Preparation method of non-iridescent structural color film with infrared anti-counterfeiting characteristics

Abstract

The present application relates to a kind of preparation methods of non-iridescent structural color film with infrared anti-fake features. First, the aqueous solution of monodisperse microspheres is configured, then a small amount of MXene and carbon black material is added, and a mixed colloidal particle suspension is obtained. By using spray, spin coating or roll coating method, three-dimensional amorphous photonic crystal film is formed on the surface of the substrate by rapid evaporation of solvent. The black material absorbs light and scatters multiple times in the amorphous photonic structure, improving the color quality of the amorphous photonic crystal film and showing good non-iridescent structural color display. By using the better absorption in the solar spectrum and the extremely low emissivity in the mid-infrared band of MXene material, as well as the optical characteristic difference with carbon black and other materials, the structural color film realizes the thermal anti-fake property. After micro-heating, the hidden information can be read by an infrared camera.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation of structural color thin films, and particularly relates to a preparation method of a non-iridescent structural color thin film with infrared anti-counterfeiting characteristics. BACKGROUND

[0002] Both industrial production and social management are looking for more advanced and reliable encryption anti-counterfeiting technology. In recent years, structural color materials have attracted widespread attention in the field of information security and anti-counterfeiting. The colorful structural color increases the interest of people's visual experience, and the characteristics that cannot be identified by the naked eye become the main way of information hiding and anti-counterfeiting.

[0003] Structural color widely exists in animals in nature, such as birds, butterflies, beetles, peacocks, and even in the flowers and fruits of plants. Structural color is derived from the periodic microstructure on the surface of the above animals and plants, such as linear array, multilayer film and photonic crystal, etc. Light interacts with these periodic structures, resulting in specific light behavior of grating diffraction or Bragg reflection or photonic bandgap reflection. Compared with dyes or pigments, structural color looks more vivid and bright. The generation of structural color does not require toxic metal ions or organic components, which is more conducive to environmental protection and human survival and development. Although the rainbow structural color has unique optical effects, non-iridescent structural color is needed in many applications because they are compatible with a wider range of viewing angles, thereby having more design flexibility. Amorphous colloidal array (ACA) is a "defect state" of photonic crystal, the lattice order is low, and the photonic bandgap is incomplete, so light is uniformly scattered in all directions, forming a non-iridescent structural color that is not constrained by the viewing angle. Among them, the key to the preparation of amorphous colloidal array is to avoid colloidal crystallization. In recent years, various assembly methods have been proposed, such as spin coating, spraying, electrophoretic deposition or microfluidic preparation, etc., among which spraying is a method that uses atomization to quickly evaporate colloidal liquid to prevent colloidal particles from being ordered assembled, and with the help of a template, a non-iridescent structural color film with a specified pattern can be quickly prepared.

[0004] It is worth noting that due to strong multiple scattered light, ACAs often appear white, which directly affects the quality of their color, so black substances such as carbon black or black background can be used to absorb multiple scattered light to improve the quality of their structural color. MXene is a new two-dimensional material with special physical and chemical properties, such as adjustable chemical properties, ultra-high electrical conductivity, and shows great potential in the fields of catalytic energy, sensing, and high-temperature anti-counterfeiting. MXene (Ti3C2T X) in the solar spectrum (90%) while having a lower emissivity in the mid-infrared. This property makes MXene (Ti3C2T X ) materials have excellent high-temperature thermal camouflage properties, and in addition, their black appearance increases the contrast of the structural color, improving the color quality of the thin film. SUMMARY

[0005] The present application provides a method for preparing non-iridescent structural color materials, which can quickly and large-area prepare high-quality patterned non-iridescent structural color materials, and the prepared structural color materials have infrared thermal anti-counterfeiting characteristics.

[0006] The technical scheme adopted by the present application to solve its technical problems is:

[0007] Step 1: disperse monodisperse colloidal particles in an aqueous solution to obtain a colloidal particle suspension with a mass fraction of 1-40%;

[0008] Step 2: add MXene (Ti3C2T X ) nanosheet powder to the colloidal particle suspension in step 1 and ultrasonic for 10-50 minutes to obtain a mixed suspension A containing MXene (Ti3C2T X ) nanosheet with a mass fraction of 0.1-5%;

[0009] Step 3: add black substances to the colloidal particle suspension in step 1 and ultrasonic for 10-50 minutes to obtain a mixed suspension B containing black substances with a mass fraction of 0.1-5%;

[0010] Step 4: by spin coating, spray coating or roll coating method, with the help of a mask, first form a patterned structural color thin film prepared by rapid assembly of colloidal particles in suspension A on part of the surface of the substrate, and second form a patterned structural color thin film prepared by rapid assembly of colloidal particles in suspension B on other areas of the substrate surface, thereby obtaining a non-iridescent structural color thin film with infrared anti-counterfeiting characteristics;

[0011] Step 5: perform micro-heating treatment on the thin film and use an infrared camera to read the hidden information.

[0012] In the step 1, the particle size of the monodisperse colloidal particles ranges from 150 to 500 nm.

[0013] The monodisperse colloidal particles in step 1 are SiO2, polystyrene (PS), TiO2, ZnO, CuO2, Cu2O or MOFs colloidal particles.

[0014] The shape of the monodisperse colloidal particles in step 1 is spherical or polyhedral.

[0015] The aqueous solution in step 1 is water, ethanol, methanol, ethylene glycol or a mixed solution of several of them in any proportion.

[0016] The MXene (Ti3C2T X ) prepared in step 2 is a single-layer or multi-layer nanosheet with a lateral size less than 1 μm and a thickness less than 10 nm.

[0017] The black substance in step 3 is carbon black, graphene oxide or melanin particles.

[0018] The substrate in step 4 is a silicon wafer, a glass slide, a PET plastic, an acrylic plate or a hard paper.

[0019] The substrate in step 4 needs to be subjected to plasma cleaning treatment before use to make the substrate hydrophilic.

[0020] The non-iridescent structural color thin film with infrared anti-counterfeiting characteristics in step 4 is an amorphous photonic crystal three-dimensional structure with a thickness of 220 nm-10 μm.

[0021] The mask in step 5 is a custom pattern mask, and the suspension A and B are sprayed on the substrate surface in different pattern areas to obtain a custom patterned structural color thin film.

[0022] The micro-heating treatment in step 6 is irradiation using a heating plate or an infrared lamp for 1 s-20 s.

[0023] The above technical scheme of the present application has the following beneficial effects:

[0024] The present application utilizes the black appearance characteristics of MXene (Ti3C2T X ) to improve the color saturation of the amorphous photonic structure, which has high absorption in the solar spectrum and low emission in the mid-infrared, thus improving the color saturation of the amorphous photonic structure. The optical properties of the present application are different from the light absorption properties of ordinary black materials, which makes the structural color thin film have adjustable infrared heat anti-counterfeiting characteristics. The three-dimensional amorphous photonic structure is obtained by using a solvent removal method, and the structural color thin film has non-iridescent characteristics. By adjusting the proportion of the black material, the display time and visual effect of the hidden information of the structural thin film can be controlled. The custom patterned information anti-counterfeiting label can be obtained by spraying under the assistance of a mask.

[0025] The colloidal particles used by the present application are SiO2, or microspheres such as polystyrene PS mixed with black materials, so that the preparation of structural color thin film has little environmental pollution, and the main solution used is water or ethanol solution.

[0026] The present application provides a variety of substrates for preparing amorphous photonic structure thin film, which has no angle-dependent non-iridescent visual effect in natural state. Moreover, its preparation method is simple and easy to operate, which widens its application in the fields of sensor devices, photoelectric conversion and daytime radiation temperature control.

[0027] The structural color hidden pattern prepared by the present application can be observed under an infrared camera under heating conditions below 100 degrees, and cannot be observed under normal conditions, which has important research value in the field of infrared anti-counterfeiting. It widens its application in the field of non-iridescent structural color coating and anti-counterfeiting. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the preparation flow chart in Example 1.

[0029] Figure 2 is the SEM picture of the amorphous photonic structure thin film in Example 1.

[0030] Figure 3 is the contrast digital photo of the amorphous photonic structure thin film prepared in Example 2 by adding different proportions of MXene (Ti3C2T X ).

[0031] Figure 4 is the non-iridescent structural color anti-counterfeiting pattern based on amorphous photonic structure and its angle-independent color digital photo in Example 3.

[0032] Figure 5 is the appearance photo of the non-iridescent structural color anti-counterfeiting pattern based on amorphous photonic structure under infrared camera in Example 3. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be further described in combination with the examples. It should be understood that the implementation of the present application is not limited by the following examples. In addition, in the following description, the description of the known structure and technology is omitted to avoid unnecessary confusion of the scope of the present application.

[0034] Example 1

[0035] (1) Prepare a SiO2 colloidal solution with a mass fraction of 10% at room temperature and normal pressure, and the solvent is a mixed solution prepared by mixing water and ethanol at a volume ratio of 1:1, and the SiO2 particle size is 195 nm.

[0036] (2) Take a certain mass of MXene (Ti3C2T X) powder is added to the solution in step 1, with a mass fraction of 0.2wt%, and ultrasonic treatment for 30 minutes to obtain a uniformly dispersed mixed solution.

[0037] (3) A piece of white paper with a size of 2cm*2cm is taken, 200uL of the mixed solution in step 2 is taken using a pipette, and a small spray gun is used to spray it on the white paper.

[0038] Figure 2 is the SEM picture of the amorphous photonic structure film in Example 1. From the SEM picture, the short-range ordered assembly of colloidal particles can be observed, indicating the successful preparation of the amorphous photonic crystal and the successful incorporation of MXene (Ti3C2T X ) nanosheets.

[0039] Example 2

[0040] (1) A PS colloidal solution with a mass fraction of 5% is prepared at room temperature and normal pressure, with water as the solvent and PS particle sizes of 180, 210, and 250nm, respectively.

[0041] (2) A certain amount of MXene (Ti3C2T X ) powder is added to the colloidal solution in step 1 to prepare PS colloidal solutions containing MXene (Ti3C2T X ) with mass fractions of 0, 0.1, 0.2, and 0.3wt%, respectively, and ultrasonic treatment for 30 minutes to obtain a uniformly dispersed mixed solution.

[0042] (3) A piece of white paper with a size of 2cm*2cm is taken, 200uL of the mixed solution in step 2 is taken using a pipette, and a small spray gun is used to spray it on the white paper.

[0043] Figure 3 is a contrast digital photo of the amorphous photonic structure film prepared in Example 2 with different proportions of MXene (Ti3C2T X ). From the photo, it can be clearly observed that when there is no MXene (Ti3C2T X ) incorporated, the amorphous photonic crystal film prepared by spraying method almost has no structural color, and as the content of MXene (Ti3C2T X ) increases, the structural color becomes more and more obvious, and the color quality improves.

[0044] Example 3

[0045] (1) A SiO2 colloidal solution with a mass fraction of 5% is prepared at room temperature and normal pressure, with water as the solvent and SiO2 particle sizes of 195, 240, and 295nm, respectively.

[0046] (2) A certain amount of MXene (Ti3C2T X) Powder is added to the colloidal solution in step 1, and a mixed solution containing MXene (Ti3C2T X ) with a mass fraction of 0.2wt% is prepared and ultrasonically treated for 30 minutes to obtain a uniformly dispersed mixed solution A.

[0047] (3) A certain amount of carbon black powder is added to the colloidal solution in step 1, and a mixed solution containing carbon black with a mass fraction of 0.1wt% is prepared and ultrasonically treated for 30 minutes to obtain a uniformly dispersed mixed solution B.

[0048] (4) A 2cm*2cm silicon wafer is taken, 200uL of the mixed solution A in step 2 is taken using a pipette, and a small spray gun is used to spray the letters U, J, and S in the middle position of the silicon wafer with the help of a mask plate. In the next step, the mixed solution B in step 3 is sprayed in the blank position of the silicon wafer with the help of a mask plate using a small spray gun.

[0049] (5) The structural color film-coated silicon wafer is placed under an infrared lamp for 10s, and then a digital photo is taken using an infrared camera.

[0050] Figure 4 is the digital photo of the non-crystalline photonic structural color anti-counterfeiting pattern in Example 3, and the structural color of the film does not change significantly at observation angles of 15, 30 and 45°. Figure 5 is the appearance photo of the non-crystalline photonic structural color anti-counterfeiting pattern in Example 3 under an infrared camera. Because of the difference in light absorption characteristics of the two kinds of carbon black and MXene (Ti3C2T X ), they have different temperature responses, and with the help of an infrared camera, the hidden encrypted information can be read.

Claims

1. A method for producing a non-iridescent structural color film having an infrared anti-counterfeiting feature, characterized by, The specific steps are as follows: Step 1: disperse monodisperse colloidal particles in an aqueous solution to obtain a colloidal particle suspension with a mass fraction of 1-40%; Step 2: add MXene nanosheet powder to the colloidal particle suspension in step 1 and ultrasonic to obtain a mixed suspension A containing MXene nanosheets with a mass fraction of 0.1-5%; Step 3: add black matter to the colloidal particle suspension in step 1 and ultrasonic to obtain a mixed suspension B containing black matter with a mass fraction of 0.1-5%; Step 4: by spin coating, spray coating or roll coating method, with the help of a mask plate, first form a patterned structural color film prepared by rapid assembly of colloidal particles from suspension A on part of the surface of the substrate, and second form a patterned structural color film prepared by rapid assembly of colloidal particles from suspension B on other areas of the substrate surface, thereby obtaining a non-iridescent structural color film with infrared anti-counterfeiting characteristics; Step 5: perform a micro-heating treatment on the film and use an infrared camera to read the hidden information, and the micro-heating treatment is irradiated with an infrared lamp for 1s-20s.

2. The method for preparing a non-iridescent structural color film with infrared anti-counterfeiting features as described in claim 1, characterized in that, In step 1, the particle size of the monodisperse colloidal particles ranges from 150 to 500 nm.

3. The method of claim 1, wherein the non-iridescent structural color film having an infrared anti-counterfeiting feature is prepared by the steps of: (a) preparing a mixture of a first material and a second material; (b) applying the mixture to a substrate; (c) drying the mixture to form a film; and (d) applying a third material to the film. In step 1, the monodisperse colloidal particles are SiO2, polystyrene, TiO2, ZnO, CuO2, Cu2O or MOFs colloidal particles; the shape of the monodisperse colloidal particles is spherical or polyhedral; and the aqueous solution is water, ethanol, methanol, ethylene glycol or a mixture of several of them in any ratio.

4. The method of claim 1, wherein the non-iridescent structural color film having an infrared anti-counterfeiting feature is prepared by the steps of: (a) preparing a mixture of a first material and a second material; (b) applying the mixture to a substrate; (c) drying the mixture to form a film; and (d) irradiating the film with infrared light. In step 2, the MXene nanoplatelet powder is Ti3C2T X Single or multi-layer nanoplatelets, lateral dimension less than 1 pm, thickness less than 10 nm; sonication time is 10 - 50 minutes.

5. The method of claim 1, wherein the non-iridescent structural color film having an infrared anti-counterfeiting feature is prepared by the steps of: (a) preparing a mixture of a first material and a second material; (b) applying the mixture to a substrate; (c) drying the mixture to form a film; and (d) applying a third material to the film. In step 3, the black matter is carbon black, graphene oxide or black pigment particles.

6. The method of claim 1, wherein the non-iridescent structural color film having an infrared anti-counterfeiting feature is prepared by the steps of: (a) preparing a mixture of a first material and a second material; (b) applying the mixture to a substrate; (c) drying the mixture to form a film; and (d) applying a third material to the film. In step 4, the substrate is a silicon wafer, a glass slide, PET plastic, acrylic sheet or hard paper, and the substrate needs to be treated with plasma cleaning before use to make the substrate hydrophilic.

7. The method of claim 1, wherein the non-iridescent structural color film having an infrared anti-counterfeiting feature is prepared by the steps of: (a) preparing a mixture of a first material and a second material; (b) applying the mixture to a substrate; (c) drying the mixture to form a film; and (d) applying a third material to the film. In step 4, the non-iridescent structural color film with infrared anti-counterfeiting characteristics is an amorphous photonic crystal three-dimensional structure with a thickness of 220 nm-10 μm.

8. The method of claim 1, wherein the non-iridescent structural color film having an infrared anti-counterfeiting feature is prepared by the steps of: (a) preparing a mixture of a first material and a second material; (b) applying the mixture to a substrate; (c) drying the mixture to form a film; and (d) applying a third material to the film. In step 4, the mask plate is a custom pattern mask plate, and suspensions A and B are sprayed on different pattern areas of the substrate surface in sequence to obtain a custom patterned structural color film.

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