阅读说明：本技术 一种多重响应变色防伪薄膜及制备方法 (Multi-response color-changing anti-counterfeiting film and preparation method thereof ) 是由 王文涛 周意诚 杨柳 姚玉元 于 2021-08-21 设计创作，主要内容包括：本发明公开了一种多重响应变色防伪薄膜及其制备方法,属于光学防伪领域。该变色防伪薄膜由三层结构组成,上下两层是由聚合物单体与固化剂组成的预固液经固化成膜得到,中间层则是由荧光胶体粒子自组装形成的光子晶体层。其中荧光胶体粒子由胶体微球负载量子点后在外层包覆一层壳层而得到。该变色防伪薄膜在紫外灯照射下能呈现荧光颜色,经过一定程度的拉伸会产生可视化的结构色变化,且撤销拉力后可恢复初始形状及颜色,根据薄膜颜色变化防伪,简便易行。相比于单一结构色防伪和单一荧光防伪,该薄膜具有多重响应变色特性,实现了光子晶体结构色与量子点荧光协同防伪,提升了防伪级别,在防伪领域具有广阔的应用前景。(The invention discloses a multiple-response color-changing anti-counterfeiting film and a preparation method thereof, belonging to the field of optical anti-counterfeiting. The color-changing anti-counterfeiting film is composed of three layers, wherein the upper layer and the lower layer are obtained by solidifying a pre-solid liquid composed of a polymer monomer and a curing agent into a film, and the middle layer is a photonic crystal layer formed by self-assembling fluorescent colloid particles. The fluorescent colloidal particles are obtained by coating a shell layer on the outer layer of a colloidal microsphere loaded with quantum dots. The color-changing anti-counterfeiting film can show a fluorescent color under the irradiation of an ultraviolet lamp, can generate visual structural color change after being stretched to a certain degree, can restore the initial shape and color after the tension is removed, can prevent counterfeiting according to the color change of the film, and is simple, convenient and easy to implement. Compared with single structural color anti-counterfeiting and single fluorescence anti-counterfeiting, the film has the characteristic of multiple response color change, realizes the synergistic anti-counterfeiting of photonic crystal structural color and quantum dot fluorescence, improves the anti-counterfeiting level, and has wide application prospect in the anti-counterfeiting field.)

1. A multiple response color-changing anti-counterfeiting film is characterized in that: the photonic crystal is composed of three layers, namely an upper layer and a lower layer which are formed by polymer monomers, and a middle layer which is a photonic crystal layer.

2. The multiple-response color-changing anti-counterfeiting film according to claim 1, wherein: the upper layer and the lower layer are respectively films formed by solidifying pre-solid liquid consisting of polymer monomers and a curing agent.

3. The multiple-response color-changing anti-counterfeiting film according to claim 1, wherein: the intermediate layer is a photonic crystal layer formed by self-assembly of fluorescent colloidal particles.

4. The multiple-response color-changing anti-counterfeiting film according to claim 3, wherein: the fluorescent colloid particles are prepared by the following steps:

(1) taking 180-300 nm nanometer microspheres with good monodispersity as cores, carrying out amination modification on the surfaces of the microspheres by using an aminosilane coupling agent, and stirring for 6-12 hours at 70 ℃ to enable the microspheres to have positive charges;

(2) and controlling the pH value of a solution system to be 6-8, loading water-soluble quantum dots with negative charges and 3-10 nm on the surface of the aminated modified nano microsphere by using an electrostatic self-assembly method, and finally coating a shell layer on the outer layer to obtain the fluorescent colloidal particles.

5. The multiple-response color-changing anti-counterfeiting film according to claim 4, wherein: the nano-microspheres are one or more of silicon dioxide, titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide or zinc oxide.

6. The multiple-response color-changing anti-counterfeiting film according to claim 4, wherein: the aminosilane coupling agent is one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, or N- (2-aminoethyl) -3-aminopropylmethyldiethoxysilane.

7. The multiple-response color-changing anti-counterfeiting film according to claim 4, wherein: the water-soluble quantum dots are one or more of cadmium sulfide, cadmium selenide, cadmium telluride, zinc selenide, lead sulfide, lead selenide or indium phosphide.

8. The multiple-response color-changing anti-counterfeiting film according to claim 1, wherein: the polymer monomer is one or more of polydimethylsiloxane, polydiethylsiloxane, octamethyltetrasiloxane, polymethylpolysiloxane, cyclomethicone or polymethylphenylsiloxane.

9. The method for preparing a multiple-response color-changing security film according to claims 1 to 8, wherein:

(1) the preparation method comprises the following steps of (1) carrying out amination modification on the surface of a microsphere by using nano microspheres with good monodispersity through an aminosilane coupling agent to enable the microsphere to have positive charges;

(2) loading the water-soluble quantum dots with negative charges on the surface of the nano microsphere obtained in the step (1) by using an electrostatic self-assembly method, and coating a shell layer on the outer layer to protect the quantum dots so as to obtain fluorescent colloidal particles;

(3) and (3) fully mixing a polymer monomer and a curing agent, curing the mixture in an oven to form a film, performing hydrophilization on the surface of the film by using a plasma technology, uniformly coating the fluorescent colloid particles obtained in the step (2), heating the mixture to self-assemble the mixture to form a photonic crystal layer, coating a layer of polymer monomer pre-solid liquid, penetrating the mixture into gaps of the fluorescent colloid particles at room temperature, and drying the mixture in the oven to form the film, thus obtaining the color-changing anti-counterfeiting film.

10. The method for preparing a multiple-response color-changing anti-counterfeiting film according to claim 9, characterized in that: in the step (3), the mass ratio of the polymer monomer to the curing agent is 5-15: 1, fully mixing to form a pre-solid liquid, drying in an oven at 50-70 ℃ for 1-3 h, carrying out hydrophilic treatment on the surface of the membrane through a plasma technology after membrane formation, volatilizing a solvent on a heating plate at 80-100 ℃ to enable fluorescent colloid particles to self-assemble on the surface of the membrane to form photonic crystals, finally coating a layer of pre-solid liquid, permeating into gaps of the fluorescent colloid particles for 4-8 h, and drying in the oven to form a membrane to obtain the color-changing anti-counterfeiting membrane.

Technical Field

The invention belongs to the field of optical anti-counterfeiting; in particular to a multiple response color-changing anti-counterfeiting film and a preparation method thereof.

Background

Counterfeit and counterfeit are increasingly global problems, which greatly threaten the national reputation, the rights and interests of enterprises to live and consumers, and particularly, counterfeit and counterfeit medicines and foods seriously harm the health of human beings. Therefore, the development of a novel anti-counterfeiting technology for identifying the authenticity of the product and preventing counterfeiting has important significance for improving the national image, promoting the enterprise development and maintaining the rights of consumers. Among a plurality of anti-counterfeiting technologies, the optical anti-counterfeiting technology is based on color discrimination of human eyes, is simple, convenient and reliable, has inherent advantages in public anti-counterfeiting, and is widely applied to various fields of national civilians such as coins, foods, medicines, clothes and the like. However, the common optical anti-counterfeiting technologies such as watermarks, thermoprints, holograms and the like are easy to crack and copy because the images and colors are fixed and visible. Therefore, the development of a novel optical anti-counterfeiting technology with hidden images and variable colors is urgently needed.

The structural color of the photonic crystal is generated by the interaction of diffraction, refraction, interference and the like between the periodic ordered structure and visible light, has the advantages of high brightness, high saturation, fastness to fading and the like, and can realize visual structural color change by regulating and controlling the lattice constant and the change of the refractive index of the photonic crystal. In recent years, many researches have been made to combine a photonic crystal with a stimulus-responsive material, to control the structural color by changing the lattice constant and refractive index of the photonic crystal through specific external stimuli, and to prevent counterfeiting by using the change of the structural color. The quantum dot fluorescence anti-counterfeiting is another important development direction of the optical anti-counterfeiting technology, the unique discrete energy level structure of the quantum dot fluorescence anti-counterfeiting technology can emit fluorescence in a visible light region through relaxation transition between energy bands and in the energy bands under the excitation of specific wavelength light, has the optical characteristics of instantaneous color generation, high fluorescence brightness, adjustable fluorescence color and the like, and has important application value in anti-counterfeiting. The photonic crystal structure color anti-counterfeiting and quantum dot fluorescence anti-counterfeiting have the defect of low anti-counterfeiting level caused by single response color change mechanism. Therefore, there is a need to develop a novel optical anti-counterfeiting material with multiple response color change characteristics to improve the anti-counterfeiting level.

Disclosure of Invention

The invention aims to develop a multiple-response color-changing anti-counterfeiting film and a preparation method thereof. The color-changing anti-counterfeiting film is composed of three layers, wherein the upper layer and the lower layer are obtained by solidifying a pre-solid liquid composed of a polymer monomer and a curing agent to form a film, and the middle layer is a photonic crystal layer formed by self-assembling fluorescent colloid particles. The fluorescent colloidal particles are obtained by coating a shell layer on the outer layer of a colloidal microsphere loaded with quantum dots. The color-changing anti-counterfeiting film can show a fluorescent color under the irradiation of an ultraviolet lamp, can generate visual structural color change after being stretched to a certain degree, can restore the initial shape and color after the tension is removed, can prevent counterfeiting according to the color change of the film, and is simple, convenient and easy to implement. Compared with single structural color anti-counterfeiting and single fluorescence anti-counterfeiting, the film has the characteristic of multiple response color change, realizes the synergistic anti-counterfeiting of photonic crystal structural color and quantum dot fluorescence, improves the anti-counterfeiting level, and has wide application prospect in the anti-counterfeiting field.

The invention is solved by the following technical scheme:

a multiple response color-changing anti-counterfeiting film is characterized in that: the photonic crystal is composed of three layers, namely an upper layer and a lower layer which are formed by polymer monomers, and a middle layer which is a photonic crystal layer.

Preferably, the upper layer and the lower layer of the above-mentioned multiple-response color-changing anti-counterfeiting film are respectively films formed by solidifying a pre-solid liquid composed of a polymer monomer and a curing agent.

Preferably, the intermediate layer in the above-mentioned multiple-response color-changing security film is a photonic crystal layer formed by self-assembly of fluorescent colloidal particles.

Preferably, the fluorescent colloid particles in the above multiple-response color-changing anti-counterfeiting film are prepared by the following steps:

(1) taking 180-300 nm nanometer microspheres with good monodispersity as cores, carrying out amination modification on the surfaces of the microspheres by using an aminosilane coupling agent, and stirring for 6-12 hours at 70 ℃ to enable the microspheres to have positive charges;

(2) and controlling the pH value of a solution system to be 6-8, loading water-soluble quantum dots with negative charges and 3-10 nm on the surface of the aminated modified nano microsphere by using an electrostatic self-assembly method, and finally coating a shell layer on the outer layer to obtain the fluorescent colloidal particles.

Preferably, the nano-microspheres in the multi-response color-changing anti-counterfeiting film are one or more of silicon dioxide, titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide and zinc oxide.

Preferably, the aminosilane coupling agent in the multiple-response color-changing anti-counterfeiting film is one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, or N- (2-aminoethyl) -3-aminopropylmethyldiethoxysilane.

Preferably, the water-soluble quantum dots in the multi-response color-changing anti-counterfeiting thin film are one or more of cadmium sulfide, cadmium selenide, cadmium telluride, zinc selenide, lead sulfide, lead selenide or indium phosphide.

Preferably, the polymer monomer in the multiple-response color-changing anti-counterfeiting film is one or more of polydimethylsiloxane, polydiethylsiloxane, octamethyltetrasiloxane, polymethylpolysiloxane, cyclomethicone and polymethylphenylsiloxane.

A preparation method of a multiple response color-changing anti-counterfeiting film is characterized by comprising the following steps:

(1) the preparation method comprises the following steps of (1) carrying out amination modification on the surface of a microsphere by using nano microspheres with good monodispersity through an aminosilane coupling agent to enable the microsphere to have positive charges;

(2) loading the water-soluble quantum dots with negative charges on the surface of the nano microsphere obtained in the step (1) by using an electrostatic self-assembly method, and coating a shell layer on the outer layer to protect the quantum dots so as to obtain fluorescent colloidal particles;

(3) and (3) fully mixing a polymer monomer and a curing agent, curing the mixture in an oven to form a film, performing hydrophilization on the surface of the film by using a plasma technology, uniformly coating the fluorescent colloid particles obtained in the step (2), heating the mixture to self-assemble the mixture to form a photonic crystal layer, coating a layer of polymer monomer pre-solid liquid, penetrating the mixture into gaps of the fluorescent colloid particles at room temperature, and drying the mixture in the oven to form the film, thus obtaining the color-changing anti-counterfeiting film.

Preferably, in the step (3) of the preparation method of the multiple-response color-changing anti-counterfeiting film, the polymer monomer and the curing agent are mixed in a mass ratio of 5-15: 1, fully mixing to form a pre-solid liquid, drying in an oven at 50-70 ℃ for 1-3 h, carrying out hydrophilic treatment on the surface of the membrane through a plasma technology after membrane formation, volatilizing a solvent on a heating plate at 80-100 ℃ to enable fluorescent colloid particles to self-assemble on the surface of the membrane to form photonic crystals, finally coating a layer of pre-solid liquid, permeating into gaps of the fluorescent colloid particles for 4-8 h, and drying in the oven to form a membrane to obtain the color-changing anti-counterfeiting membrane.

Preferably, the particle size of the nano-microsphere is 180-300 nm, the monodispersity is good, the sphericity is good, and the size is uniform.

Preferably, the particle size of the water-soluble semiconductor quantum dot is 3-10 nm, the sphericity is good, and the size is uniform.

Preferably, the mass ratio of the polymer matrix to the curing agent is 10: 1.

The invention has the advantages of

1. The color-changing anti-counterfeiting film prepared by the invention combines the physical color change of the photonic crystal and the ultraviolet response color-changing characteristic of the quantum dots, has multiple anti-counterfeiting functions and is high in anti-counterfeiting level.

2. The color-changing anti-counterfeiting film prepared by the invention has higher mechanical strength, is not easy to damage and is convenient to use.

Drawings

FIG. 1 is an optical photograph of the color-changeable security film obtained in example 1;

FIG. 2 is a fluorescence spectrum and a reflectance spectrum of the color-changeable anti-counterfeit film obtained in example 1.

FIG. 3 is a stretch relaxation cycle spectrum of the color-changeable security film obtained in example 1.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it will be appreciated that various changes and modifications can be made by those skilled in the art after reading the teachings herein, and that such equivalents will fall within the scope of the appended claims.

Example 1

Firstly, preparing fluorescent colloid particles, which are prepared by the following steps: (1) taking silica nano microspheres with good monodispersity and particle size of 180-300 nm as cores, performing amination modification on the surfaces of the microspheres by using 3-aminopropyltriethoxysilane, and stirring at 70 ℃ for 12 hours to enable the microspheres to have positive charges; the fluorescent colloidal particles are uniformly mixed with cadmium telluride water-soluble quantum dots with negative charges of 3-10 nm, the pH value of the mixed solution is adjusted to 6, the mixed solution is magnetically stirred for 3 hours, the fluorescent quantum dots are loaded on the surface of the aminated modified nano microsphere through an electrostatic self-assembly method, and finally a silicon dioxide shell layer is coated on the outer layer, so that the fluorescent colloidal particles are obtained.

(2) Fully mixing polymer monomer polydimethylsiloxane and a curing agent according to a mass ratio of 10:1 to form a pre-solid liquid, uniformly coating the pre-solid liquid on an acrylic template, drying the pre-solid liquid in a 60 ℃ oven for 2 hours to form a film, carrying out hydrophilic treatment on the surface of the film through a plasma technology, completely volatilizing a solvent on a 80 ℃ heating plate to enable fluorescent colloid particles to self-assemble on the surface of the film to form photonic crystals, finally coating a layer of polydimethylsiloxane pre-solid liquid, permeating into gaps of the fluorescent colloid particles through 8 hours at room temperature, and curing the solid in the 60 ℃ oven for 2 hours to form a film, thus obtaining the color-changing anti-counterfeiting film.

In the embodiment, silica nano microspheres of 195 nm, 230nm and 275nm are taken as cores, the particle size of the loaded cadmium telluride quantum dot is 5nm, fluorescent colloid particles of 215 nm, 255 nm and 297nm are prepared, and then a pre-solid liquid consisting of a polymer monomer and a curing agent is combined to be cured to obtain the color-changing anti-counterfeiting film. The film is transparent when not stretched, bright orange fluorescence is shown when the film is irradiated by an ultraviolet lamp, the film prepared by the fluorescent colloid particles with different particle sizes is respectively changed into purple, green and red after being stretched to a certain degree, and the optical photo is shown in figure 1. The fluorescence spectrum of the film under ultraviolet irradiation and the stretched reflection spectrum are shown in fig. 2, wherein the emission peak corresponding to the fluorescence spectrum is 557nm, and the reflection peaks corresponding to the stretched reflection spectrum are 461nm, 572 nm and 651nm, respectively. In addition, the film sample showing purple color after stretching was subjected to a stretching relaxation cycle test, the deformation amount was controlled to be 20%, the reflection spectrum of the cycle test is shown in fig. 3, after 100 stretching relaxation cycles, the reflection peaks of the film were all located around 461nm, and the intensity of the reflection peaks was substantially unchanged, indicating that the discoloration stability of the film was good.

Examples 2 to 6

Titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide and zinc oxide were used as the nanospheres instead of the silica in example 1, and the other conditions were the same as in example 1. The obtained transparent film shows the fluorescence color of the quantum dots under ultraviolet light, and shows bright photonic crystal structural color in a stretching state.

Example 7

Firstly, preparing fluorescent colloid particles, which are prepared by the following steps: (1) the preparation method comprises the following steps of (1) taking silica nano microspheres with good monodispersity and particle size of 180-300 nm as cores, carrying out amination modification on the surfaces of the microspheres by using 3-aminopropyltrimethoxysilane, and stirring at 70 ℃ for 11 hours to enable the microspheres to be positively charged; uniformly mixing the fluorescent quantum dots with negatively charged cadmium sulfide water-soluble quantum dots with the particle size of 3-10 nm, adjusting the pH value of the mixed solution to 7, magnetically stirring for 3 hours, loading the fluorescent quantum dots on the surface of the aminated modified nano microsphere by an electrostatic self-assembly method, and finally coating a silicon dioxide shell layer on the outer layer to obtain the fluorescent colloidal particles.

(2) Fully mixing polymer monomer poly-diethylsiloxane and a curing agent according to a mass ratio of 10:1 to form a pre-solid liquid, uniformly coating the pre-solid liquid on an acrylic template, drying the pre-solid liquid in a 50 ℃ oven for 3h to form a film, carrying out hydrophilic treatment on the surface of the film through a plasma technology, completely volatilizing the solvent on a 90 ℃ heating plate to enable fluorescent colloid particles to self-assemble on the surface of the film to form photonic crystals, finally coating a layer of poly-diethylsiloxane pre-solid liquid, permeating into gaps of the fluorescent colloid particles through 7h at room temperature, and curing the pre-solid liquid in the 50 ℃ oven for 3h to form the film, thus obtaining the color-changing anti-counterfeiting film. The method comprises the following steps of taking 210nm silicon dioxide nano microspheres as cores, loading cadmium sulfide quantum dots with the particle size of 3nm, preparing fluorescent colloidal particles with the particle size of 230nm for preparing a transparent film, wherein the obtained film is green under the irradiation of ultraviolet light, and is blue in a stretching state.

Examples 8 to 12

Titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide and zinc oxide were used as nanospheres instead of the silica in example 7, and the other conditions were the same as in example 7. The obtained transparent film shows the fluorescence color of the quantum dots under ultraviolet light, and shows bright photonic crystal structural color in a stretching state.

Example 13

Firstly, preparing fluorescent colloid particles, which are prepared by the following steps: (1) the preparation method comprises the following steps of (1) taking silica nano microspheres with good monodispersity and particle size of 180-300 nm as cores, carrying out amination modification on the surfaces of the microspheres by using N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, and stirring at 70 ℃ for 10 hours to enable the microspheres to be positively charged; the fluorescent colloidal particle is uniformly mixed with a negatively charged cadmium selenide water-soluble quantum dot with the particle size of 3-10 nm, the pH value of the mixed solution is adjusted to 8, the mixed solution is magnetically stirred for 3 hours, the fluorescent quantum dot is loaded on the surface of the aminated modified nano microsphere through an electrostatic self-assembly method, and finally a silicon dioxide shell layer is coated on the outer layer, so that the fluorescent colloidal particle is obtained.

(2) Fully mixing polymer monomer cyclomethicone and curing agent according to a mass ratio of 10:1 to form a pre-solid liquid, uniformly coating the pre-solid liquid on an acrylic template, drying the pre-solid liquid in an oven at 70 ℃ for 1 hour to form a film, carrying out hydrophilic treatment on the surface of the film through a plasma technology, completely volatilizing the solvent on a heating plate at 100 ℃ to enable fluorescent colloid particles to self-assemble on the surface of the film to form photonic crystals, finally coating a layer of cyclomethicone pre-solid liquid, permeating the mixture into gaps of the fluorescent colloid particles through 6 hours at room temperature, and curing the mixture in the oven at 70 ℃ for 1 hour to form the film through drying, thereby obtaining the color-changing anti-counterfeiting film. The method comprises the following steps of taking silica nano microspheres of 260nm as cores, loading cadmium selenide quantum dots with the particle size of 4nm, preparing fluorescent colloidal particles with the particle size of 285nm for preparing a transparent film, wherein the obtained film is yellow under the irradiation of ultraviolet light, and the obtained film is orange in a stretched state.

Examples 14 to 18

Titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide and zinc oxide were used as nanospheres instead of the silica in example 13, and the other conditions were the same as in example 13. The obtained transparent film shows the fluorescence color of the quantum dots under ultraviolet light, and shows bright photonic crystal structural color in a stretching state.

Example 19

Firstly, preparing fluorescent colloid particles, which are prepared by the following steps: (1) taking silica nano-microspheres with good monodispersity and particle size of 180-300 nm as cores, performing amination modification on the surfaces of the microspheres by using N- (2-aminoethyl) -3-aminopropyltriethoxysilane, and stirring for 9 hours at 70 ℃ to enable the microspheres to have positive charges; the fluorescent colloidal particle is uniformly mixed with zinc selenide water-soluble quantum dots with negative charges of 3-10 nm, the pH value of the mixed solution is adjusted to 7, the mixed solution is magnetically stirred for 3 hours, the fluorescent quantum dots are loaded on the surface of the aminated modified nano microsphere through an electrostatic self-assembly method, and finally a silicon dioxide shell layer is coated on the outer layer, so that the fluorescent colloidal particle is obtained.

(2) Fully mixing polymer monomer octamethyltetrasiloxane and curing agent according to the mass ratio of 10:1 to form pre-solid liquid, uniformly coating the pre-solid liquid on an acrylic template, drying the pre-solid liquid in an oven at 60 ℃ for 2 hours to form a film, carrying out hydrophilic treatment on the surface of the film through a plasma technology, completely volatilizing the solvent on a heating plate at 90 ℃ to enable fluorescent colloid particles to self-assemble on the surface of the film to form photonic crystals, finally coating a layer of octamethyltetrasiloxane pre-solid liquid, permeating into gaps of the fluorescent colloid particles through 5 hours at room temperature, and curing the solid in the oven at 60 ℃ for 2 hours to form the film, thus obtaining the color-changing anti-counterfeiting film. The 245nm silicon dioxide nano-microspheres are used as cores to load zinc selenide quantum dots with the particle size of 8nm, the prepared fluorescent colloidal particles with the particle size of 270nm are used for preparing transparent films, and the obtained films are red under the irradiation of ultraviolet light and yellow in a stretching state.

Examples 20 to 24

Titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide and zinc oxide were used as nanospheres instead of the silica in example 19, and the other conditions were the same as in example 19. The obtained transparent film shows the fluorescence color of the quantum dots under ultraviolet light, and shows bright photonic crystal structural color in a stretching state.

Example 25

Firstly, preparing fluorescent colloid particles, which are prepared by the following steps: (1) taking silica nano-microspheres with good monodispersity and particle size of 180-300 nm as cores, performing amination modification on the surfaces of the microspheres by using N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, and stirring at 70 ℃ for 8 hours to enable the microspheres to have positive charges; uniformly mixing the fluorescent quantum dots with lead sulfide water-soluble quantum dots with negative charges and the particle size of 3-10 nm, adjusting the pH value of the mixed solution to 6, magnetically stirring for 3 hours, loading the fluorescent quantum dots on the surface of the aminated modified nano microsphere by an electrostatic self-assembly method, and finally coating a silicon dioxide shell layer on the outer layer to obtain the fluorescent colloidal particles.

(2) Fully mixing polymer monomer polymethylphenylsiloxane and a curing agent according to a mass ratio of 10:1 to form a pre-solid liquid, uniformly coating the pre-solid liquid on an acrylic template, drying the pre-solid liquid in a 50 ℃ oven for 3 hours to form a film, carrying out hydrophilic treatment on the surface of the film through a plasma technology, completely volatilizing a solvent on a 80 ℃ heating plate to enable fluorescent colloidal particles to self-assemble on the surface of the film to form photonic crystals, finally coating a layer of polymethylphenylsiloxane pre-solid liquid, permeating the pre-solid liquid into gaps of the fluorescent colloidal particles at room temperature for 4 hours, and curing the pre-solid liquid in the 50 ℃ oven for 3 hours to form a film, thus obtaining the color-changing anti-counterfeiting film. The fluorescent colloidal particles with the particle size of 260nm are prepared by taking 240nm silicon dioxide nano microspheres as cores and loading lead sulfide quantum dots with the particle size of 6nm, and are used for preparing transparent films, and the obtained films are orange under the irradiation of ultraviolet light and green in a stretching state.

Examples 26 to 30

Titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide and zinc oxide were used as nanospheres instead of the silica in example 25, and the other conditions were the same as in example 25. The obtained transparent film shows the fluorescence color of the quantum dots under ultraviolet light, and shows bright photonic crystal structural color in a stretching state.

Example 31

Firstly, preparing fluorescent colloid particles, which are prepared by the following steps: (1) taking silica nano-microspheres with good monodispersity and particle size of 180-300 nm as cores, performing amination modification on the surfaces of the microspheres by using N- (2-aminoethyl) -3-aminopropylmethyldiethoxysilane, and stirring at 70 ℃ for 7 hours to enable the microspheres to have positive charges; the fluorescent colloidal particle is uniformly mixed with lead selenide water-soluble quantum dots with negative charges and 3-10 nm, the pH value of the mixed solution is adjusted to 7, the mixed solution is magnetically stirred for 3 hours, the fluorescent quantum dots are loaded on the surface of the aminated modified nano microsphere through an electrostatic self-assembly method, and finally a layer of silicon dioxide shell layer is coated on the outer layer, so that the fluorescent colloidal particle is obtained.

(2) Fully mixing polymer monomer polymethyl polysiloxane and a curing agent according to a mass ratio of 10:1 to form a pre-solid liquid, uniformly coating the pre-solid liquid on an acrylic template, drying the pre-solid liquid in an oven at 70 ℃ for 1h to form a film, performing hydrophilic treatment on the surface of the film by using a plasma technology, completely volatilizing the solvent on a heating plate at 100 ℃ to enable fluorescent colloid particles to self-assemble on the surface of the film to form photonic crystals, finally coating a layer of polymethyl polysiloxane pre-solid liquid, permeating the mixture into gaps of the fluorescent colloid particles at room temperature for 6h, and curing the mixture in the oven at 70 ℃ for 1h to form a film, thereby obtaining the color-changing anti-counterfeiting film. The preparation method comprises the following steps of taking 285nm silicon dioxide nano microspheres as cores, loading lead selenide quantum dots with the particle size of 4nm, preparing fluorescent colloidal particles with the particle size of 305nm for preparing a transparent film, wherein the obtained film is green under the irradiation of ultraviolet light, and is red in a stretching state.

Examples 32 to 36

Titanium dioxide, zirconium dioxide, tin dioxide, cerium dioxide and zinc oxide were used as nanospheres instead of the silica in example 31, and the other conditions were the same as in example 31. The obtained transparent film shows the fluorescence color of the quantum dots under ultraviolet light, and shows bright photonic crystal structural color in a stretching state.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.