A dynamic anti-counterfeiting and information encryption method based on time-dependent structural color

Abstract

The application discloses a dynamic anti-fake and information encryption method based on time-dependent structural color. A thin film sample with structural color is prepared by mixing a photoresponsive polymer and a functional small molecule in proportion to form a host-guest system, and the sample is used as an anti-fake label or an information carrier. The sample is heated at a specific temperature, and the structural color state can change over time, thereby realizing the functions of dynamic anti-fake and double-lock information encryption. The application utilizes the phenomenon that cis isomers revert to trans isomers during the heating process, and the trans isomers subsequently self-assemble, thereby accurately controlling the whole process of the structural color state change. On this basis, by adjusting the host-guest ratio of the system, multiple information display can be realized, that is, the same information can appear multiple times on a time scale, and only when the whole process of the structural color state change and the decoding method are obtained, the information can be decrypted. The double-lock strategy significantly improves the security of information encryption, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a dynamic anti-counterfeiting and information encryption technology, in particular to a method for realizing dynamic anti-counterfeiting and information encryption by regulating the ratio between light-responsive polymers and functional small molecules in a host-guest system, and then changing the time of structural color disappearance and appearance, so as to realize dynamic anti-counterfeiting and information encryption by using the change of structural color state over time. BACKGROUND

[0002] With the development of information technology, it is urgent to improve the security of information storage, and various anti-counterfeiting materials such as luminescent materials, photonic crystals, self-erasing materials, etc. need to be developed. Among them, light-responsive polymers can realize remote precise control, and can change the molecular structure and polymer chain structure properties without complex adjustment system, so as to change the macroscopic characteristics of polymers such as color, phase state, solubility, refractive index, glass transition temperature (T g ), surface energy, etc. Because of the small density, good film-forming property and strong designability of polymer materials, the combination of the anisotropy and self-assembly performance of functional small molecules can obtain a common host-guest system, and then be widely applied in the field of anti-counterfeiting and information encryption.

[0003] Typical light-responsive polymers include azobenzene, stilbene, Schiff base, spiropyran, etc., which can all undergo isomerization under light. Among them, azobenzene derivatives have fast response speed, simple chemical process and high reliability, and are often widely used in the preparation of surface micro-nano structures. In addition, considering that azobenzene is a liquid crystal unit, it usually exists in a stable rod-shaped trans structure, and after light irradiation, it isomerizes to a curved cis structure, and the order of molecular arrangement disappears. However, under high temperature heating, the cis azobenzene will return to the trans structure, and the returned trans isomer will self-assemble to form an ordered phase, which provides the possibility for the functional design of azobenzene system.

[0004] Traditional anti-counterfeiting and information encryption materials often have only two states, limiting their application field, because these simple state changes are easy to copy. In contrast, materials with multiple intermediate states would be a better choice. There are currently two ways to achieve this goal: one is to organically combine multiple materials together, and the other is to provide multiple stimuli to induce state changes in the material. However, these methods are limited to linear superposition of multiple simple processes and cannot reproduce information on a time scale. If the counterfeit information looks exactly the same to the naked eye, it is impossible to identify the authenticity. In order to obtain a dynamic anti-counterfeiting material with complex time-dependent characteristics, which contains a nonlinear combination of multiple processes, the best choice is to use the mass transfer phenomenon in thin films and the visible structural color exhibited by periodic surface micro-nano structures to reasonably control the flow direction, and then make the structural color state change over time, so as to prepare dynamic anti-counterfeiting labels and higher-level information encryption storage devices. A new method for preparing surface micro-nano structures is given in Chinese Patent ZL202111434432.X. Under certain conditions, a host-guest system composed of a photoresponsive polymer and a functional small molecule can exhibit bidirectional flow at room temperature, in which the mass transfer induced by surface energy gradient is called Marangoni flow, and the mass transfer driven by capillary force is called capillary flow. Both of these two flows have been reported (Kitamura, I. et al. Sci. Rep. 2019, 9, 2556; Benzaquen, M. et al. Appl. Phys. Lett. 2015, 107, 053103), but there is no material that can combine these two flows together with the help of intermediate states, so that the entire change process has only two states of appearance and disappearance. SUMMARY

[0005] The present application aims to provide an anti-counterfeiting and information encryption technology based on a host-guest system with time-varying structural color when heated, which mainly includes two aspects: one is to design a dynamic anti-counterfeiting label by taking advantage of the phenomenon that cis-isomers revert to trans-isomers, which then self-assemble; the other is to realize multi-information display by adjusting the host-guest ratio of the system, so that the same information can appear multiple times on a time scale, and only when the entire process of structural color state change and the decoding method are obtained can the information be decrypted. This "double lock" strategy significantly improves the security of information encryption.

[0006] The dynamic anti-counterfeiting and information encryption technology proposed in the present application first needs to prepare periodic surface micro-nano structures using the method reported in Chinese Patent ZL202111434432.X, and the obtained sample is as shown in Figure 1As shown, having visible structural color. Then the sample with structural color is heated sufficiently, in the process of heating at a specific temperature, the structural color can be seen to disappear first and then appear again. The time of structural color disappearance and appearance can be accurately controlled, thus can be used for anti-counterfeiting and information encryption.

[0007] The host-guest system involved in the present application is composed of a photoresponsive polymer and a functional small molecule. The functional small molecule can be selected from commercially widely used liquid crystal molecules, including but not limited to 4-cyano-4'-pentyl biphenyl (5CB), 4-cyano-4'-octyl biphenyl (8CB), etc. The photoresponsive polymer refers to a class of polymers such as azobenzene, stilbene, Schiff base, and spiropyran that can undergo cis-trans isomerization under light irradiation of a certain wavelength, as shown in formula I-IV:

[0008]

[0009] In the azobenzene photoresponsive polymer shown in formula I, the stilbene photoresponsive polymer shown in formula II, the Schiff base photoresponsive polymer shown in formula III, and the spiropyran photoresponsive polymer shown in formula IV, R1 is a hydrogen atom or a methyl group; m represents the number of spacers, which is a positive integer of 6-11; R2 is a C1-C12 normal alkyl group or a normal alkoxy group, a nitro group, a cyano group, or a carboxyl group; R3 is a hydrogen atom or a cyano group; n represents the degree of polymerization (the number of repeating units), which is preferably an integer of 25-250, i.e., the molecular weight of the polymer is between 10,000 and 100,000. The polymerization methods include but are not limited to traditional free radical polymerization (initiated by initiators such as azobisisobutyronitrile and benzoyl peroxide), atom transfer radical polymerization (ATRP active polymerization), ring-opening metathesis polymerization (ROMP), reversible addition-fragmentation chain transfer (RAFT active polymerization), etc.

[0010] Specifically, the dynamic anti-counterfeiting and information encryption technology proposed by the present application includes the following contents:

[0011] (1) The sample with structural color is heated at a specific temperature, and the structural color state can be seen to change over time. When the temperature is appropriate, the sample can appear multiple intermediate states, i.e., the structural color will disappear and then appear again and finally disappear, as shown in Figure 2 The situation is more complex.

[0012] (2) If the substrate selected for sample preparation is a flexible substrate, the sample with structural color obtained by the method reported in Chinese patent ZL202111434432.X can be used as a dynamic anti-counterfeiting label to be pasted on any type of curved surface to achieve anti-counterfeiting function, such as on the packaging of commodities (alcoholic beverages, high-end cosmetics, etc.), greatly expanding its application field. This is because heating the anti-counterfeiting label at a specific temperature, the surface structural color will first disappear and then appear, while the structural color caused by the periodic surface relief prepared by traditional methods (including but not limited to periodic surface micro-nano structures prepared by hot embossing, non-thermal embossing, coherent argon ion laser interference writing, etc.) will gradually disappear at high temperature, i.e. with the thermal erasure of surface micro-nano structures, the structural color gradually weakens and will not have the situation of structural color disappearing and then appearing again, so the authenticity of the information can be identified by observing whether the structural color can disappear and then appear again when the label is heated at a specific temperature;

[0013] (3) By adjusting the host-guest ratio, the time of structural color disappearance and appearance can be changed. When preparing a sample with structural color, changing the molar ratio of repeating units to functional small molecules in the photoresponsive polymer and combining thin film samples with different host-guest ratios together, a combination with more complex structural color state changes over time can be obtained. Using this time-dependent multi-information display, the password can be encrypted and stored in the mass transfer process. Structural color disappearance corresponds to the number 0, and structural color appearance corresponds to the number 1. Different combinations of 0 and 1 can be converted into different numbers by binary rules, so only three sample combinations with different host-guest ratios can express numbers 0-7. The decryption process is more complex: the same mass transfer process will get different passwords with different decoding methods, because a certain bit of the password corresponds to the information at a certain time in the structural color state change video, and selecting different information at different times in the same structural color state change process can get many different passwords; in addition, the same decoding method applied to different mass transfer processes will also get different passwords, which takes advantage of the permutation and combination of the order of samples with different host-guest ratios. Therefore, this encryption method can be regarded as a kind of "double lock" mechanism, only the correct structural color state change over time and the correct decoding method can get the correct information, which significantly improves the security of information storage.

[0014] The application can realize the principle of dynamic anti-counterfeiting and "double lock" information encryption: during the heating process, the photoresponsive polymer such as azobenzene will recover from cis to trans, which reduces the surface energy difference between the original trans isomer and the cis isomer, and further weakens the marangoni effect, so that the mass transfer driven by capillary force dominates. Because the direction of capillary flow is opposite to that of marangoni flow, the surface undulation is reduced in this process, and the corresponding structural color gradually weakens until disappears. When the surface energy gradient approaches 0, there will be no marangoni flow induced by the surface energy gradient, and the surface undulation is minimal at this time. Subsequently, both the original trans isomer and the cis isomer that has recovered to trans will self-assemble, and the time required for the original trans isomer to complete the assembly is shorter. At this time, there is a surface energy difference between the assembled and unassembled parts, so that the marangoni flow can occur again. This means that the surface undulation appears again, and the corresponding structural color also appears again. But as the original trans isomer and the cis isomer that has recovered to trans are both assembled, the surface energy gradient disappears, and the marangoni flow no longer appears, so that the capillary flow dominates again, making the final equilibrium state of the host-guest system a flat film without surface undulation. At this time, due to the thermal erasing of the periodic surface micro-nano structure, the structural color finally disappears, and the entire mass transfer process is completed. The schematic diagram of the principle is shown in Figure 3 .

[0015] The method for realizing dynamic anti-counterfeiting provided by the application utilizes the change process of the structural color state over time, which includes:

[0016] 1a) Select a host-guest system composed of a photoresponsive polymer and a functional small molecule according to a certain proportion, and use the method reported in Chinese patent ZL202111434432.X to prepare a thin film sample with structural color on a flexible substrate as an anti-counterfeiting label.

[0017] The specific steps for preparing the sample with structural color are described in detail in Chinese patent ZL202111434432.X, including: mixing and preparing a solution of the photoresponsive polymer and the functional small molecule according to a certain proportion, forming a polymer thin film on a flexible substrate, then using an optical mask containing a grating structure to perform photo-patterning on the polymer thin film, and finally obtaining a surface micro-nano structure with periodic surface undulation by solvent soaking or solvent vapor fumigation, which exhibits a visible structural color. The flexible substrate includes but is not limited to polyester (PET), polyimide (PI), polyethylene (PE), polydimethylsiloxane (PDMS) and other materials, and the thickness of the polymer thin film formed on the substrate is preferably 100-500 nm.

[0018] 1b) When verifying the authenticity, the thin film sample needs to be heated at a certain temperature, and the sample can appear multiple intermediate states, the structural color will disappear and then appear again and finally disappear, realizing the function of dynamic anti-counterfeiting label.

[0019] The specific temperature refers to a temperature at which the photoresponsive polymer can quickly recover from the cis isomer to the trans isomer, but cannot be higher than a temperature at which the photoresponsive polymer is transformed from an ordered phase to an isotropic disordered phase, and the heating mode includes but is not limited to heating by using a hot stage, a hot air gun, a heating jacket and the like.

[0020] The sample is prepared by using a flexible substrate, and thus can be attached to any type of curved surface as a dynamic anti-counterfeiting label to achieve the anti-counterfeiting function. When the dynamic anti-counterfeiting label is heated, it is preferably removed from the surface of the commodity to prevent the influence of the curved surface on the observation of the structural color, because the structural color needs to be observed at a specific angle. The whole process including disappearance, appearance and re-disappearance of the structural color should be observed at the same angle to ensure the accuracy of the true and false identification.

[0021] By regulating the host-guest ratio of the photoresponsive polymer and the functional small molecule blending system, the time of disappearance and appearance of the structural color upon heating can be changed. By combining the film samples with different host-guest ratios together, a more complex combination of the structural color state with time can be obtained, and thus applied in information encryption storage.

[0022] The information encryption storage method provided by the application is realized by combining different structural color states with time, and includes the following steps:

[0023] 2a) selecting a plurality of host-guest systems composed of photoresponsive polymers and functional small molecules blended in different ratios, preparing film samples with structural colors, and combining them together as a carrier for information encryption;

[0024] 2b) heating the film sample combination at a specific temperature, each sample can appear a plurality of intermediate states, the structural color will disappear and then appear again and finally disappear, the structural color of the samples with different host-guest ratios will disappear and appear at different times, so that the film sample combination presents different states at different time points, and realizes dynamic encryption storage of information.

[0025] The adjustment range of the host-guest ratio, i.e., the molar ratio of the repeating unit in the photoresponsive polymer to the functional small molecule, is preferably in the range of 1:1 to 15:1. The pattern of the sample surface with structural color includes, but is not limited to, various shapes such as a heart, a four-leaf clover, etc., and the shape and the region where the structural color is located are determined by the optical mask used in the photo patterning. The period of the periodic surface relief structure is preferably in the range of 10 to 100 μm. In the actual application scenario, the whole process of the change of the structural color state over time can be obtained by recording a video, and the decryption video recording the change of the structural color state over time and the document writing the decoding rule constitute a "double lock" encryption device, i.e., as long as the correct decryption video is obtained and the correct decoding rule is obtained, the decryption of the information can be realized. The samples with different host-guest ratios can be arranged and combined in sequence to form a whole, and the states of the disappearance and appearance of the structural color of the samples are combined and converted into numbers by using binary, and the states are different, and the numbers are different. With the change of the structural color over time, the states at different time points are selected for information combination, and different passwords can be obtained, i.e., different decoding rules can obtain different passwords for the same sample combination. In addition, for different sample combinations, even if the decoding rule is the same, the obtained password is different.

[0026] In the information encryption method of the present application, the encrypted stored information does not need to rely on an actual object, and the password can be obtained directly by sending the recorded video and the text document with the decoding rule by mail, which is convenient, efficient and fast, and the security of information storage is significantly improved due to the existence of the "double lock" mechanism.

[0027] The present application provides a method for realizing dynamic anti-counterfeiting and information encryption by using the change of the structural color state over time, which does not need complex processing methods, and only needs to be heated at a specific temperature to observe the disappearance and reappearance of the structural color. This special phenomenon lays a foundation for dynamic anti-counterfeiting and "double lock" information encryption. Moreover, the authenticity of the information is identified by observing the change process of the structural color, and the encrypted storage of the password is realized by different information combinations with the "double lock" mechanism, which is easy to operate and suitable for large-scale promotion, and has a very broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 . The photos of the samples with structural color prepared by the method reported in Chinese patent ZL202111434432.X.

[0029] Figure 2 . The whole process photos of the samples with structural color in the present application when heated at a specific temperature, the disappearance (1 st DA) and reappearance (RA) and finally disappearance (2 nd DA) of the structural color.

[0030] Figure 3 . The schematic diagram of the principle of realizing dynamic anti-counterfeiting and double-lock information encryption in the application.

[0031] Figure 4 . The structural color state change process of the dynamic anti-counterfeiting label in Example 1 with heating at 100℃, wherein: a is a true label, and the structural color can reappear after disappearing; b is a false label, and the structural color gradually weakens and disappears with the extension of heating time.

[0032] Figure 5 . The structural color state change process of the dynamic anti-counterfeiting label in Example 2 with heating at 100℃, wherein: a is a true label, and the structural color can reappear after disappearing; b is a false label, and the structural color directly disappears and does not reappear.

[0033] Figure 6 . The structural color state change process of the double-lock information encryption device in Example 3 with heating at 100℃, wherein the structural color states at different time nodes are combined to obtain different passwords.

[0034] Figure 7 . The two different double-lock information encryption devices prepared in Example 3 and Example 4 are heated at 100℃, and for two different structural color change processes, the information at the same time node is combined to obtain different passwords. DETAILED DESCRIPTION

[0035] In order to further illustrate the technical means adopted by the application and its effects, the preferred embodiments of the application and their drawings will be described in detail below.

[0036] Example 1

[0037] 1. Selection of materials

[0038]

[0039] The photoresponsive polymer used in this embodiment is an azobenzene homopolymer represented by formula I with a spacer length m = 6, a n-butyl group as the end group R2, and a methyl methacrylate type main chain, denoted as PM6AzC4, with a molecular weight of 3.3 × 10 4 , a polydispersity coefficient of 2.30, a T g of 76℃ measured by DSC, and a T g of 5℃ after sufficient ultraviolet irradiation; and the functional small molecule is a common room temperature nematic liquid crystal 5CB with a melting point of 20℃ and a clearing point of 36.5℃.

[0040] 2. Preparation of dynamic anti-counterfeiting label

[0041] PDMS was chosen as the flexible substrate, and the structured pattern was prepared according to the method reported in Chinese patent ZL202111434432.X, wherein the molar ratio of the repeating unit of PM6AzC4 to 5CB was 8:1, the optical mask containing the grating structure was a stripe mask with a period of 10 μm, and the pattern was a transparent heart pattern, i.e., the finally structured area was the inside of the heart.

[0042] 3. True and false identification process

[0043] The structured heart pattern label was placed on a 100℃ hot stage for heating. Since the cis isomer reverted to the trans isomer, the trans isomer subsequently self-assembled, and the change in the structural color state over time was as shown in FIG. 8a. The structural color first disappeared and then appeared, indicating a true label. Since the reappeared structural color was very similar to the initial structural color, it was not feasible to fake it as a true label, because if the reappeared structural color was heated, it would be found that the structural color gradually weakened and eventually disappeared with the extension of the heating time, and after the disappearance, it did not reappear, as shown in FIG. 8b, indicating a false label. This further proved the irreplaceability of the true label. Figure 4 Figure 4

[0044] Example 2

[0045] 1. Selection of materials

[0046] The same as Example 1.

[0047] 2. Preparation of dynamic anti-counterfeiting label

[0048] The molar ratio of the repeating unit of PM6AzC4 to 5CB in Example 1 was changed from 8:1 to 5:1, the PDMS substrate was changed to a PET substrate, and the transparent heart pattern was changed to a transparent four-leaf clover pattern. The finally obtained sample had a structured area inside the four-leaf clover, and the rest remained unchanged.

[0049] 3. True and false identification process

[0050] The same as Example 1. The change in the structural color state over time of the true label was as shown in FIG. 8a, and the change in the structural color state over time of the false label was as shown in FIG. 8b. Figure 5 Figure 5

[0051] Example 3

[0052] 1. Selection of materials

[0053] The same as Example 1.

[0054] 2. Preparation of “double-lock” information encryption device

[0055] ​​​​The pattern with structural color was prepared on a silicon substrate according to the method reported in Chinese patent ZL202111434432.X. Three samples with different host-guest ratios were selected, and the molar ratio of the repeating unit of PM6AzC4 to 5CB was 8:1, 10:1, and 15:1, respectively. The optical mask containing the grating structure selected a stripe mask with a period of 10 μm, and the pattern selected a transparent four-leaf clover pattern. The region with structural color was the inside of the four-leaf clover. The three samples were combined into one whole in the order of 8:1, 10:1, and 15:1 from left to right. Due to the different times of disappearance and appearance of structural color in samples with different host-guest ratios, a total of 8 states can appear, of which 4 are different states. The 0 and 1 combinations corresponding to these states can be converted to numbers using binary conversion, and different states result in different numbers. With the help of the whole mass transfer process, the encrypted information is stored.

[0056] 3. Decryption process

[0057] For the information encryption device composed of three samples with different host-guest ratios, the whole mass transfer process can be regarded as a codebook, because different decoding methods can obtain different codes for this mass transfer process. As shown in Figure 6 , for a specific four-leaf clover pattern combination, the structural color state change process is certain when heated at 100℃, but selecting information at different time nodes for combination can obtain different codes.

[0058] Example 4

[0059] 1. Material selection

[0060] The same as Example 1.

[0061] 2. Preparation of "double-lock" information encryption device

[0062] The arrangement order of combining the three samples in Example 3 into one whole was changed to 8:1, 15:1, and 10:1 from left to right, and the rest remained unchanged.

[0063] 3. Decryption process

[0064] The information encryption device prepared in Example 3 and the information encryption device prepared in Example 4 were respectively placed on a 100℃ hot stage for heating, which can obtain two different mass transfer processes, i.e., using the same decoding method for information decryption, the obtained codes are also different. As shown in Figure 7 , the structural color state change of two different four-leaf clover combinations is also different when heated at 100℃, even if the information at the same time node is selected for combination, the obtained code is also different.

Claims

1. A dynamic anti-counterfeiting method, characterized in that, Dynamic anti-counterfeiting is achieved by using the change of structural color state over time, comprising: 1a) selecting a host-guest system composed of a light-responsive polymer and a functional small molecule mixed in proportion to prepare a thin film sample with structural color on a flexible substrate as a dynamic anti-counterfeiting label; wherein the light-responsive polymer is selected from one of the polymers with the following molecular structure: Formula I Formula II Formula III Formula IV In formula I to formula IV, R1 is a hydrogen atom or a methyl group; m is a positive integer of 6-11; R2 is a positive alkyl or a positive alkoxy group, a nitro group, a cyano group or a carboxyl group; R3 is a hydrogen atom or a cyano group; n is a positive integer representing the degree of polymerization; The functional small molecule is a liquid crystal small molecule. 1b) When verifying authenticity, the thin film sample is heated at a specific temperature, the sample can appear multiple intermediate states, the structural color will disappear and then appear again and finally disappear, realizing the function of the dynamic anti-counterfeiting label.

2. An information encryption method characterized by, Dynamic encryption storage of information is achieved by combining different structural color state change processes over time, comprising: 2a) Selecting multiple host-guest systems composed of light-responsive polymers and functional small molecules mixed in different proportions to prepare multiple thin film samples with structural color, which are combined together as an information encryption carrier; wherein the light-responsive polymer is selected from one of the polymers with the following molecular structure: Formula I Formula II Formula III Formula IV In formula I to formula IV, R1 is a hydrogen atom or a methyl group; m is a positive integer of 6-11; R2 is a positive alkyl or a positive alkoxy group, a nitro group, a cyano group or a carboxyl group; R3 is a hydrogen atom or a cyano group; n is a positive integer representing the degree of polymerization; The functional small molecule is a liquid crystal small molecule. 2b) Heating the thin film sample combination at a specific temperature, each sample can appear multiple intermediate states, the structural color will disappear and then appear again and finally disappear, the structural color of the samples with different host-guest ratios disappears and appears at different times, making the thin film sample combination present different states at different time points, realizing dynamic encryption storage of information.

3. The information encryption method of claim 2, wherein, When decrypting, record the whole process of the structural color state change of the thin film sample combination as a video, and compose a "double-lock" encryption device with the decryption video recording the structural color state change over time and the document writing the decoding rules, only the correct decryption video and the correct decoding rules can obtain the correct information.

4. The information encryption method of claim 2, wherein, The samples with different host-guest ratios are arranged in sequence to form a whole, the sample structural color disappearance and appearance states are combined and converted into numbers using binary, different states result in different numbers, and the state information at different time points in the structural color change process is selected for combination to obtain different passwords.

5. The method according to any one of claims 1 to 4, characterized in that, In formula I to formula IV, n is an integer of 25-250.

6. The method of any one of claims 1 to 4, wherein, The functional small molecule is 4-cyano-4'-pentyl biphenyl and / or 4-cyano-4'-octyl biphenyl.

7. The method of any one of claims 1 to 4, wherein, The specific temperature is the temperature at which the light-responsive polymer can quickly recover from cis isomer to trans isomer, but cannot be higher than the temperature at which the light-responsive polymer transitions from an ordered phase to an isotropic disordered phase.

8. The method of any one of claims 1-4, wherein, The method for preparing the thin film sample with structural color comprises the following steps: mixing a light-responsive polymer and a functional small molecule in a solution in a certain proportion, forming a polymer thin film on a substrate, performing photo-patterning on the polymer thin film by using an optical mask containing a grating structure, and finally obtaining a surface micro-nano structure with periodic surface relief by using a solvent soaking or solvent vapor fumigation method, so as to show a structural color visible to the naked eye.

9. The method of claim 8, wherein, The substrate is a hard material or a flexible material, and the polymer thin film formed on the substrate has a thickness of 100-500 nm; wherein the thin film sample prepared by using the flexible substrate is used as a dynamic anti-counterfeiting label and is attached to the surface of a commodity.

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