A hard film / soft substrate bilayer system material and its synthesis method and application

Abstract

The application discloses a hard film / soft substrate double-layer system material and a synthesis method and application thereof, and the synthesis method comprises the following steps: doping anthracene photosensitizers into a hard film, and coating the hard film on a soft substrate to obtain a hard film / soft substrate double-layer system material. Subsequently, the double-layer system is stimulated by ultraviolet light and / or stretching, and a wrinkle pattern is generated by stretching-release, and the wrinkle pattern will undergo a series of optical changes over time. Compared with a structural color anti-counterfeiting label on the market, the double-layer system not only has bright structural colors, but also has optical behaviors changing over time. The characteristic makes the hard film / soft substrate double-layer system in the application have higher encryption security in optical encryption.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials science and technology, specifically relating to a hard film / flexible substrate bilayer system material, its synthesis method, and its application. Background Technology

[0002] With the development of society and technology, optical information encryption plays an increasingly important role in fields such as personal identity verification, currency security, product anti-counterfeiting, and information storage. Currently, research on optical information encryption mainly focuses on phosphorescence / fluorescence, metasurfaces, and structural colors. Optical encryption using structural colors is widely used due to its low cost and ease of identification.

[0003] However, traditional structural color anti-counterfeiting labels can be easily copied or imitated. Increasing the complexity or stimulus-responsiveness of structural color materials can help improve encryption security. Furthermore, unlike traditional structural color materials, micro-nano wrinkled materials such as photonic crystals and photolithographic micro / nano surfaces have attracted attention because they can be constructed with structural color anti-counterfeiting materials exhibiting specific responses (temperature, light) by adjusting the polymer molecular structure. At the same time, wrinkles can form periodic micro / nano patterns through spraying or rolling without the need for high-precision templates, offering unique advantages in the fabrication of large-area periodic micro / nano structures. However, current wrinkled structural color anti-counterfeiting materials still suffer from insufficient structural color brightness, resulting in low security in optical encryption. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of traditional structural color anti-counterfeiting labels, which are easily counterfeited and thus become ineffective. This invention utilizes a hard film / flexible substrate dual-layer system to construct a dynamic structural color anti-counterfeiting label, and provides a hard film / flexible substrate dual-layer system material, its synthesis method, and its application. Compared with the production of traditional structural color anti-counterfeiting labels, this method does not require a high-precision template and has the advantages of being simple, having low production cost, and high output efficiency.

[0005] To achieve the above objectives, the following technical solutions are specifically included:

[0006] A hard film / flexible substrate bilayer material, comprising a hard film material and a flexible material serving as the substrate of the hard film material;

[0007] The hard membrane comprises a polymer and an anthracene-containing photosensitizer;

[0008] The chemical structural formula of the polymer is shown in (I):

[0009]

[0010] (I)

[0011] Wherein, R is any one of C1-20 aryl, C1-20 heterocyclic aryl, C1-20 alkyl, C1-20 acyl, C1-20 ester, C1-20 ketone, C1-20 aldehyde, C1-20 alkoxy, and C1-20 aryloxy; R' is a hydrogen bond acceptor functional group, and R' is any one of C1-20 nitrogen-containing heterocyclic aryl, C1-20 amide, C1-20 ester, C1-20 alkoxy, C1-20 carboxylic acid, and cyano.

[0012] The chemical structural formula of the flexible material is shown in (II):

[0013]

[0014] II

[0015] Wherein, R is any one of C1~20 aryl, C1~20 heterocyclic aryl, C1~20 alkyl, C1~20 acyl, C1~20 ester, C1~20 ketone, C1~20 aldehyde, C1~20 alkoxy, and C1~20 aryloxy, and m and n represent the number of complex units of acrylate and diacetone acrylamide, respectively, and m and n are natural numbers greater than 0.

[0016] The rigid film / flexible substrate bilayer material of this invention can generate wrinkled patterns through ultraviolet light and / or stretching stimulation. After the wrinkled patterns are generated, they undergo a series of optical changes over time, exhibiting a dynamic self-erasing wrinkle function. Compared with structural color anti-counterfeiting labels on the market, this bilayer system not only has bright structural colors, but its optical behavior also changes over time. This characteristic makes the rigid film / flexible substrate bilayer system of this invention have higher encryption security in optical encryption.

[0017] A method for synthesizing a hard film / flexible substrate bilayer material includes the following steps:

[0018] S1. Synthesis of hard membrane materials:

[0019] Acrylates, hydrogen bond acceptor functional monomers, and solvents are mixed, and then an initiator is added to carry out a free radical polymerization reaction to generate a polymer, the chemical structure of which is shown in (I):

[0020]

[0021] (I)

[0022] Wherein, R is any one of C1-20 aryl, C1-20 heterocyclic aryl, C1-20 alkyl, C1-20 acyl, C1-20 ester, C1-20 ketone, C1-20 aldehyde, C1-20 alkoxy, and C1-20 aryloxy; R' is a hydrogen bond acceptor functional group, and R' is any one of C1-20 nitrogen-containing heterocyclic aryl, C1-20 amide, C1-20 ester, C1-20 alkoxy, C1-20 carboxylic acid, and cyano.

[0023] S2. Synthesis of flexible materials:

[0024] Acrylic acid ester, diacetone acrylamide, emulsifier, and initiator are dissolved in a solvent to form an emulsion, which is then subjected to a polymerization reaction. A curing agent is added for curing, and the mixture is dried to obtain a flexible material. The chemical structural formula of the flexible material is shown in (II).

[0025]

[0026] II

[0027] Wherein, R is any one of C1~20 aryl, C1~20 heterocyclic aryl, C1~20 alkyl, C1~20 acyl, C1~20 ester, C1~20 ketone, C1~20 aldehyde, C1~20 alkoxy, and C1~20 aryloxy, and m and n represent the number of repeating units of acrylate and diacetone acrylamide, respectively, and m and n are natural numbers greater than 0;

[0028] S3. Construction of a rigid membrane / flexible substrate bilayer system

[0029] A mixture of anthracene photosensitizer and the polymer is coated onto the surface of the flexible material to obtain the hard film / flexible substrate bilayer material.

[0030] Preferably, in step S1, the hydrogen bond acceptor functional monomer includes acrylic acid.

[0031] Preferably, in steps S1 and S2, the acrylate includes at least one of methyl acrylate and ethyl acrylate.

[0032] Preferably, in step S1, the temperature of the free radical polymerization reaction is 20~100℃, and the time of the free radical polymerization reaction is 1-24h.

[0033] Preferably, in step S1, the solvent includes dioxane.

[0034] Preferably, in step S1, the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

[0035] Preferably, in step S2, the polymerization reaction temperature is 20~100℃, and the polymerization reaction time is 1-24h.

[0036] Preferably, in step S2, the emulsifier includes at least one of oleic acid, sorbitan esters, polyoxyethylene esters, and dodecyl sulfate.

[0037] Preferably, the solvent comprises at least one of water, methanol, ethanol, acetonitrile, tetrahydrofuran, acetone, cyclopentanone, cyclohexanone, dichloromethane, chloroform, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dioxane, hexafluoroisopropanol, sulfolane, N-methyl-2-pyrrolidone, m-cresol, xylenol, benzene, toluene, xylene, N-vinyl-2-pyrrolidone, butyrolactone, and butyl acetate.

[0038] Preferably, in step S2, the initiator includes at least one of benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxide, tert-butyl valerate peroxide, diisopropyl peroxide, dicyclohexyl peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate.

[0039] Preferably, in step S2, the curing agent includes adipic acid hydrazine.

[0040] Preferably, in step S3, the anthracene-containing photosensitizer is an anthracene derivative, which includes any mono- or poly-substituted derivatives of anthracene selected from C1-20 aryl, C1-20 heterocyclic aryl, C1-20 alkyl, C1-20 acyl, C1-20 ester, C1-20 ketone, C1-20 aldehyde, C1-20 alkoxy, and C1-20 aryloxy groups.

[0041] More preferably, in step S3, the anthracene-containing photosensitizer includes anthracene formic acid.

[0042] Preferably, in step S1, the molar ratio of the acrylate to the hydrogen bond acceptor functional monomer is (0.1-0.5):(0.01-0.2).

[0043] Preferably, in step S1, the molar ratio of the acrylate to the initiator is (0.1-0.5):(0.001-0.1).

[0044] Preferably, in step S1, the concentration of the acrylate in the solvent is 0.5-5 mol / L.

[0045] Preferably, in step S2, the concentration of the acrylate in the solvent is 1-10 mol / L.

[0046] Preferably, in step S2, the molar ratio of the acrylate to the diacetone acrylamide is (0.1-0.5):(0.001-0.005).

[0047] Preferably, in step S2, the molar ratio of acrylate, emulsifier and initiator is acrylate: emulsifier: initiator = (0.1-0.5): (0.001-0.005): (0.0001-0.01).

[0048] Preferably, in step S2, the molar ratio of the acrylate to the curing agent is (0.1-0.5):(0.01-0.1).

[0049] Preferably, in step S3, the amount of anthracene photosensitizer added is 5%-80% of the molar amount of the hydrogen bond acceptor functional monomer.

[0050] Preferably, in step S3, the coating includes at least one of spin coating and spray coating.

[0051] Preferably, the spin coating speed is 300 rpm to 9500 rpm.

[0052] Application of a hard film / flexible substrate bilayer material in optical encryption or anti-counterfeiting.

[0053] The application of the hard film / flexible substrate bilayer material in optical encryption or anti-counterfeiting includes at least one stimulus response, such as stretching the hard film / flexible substrate bilayer material or exposing it to ultraviolet light.

[0054] Preferably, the tensile strain is 50%-500%, and the strain fixing time is 0s-600s.

[0055] Preferably, the wavelength of the ultraviolet light is 300-400nm.

[0056] The hard film / flexible substrate bilayer material was wrinkled by stretching: the material was stretched, and after a period of time with a fixed strain, the stress was released, allowing the system to return to its original length. Upon returning to its original length, the material surface was observed to change from a smooth state before stretching to a frosted glass state, demonstrating wrinkle formation. After wrinkle formation, the optical appearance of the material surface gradually changed from a colorless frosted glass state to a bright structural color state. With further time, the structural color gradually disappeared, restoring the smooth surface before stretching.

[0057] Patterning of wrinkles in a hard / flexible substrate bilayer system using ultraviolet light exposure: The bilayer system is subjected to localized exposure for a specific duration using an ultraviolet light source and a photomask. Before and after exposure, the material surface exhibits a smooth, specular reflective state. The resulting bilayer system is then stretched, and the stress is released after a period of time while maintaining a fixed strain, allowing the system to return to its original length. After returning to its original length, the material surface can be observed to transform from a smooth state before stretching to a frosted glass state. After a period of time, the structural color image of the photomask appears in the exposed area of ​​the wrinkled surface. As time continues, the structural color of the material surface gradually disappears, restoring the smooth surface before stretching.

[0058] Temporally Resolved Encryption of Wrinkles in a Hard / Flexible Substrate Bilayer System Using Ultraviolet Light and Stretching: A specific region (region A) of the hard / flexible substrate bilayer system is exposed for a certain duration (exposure time t1) using an ultraviolet light source and a photomask. Then, another specific region (region B) of the same system is exposed for a certain duration (exposure time t2) using the same photomask, where t1 > t2. Before and after exposure, the material surface exhibits a smooth, specular reflection. The resulting hard / flexible substrate bilayer system is then stretched, and the stress is released after a period of time while maintaining a fixed strain, allowing the system to return to its original length. After returning to its original length, the material surface is observed to change from a smooth state before stretching to a frosted glass state. After a period of time, the structural color image of the photomask appears in the specific region (region A) of the wrinkled surface. As time increases, a structural color pattern also appears in the other specific region (region B) of the bilayer system. Finally, with further time, the structural color on the material surface gradually disappears, restoring the smooth surface before stretching. By exposing different specific regions of the bilayer system for different times, the sequential appearance of the structural color pattern is achieved.

[0059] Preferably, the exposure times t1 and t2 vary in the range of 5s to 600s.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The hard film / flexible substrate bilayer system material of the present invention can form a regular micro-nano structure on the surface of the bilayer material through stretching-release, with a thickness of 4μm~20μm.

[0062] (2) The regular micro / nano structure formed by the hard film / flexible substrate bilayer system of the present invention, due to the spontaneous mechanical relaxation effect of the surface film, can endow the material surface structure with the characteristic of evolving over time, and endow the material surface optical properties with the characteristic of changing over time. By adjusting the interaction of the polymer network, the relaxation rate of the wrinkles can be controlled. For example, the system can be used to regionally expose the bilayer system with an ultraviolet light source and a photomask to achieve delayed appearance of the exposure pattern; furthermore, when different specific areas of the hard film / flexible substrate bilayer system containing anthracene photosensitizer are exposed for different durations, the pattern can appear sequentially, realizing the application of time-resolved encryption of the system. Moreover, the above-mentioned time-resolved encrypted information does not require external equipment for reading and can be identified by hand stretching and naked eye. Compared with phosphorescent fluorescence encryption and traditional structural color encryption, it has higher encryption security and economic practical value.

[0063] (3) Compared with the traditional structural color anti-counterfeiting label production, the synthesis method of the hard film / flexible substrate double-layer system material of the present invention does not require a high-precision template and has the advantages of being simple, having low production cost and high output efficiency. Attached Figure Description

[0064] Figure 1 This is a synthesis route diagram of the hard film materials in Examples 1 and 2.

[0065] Figure 2 This is a synthesis route diagram of the hard film material in Example 3.

[0066] Figure 3 This is a physical image of the flexible substrate in Example 1.

[0067] Figure 4 This is a diagram of the wrinkles formed in Example 1 under an optical microscope.

[0068] Figure 5 The reflectance diagram of the hard film / flexible substrate bilayer system formed in Example 1 at different reflection angles when the material exhibits a colorless state similar to frosted glass after stretch-release induced wrinkle formation.

[0069] Figure 6 The reflectance diagram of the hard film / flexible substrate bilayer system formed in Example 1 at different reflection angles after stretch-release induced wrinkle generation and when structural color appears, is shown.

[0070] Figure 7 The reflectance diagram of the hard film / flexible substrate bilayer system formed in Example 1 at different reflection angles after stretch-release induced wrinkle formation and a longer period of time, shows the reflectance of light incident at 30°.

[0071] Figure 8 This is a diagram of the wrinkles formed in Example 2 under an optical microscope.

[0072] Figure 9 This is a diagram of the wrinkles formed in Example 3 under an optical microscope.

[0073] Figure 10 This is a diagram showing the change in the optical behavior of the dynamically patterned structural color label in Example 2 over time after wrinkle generation.

[0074] Figure 11 This describes the change in the optical behavior of the dynamically patterned structural color label in Example 3 over time after wrinkle generation.

[0075] Figure 12 This describes the change in the optical behavior of the dynamically patterned structural color label in Example 4 over time after wrinkle generation.

[0076] Figure 13 This describes the change in the optical behavior of the dynamically patterned structural color label in Example 5 over time after wrinkle generation. Detailed Implementation

[0077] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further explain the invention below. Unless otherwise specified, the test methods used in the embodiments and / or comparative examples are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0078] Example 1

[0079] The material synthesis in this embodiment is as follows: Figure 1 As shown in the figure.

[0080] The preparation method is carried out according to the following steps:

[0081] S1. Synthesis of hard membrane materials:

[0082] 18.07 g of methyl acrylate and 6.48 g of acrylic acid were added to a flask and dissolved in 100 mL of dioxane. Then, 0.24 g of azobisisobutyronitrile (AIBN) was added to remove oxygen, and the flask was sealed. The mixture was heated to 70 °C and reacted for 12 h. After the reaction was complete, 5.64 g of anthracene-containing photosensitizer was added to obtain a polymer solution.

[0083] S2. Synthesis of flexible substrates:

[0084] An emulsion was formed by mixing 0.1 g ammonium persulfate, 1 g sodium dodecylbenzenesulfonate, 0.5077 g diacetone acrylamide, and 30 g ethyl acrylate with 60 mL distilled water. The mixture was slowly heated to 70 °C to initiate the reaction. The mixture was kept at this temperature for 3 hours. Then, the emulsion was cooled to room temperature, and 0.2613 g adipamide was added to form a self-crosslinking emulsion. Finally, the self-crosslinking emulsion was transferred to a mold and dried at 60 °C to solidify and shape the product.

[0085] S3. Construction of a rigid membrane / flexible substrate bilayer system

[0086] The solution obtained in step S1 is spin-coated onto the surface of a latex film to form a hard film / flexible substrate bilayer system.

[0087] S4. Tensile stimulus response of the dura mater / flexible substrate bilayer system

[0088] The resulting bilayer system was then stretched, and after a fixed strain of 200% for 5 seconds, the stress was released, allowing the system to return to its original length. Upon returning to its original length, the material surface was observed to change from a smooth state before stretching to a frosted glass-like state, a phenomenon demonstrating wrinkle formation. After wrinkle formation, the optical appearance of the material surface gradually changed from a colorless frosted glass state to a bright structural color state. With further time, the structural color gradually disappeared, restoring the smooth surface before stretching, exhibiting the smooth specular reflection characteristic of the pre-stretching state.

[0089] Example 2

[0090] The material synthesis in this embodiment is as follows: Figure 1 As shown.

[0091] S1. Synthesis of hard membrane materials:

[0092] 18.07 g of methyl acrylate and 6.48 g of acrylic acid were added to a flask and dissolved in 100 mL of dioxane. Then, 0.24 g of azobisisobutyronitrile (AIBN) was added to remove oxygen, and the flask was sealed. The mixture was heated to 70 °C and reacted for 12 h. After the reaction was complete, 5.64 g of anthracene-containing photosensitizer was added.

[0093] S2. Synthesis of flexible substrates:

[0094] An emulsion was formed by mixing 0.1 g ammonium persulfate, 1 g sodium dodecylbenzenesulfonate, 0.5077 g diacetone acrylamide, and 30 g ethyl acrylate with 60 mL distilled water. The mixture was slowly heated to 70 °C to initiate the reaction. The mixture was kept at this temperature for 3 hours. Then, the emulsion was cooled to room temperature, and 0.2613 g adipamide was added to form a self-crosslinking emulsion. Finally, the self-crosslinking emulsion was transferred to a mold and dried at 60 °C to solidify and shape the product.

[0095] S3. Construction of a rigid membrane / flexible substrate bilayer system

[0096] The polymer solution obtained in step S1 is spin-coated onto the surface of a latex film to form a hard film / flexible substrate bilayer system.

[0097] S4. UV-stimulated response of the rigid membrane / flexible substrate bilayer system

[0098] Subsequently, a 365nm ultraviolet light source and a photomask were used to perform 30s of localized exposure on the bilayer system. Before and after exposure, the material surface exhibited a smooth, specular reflective state. The resulting bilayer system was then stretched with a fixed strain of 200%, and the stress was released after 5 seconds, allowing the system to return to its original length. After returning to its original length, the material surface was observed to change from a smooth state before stretching to a frosted glass state. After a period of time, the structural color image of the photomask appeared in the exposed area of ​​the wrinkled surface. As time continued, the structural color of the material surface gradually disappeared, restoring the smooth surface before stretching.

[0099] Example 3

[0100] S1. Synthesis of hard membrane materials:

[0101] 18.07 g of propyl acrylate and 6.48 g of acrylic acid were added to a flask and dissolved in 100 mL of dioxane. Then, 0.24 g of azobisisobutyronitrile (AIBN) was added to remove oxygen, and the flask was sealed. The mixture was heated to 70 °C and reacted for 12 h. After the reaction was complete, 3.48 g of anthracene-containing photosensitizer was added to obtain a polymer solution.

[0102] S2. Synthesis of flexible substrates:

[0103] An emulsion was formed by mixing 0.1 g ammonium persulfate, 1 g sodium dodecylbenzenesulfonate, 0.5077 g diacetone acrylamide, and 30 g ethyl acrylate with 60 mL distilled water. The mixture was slowly heated to 70 °C to initiate the reaction. The mixture was kept at this temperature for 3 hours. Then, the emulsion was cooled to room temperature, and 0.2613 g adipamide was added to form a self-crosslinking emulsion. Finally, the self-crosslinking emulsion was transferred to a mold and dried at 60 °C to solidify and shape the product.

[0104] S3. Construction of the rigid membrane / flexible substrate bilayer system:

[0105] The polymer solution obtained in step S1 is spin-coated onto the surface of a latex film to form a hard film / flexible substrate bilayer system.

[0106] S4. The rigid / flexible substrate bilayer system achieves time-resolved wrinkle densification through stimulation response to ultraviolet light and stretching:

[0107] Subsequently, a specific region (number 1) of the hard / flexible substrate bilayer system was exposed for a certain duration (120 s) using an ultraviolet light source and a photomask. Then, another specific region (number 2) of the same system was exposed for a certain duration (30 s) using the same photomask. Before and after exposure, the material surface exhibited a smooth, specular reflective state. The resulting hard / flexible substrate bilayer system was stretched, and a 200% strain was fixed. After 5 s, the stress was released, allowing the system to return to its original length. After returning to its original length, the material surface was observed to change from a smooth state before stretching to a frosted glass state. After a period of time, the structural color image of the photomask appeared in the specific region (number 1) of the wrinkled surface. As time increased, a structural color pattern also appeared in the other specific region (number 2) of the bilayer system. Finally, with further time, the structural color on the material surface gradually disappeared, restoring the smooth surface before stretching. By exposing different specific regions of the bilayer system for different durations, the sequential appearance of the structural color pattern was achieved.

[0108] Example 4

[0109] S1. Synthesis of hard membrane materials:

[0110] 18.07 g of propyl acrylate and 6.48 g of acrylonitrile were added to a flask, and 100 mL of dioxane was added to dissolve them. Then, 0.24 g of azobisisobutyronitrile was added to remove oxygen, and the flask was sealed. The mixture was heated to 70 °C and reacted for 12 h. After the reaction was complete, 3.48 g of anthracene-containing photosensitizer was added to obtain a polymer solution.

[0111] S2. Synthesis of flexible substrates:

[0112] An emulsion was formed by mixing 0.1 g ammonium persulfate, 1 g sodium dodecylbenzenesulfonate, 0.5077 g diacetone acrylamide, and 30 g ethyl acrylate with 60 mL distilled water. The mixture was slowly heated to 70 °C to initiate the reaction. The mixture was kept at this temperature for 3 hours. Then, the emulsion was cooled to room temperature, and 0.2613 g adipamide was added to form a self-crosslinking emulsion. Finally, the self-crosslinking emulsion was transferred to a mold and dried at 60 °C to solidify and shape the product.

[0113] S3. Construction of the rigid membrane / flexible substrate bilayer system:

[0114] The polymer solution obtained in step S1 is spin-coated onto the surface of a latex film to form a hard film / flexible substrate bilayer system.

[0115] S4. The rigid / flexible substrate bilayer system achieves time-resolved wrinkle densification through stimulation response to ultraviolet light and stretching:

[0116] Subsequently, a specific region (number 9) of the hard / flexible substrate bilayer system was exposed for a certain duration (120 s) using an ultraviolet light source and a photomask. Then, another specific region (number 4) of the hard / flexible substrate bilayer system was exposed for a certain duration (30 s) using the same photomask. Before and after exposure, the material surface exhibited a smooth, specular reflective state. The resulting hard / flexible substrate bilayer system was stretched and subjected to a fixed strain of 200%. After 5 s, the stress was released, allowing the system to return to its original length. After returning to its original length, the material surface was observed to change from a smooth state before stretching to a frosted glass state. After a period of time, the structural color image of the photomask appeared in the specific region (number 9) of the wrinkled surface. As time increased, a structural color pattern also appeared in the other specific region (number 4) of the bilayer system. Finally, with further time, the structural color on the material surface gradually disappeared, restoring the smooth surface before stretching. By exposing different specific regions of the bilayer system for different durations, the sequential appearance of the structural color pattern was achieved.

[0117] Example 5

[0118] The material synthesis in this embodiment is as follows: Figure 1 As shown.

[0119] S1. Synthesis of hard membrane materials:

[0120] 15.03 g of vinyl ethyl ether and 2.31 g of N,N-dimethylacrylamide were added to a flask and dissolved in 100 mL of dioxane. Then, 0.17 g of azobisisobutyronitrile was added to remove oxygen, and the flask was sealed. The mixture was heated to 70 °C and reacted for 12 h. After the reaction was complete, 3.21 g of anthracene-containing photosensitizer was added.

[0121] S2. Synthesis of flexible substrates:

[0122] An emulsion was formed by mixing 0.1 g ammonium persulfate, 1 g sodium dodecylbenzenesulfonate, 0.5077 g diacetone acrylamide, and 30 g ethyl acrylate with 60 mL distilled water. The mixture was slowly heated to 70 °C to initiate the reaction. The mixture was kept at this temperature for 3 hours. Then, the emulsion was cooled to room temperature, and 0.2613 g adipamide was added to form a self-crosslinking emulsion. Finally, the self-crosslinking emulsion was transferred to a mold and dried at 60 °C to solidify and shape the product.

[0123] S3. Construction of a rigid membrane / flexible substrate bilayer system

[0124] The polymer solution obtained in step S1 is spin-coated onto the surface of a latex film to form a hard film / flexible substrate bilayer system.

[0125] S4. UV-stimulated response of the rigid membrane / flexible substrate bilayer system

[0126] Subsequently, a 365nm ultraviolet light source and a photomask were used to perform 30s of localized exposure on the bilayer system. Before and after exposure, the material surface exhibited a smooth, specular reflective state. The resulting bilayer system was then stretched with a fixed strain of 200%, and the stress was released after 5 seconds, allowing the system to return to its original length. After returning to its original length, the material surface was observed to change from a smooth state before stretching to a frosted glass state. After a period of time, the structural color image of the photomask appeared in the exposed area of ​​the wrinkled surface. As time continued, the structural color of the material surface gradually disappeared, restoring the smooth surface before stretching.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for synthesizing a hard film / flexible substrate bilayer material, characterized in that, Includes the following steps: S1. Synthesis of hard membrane materials: Acrylates, hydrogen bond acceptor functional monomers, and solvents are mixed, and then an initiator is added to carry out a free radical polymerization reaction to generate a polymer, the chemical structure of which is shown in (I): （I） Wherein, R is any one of C1-20 aryl, C1-20 heterocyclic aryl, and C1-20 alkyl; R' is a hydrogen bond acceptor functional group, and R' is any one of C1-20 nitrogen-containing heterocyclic aryl, C1-20 amide, C1-20 ester, C1-20 alkoxy, C1-20 carboxylic acid, and cyano. The molar ratio of the acrylate to the hydrogen bond acceptor functional monomer is (0.1-0.5):(0.01-0.2). S2. Synthesis of flexible materials: Acrylic ester, diacetone acrylamide, emulsifier and initiator are dissolved in a solvent to form an emulsion, and a polymerization reaction is carried out. A curing agent is added for curing, and after drying, a flexible material is obtained; the molar ratio of acrylate to diacetone acrylamide is (0.1-0.5):(0.001-0.005). The chemical structural formula of the flexible material is shown in (II): II Wherein, R is any one of C1~20 aryl, C1~20 heterocyclic aryl, and C1~20 alkyl, m and n represent the number of repeating units of diacetone acrylamide and acrylate, respectively, and m and n are natural numbers greater than 0; S3. Construction of a rigid membrane / flexible substrate bilayer system A mixture of anthracene photosensitizer and the polymer is coated onto the surface of the flexible material to obtain the hard film / flexible substrate bilayer material.

2. The method for synthesizing the hard film / flexible substrate bilayer material as described in claim 1, characterized in that, Includes at least one of the following: In step S1, the hydrogen bond acceptor functional monomer includes acrylic acid; In steps S1 and S2, the acrylate includes at least one of methyl acrylate and ethyl acrylate; In step S1, the temperature of the free radical polymerization reaction is 20~100℃, and the time of the free radical polymerization reaction is 1-24h; In step S1, the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate; In step S2, the polymerization reaction temperature is 20~100℃, and the polymerization reaction time is 1-24h.

3. The method for synthesizing the hard film / flexible substrate bilayer material as described in claim 1, characterized in that, Includes at least one of the following: In step S2, the emulsifier includes at least one of oleic acid, sorbitan esters, polyoxyethylene esters, and dodecyl sulfate; In step S2, the solvent includes at least one of water, methanol, ethanol, acetonitrile, tetrahydrofuran, acetone, cyclopentanone, cyclohexanone, dichloromethane, chloroform, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dioxane, hexafluoroisopropanol, sulfolane, N-methyl-2-pyrrolidone, m-cresol, xylenol, benzene, toluene, xylene, N-vinyl-2-pyrrolidone, butyrolactone, and butyl acetate. In step S2, the initiator includes at least one of benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dicumene peroxide, tert-butyl peroxide, tert-butyl valerate peroxide, diisopropyl peroxide, dicyclohexyl peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate. In step S2, the curing agent includes adipamide hydrazine; In step S3, the anthracene-containing photosensitizer is a derivative of anthracene, and the anthracene derivative includes any mono- or poly-substituted derivative of anthracene among C1-20 aryl, C1-20 heterocyclic aryl, C1-20 alkyl, C1-20 acyl, C1-20 ester, C1-20 ketone, C1-20 aldehyde, C1-20 alkoxy, and C1-20 aryloxy groups.

4. The method for synthesizing the hard film / flexible substrate bilayer material as described in claim 1, characterized in that, Includes at least one of the following: The anthracene-containing photosensitizer includes anthracene formic acid; In step S1, the molar ratio of the acrylate to the initiator is (0.1-0.5):(0.001-0.1); In step S1, the concentration of the acrylate in the solvent is 0.5-5 mol / L; In step S2, the concentration of the acrylate in the solvent is 1-10 mol / L.

5. The method for synthesizing the hard film / flexible substrate bilayer material as described in claim 1, characterized in that, Includes at least one of the following: In step S2, the molar ratio of acrylate, emulsifier, and initiator is acrylate: emulsifier: initiator = (0.1-0.5): (0.001-0.005): (0.0001-0.01). In step S2, the molar ratio of the acrylate to the curing agent is (0.1-0.5):(0.01-0.1).

6. The method for synthesizing the hard film / flexible substrate bilayer system material as described in claim 1, characterized in that, Includes at least one of the following: In step S3, the amount of anthracene photosensitizer added is 5%-80% of the molar amount of the hydrogen bond acceptor functional monomer; In step S3, the coating includes at least one of spin coating and spray coating.

7. A hard film / flexible substrate bilayer material, characterized in that, It is prepared by the synthesis method of the hard film / flexible substrate bilayer system material according to any one of claims 1-6, and includes a hard film material and a flexible material as the substrate of the hard film material. The hard membrane comprises a polymer and an anthracene-containing photosensitizer; The chemical structural formula of the polymer is shown in (I): （I） Wherein, R is any one of C1-20 aryl, C1-20 heterocyclic aryl, and C1-20 alkyl; R' is a hydrogen bond acceptor functional group, and R' is any one of C1-20 nitrogen-containing heterocyclic aryl, C1-20 amide, C1-20 ester, C1-20 alkoxy, C1-20 carboxylic acid, and cyano. The chemical structural formula of the flexible material is shown in (II): II Wherein, R is any one of C1~20 aryl, C1~20 heterocyclic aryl, and C1~20 alkyl, m and n represent the number of repeating units of diacetone acrylamide and acrylate, respectively, and m and n are natural numbers greater than 0.

8. The hard film / flexible substrate bilayer system material as described in claim 7, characterized in that, The anthracene-containing photosensitizer is a derivative of anthracene, and the anthracene derivative includes any mono- or poly-substituted derivative of anthracene selected from C1-20 aryl, C1-20 heterocyclic aryl, C1-20 alkyl, C1-20 acyl, C1-20 ester, C1-20 ketone, C1-20 aldehyde, C1-20 alkoxy, and C1-20 aryloxy groups.

9. The application of the hard film / flexible substrate bilayer system material as described in claim 7 or 8 in optical encryption or anti-counterfeiting.

10. The application as described in claim 9, characterized in that, This includes at least one stimulus response, such as stretching the hard film / flexible substrate bilayer material or exposure to ultraviolet light.

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