Anti-counterfeiting film with fluorescence changing color along with angle and preparation method of anti-counterfeiting film

Abstract

The invention discloses an anti-counterfeiting film with fluorescence changing color along with angles and a preparation method thereof, the anti-counterfeiting film comprises a single-layer dielectric microsphere array, a patterned second quantum dot light-emitting film, a middle-layer high-molecular polymer film, a patterned first quantum dot film and a substrate which are sequentially stacked and connected, and the single-layer dielectric microsphere array is a single-layer high-refractive-index glass microsphere array; the patterned first quantum dot light-emitting film and the patterned second quantum dot light-emitting film are films formed by mixing and curing a quantum dot solution and a high-molecular polymer, and have InP / ZnS quantum dots with various different photoluminescence peak positions; the middle-layer high-molecular polymer film is a film formed by curing a pre-solid liquid consisting of a polymer monomer and a curing agent; and the substrate is a PDMS high-molecular polymer film. The film not only can present a fluorescent color under the irradiation of an ultraviolet lamp, but also can generate color change along with the change of an observation angle, and the film is high in anti-counterfeiting level, good in flexibility, low in preparation cost and simple in method.

Description

Technical Field

[0001] The invention relates to the technical field of optical anti-counterfeiting, and in particular to a fluorescent angularly color-changing anti-counterfeiting film and a preparation method thereof. Background Art

[0002] As the process of economic globalization continues to accelerate, the problem of counterfeiting and shoddy products is becoming increasingly serious around the world, posing a major threat to national reputation, corporate survival and consumer rights. At present, relevant personnel from the government, enterprises and scientific research institutions have developed a series of anti-counterfeiting technologies to combat fraud, including fluorescent anti-counterfeiting, structural color anti-counterfeiting, optically variable ink anti-counterfeiting and laser holographic anti-counterfeiting. Among the many anti-counterfeiting technologies, fluorescent anti-counterfeiting technology has become one of the most widely used anti-counterfeiting technologies due to its many advantages such as bright colors, rapid response, strong concealment and easy identification.

[0003] However, the traditional fluorescent anti-counterfeiting strategy presents a relatively fixed luminescence pattern under a single stimulus condition, and the fluorescent color and pattern lack dynamic changes and diversity, which makes its anti-counterfeiting effect very easy to be analyzed and copied by counterfeiters, limiting its further application and development in the field of advanced anti-counterfeiting. Therefore, it is particularly urgent to research and develop new anti-counterfeiting technologies, especially high-security level technologies. Summary of the invention

[0004] The purpose of the present invention is to provide a fluorescent angularly color-changing anti-counterfeiting film and a preparation method thereof. The film can not only present fluorescent color under ultraviolet light, but also change color as the observation angle changes. Compared with single fluorescent anti-counterfeiting, the film has a high anti-counterfeiting level, good flexibility, low preparation cost, and simple method, and has great application prospects in the anti-counterfeiting field.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A fluorescent angularly color-changing anti-counterfeiting film, the film comprising a single-layer dielectric microsphere array, a patterned second quantum dot luminescent film, a high molecular polymer film, a patterned first quantum dot film and a substrate, which are sequentially stacked and connected, wherein:

[0007] The single-layer dielectric microsphere array is a single-layer high-refractive-index glass microsphere array;

[0008] The patterned first quantum dot luminescent film and the patterned second quantum dot luminescent film are films formed by mixing and curing a quantum dot solution and a high molecular polymer, and have indium phosphide / zinc sulfide quantum dots with a variety of different photoluminescence peak positions;

[0009] The intermediate layer polymer film is a film formed by curing a pre-solidified liquid composed of a polymer monomer and a curing agent, and is specifically prepared by a coating method or a screen printing method;

[0010] The substrate is a PDMS macromolecular polymer film.

[0011] A method for preparing a fluorescent angularly color-changing anti-counterfeiting film, the method comprising:

[0012] Step 1: First, prepare a flexible substrate;

[0013] Step 2: preparing a patterned first quantum dot light-emitting film on the prepared substrate;

[0014] Step 3, preparing an intermediate layer of high molecular polymer film on the upper surface of the patterned first quantum dot light-emitting film;

[0015] Step 4, preparing a patterned second quantum dot light-emitting film on the intermediate layer polymer film;

[0016] Step 5: Finally, a single-layer dielectric microsphere array is prepared on the patterned second quantum dot light-emitting film.

[0017] It can be seen from the technical solution provided by the present invention that the above-mentioned film can not only present fluorescent color under ultraviolet light, but also change color as the observation angle changes. Compared with single fluorescent anti-counterfeiting, the film has a high anti-counterfeiting level, good flexibility, low preparation cost, and simple method, and has great application prospects in the anti-counterfeiting field. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the structure of a fluorescent angularly color-changing anti-counterfeiting film provided in an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of a process of the method according to an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of the morphology of a dielectric microsphere array according to an example of the present invention;

[0022] Figure 4 This is a schematic diagram of the film according to an embodiment of the present invention under a vertical observation angle;

[0023] Figure 5 This is a schematic diagram of the film described in an embodiment of the present invention at an inclined observation angle. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] like Figure 1 The figure shows a schematic diagram of the structure of a fluorescent angularly variable anti-counterfeiting film provided by an embodiment of the present invention, wherein the film comprises a single-layer dielectric microsphere array (A), a patterned second quantum dot luminescent film (B), an intermediate polymer film (C), a patterned first quantum dot film (D) and a substrate (E) which are sequentially stacked and connected, wherein:

[0026] The single-layer dielectric microsphere array is a single-layer high-refractive-index glass microsphere array;

[0027] The patterned first quantum dot luminescent film and the patterned second quantum dot luminescent film are films formed by mixing and curing a quantum dot solution and a high molecular polymer, and have indium phosphide / zinc sulfide (InP / ZnS) quantum dots with a variety of different photoluminescence peak positions;

[0028] The intermediate layer polymer film is a film formed by curing a pre-solidified liquid composed of a polymer monomer and a curing agent, and is specifically prepared by a coating method or a screen printing method;

[0029] The substrate is a PDMS macromolecular polymer film.

[0030] In a specific implementation, the diameter of the microspheres in the single-layer dielectric microsphere array is 55 μm, and the refractive index is 1.95.

[0031] The thicknesses of the patterned first quantum dot light-emitting film and the patterned second quantum dot light-emitting film are 4.3 μm and 4.2 μm respectively.

[0032] The high molecular polymer in the intermediate high molecular polymer film is PDMS, and the thickness of the intermediate high molecular polymer film is 40.6 μm.

[0033] The thickness of the substrate is 95.9 μm.

[0034] In addition, the quantum dot luminescent film uses screen printing technology to achieve patterning of the quantum dot film, and the quantum dot film has a variety of different sizes, precisions and patterns.

[0035] The present invention also provides a method for preparing a fluorescent anti-counterfeiting film with angular color change, such as Figure 2FIG. 1 is a flow chart of a method according to an embodiment of the present invention, wherein the method comprises:

[0036] Step 1: First, prepare a flexible substrate;

[0037] In step 1, the glass sheet is first immersed in acetone and ultrasonically cleaned to remove organic matter on the surface of the substrate, and then the glass sheet is repeatedly rinsed with deionized water and dried at room temperature;

[0038] Then, the polymer monomer and the curing agent are fully mixed in a mass ratio of 10:1 to form a pre-solidified liquid;

[0039] Then the prepared pre-solidified liquid is spin-coated on a clean glass sheet, and the thickness of the film is controlled by the rotation speed of the coating machine;

[0040] Finally, after the spin coating is completed, the sample is placed on a heating platform for heating and curing to obtain a substrate.

[0041] Step 2: preparing a patterned first quantum dot light-emitting film on the prepared substrate;

[0042] Step 3, preparing an intermediate layer of high molecular polymer film on the upper surface of the patterned first quantum dot light-emitting film;

[0043] In step 3, the preparation method of the intermediate layer polymer film is:

[0044] The polymer monomer and the curing agent are fully mixed in a mass ratio of 10:1 to form a pre-solidified liquid;

[0045] Then the prepared pre-solidified liquid is spin-coated on the patterned first quantum dot light-emitting film, and the thickness of the film is controlled by the rotation speed of the coating machine;

[0046] After the spin coating is completed, the sample is placed on a heating platform for heating and curing to obtain an intermediate layer polymer film.

[0047] Step 4, preparing a patterned second quantum dot light-emitting film on the intermediate layer polymer film;

[0048] In steps 2 and 4, the preparation process of the patterned first quantum dot luminescent film and the patterned second quantum dot luminescent film is:

[0049] dispersing quantum dots in an organic solvent to obtain a quantum dot solution;

[0050] Then, the quantum dot solution and the polymer are fully mixed, and the excess organic solvent is evaporated to remove, so as to obtain a quantum dot-polymer mixed solution;

[0051] The obtained quantum dot-polymer mixture is poured into a screen printing plate, and a patterned quantum dot film is obtained by scraping.

[0052] Step 5: Finally, a single-layer dielectric microsphere array is prepared on the patterned second quantum dot light-emitting film.

[0053] In step 5, the preparation process of the single-layer dielectric microsphere array is specifically as follows:

[0054] Firstly, dielectric microspheres are sprayed on the surface of the patterned second quantum dot light-emitting film;

[0055] Then the microspheres that were not attached to the film surface were removed with a low-tack tape by repeatedly scraping and pressing the film surface;

[0056] Repeat the above operation several times until a single-layer microsphere array is formed;

[0057] Finally, the film is heated again to fix the microsphere array on the film surface.

[0058] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in the field.

[0059] The preparation process of the fluorescent angular color-changing anti-counterfeiting film is described below by taking a specific process example:

[0060] Step 1: Take a 4cm×4cm glass sheet, immerse the glass sheet in acetone, and ultrasonically clean it for 5 minutes to remove chemical stains such as organic matter on the surface of the substrate. Finally, rinse the glass sheet repeatedly with deionized water and dry it at room temperature; mix the PDMS main agent and the curing agent in a mass ratio of 10:1 to obtain a PDMS colloid solution, and then stir the PDMS colloid thoroughly and put it into a vacuum drying oven to evacuate to remove bubbles in the colloid; then spin coat the prepared PDMS solution on the cleaned glass sheet, set the low speed of the coating machine to 800r / min, and the time is 18s. After the spin coating is completed, place the sample on a heating platform for heating and curing. The temperature of the heating platform is set to 100℃ for about 10 minutes to obtain a thin film substrate.

[0061] Step 2: Mix the InP / ZnS quantum dot solution with a photoluminescence peak of 630nm and a concentration of 5mg / ml with the PDMS colloidal solution, and ultrasonicate for 5 minutes to make them evenly mixed; pour the mixed quantum dot-PDMS colloidal solution into a screen printing plate with a mesh number of 420, and scrape it once with a scraper to obtain a patterned first quantum dot film; place the film on a heating platform, the heating temperature is 100°C, and the heating time is 5 minutes to obtain a patterned first quantum dot luminescent film.

[0062] Step 3: Spin coat the PDMS colloidal solution on the patterned first quantum dot luminescent film, set the low speed of the coating machine to 1000r / min for 18s, and the high speed to 4000r / min for 10s; after the spin coating, place the sample on a heating platform for heating and curing, set the temperature of the heating platform to 100°C for about 10min, and obtain a PDMS film, i.e., an intermediate layer polymer film.

[0063] Step 4: Using the same method and parameters as those for preparing the patterned first quantum dot film, a patterned second quantum dot luminescent film is prepared on the PDMS film, and the photoluminescence peak position of the quantum dots in the second quantum dot film is 525 nm.

[0064] Step 5: Spray dielectric microspheres with a diameter of 55 μm on the surface of the second quantum dot film; adhere to the film surface by repeated scraping and pressing, and remove the microspheres not attached to the film surface with 3M low-viscosity tape; then repeat the above operation several times until a single-layer microsphere array is formed, such as Figure 3 FIG. 4 is a schematic diagram of the morphology of the dielectric microsphere array of the present invention; finally, the film is heated at a heating temperature of 100° C. for 5 min to fix the microsphere array on the surface of the film, and the film is obtained as shown in FIG. Figure 1 The structure of the fluorescent angle-dependent anti-counterfeiting film is shown.

[0065] In a specific implementation, 365 nm ultraviolet excitation light is used to excite the film described in the embodiment of the present invention, such as Figure 4 FIG. 1 is a schematic diagram of a film according to an embodiment of the present invention under a vertical observation angle. Figure 5 The figure shows a schematic diagram of the film of the embodiment of the present invention at an inclined observation angle. The film not only exhibits fluorescent color under ultraviolet light, but also changes color as the observation angle changes.

[0066] In summary, the film described in the embodiment of the present invention has the following advantages:

[0067] (1) Based on the principle of dielectric microsphere light field regulation and color light addition, the film can not only show fluorescent color under ultraviolet light, but also show different color changes as the observation angle changes. Compared with single fluorescent anti-counterfeiting, the film has a high anti-counterfeiting level, good flexibility, low preparation cost, simple method, and great application prospects in the field of anti-counterfeiting;

[0068] (2) This preparation method can adjust the luminescent color of the quantum dot luminescent film according to the different needs of practical applications, so that the film color tone can be continuously adjusted;

[0069] (3) The single-layer dielectric microsphere array in the film structure has stable physical and chemical properties in the air and can stably regulate the luminescence of the film over a long period of time.

[0070] In addition, a person skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be implemented by instructing related hardware through a program, and the corresponding program can be stored in a computer-readable storage medium. The above-mentioned storage medium can be a read-only memory, a disk or an optical disk, etc.

[0071] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A fluorescent anti-counterfeiting film with angular color change, characterized in that: The film comprises a monolayer dielectric microsphere array, a patterned second quantum dot luminescent film, a high molecular polymer film, a patterned first quantum dot film and a substrate which are sequentially stacked and connected, wherein: The single-layer dielectric microsphere array is a single-layer high-refractive-index glass microsphere array; The patterned first quantum dot luminescent film and the patterned second quantum dot luminescent film are films formed by mixing and curing a quantum dot solution and a high molecular polymer, and have indium phosphide / zinc sulfide quantum dots with a variety of different photoluminescence peak positions; The intermediate layer polymer film is a film formed by curing a pre-solidified liquid composed of a polymer monomer and a curing agent, and is specifically prepared by a coating method or a screen printing method; The substrate is a PDMS macromolecular polymer film.

2. The fluorescent angularly variable anti-counterfeiting film according to claim 1, characterized in that: The microspheres in the single-layer dielectric microsphere array have a diameter of 55 μm and a refractive index of 1.

95.

3. The fluorescent angularly variable anti-counterfeiting film according to claim 1, characterized in that: The thicknesses of the patterned first quantum dot light-emitting film and the patterned second quantum dot light-emitting film are 4.3 μm and 4.2 μm respectively.

4. The fluorescent angularly variable anti-counterfeiting film according to claim 1, characterized in that: The high molecular polymer in the intermediate high molecular polymer film is PDMS, and the thickness of the intermediate high molecular polymer film is 40.6 μm.

5. The fluorescent angularly variable anti-counterfeiting film according to claim 1, characterized in that: The thickness of the substrate is 95.9 μm.

6. The fluorescent angularly variable anti-counterfeiting film according to claim 1, characterized in that: The quantum dot luminescent film adopts screen printing technology to realize the patterning of quantum dot film, and the quantum dot film has a variety of different sizes, precisions and patterns.

7. A method for preparing a fluorescent angularly color-changing anti-counterfeiting film, characterized in that: The method comprises: Step 1: First, prepare a flexible substrate; Step 2: preparing a patterned first quantum dot light-emitting film on the prepared substrate; Step 3, preparing an intermediate layer of high molecular polymer film on the upper surface of the patterned first quantum dot light-emitting film; Step 4, preparing a patterned second quantum dot light-emitting film on the intermediate layer polymer film; Step 5: Finally, a single-layer dielectric microsphere array is prepared on the patterned second quantum dot light-emitting film.

8. The method for preparing the fluorescent angularly color-changing anti-counterfeiting film according to claim 7, characterized in that: In step 1, the glass sheet is first immersed in acetone and ultrasonically cleaned to remove organic matter on the surface of the substrate, and then the glass sheet is repeatedly rinsed with deionized water and dried at room temperature; Then, the polymer monomer and the curing agent are fully mixed in a mass ratio of 10:1 to form a pre-solidified liquid; Then the prepared pre-solidified liquid is spin-coated on a clean glass sheet, and the thickness of the film is controlled by the rotation speed of the coating machine; Finally, after the spin coating is completed, the sample is placed on a heating platform for heating and curing to obtain a substrate.

9. The method for preparing the fluorescent angularly color-changing anti-counterfeiting film according to claim 7, characterized in that: In steps 2 and 4, the preparation process of the patterned first quantum dot luminescent film and the patterned second quantum dot luminescent film is: dispersing quantum dots in an organic solvent to obtain a quantum dot solution; Then, the quantum dot solution and the polymer are fully mixed, and the excess organic solvent is evaporated to remove, so as to obtain a quantum dot-polymer mixed solution; The obtained quantum dot-polymer mixture is poured into a screen printing plate, and a patterned quantum dot film is obtained by scraping; In step 3, the preparation method of the intermediate layer polymer film is: The polymer monomer and the curing agent are fully mixed in a mass ratio of 10:1 to form a pre-solidified liquid; Then the prepared pre-solidified liquid is spin-coated on the patterned first quantum dot light-emitting film, and the thickness of the film is controlled by the rotation speed of the coating machine; After the spin coating is completed, the sample is placed on a heating platform for heating and curing to obtain an intermediate layer polymer film.

10. The method for preparing the fluorescent angularly color-changing anti-counterfeiting film according to claim 7, characterized in that: In step 5, the preparation process of the single-layer dielectric microsphere array is specifically as follows: Firstly, dielectric microspheres are sprayed on the surface of the patterned second quantum dot light-emitting film; Then the microspheres that were not attached to the film surface were removed with a low-tack tape by repeatedly scraping and pressing the film surface; Repeat the above operation several times until a single-layer microsphere array is formed; Finally, the film is heated again to fix the microsphere array on the film surface.

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