °C drying oven for evaporation-induced self-assembly to obtain a CNC photonic film.

[0064] (2) Add 4 ml of deionized water and 0.012 g of SiO 2 to a beaker, stir evenly to obtain SiO 2 aqueous dispersion.

[0065] (3) Add 100 ml of deionized water and 0.003 g of RhB to a beaker, stir evenly to obtain RhB aqueous dispersion.

[0066] (4) Add 0.12 g of PVP to 4 ml of SiO 2 aqueous dispersion, and add 4 g of RhB aqueous dispersion. Ultrasonically disperse for 30 min to obtain SiO 2 / PVP / RhB aqueous dispersion.

[0067] (5) Place the CNC photonic film in a 30 °C water bath, soak it in deionized water for 2 h, take it out and pour SiO 2 / PVP / RhB aqueous dispersion, and place it in a 30 °C drying oven for self-assembly to obtain SiO 2 / CNC composite film.

[0068] Figure 5 is the optical photo of the SiO 2 / CNC composite film prepared in this example under different lighting conditions. As can be seen from the figure, the composite film shows the blue color of the CNC photonic layer under natural light and SiO 2The gorgeous iridescent color of the photonic crystal layer.

[0069] Example 6 (1) Pour 4 g of CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in an oven at 60 °C for evaporation-induced self-assembly to obtain a CNC photonic film.

[0070] (2) Add 4 ml of deionized water and 0.012 g of SiO 2 to a beaker, stir evenly to obtain a SiO 2 aqueous dispersion.

[0071] (3) Add 100 ml of deionized water and 0.003 g of RhB to a beaker, stir evenly to obtain a RhB aqueous dispersion.

[0072] (4) Add 0.12 g of PVP to 4 ml of the SiO 2 aqueous dispersion, and add 3 g of the RhB aqueous dispersion, and ultrasonically disperse for 30 min to obtain a SiO 2 / PVP / RhB aqueous dispersion.

[0073] (5) Place the CNC photonic film in a water bath at 40 °C, soak it with deionized water for 2 h, take it out, pour the SiO 2 / PVP / RhB aqueous dispersion, and place it in an oven at 40 °C for self-assembly to obtain a SiO 2 / CNC composite film.

[0074] Figure 6 is the POM image of the SiO 2 / CNC composite film prepared in this example. As can be seen from the figure, the POM image of the composite film presents a blue-violet color, has a bright birefringence phenomenon, and retains the chiral nematic phase structure of CNC.

[0075] Example 7 (1) Pour 4 g of CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in an oven at 50 °C for evaporation-induced self-assembly to obtain a CNC photonic film.

[0076] (2) Add 4 ml of deionized water and 0.012 g of SiO 2 to a beaker, stir evenly to obtain a SiO 2 aqueous dispersion.

[0077] (3) Add 100 ml of deionized water and 0.003 g of RhB to a beaker, stir evenly to obtain a RhB aqueous dispersion.

[0078] (4) Add 0.12 g of PVP to 4 ml of the SiO2 In the aqueous dispersion, 3 g of the RhB aqueous dispersion was added, and ultrasonic dispersion was carried out for 30 min to obtain SiO 2 / PVP / RhB aqueous dispersion.

[0079] (5) The CNC photonic film was placed in a water bath at 40 °C and soaked in deionized water for 2 h. After taking it out, SiO 2 / PVP / RhB aqueous dispersion was poured, and it was placed in a drying oven at 40 °C for self-assembly to obtain SiO 2 / CNC composite film.

[0080] Figure 7 is the super-depth-of-field microscopic 3D map of the SiO 2 / CNC composite film prepared in this example. It can be seen from the figure that the composite film has a high flatness.

[0081] Example 8 (1) 4 g of the CNC aqueous dispersion (the mass fraction of CNC is 2%) was poured on a glass mold and placed in a drying oven at 60 °C for evaporation-induced self-assembly to obtain a CNC photonic film.

[0082] (2) 4 ml of deionized water and 0.012 g of SiO 2 were added to a beaker and stirred evenly to obtain SiO 2 aqueous dispersion.

[0083] (3) 100 ml of deionized water and 0.003 g of RhB were added to a beaker and stirred evenly to obtain a RhB aqueous dispersion.

[0084] (4) 0.12 g of PVP was added to 3 ml of the SiO 2 aqueous dispersion, and 3 g of the RhB aqueous dispersion was added, and ultrasonic dispersion was carried out for 30 min to obtain SiO 2 / PVP / RhB aqueous dispersion.

[0085] (5) The CNC photonic film was placed in a water bath at 40 °C and soaked in deionized water for 2 h. After taking it out, SiO 2 / PVP / RhB aqueous dispersion was poured, and it was placed in a drying oven at 40 °C for self-assembly to obtain SiO 2 / CNC composite film.

[0086] Figure 8 is the SiO 2Optical photos of the CNC composite film under different lighting conditions. As can be seen from the figure, under natural light, the film shows a uniform and bright blue-violet color; under a point light source, the film shows an iridescent color; under 365 nm ultraviolet light excitation, the film emits orange-red fluorescence; under 302 nm and 254 nm ultraviolet light excitation, the film emits yellow fluorescence, indicating that the film has different color rendering effects under different lighting conditions.

[0087] Example 9 (1) Pour 4 g of the CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in an 80 °C drying oven for evaporation-induced self-assembly to obtain a CNC photonic film.

[0088] (2) Add 5 ml of deionized water and 0.03 g of SiO 2 to a beaker, stir evenly to obtain a SiO 2 aqueous dispersion.

[0089] (3) Add 100 ml of deionized water and 0.003 g of RhB to a beaker, stir evenly to obtain a RhB aqueous dispersion.

[0090] (4) Add 0.1 g of PVP to 4 ml of the SiO 2 aqueous dispersion, and add 3 g of the RhB aqueous dispersion, and ultrasonically disperse for 30 min to obtain a SiO 2 / PVP / RhB aqueous dispersion.

[0091] (5) Place the CNC photonic film in a 25 °C water bath, soak it in deionized water for 4 h, take it out, pour the SiO 2 / PVP / RhB aqueous dispersion, and place it in a 20 °C drying oven for self-assembly to obtain a SiO 2 / CNC composite film.

[0092] Example 10 (1) Pour 4 g of the CNC aqueous dispersion (CNC mass fraction is 2%) onto a glass mold, and place it in a 20 °C drying oven for evaporation-induced self-assembly to obtain a CNC photonic film.

[0093] (2) Add 5 ml of deionized water and 0.03 g of SiO 2 to a beaker, stir evenly to obtain a SiO 2 aqueous dispersion.

[0094] (3) Add 100 ml of deionized water and 0.003 g of RhB to a beaker, stir evenly to obtain a RhB aqueous dispersion.

[0095] (4) Add 0.3 g of PVP to 5 ml of the SiO 2In the aqueous dispersion, 3 g of RhB aqueous dispersion was added, and ultrasonic dispersion was carried out for 30 min to obtain SiO 2 / PVP / RhB aqueous dispersion.

[0096] (5) The CNC photonic film was placed in a water bath at 40 °C and soaked in deionized water for 3 h. After taking it out, SiO 2 / PVP / RhB aqueous dispersion was poured, and it was placed in an oven at 80 °C for self-assembly to obtain SiO 2 / CNC composite film.

[0097] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a layer stack of SiO2 / CNC composite films with multiple optical characteristics, characterized in that: The following steps are involved: Step 1, pouring CNC aqueous dispersion on a glass mold, drying and self-assembling to obtain a CNC photonic film; Step 2, dispersing SiO2 microspheres in water to obtain SiO2 aqueous dispersion; Step 3, dispersing RhB in water to obtain a RhB aqueous dispersion; Step 4, adding PVP to SiO2 aqueous dispersion to obtain PVP / SiO2 aqueous dispersion; mixing the PVP / SiO2 aqueous dispersion and the RhB aqueous dispersion to obtain SiO2 / PVP / RhB aqueous dispersion; Step 5, soaking the CNC photonic film in a water bath, pouring SiO2 / PVP / RhB aqueous dispersion on the soaked CNC photonic film, and obtaining a SiO2 / CNC composite film after self-assembly.

2. The method for preparing a layer stack of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 1, the mass fraction of the CNC aqueous dispersion is 2%.

3. The method for preparing a layer stack of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 1, the temperature of the drying self-assembly process is 20-80°C.

4. The method for preparing a layer stacking of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 2, the mixing ratio of SiO2 microspheres and water is (0.01-0.03) g: (3-5) mL.

5. The method for preparing a layer stacking of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 2, the mixing ratio of RhB and water is 0.003 g:100 mL.

6. The method for preparing a layer stacking of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 4, the mixing ratio of PVP and SiO2 aqueous dispersion is (0.1-0.3) g: (3-5) mL.

7. The method for preparing a layer stacking of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 4, the mixing ratio of the PVP / SiO2 aqueous dispersion and the RhB aqueous dispersion is (3-5) mL: (3-5) g.

8. The method for preparing a layer stacking of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 5, the soaking temperature is 25-45° C. and the soaking time is 2-4 hours.

9. The method for preparing a layer stacking of a SiO2 / CNC composite film with multiple optical characteristics according to claim 1, characterized in that: In step 5, the drying temperature is 20-80°C.

10. A SiO2 / CNC composite film with multiple optical characteristics prepared by the layer stacking preparation method according to any one of claims 1 to 9, characterized in that: It comprises a lower CNC photonic film and an upper SiO2 photonic crystal layer; wherein the matrix of the upper SiO2 photonic crystal layer is PVP, and SiO2 microspheres and RhB are dispersed in the matrix.

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