Thermal-sensing impressing anti-counterfeit label as well as preparation method and application thereof
By mixing nematic liquid crystal with chiral agent to make cholesteric liquid crystals, forming an emulsion with the polymer, scraping and filming, annealing treatment and constant force pressing, a thermally-sensitive imprinted anti-counterfeiting label is prepared, which solves the problem of poor anti-counterfeiting effect in the prior art, and realizes the anti-counterfeiting effect of displaying patterns at a specific temperature, which is concealed and safe.
Patent Information
- Application Number
- CN202510138164.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-08
- Publication Date
- 2025-04-22
AI Technical Summary
The anti-counterfeiting effect of existing cholesteric liquid crystal preparation anti-counterfeiting labels is poor, easy to be cracked and verified, and it is not able to achieve anti-counterfeiting effect through precise temperature control.
By mixing nematic liquid crystal with chiral agent to make cholesteric liquid crystal, dissolved with the polymer in water to form an emulsion, scraped and coated into a film, annealed treatment, constant force pressing was performed to prepare a thermally-sensitive imprinted anti-counterfeiting label. The label despirates the liquid crystal molecules at a specific temperature, resulting in inconsistent reflectivity between the pressure-bearing area and the unpressed area, thereby displaying the pattern and achieving anti-counterfeiting effect.
It realizes the anti-counterfeiting effect of displaying patterns at specific temperatures, is concealed and safe, and is simple and easy to perform in the preparation process, suitable for large-scale production.
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Figure CN119863973A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of liquid crystal materials, and in particular relates to a thermal embossing anti-counterfeiting label and a preparation method and application thereof. Background Art
[0002] Cholesteric liquid crystals are a type of photonic crystal with a periodic helical superstructure. According to the Bragg equation, this type of material can selectively reflect certain wavelengths of light, thereby showing different colors under sunlight. Adding chiral molecules to nematic liquid crystals is a common method for preparing cholesteric liquid crystals. The cholesteric helix p and its reflected color can be easily dynamically modulated by light, temperature, humidity, magnetic field, voltage and mechanical stress, and it has important applications in display, optics and anti-counterfeiting.
[0003] At present, with the continuous deepening of the application research of cholesteric liquid crystals, the structural color change based on the external field or the permanent structural color change after the external field no longer meets the application requirements. It is necessary to develop precise and safe anti-counterfeiting labels to meet the application requirements. In addition, there is no public report on the anti-counterfeiting effect achieved by precise temperature control at this stage. Summary of the invention
[0004] The present application discloses a thermal embossing anti-counterfeiting label and a preparation method and application thereof, aiming to solve the technical problems existing in the anti-counterfeiting labels prepared with cholesteric liquid crystals, such as poor anti-counterfeiting effect, easy cracking and difficulty in verification.
[0005] In order to achieve the above purpose, the technical solution of this application is:
[0006] The first aspect of the present application provides a method for preparing a thermal embossing anti-counterfeiting label, the method comprising:
[0007] Adding nematic liquid crystal and chiral agent into organic solvent, evaporating the organic solvent after reaction, and obtaining cholesteric liquid crystal;
[0008] dissolving the cholesteric liquid crystal and the polymer in water to obtain a precursor emulsion;
[0009] The precursor emulsion is coated into a film, annealed, and then pressed with a constant force by a mold to obtain a thermal embossing anti-counterfeiting label.
[0010] In combination with the first aspect, preferably, the nematic liquid crystal is one or more of 4-cyano-4-pentylbiphenyl, 4-cyano-4-n-butylbiphenyl, 4-cyano-4-propylbiphenyl, 4-(trans-4-pentylcyclohexyl)benzonitrile, 4-pentylbenzonitrile, trans-4-[4-(4-n-pentylcyclohexyl)phenylcyanophenyl, 4-cyano-4-pentyloxybiphenyl, 4-(trans-4-butylcyclohexyl)benzonitrile, and 4-cyano-4-n-pentyl-p-terphenyl.
[0011] In combination with the first aspect, preferably, the chiral agent is one or more of R5011, S5011, R811, S811, R1011, and S1011.
[0012] In combination with the first aspect, preferably, the organic solvent is one or more of chloroform, ethanol, methanol, xylene, tetrahydrofuran, and dichlorothionyl.
[0013] In combination with the first aspect, preferably, the mass ratio of the nematic liquid crystal, the chiral agent and the polymer is (20-29): (0.4-1): (70-80).
[0014] In combination with the first aspect, preferably, the polymer is one or more of polyvinyl alcohol type 1788, polyvinyl alcohol type 1799, polyethylene oxide, polyethylene glycol, and hydroxypropyl methylcellulose.
[0015] In combination with the first aspect, preferably, the scraping temperature is 40-60° C., and the scraping speed is 20-50 mm / s.
[0016] In combination with the first aspect, preferably, the annealing treatment temperature is 60-100° C., and the time is 30-60 min.
[0017] The second aspect of the present application provides a thermal embossing anti-counterfeiting label made by the preparation method described in the first aspect.
[0018] The third aspect of the present application provides the application of the heat-sensitive embossing anti-counterfeiting label made by the preparation method described in the first aspect or the heat-sensitive embossing anti-counterfeiting label described in the second aspect in the field of anti-counterfeiting.
[0019] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present application include at least:
[0020] The preparation method of the heat-sensitive embossing anti-counterfeiting label provided by the present application is obtained by mixing nematic liquid crystal and chiral agent to form cholesteric liquid crystal, and then preparing emulsion with polymer, scraping film, annealing and pressing. On the one hand, nematic liquid crystal and chiral agent are self-assembled to form cholesteric liquid crystal with molecular arrangement in a spiral shape, and cholesteric liquid crystal is dispersed in polymer aqueous solution as oil phase spheres. When the temperature rises, the cholesteric phase is transformed into isotropic phase, and the spiral structure of liquid crystal begins to unwind, and the rigid structure is transformed into a flexible structure; on the other hand, by pressing the film with constant force, the polymer network will be deformed, and the deformation still exists after the pressure is removed, and at room temperature, the color and reflectivity of the stressed area and the unstressed area are the same; and only when it rises to a specific temperature, the liquid crystal molecules begin to unwind, and because the reflectivity of the stressed area and the unstressed area is inconsistent, the pattern is displayed and the technical effect of anti-counterfeiting is achieved, which has the concealment and security of anti-counterfeiting; at the same time, the preparation process of the present application is simple and easy to implement, and easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0022] Figure 1 This is an encryption effect diagram of the single digit "2025" of the A1-anti-counterfeiting label provided in an embodiment of the present application;
[0023] Figure 2 This is an encryption effect diagram of multiple digits "6" of the A2-anti-counterfeiting label provided in an embodiment of the present application;
[0024] Figure 3 This is an encryption effect diagram of multiple digits "5" of the A3 anti-counterfeiting label provided in an embodiment of the present application;
[0025] Figure 4 Spectral data diagram of the A1-anti-counterfeiting label provided in the embodiment of the present application;
[0026] Figure 5 This is an in-situ constant pressure droplet morphology monitoring diagram of the A1-anti-counterfeiting label provided in an embodiment of the present application at 31.5°C;
[0027] Figure 6 This is an in-situ constant pressure droplet morphology monitoring diagram at room temperature of the A1-anti-counterfeiting label provided in an embodiment of the present application. DETAILED DESCRIPTION
[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0029] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.
[0030] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.
[0031] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
[0032] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.
[0033] It should be noted that all raw materials and reagents in the examples of the present application were purchased on the market or prepared according to conventional methods well known to those skilled in the art.
[0034] In a first aspect, an embodiment of the present application provides a method for preparing a thermal embossing anti-counterfeiting label, the method comprising:
[0035] Adding nematic liquid crystal and chiral agent into organic solvent, evaporating the organic solvent after reaction, and obtaining cholesteric liquid crystal;
[0036] dissolving the cholesteric liquid crystal and the polymer in water to obtain a precursor emulsion;
[0037] The precursor emulsion is coated into a film, annealed, and then pressed with a constant force by a mold to obtain a thermal embossing anti-counterfeiting label.
[0038] Among them, on the one hand, the nematic liquid crystal and the chiral agent are combined into a helical cholesteric liquid crystal through self-assembly, and the cholesteric liquid crystal is dispersed in the polymer aqueous solution in the form of oil phase spheres. When the temperature rises, the cholesteric phase changes to isotropic, and the helical structure of the liquid crystal begins to untwist, changing from a rigid structure to a flexible structure; on the other hand, by pressing the film with a constant force, the polymer network will deform, and the deformation still exists after the pressure is removed, and at room temperature, the color and reflectivity of the stressed area and the unstressed area are the same; and only when a specific temperature is reached, the liquid crystal molecules begin to untwist, and due to the inconsistent reflectivity of the stressed area and the unstressed area, the pattern is displayed and the technical effect of anti-counterfeiting is achieved, which has the concealment and security of anti-counterfeiting; at the same time, the preparation process of the present application is simple and easy, and easy to mass produce.
[0039] It should be noted that the present application does not impose any particular limitation on the mold used, and any pattern that needs to be protected can be used. The present application uses a convex dot stamp for constant force pressing.
[0040] In the embodiment of the present application, the nematic liquid crystal is preferably one or more of 4-cyano-4-pentylbiphenyl, 4-cyano-4-n-butylbiphenyl, 4-cyano-4-propylbiphenyl, 4-(trans-4-pentylcyclohexyl)benzonitrile, 4-pentylbenzonitrile, trans-4-[4-(4-n-pentylcyclohexyl)phenylcyanobenzene, 4-cyano-4-pentyloxybiphenyl, 4-(trans-4-butylcyclohexyl)benzonitrile, and 4-cyano-4-n-pentyl-p-terphenyl.
[0041] In the embodiments of the present application, the chiral agent is preferably one or more of R5011, S5011, R811, S811, R1011, and S1011. These chiral agents can be purchased directly from the market or synthesized according to methods known in the art, and the embodiments of the present application do not impose any particular restrictions on their specific chemical structures and sources. The chiral agent selected in the present application has similarities with nematic liquid crystals, does not contain strong polar groups, and can cause the liquid crystal material to undergo an anti-twist phenomenon, thereby increasing the stability of the liquid crystal film.
[0042] It should be noted that the present application uses nematic liquid crystal and chiral agent to combine into a spiral cholesteric liquid crystal through self-assembly; then cholesteric liquid crystal is used as oil phase and polymer aqueous solution is used as water phase, and the two are emulsified to form an emulsion, and cholesteric liquid crystal is dispersed in the polymer aqueous solution as small spheres; in the formed polymer dispersed liquid crystal film, the liquid crystal is dispersed in the polymer network in the form of oblate spheres, which is different from other cholesteric liquid crystals that reflect the entire visible light spectrum with the change of reflection wavelength as the temperature rises, and the reflection wavelength of the cholesteric liquid crystal made in the present application does not change with the increase of temperature. Based on the selection of different nematic liquid crystals, the anti-counterfeiting label made can realize the display of patterns at different decryption temperatures. Based on the selection of different chiral agents, the anti-counterfeiting label made can present different colors. Therefore, the anti-counterfeiting label made can have different colors and different decryption temperatures, which expands the application scenarios.
[0043] In the embodiment of the present application, the organic solvent is preferably one or more of chloroform, ethanol, methanol, xylene, tetrahydrofuran, and thionyl chloride, wherein these organic solvents can interact with nematic liquid crystals and chiral agents, thereby being uniformly dissolved in the organic solvent.
[0044] In the embodiment of the present application, the mass ratio of the nematic liquid crystal, the chiral agent and the polymer is preferably (20-29): (0.4-1): (70-80). By controlling the amount of each substance added, the color of the film can be changed to any color in the red-blue (full visible light spectrum) range.
[0045] In the embodiment of the present application, the polymer is preferably one or more of polyvinyl alcohol type 1788, polyvinyl alcohol type 1799, polyethylene oxide, polyethylene glycol, and hydroxypropyl methylcellulose. Among them, these polymers play the role of emulsifying cholesteric liquid crystals in the precursor emulsion, and at the same time play the role of anchoring cholesteric liquid crystals in the film, providing space for external pressure to be applied.
[0046] In the embodiment of the present application, the scraping temperature is 40-60° C., and the scraping speed is 20-50 mm / s. By controlling the scraping temperature and speed, the precursor emulsion is evenly spread on the glass substrate, which is convenient for subsequent experiments.
[0047] In the embodiment of the present application, the annealing temperature is 60-100°C and the time is 30-60min. Among them, by controlling the temperature and time of the annealing treatment, the water in the emulsion evaporates to form a thin and uniform film, so that the cholesteric liquid crystal orientation is uniform and can selectively reflect. Through thermal excitation, the bonds between the molecules of the substance are broken and rearranged, thereby eliminating these stresses and making the structure of the film more stable. It can also eliminate structural defects or impurities in the film, improve the crystal quality and grain boundary strength, and thus improve the physical properties and chemical stability of the film.
[0048] The second aspect of the present application provides a thermal embossing anti-counterfeiting label made by the preparation method described in the first aspect. Among them, the anti-counterfeiting label made in the present application can only realize the appearance of the anti-counterfeiting mark at a specific temperature, realize the selectability of the decryption temperature, and ensure the concealment and security of the anti-counterfeiting. For example, in Example 1, the appearance of the anti-counterfeiting mark can only be realized at 31-32°C. In Example 2, the appearance of the anti-counterfeiting mark can only be realized at 50-51°C. In Example 3, the appearance of the anti-counterfeiting mark can only be realized at 28-29°C.
[0049] It should be noted that the pitch of the cholesteric liquid crystal made in the present application does not change in the cholesteric phase interval, and it belongs to a rigid structure supported by a spiral structure. When the temperature rises gradually and approaches the cholesteric liquid crystal from the cholesteric phase to the isotropic phase, the spiral structure of the liquid crystal begins to unwind, and the rigid structure is transformed into a flexible structure. By pressing the film with constant force, the polymer network will be deformed and the deformation will still exist after the pressure is removed, and the internal contraction force of the polymer network on the liquid crystal microsphere will increase. When the temperature is at room temperature, the liquid crystal molecules are in a rigid stage, and the internal contraction force of the polymer is less than the force that deforms the liquid crystal pitch, and the color and reflectivity of the stressed area are the same as those of the unstressed area. When it rises to a specific temperature, the liquid crystal molecules begin to unwind, and the internal contraction force of the polymer is greater than the force that unwinds the liquid crystal molecules, so that the unwinding process of the stressed part is faster, the reflectivity decreases more, and the reflectivity of the unstressed area decreases less. Therefore, the reflectivity of different regions is inconsistent, and the display pattern achieves the technical effect of anti-counterfeiting, and the anti-counterfeiting label made at the same time is not easy to be cracked and the verification is simple.
[0050] The third aspect of the present application provides the application of the heat-sensitive embossing anti-counterfeiting label made by the preparation method described in the first aspect or the heat-sensitive embossing anti-counterfeiting label described in the second aspect in the field of anti-counterfeiting. The anti-counterfeiting label prepared as above is highly sensitive to temperature, improves the anti-counterfeiting effect, ensures the concealment and security of anti-counterfeiting, and has a wide market application prospect.
[0051] The technical solution of the present application will be further described below in conjunction with specific embodiments.
[0052] Example 1
[0053] This embodiment provides a method for preparing an A1-anti-counterfeiting label, which specifically includes:
[0054] S101: Weigh 500 mg of 4-cyano-4-pentylbiphenyl (nematic liquid crystal) and 20 mg of R5011 (chiral agent), add chloroform and place the solution in an ultrasonic cleaner to mix it thoroughly. Then, heat it at a constant temperature to evaporate the chloroform and obtain cholesteric liquid crystal;
[0055] S102: Add 23 g of 1788 polyvinyl alcohol aqueous solution (PVA mass fraction 11%) to the above cholesteric liquid crystal, place on a constant speed stirring table and stir for 10 hours to obtain a white precursor emulsion;
[0056] S103: The precursor emulsion is placed on a scraper with a scraping groove thickness of 0.1-0.2 μm, the bottom temperature is set to 50°C, and the scraping speed is 50 mm / s. Then, the film is annealed on a hot plate at 80°C for 30 minutes, and the film is taken out and pressed with a constant force by a convex stamp for 30 minutes to obtain an A1-anti-counterfeiting label.
[0057] Example 2
[0058] This embodiment provides a method for preparing an A2-anti-counterfeiting label, which specifically includes:
[0059] S201: Weigh 1000 mg of 4-(trans-4-pentylcyclohexyl)benzonitrile (nematic liquid crystal) and 30 mg of S5011 (chiral agent), add 1000 μL of methanol and place the solution in an ultrasonic cleaner to mix it thoroughly. Then, heat it at a constant temperature to evaporate the methanol and obtain cholesteric liquid crystal;
[0060] S202: Add 31 g of 1799 PVA-water solution (PVA mass fraction is 10%) to the cholesteric liquid crystal, place on a constant speed stirring table and stir for 10 hours to obtain a white precursor emulsion;
[0061] S203: The precursor emulsion is placed on a scraper with a scraping groove thickness of 0.1-0.2 μm, the bottom temperature is set to 50°C, and the scraping speed is 50 mm / s. Then, the film is annealed on a hot plate at 80°C for 30 minutes, and the film is taken out and pressed with a constant force by a convex stamp for 30 minutes to obtain an A2-anti-counterfeiting label.
[0062] Example 3
[0063] This embodiment provides a method for preparing an A3 anti-counterfeiting label, which specifically includes:
[0064] S301: Weigh 1100 mg of 4-cyano-4-n-butylbiphenyl (nematic liquid crystal) and 40 mg of R811 (chiral agent), add benign solvents of both and place the solution in an ultrasonic cleaning machine to mix them thoroughly. Then, heat at a constant temperature to volatilize the benign solvent to obtain cholesteric liquid crystal;
[0065] S302: adding 21 g of an aqueous solution of hydroxypropyl methylcellulose (mass fraction of 14%) to the above cholesteric liquid crystal, placing the mixture on a constant speed stirring table and stirring for 10 h to obtain a white precursor emulsion;
[0066] S303: The precursor emulsion is placed on a scraper with a scraping groove thickness of 0.1-0.2μm, the bottom temperature is set at 50℃, and the scraping speed is 50mm / s. Then, the film is annealed on a hot plate at 80℃ for 30min, and the film is taken out and pressed with a constant force by a convex stamp for 30min to obtain an A3-anti-counterfeiting label.
[0067] In order to verify the anti-counterfeiting effect of the anti-counterfeiting labels, the anti-counterfeiting effect of Examples 1-3 was tested. The test results are as follows: Figure 1 , Figure 2 and Figure 3 shown.
[0068] according to Figure 1 It can be seen that the A1-anti-counterfeiting label is red at room temperature of 25°C, and the number "2025" appears when the temperature rises to 31°C. When the temperature rises to above 33°C, the A1-anti-counterfeiting label fades completely and the number "2025" disappears.
[0069] according to Figure 2 It can be seen that the A2-anti-counterfeiting label is light green at room temperature of 25°C. When the temperature rises to 50-51°C, the number "6" appears. When the temperature exceeds 51°C, the A2-anti-counterfeiting label completely fades and the number "6" disappears.
[0070] according to Figure 3 It can be seen that the A3-anti-counterfeiting label is yellow at room temperature of 25°C, the number "5" appears when the temperature rises to 28-29°C, and when it exceeds 29°C, the A3-anti-counterfeiting label fades completely and the number "5" disappears.
[0071] In order to further verify the anti-counterfeiting effect mechanism of the anti-counterfeiting label, the A1-anti-counterfeiting label was subjected to corresponding spectral testing and in-situ constant pressure droplet morphology monitoring. The test results are as follows: Figures 4 to 6 shown.
[0072] according to Figure 4 It can be seen that from the spectrum diagram of the A1-anti-counterfeiting label, at 25°C, the reflectivity of the pressure and non-pressure areas of the A1-anti-counterfeiting label is the same, and no encrypted information can be observed. When the temperature is raised to 31°C, the reflectivity of both the pressure area and the non-pressure area decreases, and the reflectivity of the pressure area decreases more, so the encrypted information appears.
[0073] according to Figure 5 It can be seen that the in-situ constant pressure droplet morphology monitoring diagram at 31.5°C was tested. Before pressure was applied, the droplets on the liquid crystal film maintained their initial shape. As pressure was continuously applied, the droplets gradually shrank, and the reflectivity continued to decrease, thereby being able to display patterns.
[0074] according to Figure 6It can be seen that the in-situ constant-pressure droplet morphology monitoring diagram at room temperature was tested. The droplet morphology did not change during the entire 90-minute constant pressure process, and the reflectivity remained unchanged.
[0075] Therefore, the preparation method of the thermal embossing anti-counterfeiting label provided in the present application is prepared by mixing nematic liquid crystal and chiral agent to form cholesteric liquid crystal, and then preparing an emulsion with a polymer, coating the emulsion, annealing, and pressing the emulsion. Only when the temperature is at a specific temperature can the pattern be displayed to achieve the technical effect of anti-counterfeiting. The method has a high sensitivity to temperature, improves the anti-counterfeiting effect, ensures the concealment and security of anti-counterfeiting, and has broad market application prospects.
[0076] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.
[0077] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions recorded in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.
Claims
1. A method for preparing a thermal embossing anti-counterfeiting label, characterized in that: The preparation method comprises: Adding nematic liquid crystal and chiral agent into organic solvent, evaporating the organic solvent after reaction, and obtaining cholesteric liquid crystal; dissolving the cholesteric liquid crystal and the polymer in water to obtain a precursor emulsion; The precursor emulsion is coated into a film, annealed, and pressed with a constant force by a mold to obtain a thermal embossing anti-counterfeiting label.
2. The method for preparing a thermal embossing anti-counterfeiting label according to claim 1, characterized in that: The nematic liquid crystal is one or more of 4-cyano-4-pentylbiphenyl, 4-cyano-4-n-butylbiphenyl, 4-cyano-4-propylbiphenyl, 4-(trans-4-pentylcyclohexyl)benzonitrile, 4-pentylbenzonitrile, trans-4-[4-(4-n-pentylcyclohexyl)phenylcyanophenyl, 4-cyano-4-pentyloxybiphenyl, 4-(trans-4-butylcyclohexyl)benzonitrile, and 4-cyano-4-n-pentyl-p-terphenyl.
3. The method for preparing a thermal embossing anti-counterfeiting label according to claim 1, characterized in that: The chiral agent is one or more of R5011, S5011, R811, S811, R1011, and S1011.
4. The method for preparing a thermal embossing anti-counterfeiting label according to claim 3, characterized in that: The organic solvent is one or more of chloroform, ethanol, methanol, xylene, tetrahydrofuran and thionyl chloride.
5. The method for preparing a thermal embossing anti-counterfeiting label according to claim 1, characterized in that: The mass ratio of the nematic liquid crystal, the chiral agent and the polymer is (20-29): (0.4-1): (70-80).
6. The method for preparing a thermal embossing anti-counterfeiting label according to claim 1, characterized in that: The polymer is one or more of 1788 type polyvinyl alcohol, 1799 type polyvinyl alcohol, polyethylene oxide, polyethylene glycol, and hydroxypropyl methylcellulose.
7. The method for preparing a thermal embossing anti-counterfeiting label according to claim 1, characterized in that: The scraping temperature is 40-60° C., and the scraping speed is 20-50 mm / s.
8. The method for preparing a thermal embossing anti-counterfeiting label according to claim 1, characterized in that: The annealing treatment temperature is 60-100° C. and the time is 30-60 min.
9. A thermal embossing anti-counterfeiting label made by the preparation method according to any one of claims 1 to 8.
10. Use of the thermal embossing anti-counterfeiting label made by the preparation method according to any one of claims 1 to 8 or the thermal embossing anti-counterfeiting label according to claim 9 in the field of anti-counterfeiting.