Anti-fake composite material and preparation method and application thereof

Abstract

The application provides a kind of anti-counterfeiting composite material and its preparation method and application, more particularly to a kind of near infrared circular polarized light, unclonable function anti-counterfeiting composite material and its preparation method and application.The anti-counterfeiting composite material includes chiral polymer film and luminescent particles loaded on the chiral polymer film;The chiral polymer film has a photonic band gap, and the band gap center position matches the luminescent wavelength of the luminescent particles.The application designs the specific composition of the anti-counterfeiting composite material, and obtains the anti-counterfeiting composite material with near infrared circular polarized light physical unclonable function, which has three dimensions of information of near infrared, circular polarized luminescence and luminescence asymmetry factor, encodes the information of the three dimensions to obtain the binary key of the physical unclonable function, and only when the triple key matches can it be confirmed as a genuine product, greatly improving the information security.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical anti-counterfeiting materials, and particularly relates to an anti-counterfeiting composite material and a preparation method and application thereof, and more particularly relates to an anti-counterfeiting composite material with near-infrared circularly polarized light and a non-cloning function and a preparation method and application thereof. BACKGROUND

[0002] Counterfeiting is a problem that cannot be completely eradicated in human society. Anti-counterfeiting technology is widely used in daily life. However, with the progress of science and technology, the level of counterfeiting is constantly improving, which poses a serious threat to the property safety of the people, and therefore more advanced anti-counterfeiting technology is becoming increasingly important.

[0003] Optical anti-counterfeiting technology is generally favored because of its diverse forms and low cost, such as anti-counterfeiting based on changes in parameters such as luminous intensity, luminous wavelength, and luminous lifetime. Some special types of hidden light have also begun to be used in the field of anti-counterfeiting. This type of light carries information hidden under certain rules and cannot be directly obtained, thus improving the security of information encryption. Among them, near-infrared circularly polarized light has the advantages of being invisible to the naked eye and having information encryption based on circularly polarized dichroism under certain rules, which can provide excellent anti-counterfeiting capability for the optical anti-counterfeiting system. However, how to improve the luminous asymmetry factor (g lum ) of circular polarization to expand the information encryption capability based on circularly polarized dichroism under certain rules is still a key problem that needs to be solved in the field of anti-counterfeiting.

[0004] Physical unclonable function (PUF) represents a technology that uses external random properties to determine encoded information, and the randomness of the encoding effectively prevents third parties, even manufacturers, from copying the encoded information. Optical PUF is a technical means of obtaining encoded information from the optical properties of luminescent materials, which has obvious advantages over traditional PUF, including solution processability, material versatility, and adjustable luminescent performance. Since its encoding relies on optical systems, it is also suitable for the characteristics of optical systems. Current research on optical PUFs mainly focuses on visible light fluorescence, and advanced optical PUFs based on more covert light still need to be explored.

[0005] Therefore, how to provide a new type of near-infrared circularly polarized light and non-cloning function anti-counterfeiting composite material has become a technical problem that needs to be solved at present. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide an anti-counterfeiting composite material and a preparation method and application thereof. The present application designs the specific composition of the anti-counterfeiting composite material and obtains an anti-counterfeiting composite material with near-infrared circularly polarized light physical unclonable function, thereby improving the information security level.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a security composite material, which comprises a chiral polymer film and luminescent particles loaded on the chiral polymer film.

[0009] The chiral polymer film has a photonic band gap, the emission wavelength of the luminescent particles is located at the center of the photonic band gap, and the width of the photonic band gap is greater than the half-wave width of the emission wavelength of the luminescent particles.

[0010] The present application improves the level of information security by designing the specific composition of the security composite material to obtain a security composite material with near-infrared circularly polarized light physical unclonable function.

[0011] In the present application, the raw materials for preparing the chiral polymer film include nematic liquid crystal, chiral dopant, polymer monomer, crosslinking agent and photoinitiator. The chiral nematic liquid crystal is used as a template, and the liquid crystal is removed after polymerization of other raw materials to prepare a polymer film with chirality. The chiral polymer film retains the photonic band gap of the chiral nematic liquid crystal, and avoids the quenching of luminescent ions by the strong polarity environment of the liquid crystal.

[0012] The following is a preferred technical solution of the present application, but not as a limitation on the technical solutions provided by the present application. Through the following preferred technical solution, the purpose and beneficial effects of the present application can be better achieved and realized.

[0013] As a preferred technical solution of the present application, the maximum emission wavelength of the luminescent particles is greater than or equal to 750 nm, for example, it can be 750 nm, 800 nm, 900 nm, 920 nm, 940 nm, 960 nm, 980 nm, 1000 nm, 1020 nm, 1040 nm, 1060 nm, 1080 nm or 1100 nm, etc.

[0014] It should be noted that the present application does not have any special restrictions on the specific selection of luminescent particles. All luminescent materials commonly used in the art in the near-infrared region are suitable, including but not limited to: ytterbium ion doped perovskite nanocrystals, copper indium tin quantum dots, lead sulfide quantum dots, silver sulfide quantum dots, near-infrared carbon dots.

[0015] It should be noted that the present application does not have any special restrictions on the preparation method of the luminescent particles. Taking ytterbium ion doped perovskite nanocrystals as an example, its preparation method exemplarily includes hot injection method, which specifically includes the following steps:

[0016] (1) A mixture of 0.4 mmol of lead acetate hydrate, 0.4 mmol of ytterbium acetate hydrate, 280 μL of 2M cesium acetate methanol solution, 10 mL of octadecene, 2 mL of oleic acid and 1 mL of oleylamine was added to a 100 mL three-necked flask, vacuumed for 10 minutes at room temperature, then heated to 120°C for 30 minutes, and the methanol, water and air were removed, after which dry nitrogen was introduced, and the temperature was raised to 250°C, as soon as the temperature reached, 0.7 mL of octadecene solution containing trimethylchlorosilane (the solution was composed of 1 mL of trimethylchlorosilane and 5 mL of octadecene) was immediately injected into the reaction flask with a syringe, and the reaction was maintained for 20 seconds under nitrogen flow, then the reaction was extinguished by cooling the flask with an ice bath, and the product was precipitated by a dry methyl acetate solution, washed, and collected by centrifugation at 12000 rpm for 5 minutes to obtain the ytterbium ion-doped perovskite nanocrystals (Yb 3+ :CsPbCl3).

[0017] As a preferred technical scheme of the present application, the preparation raw material of the chiral polymer film comprises the following components in weight fraction:

[0018] Nematic liquid crystal 100 parts, chiral dopant 0.9-1.7 parts, polymerizable monomer 40-60 parts, crosslinking agent 5-8 parts and photoinitiator 1-4 parts.

[0019] It should be noted that the preparation of the chiral polymer film of the present application does not have any special restrictions on the specific selection of nematic liquid crystal and photoinitiator, and different types of ingredients only need to change the fraction of chiral dopant to adjust the photonic band gap position, so that the center of the band gap is located at the light emitting center of the light emitting particle. Exemplarily, it includes but is not limited to:

[0020] Nematic liquid crystal: commercial liquid crystal SLC1717, HTG135200, E7.

[0021] Chiral dopant: S5011, R5011, S811 and R811.

[0022] Polymerizable monomer: 1,4-bis[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (C6M), 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene (RM257).

[0023] Crosslinking agent: trimethylolpropane triacrylate (TMPTA), (4-(((4-(acryloyloxy) butoxy) carbonyl) oxy) benzyl-2-methyl-1,4-diphenol ester (LC242).

[0024] Photoinitiator: 2,2-dimethoxy-2-phenylphenylacetophenone (I651), methyl benzoylformate (MBF).

[0025] In the present application, the weight fraction of the chiral dopant in the preparation raw material of the chiral polymer film can be 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, or 1.7 parts, etc.

[0026] The weight fraction of the polymer monomer in the preparation raw material of the chiral polymer film can be 40 parts, 42 parts, 44 parts, 46 parts, 48 parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, or 60 parts, etc.

[0027] The weight fraction of the crosslinking agent in the preparation raw material of the chiral polymer film can be 5 parts, 5.2 parts, 5.5 parts, 5.7 parts, 6 parts, 6.3 parts, 6.6 parts, 7 parts, 7.2 parts, 7.4 parts, 7.7 parts, or 8 parts, etc.

[0028] The weight fraction of the photoinitiator in the preparation raw material of the chiral polymer film can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts, etc.

[0029] As a preferred technical solution of the present application, the chiral dopant is selected from any one or a combination of at least two of R5011, S5011, R811 and S811.

[0030] Preferably, the polymer monomer is selected from 1,4-bis[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (C6M) and / or 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene (RM257).

[0031] Preferably, the crosslinking agent is selected from trimethylolpropane triacrylate (TMPTA) and / or (4-(((4-(acryloyloxy)butyloxy)carbonyl)oxy)benzene-2-methyl-1,4-diphenol ester (LC242).

[0032] As a preferred technical solution of the present application, the chiral polymer film is prepared by the following method, which comprises the following steps:

[0033] After the preparation raw material of the chiral polymer film and the auxiliary solvent are uniformly mixed, the temperature is raised to the isotropic temperature of the nematic liquid crystal, then it is poured into a liquid crystal cell, irradiated with ultraviolet light, polymerized, and soaked with an organic solvent to obtain the chiral polymer film.

[0034] In the present application, when the preparation raw material of the chiral polymer film is mixed, dichloromethane with a low boiling point is used as a solvent for auxiliary mixing, and the temperature needs to be raised to the isotropic temperature of the liquid crystal molecules before pouring into the liquid crystal cell. In this process, the dichloromethane volatilizes, and the isotropic liquid crystal presents a liquid flow state.

[0035] In the present application, the nematic liquid crystal and the monomer small molecules that do not undergo polymerization are removed by organic solvent immersion.

[0036] Preferably, the auxiliary solvent comprises dichloromethane.

[0037] Preferably, the wavelength of the ultraviolet light is 365 nm.

[0038] Preferably, the polymerization time is ≥ 5 min, for example, it can be 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min, etc.

[0039] Preferably, the organic solvent is selected from any one or a combination of at least two of n-hexane, toluene, and cyclohexane.

[0040] In a second aspect, the present application provides a preparation method of the anti-counterfeiting composite material according to the first aspect, and the preparation method comprises the following steps:

[0041] The chiral polymer film is immersed in a luminescent particle solution, washed and dried to obtain the anti-counterfeiting composite material.

[0042] In the present application, the nematic liquid crystal and the monomer small molecules that do not undergo polymerization are removed by organic solvent immersion to obtain a chiral polymer film with randomly distributed pores, and then the luminescent particles are randomly loaded on the surface of the chiral polymer film and in the randomly distributed pores by solution immersion, and the randomness of the loading is used to encode using a physically unclonable function.

[0043] In the present application, the photonic band gap of the chiral polymer film can be coupled with the luminescent wavelength of the luminescent particles to obtain a near-infrared circularly polarized luminescent material. After the chiral polymer film loaded with luminescent particles is irradiated with excitation light corresponding to the luminescent particles, a random near-infrared circularly polarized luminescent pattern is formed.

[0044] As a preferred technical solution of the present application, the mass concentration of the luminescent particle solution is 0.1-2 mg / mL (for example, it can be 0.1 mg / mL, 0.2 mg / mL, 0.4 mg / mL, 0.6 mg / mL, 0.8 mg / mL, 1 mg / mL, 1.2 mg / mL, 1.4 mg / mL, 1.6 mg / mL, 1.8 mg / mL, or 2 mg / mL, etc.), and the solvent of the luminescent particle solution comprises n-hexane.

[0045] Preferably, the immersion temperature is 30-60℃ (for example, it can be 30℃, 33℃, 36℃, 39℃, 42℃, 44℃, 46℃, 49℃, 50℃, 52℃, 55℃, 57℃, or 60℃, etc.), and the time is ≥ 30 min (for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, or 45 min, etc.).

[0046] Preferably, the washing solvent is selected from any one or a combination of at least two of n-hexane, toluene or cyclohexane.

[0047] Preferably, the method for preparing the anti-counterfeiting composite material specifically comprises the following steps:

[0048] After the chiral polymer film is soaked in the luminescent particle solution at 30-60℃ for ≥30 min, the anti-counterfeiting composite material is obtained after washing and drying.

[0049] In a third aspect, the present application provides an application of the anti-counterfeiting composite material according to the first aspect, which is used as a near-infrared circularly polarized light physical unclonable function advanced anti-counterfeiting material.

[0050] In a fourth aspect, the present application provides an anti-counterfeiting method of the anti-counterfeiting composite material according to the first aspect, which comprises the following steps:

[0051] The anti-counterfeiting composite material according to the first aspect is cut into a square, the anti-counterfeiting composite material is excited to emit near-infrared circularly polarized light by using the excitation light corresponding to the luminescent particles, the excitation light is filtered out by using a filter, the luminescent pattern of the anti-counterfeiting composite material is photographed by using a near-infrared camera, and the circularly polarized luminescent pattern is photographed by cooperating with a circular polarizer. The near-infrared luminescent pattern is encoded to obtain a near-infrared mode two-dimensional code and a derived binary key; and the circularly polarized luminescent pattern is encoded after image processing to obtain a two-dimensional code in a circularly polarized luminescent mode and a luminescent asymmetry factor mode and a derived binary key.

[0052] It should be noted that the size of the square in the present application is not subject to any special limitation and can be cut according to requirements.

[0053] As a preferred technical solution of the present application, the encoding method comprises: the photographed pattern is deformed by twisting, cut, the luminescent pattern part is reserved and converted into a standard rectangular image of the same pixel size in grayscale, and then the standard rectangular image is converted into a black-and-white two-dimensional code by setting a threshold value and a binary key is derived.

[0054] Preferably, the method for processing the circularly polarized luminescent image comprises: after twisting, cutting and converting into a standard grayscale rectangle of the same pixel size, the grayscale values of each pixel point of the grayscale images photographed by the left and right circular polarizers are subjected to different operations to obtain new grayscale images representing the circularly polarized luminescent mode and the luminescent asymmetry factor mode, and then the grayscale images are converted into black-and-white two-dimensional codes by setting a threshold value.

[0055] Preferably, the operation method in the circularly polarized luminescent mode comprises: difference operation is performed on the grayscale values of the pixel points of the left and right circularly polarized images.

[0056] Preferably, the operation method in the luminescence asymmetry factor mode comprises: the difference value of the left and right circular polarization image pixel point gray values is divided by the sum value of the left and right circular polarization image pixel point gray values, and then multiplied by two.

[0057] In the present application, the near-infrared camera and the corresponding circular polarizer combination are used to capture the near-infrared light pattern and the near-infrared circular polarization pattern of the anti-counterfeiting composite material, and then the image processing method is used to encode these randomly generated patterns into binary unclonable keys in the near-infrared light mode, the near-infrared circular polarization light mode and the near-infrared circular polarization luminescence asymmetry factor mode.

[0058] When the anti-counterfeiting composite material is used for covert light anti-counterfeiting, the generated near-infrared pattern cannot be directly observed by the naked eye, and the pattern and the key are unique and cannot be copied and are unclonable. Moreover, the anti-counterfeiting composite material provided by the present application has near-infrared, circular polarization luminescence and luminescence asymmetry factor three-dimensional information when used for anti-counterfeiting. The three-dimensional information is encoded to obtain a binary key of the physical unclonable function. Only when all three keys match can it be confirmed as a genuine product. Therefore, the circular polarization and unclonable characteristics of the anti-counterfeiting composite material provided by the present application greatly increase the difficulty of counterfeiting and greatly improve the information security.

[0059] Compared with the prior art, the present application has the following beneficial effects:

[0060] (1) The present application designs the specific composition of the anti-counterfeiting composite material, uses nematic liquid crystal as a template, polymerizes other raw materials, and then removes the nematic liquid crystal and monomer small molecules that do not undergo polymerization reaction by soaking in an organic solvent to prepare a chiral polymer film with randomly distributed holes. Then, luminescent particles are randomly loaded on the surface of the chiral polymer film and in the randomly distributed holes to obtain an anti-counterfeiting composite material with a physical unclonable function by utilizing the randomness of the loading.

[0061] (2) The anti-counterfeiting composite material provided by the present application has near-infrared, circular polarization luminescence and luminescence asymmetry factor three-dimensional information when used for anti-counterfeiting. The three-dimensional information is encoded to obtain a binary key of the physical unclonable function. Only when all three keys match can it be confirmed as a genuine product. Therefore, the circular polarization and unclonable characteristics of the anti-counterfeiting composite material provided by the present application greatly increase the difficulty of counterfeiting and greatly improve the information security. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1The photoluminescence spectrum of the anti-counterfeiting composite material provided for the present application embodiment 1-2;

[0063] Figure 2 The near-infrared circularly polarized luminescence spectrum of the anti-counterfeiting composite material provided for the present application embodiment 1-2;

[0064] Figure 3 The luminescence asymmetry factor curve of the anti-counterfeiting composite material provided for the present application embodiment 1-2;

[0065] Figure 4 The key in near-infrared mode, the key in circularly polarized luminescence mode, the shooting image in luminescence asymmetry factor mode, the gray image, the two-dimensional code and the physical unclonable key image of the anti-counterfeiting composite material provided for the present application embodiment 1 using the anti-counterfeiting composite material provided for the present application embodiment 1 are respectively in near-infrared mode, circularly polarized luminescence mode, luminescence asymmetry factor mode, binary key encoding repetition rate test result image;

[0066] Figure 5 The key in near-infrared mode, the key in circularly polarized luminescence mode, the shooting image in luminescence asymmetry factor mode, the gray image, the two-dimensional code and the physical unclonable key image of the anti-counterfeiting composite material provided for the present application embodiment 1 are respectively in near-infrared mode, circularly polarized luminescence mode, luminescence asymmetry factor mode, binary key encoding repetition rate test result image;

[0067] Figure 6 The key in near-infrared mode, the key in circularly polarized luminescence mode, the shooting image in luminescence asymmetry factor mode, the gray image, the two-dimensional code and the physical unclonable key image of the anti-counterfeiting composite material provided for the present application embodiment 1 are respectively in near-infrared mode, circularly polarized luminescence mode, luminescence asymmetry factor mode, binary key encoding repetition rate test result image. DETAILED DESCRIPTION

[0068] The technical solutions of the present application will be further described below in conjunction with the drawings and through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations on the present application.

[0069] Some components in the following examples and comparative examples are as follows:

[0070] Ytterbium ion doped perovskite nanocrystals: prepared according to the method provided in “Picosecond Quantum Cutting Generates Photoluminescence Quantum Yields Over 100%in Ytterbium-Doped CsPbCl3 Nanocrystals, Nano Lett. 2018, 18, 3792-3799 DOI: 10.1021 / acs.nanolett.8b01066”;

[0071] Near-infrared carbon dots: prepared according to the method provided in "Near-Infrared Blinking Carbon Dots Designed for Quantitative Nanoscopy, Nano Lett. 2023, 23(1), 124-131, DOI: 10.1007 / s10570-017-1594-1";

[0072] Silver sulfide quantum dots: prepared according to the method provided in "Near-Infrared Photoluminescent Ag2S Quantum Dots from a Single Source Precursor, Journal of the American Chemical Society 2010, 132, 1470-1471, DOI: 10.1021 / ja909490r";

[0073] Copper indium tin quantum dots: prepared according to the method provided in "Biocompatible near-infrared quantum dots delivered to the skin by microneedle patches record vaccination, Sci. Transl. Med. 2019, 11, eaay7162, DOI: 10.1126 / scitranslmed.aay7162";

[0074] Nematic liquid crystal SLC1717: Shijiazhuang Chengzhi Yonghua Display Material Co., Ltd.;

[0075] Nematic liquid crystal HTG135200: Jiangsu Hecheng Display Technology Co., Ltd.;

[0076] Nematic liquid crystal E7: Jiangsu Hecheng Display Technology Co., Ltd.

[0077] Example 1

[0078] The present embodiment provides a kind of anti-fake composite material and preparation method thereof, the anti-fake composite material includes chiral polymer film and the luminescent particle loaded in the chiral polymer film;

[0079] The luminescent particle is ytterbium ion doped perovskite nanocrystal, maximum emission wavelength is 980 nm, and half peak width is 70 nm;

[0080] The chiral polymer in the polymer film has photonic band gap, and the band gap center position is 980 nm, and the band gap width is 150 nm;

[0081] The preparation raw material of the chiral polymer film comprises the following components in parts by weight:

[0082] Nematic liquid crystal SLC1717 100 parts, chiral dopant S5011 1.2 parts, monomer C6M 50 parts, crosslinking agent TMPTA 7.8 parts, and photoinitiator I651 2.5 parts;

[0083] The preparation method of the chiral polymer film is as follows:

[0084] After the above preparation raw material of the chiral polymer film and dichloromethane (500 parts) are uniformly mixed, the temperature is raised to the isotropic temperature of the nematic liquid crystal, then the mixture is poured into a liquid crystal cell, irradiated with ultraviolet light with a wavelength of 365 nm, and polymerized for 20 min. The nematic liquid crystal and unreacted monomer molecules are removed by soaking in n-hexane, thereby obtaining the chiral polymer film.

[0085] The preparation method of the above anti-counterfeiting composite material is as follows:

[0086] After the above chiral polymer film is soaked in the luminescent particle solution at 40℃ for 1 h, the chiral polymer film is taken out, the surface of the polymer film is washed with n-hexane, and then dried, thereby obtaining the anti-counterfeiting composite material, which is denoted as S1-chiral anti-counterfeiting film.

[0087] It should be noted that, due to the special nature of the anti-counterfeiting material that cannot be cloned, the optical properties of the same material prepared by the above method are not exactly the same, and therefore different n-batches of the material are denoted as S1-chiral anti-counterfeiting film-1, S1-chiral anti-counterfeiting film-2, S1-chiral anti-counterfeiting film-3, …, S1-chiral anti-counterfeiting film-n.

[0088] Example 2

[0089] The anti-counterfeiting composite material provided in this example is denoted as R1-chiral anti-counterfeiting film-1, R1-chiral anti-counterfeiting film-2, R1-chiral anti-counterfeiting film-3, …, R1-chiral anti-counterfeiting film-n.

[0090] The anti-counterfeiting composite material provided in this example is denoted as R1-chiral anti-counterfeiting film-1, R1-chiral anti-counterfeiting film-2, R1-chiral anti-counterfeiting film-3, …, R1-chiral anti-counterfeiting film-n.

[0091] The anti-counterfeiting composite materials S1-chiral anti-counterfeiting film-1 and R1-chiral anti-counterfeiting film-1 provided in Examples 1-2 are respectively subjected to luminescent spectrum testing, and the near-infrared luminescence and corresponding photon bandgap spectrum, circularly polarized luminescence spectrum diagram, and luminescence asymmetry factor results are shown in Figure 1 、 Figure 2 、 Figure 3 Figure 1 、 2 ​, 3 it can be known that the near-infrared luminescence wavelength of the ytterbium ion doped perovskite nanocrystal is greater than or equal to 900 nm, and the photonic band gap center is located at the luminescence center; the S1-chiral anti-counterfeiting film-1 can obtain a positive circularly polarized luminescence signal, representing left-handed circularly polarized luminescence; the R1-chiral anti-counterfeiting film-1 can obtain a negative circularly polarized signal, representing right-handed circularly polarized luminescence; and the corresponding g lum value can reach 0.9 at most.

[0092] Example 3

[0093] The embodiment provides an anti-counterfeiting composite material and a preparation method thereof, and the anti-counterfeiting composite material comprises a chiral polymer film and luminescent particles loaded on the chiral polymer film.

[0094] The luminescent particles are near-infrared carbon dots, and the maximum emission wavelength is 750 nm.

[0095] The chiral polymer in the polymer film has a photonic band gap, and the band gap center position is 750 nm, and the band gap width is 140 nm.

[0096] The preparation raw materials of the chiral polymer film comprise the following components in parts by weight:

[0097] Nematic liquid crystal HTG135200 100 parts, chiral dopant S5011 1.4 parts, monomer RM257 50 parts, crosslinking agent LC242 7.8 parts and photoinitiator MBF 2.5 parts;

[0098] The preparation method of the chiral polymer film is as follows:

[0099] After the above preparation raw materials of the chiral polymer film and dichloromethane (500 parts) are uniformly mixed, the isotropic temperature of the nematic liquid crystal is reached, the nematic liquid crystal cell is filled, and the nematic liquid crystal and unreacted monomer molecules are removed by using n-hexane soaking after irradiation with ultraviolet light with a wavelength of 365 nm for 20 min, to obtain the chiral polymer film.

[0100] The preparation method of the above anti-counterfeiting composite material is as follows:

[0101] After the above chiral polymer film is soaked in the luminescent particle solution at 40 DEG C for 1 h, the chiral polymer film is taken out, the polymer film surface is washed using n-hexane, and then dried to obtain the anti-counterfeiting composite material, which is recorded as S2-chiral anti-counterfeiting film-1, …, S2-chiral anti-counterfeiting film-n.

[0102] Example 4

[0103] The embodiment provides an anti-counterfeiting composite material and a preparation method thereof, and the difference from the embodiment 3 is that the chiral dopant S5011 is replaced by the chiral dopant R5011 with the same weight fraction, and other conditions are the same as those in the embodiment 3.

[0104] The anti-counterfeiting composite material provided in the embodiment is recorded as R2-chiral anti-counterfeiting film-1, …, R2-chiral anti-counterfeiting film-n.

[0105] Embodiment 5

[0106] The anti-counterfeiting composite material provided in the embodiment is recorded as R2-chiral anti-counterfeiting film-1, …, R2-chiral anti-counterfeiting film-n.

[0107] The luminescent particle is a silver sulfide quantum dot, and the maximum emission wavelength is 1050 nm.

[0108] The chiral polymer in the polymer film has a photonic band gap, the center position of the band gap is 1050 nm, and the band gap width is 155 nm.

[0109] The preparation raw material of the chiral polymer film comprises the following components in parts by weight:

[0110] 100 parts of nematic liquid crystal E7, 0.9 parts of chiral dopant S811, 40 parts of monomer C6M, 5 parts of crosslinking agent TMPTA, and 1 part of photoinitiator MBF;

[0111] The preparation method of the chiral polymer film is as follows:

[0112] After the above preparation raw material of the chiral polymer film and dichloromethane (500 parts) are uniformly mixed, the isotropic temperature of the nematic liquid crystal is reached, the nematic liquid crystal cell is filled, and the surface of the polymer film is irradiated with ultraviolet light with a wavelength of 365 nm for 30 min, then the nematic liquid crystal and unreacted monomer small molecules are removed by soaking in n-hexane to obtain the chiral polymer film.

[0113] The preparation method of the above anti-counterfeiting composite material is as follows:

[0114] After the above chiral polymer film is soaked in the luminescent particle solution at 40°C for 1 h, the chiral polymer film is taken out, the surface of the polymer film is washed with n-hexane, and then dried to obtain the anti-counterfeiting composite material, which is recorded as S3-chiral anti-counterfeiting film-1, …, S3-chiral anti-counterfeiting film-n.

[0115] Embodiment 6

[0116] The anti-counterfeiting composite material provided in the embodiment is recorded as R2-chiral anti-counterfeiting film-1, …, R2-chiral anti-counterfeiting film-n.

[0117] The anti-counterfeiting composite material provided in the embodiment is recorded as R3-chiral anti-counterfeiting film-1, …, R3-chiral anti-counterfeiting film-n.

[0118] Example 7

[0119] The present embodiment provides a kind of anti-counterfeiting composite material and preparation method thereof, the anti-counterfeiting composite material includes chiral polymer film and the luminescent particle loaded in the chiral polymer film;

[0120] The luminescent particle is copper indium tin quantum dot, and the maximum emission wavelength is 1060nm;

[0121] The chiral polymer in the polymer film has photonic band gap, and the band gap center position is 1060nm, and the band gap width is 155nm;

[0122] The preparation raw material of the chiral polymer film includes the following components by weight fraction:

[0123] Nematic liquid crystal SLC1717 100 parts, chiral dopant S5011 1.7 parts, monomer RM257 60 parts, crosslinking agent TMPTA 8 parts and photoinitiator MBF 4 parts;

[0124] The preparation method of the chiral polymer film is as follows:

[0125] After the above preparation raw material of chiral polymer film and dichloromethane (500 parts) are uniformly mixed, heated to the anisotropic temperature of nematic liquid crystal, filled into liquid crystal cell, irradiated with ultraviolet light with wavelength of 365nm, polymerized for 10min, soaked with n-hexane, and the nematic liquid crystal and unreacted monomer small molecules are removed, to obtain the chiral polymer film.

[0126] The preparation method of the above anti-counterfeiting composite material is as follows:

[0127] After the above chiral polymer film is soaked in luminescent particle solution at 40°C for 1h, the chiral polymer film is taken out, the polymer film surface is washed with n-hexane, and then dried to obtain the anti-counterfeiting composite material, which is recorded as S4-chiral anti-counterfeiting film-1, …, S4-chiral anti-counterfeiting film-n.

[0128] Example 8

[0129] The present embodiment provides an anti-counterfeiting composite material and a preparation method thereof, which is different from example 7 only in that the chiral dopant S5011 in example 7 is replaced by chiral dopant R5011 of equal weight fraction, and other conditions are the same as example 7.

[0130] The anti-counterfeiting composite material provided in the present embodiment is recorded as R4-chiral anti-counterfeiting film-1, …, R4-chiral anti-counterfeiting film-n.

[0131] Application Example 1

[0132] The present application example provides an anti-counterfeiting method of anti-counterfeiting composite material, and the anti-counterfeiting method is as follows:

[0133] Take the anti-counterfeiting composite S1-chiral anti-counterfeiting film-1 provided in Example 1 as an example, cut it into a shape of 1 cm x 1 cm, irradiate it with the excitation light corresponding to the luminescent particles, use a 800 nm long-pass filter to filter out the excitation light, and then use a near-infrared camera to take a near-infrared image. Then, take corresponding circularly polarized luminescent patterns using left and right circular polarizers respectively. Then, twist, cut and retain the luminescent pattern part of the taken images and convert them into gray-scale images of the same size of 100 x 100 pixels, as shown in FIG. a. Figure 4

[0134] For the near-infrared image, the encoding process is to directly set a threshold to convert the gray-scale image into a black-and-white two-dimensional code, and then derive a binary key according to the principle that black pixels are "1" and white pixels are "0", which represents the key in the near-infrared mode, as shown in FIG. b. Figure 4

[0135] For the circularly polarized luminescent image, the image processing process is to subtract the gray-scale values of each pixel point of the gray-scale images taken by the left and right circular polarizers (subtract the image taken under the left circular polarizer from the image taken under the right circular polarizer), to obtain a new gray-scale image representing the circularly polarized luminescent pattern. Then, set a threshold to encode the gray-scale image into a black-and-white two-dimensional code and derive a binary key, which represents the key in the circularly polarized luminescent mode, as shown in FIG. c. Figure 4

[0136] For the luminescent asymmetry factor pattern, the image processing process is to operate the gray-scale values of each pixel point of the gray-scale images taken by the left and right circular polarizers (subtract the image taken under the left circular polarizer from the image taken under the right circular polarizer, and then divide by half of their sum), to obtain a new gray-scale image representing the luminescent asymmetry factor pattern. Then, set a threshold to encode the gray-scale image into a black-and-white two-dimensional code and derive a binary key, which represents the key in the luminescent asymmetry factor mode, as shown in FIG. d. Figure 4

[0137] For S1-chiral anti-counterfeiting film-1, the repetition rates of the keys in the three modes obtained after 30 times of photographing, image processing and encoding processes are above 88% (keys in the near-infrared mode), above 77% (keys in the circularly polarized luminescent mode) and above 79% (keys in the luminescent asymmetry factor mode), as shown in FIG. Figure 5 Thus, it is shown that the near-infrared luminescent information, circularly polarized luminescent information and luminescent asymmetry factor information carried by the same sample have stability, and the keys in the three modes derived after encoding can be repeated, with a maximum error of not more than 23%.

[0138] Application Example 2

[0139] ​​​​The application example provides a security method of security composite material, and the difference from the application example 1 is that the sample object for shooting is S1-chiral security film-1, S1-chiral security film-2, S1-chiral security film-3, …, S1-chiral security film-n in the embodiment 1, and the image processing and encoding process are the same as those in the application example 1.

[0140] The keys in the near-infrared mode, the keys in the circular polarization luminescence mode and the keys in the luminescence asymmetry factor mode of S1-chiral security film-1, S1-chiral security film-2, S1-chiral security film-3, …, S1-chiral security film-n in the embodiment 1 are compared respectively. The test results are shown in the table 1, and the difference between the keys obtained in the three modes of different samples is about 50%, 51% and 51% in turn, which is close to the theoretical value (50%). It is illustrated that the keys of the security composite material after encoding have obvious difference even if the same raw material is used and the same preparation method is used, the result cannot be cloned, each sample has its unique independent key, and the uniqueness is achieved. Figure 6

[0141] The combination of the near-infrared camera and the circular polarizer can obtain the key of the unclonable function encoding in the polarization state mode. When the keys of a security film in the three modes are encoded and saved and uploaded to the database, only the user obtains the original unique security film, and the encoded keys in the three modes are matched with all the pre-stored keys in the database (the error rate is less than 25%) to determine that the protected information is true, and the information security is further improved.

[0142] In summary, the security composite material with the random distribution of holes is prepared by designing the specific composition of the security composite material, then the luminescent particles are randomly loaded on the surface or in the holes of the chiral polymer film, and the security composite material with the physical unclonable function is obtained by using the randomness of the loading. The security composite material provided by the application has three-dimensional information of near-infrared, circular polarization luminescence and luminescence asymmetry factor, and the information security is greatly improved.

[0143] The applicant declares that the detailed process flow of the application is illustrated by the above embodiment, but the application is not limited to the above detailed process flow, that is, it does not mean that the application must rely on the above detailed process flow to be implemented. It should be understood by those skilled in the art that any improvement of the application, equivalent replacement of each raw material of the product of the application, addition of auxiliary ingredients, selection of specific modes and the like fall within the protection scope and disclosure scope of the application.​

Claims

1. An anti-counterfeiting composite material, characterized in that, The anti-counterfeiting composite material includes a chiral polymer film and luminescent particles loaded on the chiral polymer film; The chiral polymer film has a photonic bandgap, the emission wavelength of the luminescent particles is located at the center of the photonic bandgap, and the width of the photonic bandgap is greater than the half-width of the emission wavelength of the luminescent particles. The maximum emission wavelength of the luminescent particles is ≥750 nm; The raw materials for preparing the chiral polymer membrane include the following components in parts by weight: The mixture contains 100 parts of nematic liquid crystal, 0.9-1.7 parts of chiral dopant, 40-60 parts of polymeric monomer, 5-8 parts of crosslinking agent, and 1-4 parts of photoinitiator. The polymer monomer is selected from 1,4-bis[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene and / or 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene; The chiral polymer film is prepared by the following method, which includes the following steps: After the raw materials and auxiliary solvent for preparing the chiral polymer film are mixed evenly, the mixture is heated to the isotropic temperature of the nematic liquid crystal, poured into a liquid crystal cell, irradiated with ultraviolet light, polymerized, and then soaked in an organic solvent to obtain the chiral polymer film. The organic solvent is selected from any one or a combination of at least two of n-hexane, toluene, and cyclohexane.

2. The anti-counterfeiting composite material according to claim 1, characterized in that, The chiral dopant is selected from any one or a combination of at least two of R5011, S5011, R811 and S811.

3. The anti-counterfeiting composite material according to claim 1, characterized in that, The crosslinking agent is selected from trimethylolpropane triacrylate and / or (4-(((4-(acryloyloxy)butoxy)carbonyl)oxy)benzo-2-methyl-1,4-diphenol ester.

4. The anti-counterfeiting composite material according to claim 1, characterized in that, The auxiliary solvent includes dichloromethane.

5. The anti-counterfeiting composite material according to claim 1, characterized in that, The polymerization time is ≥5 min.

6. A method for preparing an anti-counterfeiting composite material as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: The chiral polymer film is immersed in a luminescent particle solution, washed, and dried to obtain the anti-counterfeiting composite material.

7. The preparation method according to claim 6, characterized in that, The mass concentration of the luminescent particle solution is 0.1-2 mg / mL, and the solvent of the luminescent particle solution includes n-hexane.

8. The preparation method according to claim 6, characterized in that, The soaking temperature is 30-60℃, and the soaking time is ≥30min.

9. The preparation method according to claim 6, characterized in that, The solvent used for washing is selected from any one or a combination of at least two of n-hexane, toluene, or cyclohexane.

10. The preparation method according to claim 8, characterized in that, The preparation method of the anti-counterfeiting composite material specifically includes the following steps: The chiral polymer film is immersed in a luminescent particle solution for ≥30 min at 30-60℃, then washed and dried to obtain the anti-counterfeiting composite material.

11. An application of the anti-counterfeiting composite material as described in any one of claims 1-5, characterized in that, The anti-counterfeiting composite material is used as an advanced anti-counterfeiting material with a near-infrared circularly polarized light physical non-clonable function.

12. A method for preventing counterfeiting of a composite material as described in any one of claims 1-5, characterized in that, The anti-counterfeiting method includes the following steps: The anti-counterfeiting composite material as described in any one of claims 1-5 is cut into a square. The anti-counterfeiting composite material is then irradiated with excitation light corresponding to the luminescent particles to emit near-infrared circularly polarized light. After filtering out the excitation light with a filter, the luminescent pattern of the anti-counterfeiting composite material is captured by a near-infrared camera. A circularly polarized luminescent pattern is then captured using a circular polarizer. The near-infrared luminescent pattern is encoded to obtain a near-infrared mode QR code and a derived binary key. The circularly polarized luminescent pattern is then image-processed and encoded to obtain QR codes in both the circularly polarized luminescent mode and the luminescence asymmetry factor mode, as well as a derived binary key.

13. The anti-counterfeiting method according to claim 12, characterized in that, The encoding method includes: distorting and cropping the captured pattern, retaining the luminous pattern portion, and converting it into a standard rectangular image of the same pixel size in grayscale, then converting the standard rectangular image into a black and white QR code by setting a threshold and exporting the binary key.

14. The anti-counterfeiting method according to claim 12, characterized in that, The method for processing circularly polarized light emission images includes: after distorting, cropping, and transforming them into standard grayscale rectangles of the same pixel size, performing different calculations on the grayscale values ​​of each pixel in the grayscale images captured by the left and right circular polarizers to obtain new grayscale images representing the circularly polarized light emission mode and the light emission asymmetry factor mode, and then converting the grayscale images into black and white QR codes by setting a threshold.

15. The anti-counterfeiting method according to claim 14, characterized in that, The calculation method in the circularly polarized light emission mode includes: performing a difference calculation on the gray values ​​of the pixels of the left and right circularly polarized images.

16. The anti-counterfeiting method according to claim 14, characterized in that, The calculation method in the light emission asymmetry factor mode includes: dividing the difference in gray values ​​of pixels in the left and right circularly polarized images by the sum of the gray values ​​of pixels in the left and right circularly polarized images, and then multiplying by two.

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