Circularly polarized light-emitting film with adjustable light-emitting wavelength and rotation direction, anti-counterfeit label and preparation method and application of circularly polarized light-emitting film and anti-counterfeit label

Abstract

The invention relates to the technical field of circularly polarized light-emitting materials, and discloses a circularly polarized light-emitting film with adjustable light-emitting wavelength and rotation direction, an anti-counterfeit label and a preparation method and application of the circularly polarized light-emitting film. The preparation method of the circularly polarized light-emitting film with adjustable light-emitting wavelength and rotation direction comprises the following steps: respectively preparing a cellulose nanocrystal suspension and an aggregation-induced light-emitting molecule solution; dropwise adding the aggregation-induced emission molecule solution into the cellulose nanocrystal suspension subjected to ultrasonic treatment and pH adjustment to obtain a precursor solution; and adding a plasticizer into the precursor solution, uniformly mixing, and carrying out induced self-assembly in a hydrophobic container at room temperature to obtain the circularly polarized light-emitting film with adjustable light-emitting wavelength and rotation direction. The circularly polarized light-emitting film with adjustable light-emitting wavelength and rotation direction prepared by the invention has multiple responsiveness, can realize multicolor circularly polarized light emitting, can realize dynamic response of structural color under high humidity, further can realize dynamic response of circularly polarized light emitting rotation direction, and can be used for preparing an anti-counterfeit label for counterfeiting prevention.

Description

Technical Field

[0001] The present application relates to the technical field of circularly polarized luminescent materials, and in particular to a circularly polarized luminescent film with adjustable luminescent wavelength and handedness, an anti-counterfeiting label, and a preparation method and application thereof. Background Art

[0002] Circularly polarized luminescent materials have aroused great research interest due to their potential applications in 3D display, anti-counterfeiting, optical information storage, asymmetric synthesis, bio-imaging, etc. Circularly polarized luminescence can be divided into left-handed circularly polarized luminescence and right-handed circularly polarized luminescence according to the rotation direction of light. The circularly polarized luminescent film with both left-handed and right-handed circularly polarized luminescence characteristics achieved by a simple and green preparation method has great application value.

[0003] Cellulose nanocrystals are a natural polysaccharide material with abundant reserves, sustainability and biodegradability, which can replace petrochemical resources to prepare high value-added functional materials. At the same time, cellulose nanocrystals are also a kind of lyotropic liquid crystal. When its suspension reaches a critical concentration, the cellulose nanocrystal structural units can self-assemble to form a left-handed chiral nematic phase. As the aqueous solution continues to evaporate, a photonic film with a left-handed chiral nematic phase structure is finally formed; thanks to its highly ordered left-handed chiral structure, right-handed circularly polarized luminescence can be achieved by simply doping fluorescent molecules. In addition, by manipulating the photonic band gap of cellulose nanocrystal films through external stimuli (such as humidity, acid, alkali and mechanical force), the size of right-handed circularly polarized luminescence can also be controlled. However, due to its single chiral helical structure, it is difficult for self-assembled cellulose films to achieve dynamic regulation of the size and direction of left-handed and right-handed circularly polarized luminescence.

[0004] In addition, most circularly polarized luminescent materials based on cellulose nanocrystals exhibit static emission characteristics, while multicolor circularly polarized luminescent materials are usually achieved by integrating chromophores with different luminescent wavelengths into a cellulose film with a chiral nematic phase structure. If dynamic multicolor circularly polarized luminescence can be achieved by doping a single component chromophore, its application scenarios will be greatly broadened. Summary of the invention

[0005] The present application provides a circularly polarized luminescent film with adjustable luminescent wavelength and handedness, an anti-counterfeiting label, and a preparation method and application thereof, aiming to solve the problems that the luminescent wavelength and handedness of existing circularly polarized luminescent materials based on cellulose nanocrystals are difficult to control, and that multi-color circularly polarized luminescence is difficult to achieve through single doping.

[0006] In order to achieve the above objectives, the present application adopts the following technical solutions.

[0007] In a first aspect of the present application, a method for preparing a circularly polarized luminescent film with adjustable luminescent wavelength and handedness is provided, comprising:

[0008] preparing cellulose nanocrystal suspension and aggregation-induced emission molecule solution respectively;

[0009] Adding the aggregation-induced emission molecule solution dropwise into the cellulose nanocrystal suspension to obtain a precursor solution;

[0010] The plasticizer is added into the precursor solution, mixed evenly, and induced to self-assemble in a hydrophobic container at room temperature to obtain a circularly polarized luminescent film with adjustable luminescent wavelength and rotational direction.

[0011] Preferably, the aggregation-induced emission molecule solution is prepared by dissolving the aggregation-induced emission molecule in an organic solvent;

[0012] The aggregation-induced emission molecule includes any one of tetraphenylethylene, tetraaldehyde tetraphenylethylene, tetra(4-pyridylphenyl)ethylene, tetra(4-carboxyphenyl)ethylene or 1-(4-carboxyphenyl)-1,2,2-triphenylethylene;

[0013] The organic solvent is N-methylpyrrolidone.

[0014] Preferably, the plasticizer comprises polyethylene glycol having different terminal groups or molecular weights.

[0015] More preferably, the plasticizer is polyethylene glycol dicarboxylic acid or polyethylene glycol with a molecular weight of 200 to 40,000.

[0016] Preferably, the ultrasonic treatment time of the cellulose nanocrystal suspension is 2-256s; the pH of the cellulose nanocrystal suspension is 1-12, and the concentration thereof is 1-8wt%;

[0017] The concentration of the aggregation-induced emission molecule solution is 1-15 mg / mL.

[0018] Preferably, the mass ratio of the cellulose nanocrystals, the aggregation-induced emission molecules and the plasticizer is (20-800):(0.01-0.75):(5-100).

[0019] The second aspect of the present application provides a circularly polarized luminescent film with adjustable luminescent wavelength and handedness prepared by the above preparation method.

[0020] The third aspect of the present application provides the application of the circularly polarized luminescent film with adjustable luminescent wavelength and rotation direction in anti-counterfeiting.

[0021] In a fourth aspect of the present application, an anti-counterfeiting label is provided, wherein a preparation method thereof comprises:

[0022] S1, cutting the circularly polarized light-emitting film into a suitable shape;

[0023] S2, using an acid solution or an alkaline solution as ink to write anti-counterfeiting information on the surface of the circularly polarized luminescent film;

[0024] S3, drying the circularly polarized luminescent film with anti-counterfeiting information to obtain an anti-counterfeiting label;

[0025] The anti-counterfeiting label has high humidity and luminous wavelength response characteristics.

[0026] Preferably, the high humidity refers to a relative humidity of 80-100%.

[0027] Compared with the prior art, the beneficial effects of this application are:

[0028] The circularly polarized luminescent film with adjustable luminescent wavelength and rotation direction prepared in the present application has multiple responsiveness, can realize multi-color circularly polarized luminescence, can realize dynamic response of structural color under high humidity, and then can realize dynamic response of circularly polarized luminescence rotation direction, and has dynamic responsiveness or static characteristics of fluorescent color and circularly polarized luminescence; it can realize structural color and / or fluorescent color changes under different humidity. During the preparation process, by adjusting the pH value of the cellulose nanocrystal suspension, films with different structural colors, fluorescent colors, circularly polarized luminescence intensities and circularly polarized luminescence rotation directions can be obtained. The preparation method of the present application uses water as a solvent, and the preparation process is green and simple, environmentally friendly and pollution-free.

[0029] The circularly polarized luminescent film with adjustable luminescent wavelength and handedness prepared in the present application can be used to prepare anti-counterfeiting labels for anti-counterfeiting. The anti-counterfeiting label of the present application has multiple dynamic responsiveness, can realize multi-color circularly polarized luminescence, and can be patterned, with anti-counterfeiting characteristics of a higher security level. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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.

[0031] Figure 1 The circularly polarized luminescence spectrum of the circularly polarized luminescent film prepared in Example 1;

[0032] Figure 2 The circularly polarized luminescence spectrum of the circularly polarized luminescent film prepared in Example 3;

[0033] Figure 3 The circularly polarized luminescence spectrum of the circularly polarized luminescent film prepared in Comparative Example 1;

[0034] Figure 4 The circularly polarized luminescence spectrum of the circularly polarized luminescent film prepared in Comparative Example 2;

[0035] Figure 5Schematic diagram of the application of the anti-counterfeiting label of the present application in anti-counterfeiting; (a) shows the change of the anti-counterfeiting label over time at different humidity under natural light, and (b) shows the change of the anti-counterfeiting label over time at different humidity under ultraviolet light. DETAILED DESCRIPTION

[0036] 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.

[0037] In the following description of this embodiment, the terms "include", "comprising", "having" and "containing" are all open terms, meaning including but not limited to.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Those skilled in the art will appreciate that the numerical ranges in the embodiments of the present application are to be construed as specifically disclosing each intermediate value between the upper and lower limits of the scope. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present application. The upper and lower limits of these smaller ranges may be independently included or excluded in the scope.

[0043] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0044] In a first aspect, the present application provides a method for preparing a circularly polarized luminescent film with adjustable luminescent wavelength and handedness, comprising:

[0045] Step 1, preparing a cellulose nanocrystal suspension and an aggregation-induced emission molecule solution respectively;

[0046] In the present application, the cellulose nanocrystals can be obtained by purchasing a commodity or making them by yourself, and the cellulose nanocrystals are dispersed in water to obtain a cellulose nanocrystal suspension. The concentration of the cellulose nanocrystal suspension is 1 to 8 wt %, and the pH is 1 to 12. By selecting different pH values, the structural color, fluorescent color, circularly polarized luminescence intensity, and circularly polarized luminescence handedness of the prepared circularly polarized luminescent film can be adjusted.

[0047] In the present application, the aggregation-induced emission molecule solution is prepared by dissolving the aggregation-induced emission molecule in an organic solvent, and the concentration of the aggregation-induced emission molecule solution is 1 to 15 mg / mL.

[0048] The aggregation-induced emission molecule includes any one of tetraphenylethylene, tetraaldehyde tetraphenylethylene, tetra(4-pyridylphenyl)ethylene, tetra(4-carboxyphenyl)ethylene or 1-(4-carboxyphenyl)-1,2,2-triphenylethylene; and the organic solvent is N-methylpyrrolidone.

[0049] Step 2, adding the aggregation-induced emission molecule solution dropwise into the cellulose nanocrystal suspension to obtain a precursor solution;

[0050] In the present application, in order to achieve a better mixing effect, the cellulose nanocrystal suspension can be ultrasonically treated, wherein the ultrasonic time is 0 to 3600 seconds, preferably 2 to 256 seconds. Among them, different ultrasonic times have an effect on the morphology of cellulose nanocrystals in the cellulose nanocrystal suspension, thereby affecting the photonic band gap of the film, and ultimately affecting the circularly polarized luminescence rotation direction of the film.

[0051] In the present application, the aggregation-induced emission molecule solution is slowly added to the cellulose nanocrystal suspension by dropwise addition and the mixture is fully stirred.

[0052] Step 3, adding a plasticizer to the precursor solution, mixing evenly, and inducing self-assembly in a hydrophobic container at room temperature to obtain a circularly polarized luminescent film with adjustable luminescent wavelength and handedness.

[0053] In the present application, the plasticizer includes polyethylene glycol with different terminal groups or molecular weights; preferably, the plasticizer is polyethylene glycol dicarboxylic acid or polyethylene glycol with a molecular weight of 200 to 40,000.

[0054] The precursor solution to which the plasticizer is added and mixed evenly is added into a hydrophobic container, such as a polystyrene culture dish, and evaporation-induced self-assembly is carried out at room temperature to obtain a cellulose nanocrystal composite film, whose luminescence wavelength and handedness are adjustable.

[0055] In the present application, the mass ratio of the cellulose nanocrystals, the aggregation-induced emission molecules and the plasticizer is preferably (20-800):(0.01-0.75):(5-100). Within this ratio range, it is beneficial to prepare a circularly polarized luminescent film with adjustable emission wavelength and handedness.

[0056] The preparation method of the present application uses water as solvent, and the preparation process is green, simple, environmentally friendly and pollution-free. The circularly polarized luminescent film with adjustable luminescent wavelength and handedness prepared by the present application has multiple responsiveness, and can realize multi-color circularly polarized luminescence. It can realize the dynamic response of structural color under high humidity, and then realize the dynamic response of circularly polarized luminescence handedness, which can be used to prepare anti-counterfeiting labels for anti-counterfeiting. In addition, the present application can obtain films with different structural colors, fluorescent colors, circularly polarized luminescence intensities and circularly polarized luminescence handedness by adjusting the pH value of the cellulose nanocrystal suspension within a specific range.

[0057] In the present application, the cellulose nanocrystal suspension is preferably prepared by the following method:

[0058] Pulp powder was added to H2SO4 solution and stirred continuously, reacted at 50℃ for 2h, and then quenched with 10 times deionized water. After being left overnight, the lower layer of higher concentration suspension was collected and centrifuged at 6000rpm for 5 minutes; the high concentration suspension obtained by centrifugation was washed with deionized water and centrifuged again; then it was transferred to a cellulose dialysis bag (molecular weight cutoff: 12000-14000) and dialyzed for one week. After the dialysis, the collected suspension was centrifuged for 20 minutes to remove unreacted pulp powder and large particles; finally, the suspension was concentrated at 40℃ using a rotary evaporator to obtain a cellulose nanocrystal suspension.

[0059] The film prepared in the present application in a specific pH range has multiple dynamic responsiveness, and its structural color, fluorescent color, circularly polarized luminescence intensity and circularly polarized luminescence rotation direction change accordingly with different pH values. It can realize multi-color circularly polarized luminescence, can realize rotation direction change under high humidity, can realize structural color and / or fluorescent color change, and can be used for anti-counterfeiting or for preparing anti-counterfeiting labels.

[0060] The present application also provides an anti-counterfeiting label, the preparation method of which includes:

[0061] S1, cutting the circularly polarized light-emitting film into a suitable shape;

[0062] S2, using an acid solution or an alkaline solution as ink to write anti-counterfeiting information on the surface of the circularly polarized luminescent film;

[0063] In the present application, the acid solution may be hydrochloric acid or dilute sulfuric acid, preferably hydrochloric acid, with a concentration of 1 to 5 mol / L; the alkaline solution may be potassium hydroxide or sodium hydroxide solution, preferably sodium hydroxide solution with a concentration of 1 to 5 mol / L.

[0064] In the present application, anti-counterfeiting information is written by recording special patterns or texts on the surface of the circularly polarized luminescent film by spraying, dripping, stamping or direct writing of hydrochloric acid or sodium hydroxide solution.

[0065] S3, drying the circularly polarized luminescent film with anti-counterfeiting information to obtain an anti-counterfeiting label;

[0066] In the present application, it is preferred to naturally dry the circularly polarized luminescent film with the anti-counterfeiting information written thereon to obtain the anti-counterfeiting label.

[0067] The anti-counterfeiting label of the present application has high humidity and luminescence wavelength response characteristics. Under different humidity, it not only realizes the dynamic responsiveness of structural color, but also has dynamic responsiveness or static characteristics of fluorescent color and circularly polarized luminescence. Under the condition of relative humidity of 80-100%, as the placement time increases, under natural light, the structural color pattern on the surface of the circularly polarized luminescent film gradually appears, and under ultraviolet light, the fluorescent color of the structural color pattern is displayed. Its rotation direction changes with the change of humidity and has humidity responsiveness; with the change of humidity, the structural color pattern disappears or appears under natural light, and under ultraviolet light, the fluorescent color of the structural pattern changes. The anti-counterfeiting label of the present application has multiple dynamic responsiveness, can realize multi-color circularly polarized luminescence, and can be patterned, with anti-counterfeiting characteristics of a higher security level.

[0068] The present application is further described below by way of examples.

[0069] Example 1

[0070] This embodiment provides a method for preparing a circularly polarized luminescent film with adjustable luminescent wavelength and handedness, comprising:

[0071] Step 1, prepare cellulose nanocrystal suspension: add 20 grams of pulp powder to 350 mL of H2SO4 with a concentration of 64wt%, stir continuously, react at 50°C for 2h, and then quench the reaction with 10 times deionized water. After naturally standing overnight, collect the lower layer of the higher concentration suspension, centrifuge at 6000rpm for 5 minutes, wash the high concentration suspension obtained by centrifugation with deionized water and centrifuge again; then transfer it to a cellulose dialysis bag (molecular weight cutoff: 12000-14000) and dialyze for one week. After the dialysis is completed, centrifuge the collected suspension at 11000rpm for 20 minutes to remove unreacted pulp powder and large particles; finally, use a rotary evaporator to concentrate the suspension at 40°C to obtain a cellulose nanocrystal suspension with a concentration of 2wt%. The pH of the cellulose nanocrystal suspension is adjusted to 6.0, and then 4g of the cellulose nanocrystal suspension is ultrasonicated for 128s for standby use.

[0072] Preparation of aggregation-induced emission molecular solution: dissolve 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethylene in N-methylpyrrolidone to prepare a solution with a concentration of 10 mg / mL.

[0073] Step 2, taking 20 μL of 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethylene N-methylpyrrolidone solution, adding it to 4 g of cellulose nanocrystal suspension, stirring well, to obtain a precursor solution;

[0074] Step 3, adding 0.02 g of polyethylene glycol to the precursor solution, stirring thoroughly, transferring to a polystyrene culture dish with a diameter of 3.5 cm, and evaporating at room temperature to induce self-assembly to obtain a circularly polarized luminescent film with adjustable emission wavelength and handedness.

[0075] The circularly polarized luminescent film prepared in Example 1 has a circularly polarized luminescent spectrum as shown in Figure 1 As shown. Figure 1 It can be seen that for the film prepared at a pH of 6, the circularly polarized light emitted from both sides of the film has opposite rotation directions under a humidity of 30%.

[0076] Example 2

[0077] This embodiment provides a method for preparing a circularly polarized luminescent film with adjustable luminescent wavelength and handedness.

[0078] The difference between Example 2 and Example 1 is that in step 1, the pH of the cellulose nanocrystal suspension is adjusted to 2.5, and the ultrasonic time is changed to 8s; in step 3, polyethylene glycol is replaced by polyethylene glycol dicarboxylic acid; the rest is the same as Example 1.

[0079] The circularly polarized luminescent film prepared in Example 2, under ultraviolet light, when the relative humidity is less than 40%, is excited to emit green fluorescence, which is left-handed circularly polarized light; when transferred to 100% relative humidity and placed for 60 minutes, the film emits yellow fluorescence, which is right-handed circularly polarized light.

[0080] Example 3

[0081] This embodiment provides a method for preparing a circularly polarized luminescent film with adjustable luminescent wavelength and handedness. The difference between Example 3 and Example 1 is that in step 1, the pH of the cellulose nanocrystal suspension is adjusted to 2.5, the ultrasonic time is changed to 8s; the concentration of the N-methylpyrrolidone solution of 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethylene is 1 mg / mL; in step 3, polyethylene glycol is replaced by polyethylene glycol dicarboxylic acid; the rest is the same as Example 1.

[0082] The circularly polarized luminescent film prepared in Example 3 has a circularly polarized luminescent spectrum as shown in Figure 2 As shown. Figure 2 It can be seen that the film prepared at pH 2.5 initially emits left-handed circularly polarized light when the relative humidity is less than 40%, and after being transferred to 100% relative humidity and placed for a certain period of time, it emits right-handed circularly polarized light.

[0083] Example 4

[0084] This embodiment provides a method for preparing a circularly polarized luminescent film with adjustable luminescent wavelength and handedness.

[0085] The difference between Example 4 and Example 1 is that in step 1, the pH of the cellulose nanocrystal suspension is adjusted to 2.5; in step 3, polyethylene glycol is replaced by polyethylene glycol dicarboxylic acid; the rest is the same as Example 1.

[0086] The circularly polarized luminescent film prepared in Example 4 emits green fluorescence under ultraviolet light and right-handed circularly polarized light when the relative humidity is less than 40%; when placed at 100% relative humidity for a certain period of time, it emits yellow fluorescence and right-handed circularly polarized light.

[0087] Comparative Example 1

[0088] This embodiment provides a method for preparing a circularly polarized light-emitting film, comprising:

[0089] Preparation of cellulose nanocrystal suspension: Add 20 g of pulp powder to 350 mL of 64 wt% H2SO4, stir continuously, react at 50 ° C for 2 h, and then quench the reaction with 10 times deionized water. After leaving it naturally overnight, collect the lower layer of the suspension with higher concentration, centrifuge it at 6000 rpm for 5 minutes, wash the high concentration suspension obtained by centrifugation with deionized water and centrifuge it again; then transfer it to a cellulose dialysis bag (molecular weight cutoff: 12000-14000) and dialyze it for one week. After the dialysis, centrifuge the collected suspension at 11000 rpm for 20 minutes to remove the unreacted pulp powder and large particles; finally, use a rotary evaporator to concentrate the suspension at 40 ° C to obtain a cellulose nanocrystal suspension with a concentration of 2 wt%. The pH of the cellulose nanocrystal suspension is adjusted to 2.5, and then 4 g of the cellulose nanocrystal suspension is ultrasonicated for 128 s for standby use.

[0090] Preparation of aggregation-induced emission molecular solution: dissolve 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethylene in N-methylpyrrolidone to prepare a solution with a concentration of 10 mg / mL.

[0091] Take 20 μL of the aggregation-induced emission molecule solution, add it to 4 g of the cellulose nanocrystal suspension, and stir thoroughly to obtain a precursor solution;

[0092] The precursor solution was transferred to a polystyrene petri dish with a diameter of 3.5 cm and evaporated at room temperature to induce self-assembly to obtain a circularly polarized luminescent film.

[0093] The circularly polarized luminescent film prepared in Comparative Example 1 has a circularly polarized luminescent spectrum as shown in Figure 3 As shown. Figure 3 It can be seen that under the condition of 30% relative humidity, the circularly polarized luminescent film emits right-handed circularly polarized light; under 100% relative humidity, the circularly polarized luminescence changes from green to yellow, and the right-handed circularly polarized light becomes weaker.

[0094] Comparative Example 2

[0095] The difference between Comparative Example 2 and Comparative Example 1 is that the pH of the cellulose nanocrystal suspension was adjusted to 2, and the rest was the same as in Comparative Example 1.

[0096] For the circularly polarized luminescent film prepared in Comparative Example 2, its circularly polarized luminescence spectrum is as Figure 4 shown. From Figure 4 it can be seen that under the condition of 30% relative humidity, the circularly polarized luminescent film emits left-handed circularly polarized light. At 100% relative humidity, the luminescence of the circularly polarized luminescent film remains unchanged.

[0097] Example 7

[0098] This example provides a preparation method and an application method of an anti-counterfeiting label, including:

[0099] S1. Cut the circularly polarized luminescent film with adjustable emission wavelength and helicity prepared in Example 1 into a 2.5 cm × 2.5 cm square label;

[0100] S2: Stick the polyester film with the artistic pattern "Fu" on the surface of the square label described in S1, and spray 1 mol / L sodium hydroxide solution;

[0101] S3: Air-dry the patterned film naturally to obtain the anti-counterfeiting label.

[0102] For the anti-counterfeiting label prepared in Example 7, the schematic diagram of its application in anti-counterfeiting is as Figure 5 shown. Among them, Figure 5 (a) is a physical picture of the anti-counterfeiting label in natural light in environments with different humidities; Figure 5 (b) is a physical picture of the anti-counterfeiting label in ultraviolet light in environments with different humidities. As Figure 5 (a) shows that in natural light, when the relative humidity is less than 40%, the "Fu" cannot be observed on the anti-counterfeiting label; when the anti-counterfeiting label is placed under 100% relative humidity conditions, as the placement time prolongs, the "Fu" pattern gradually appears; further transfer the anti-counterfeiting label from 100% relative humidity conditions to conditions with a relative humidity less than 40%, and the "Fu" gradually disappears. As Figure 5 (b) shows that in ultraviolet light, when the relative humidity is less than 40%, the "Fu" emitting green fluorescence can be seen; when the anti-counterfeiting label is placed under 100% relative humidity conditions, as the placement time prolongs, the fluorescence color of the "Fu" pattern changes from green to yellow; further transfer the anti-counterfeiting label from 100% relative humidity conditions to a relative humidity less than 40%, and the fluorescence color of the "Fu" pattern returns from yellow to green.

[0103] Although the present application has been described in detail in general terms and in specific embodiments in this specification, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application are within the scope of protection claimed in the present application.

Claims

1. A method for preparing a circularly polarized luminescent film with adjustable luminescent wavelength and handedness, characterized in that: include: preparing cellulose nanocrystal suspension and aggregation-induced emission molecule solution respectively; The aggregation-induced emission molecule solution is added dropwise to the cellulose nanocrystal suspension after ultrasonic treatment and pH adjustment to obtain a precursor solution; The plasticizer is added into the precursor solution, mixed evenly, and induced to self-assemble in a hydrophobic container at room temperature to obtain a circularly polarized luminescent film with adjustable luminescent wavelength and rotational direction.

2. The preparation method according to claim 1, characterized in that: The aggregation-induced emission molecule solution is prepared by dissolving the aggregation-induced emission molecule in an organic solvent; The aggregation-induced emission molecule includes any one of tetraphenylethylene, tetraaldehyde tetraphenylethylene, tetra(4-pyridylphenyl)ethylene, tetra(4-carboxyphenyl)ethylene or 1-(4-carboxyphenyl)-1,2,2-triphenylethylene; The organic solvent is N-methylpyrrolidone.

3. The preparation method according to claim 1, characterized in that: The plasticizer includes polyethylene glycol having different terminal groups or molecular weights.

4. The preparation method according to claim 3, characterized in that: The plasticizer is polyethylene glycol dicarboxylic acid or polyethylene glycol with a molecular weight of 200 to 40,000.

5. The preparation method according to claim 1, characterized in that: The ultrasonic treatment time of the cellulose nanocrystal suspension is 2 to 256 seconds; the pH of the cellulose nanocrystal suspension is 1 to 12, and the concentration thereof is 1 to 8 wt%; The concentration of the aggregation-induced emission molecule solution is 1-15 mg / mL.

6. The preparation method according to claim 2, characterized in that: The mass ratio of the cellulose nanocrystals, the aggregation-induced emission molecules and the plasticizer is (20-800):(0.01-0.75):(5-100).

7. A circularly polarized luminescent film with adjustable luminescent wavelength and handedness prepared by the preparation method according to any one of claims 1 to 6.

8. Application of the circularly polarized luminescent film with adjustable luminescent wavelength and rotation direction as described in claim 7 in anti-counterfeiting.

9. An anti-counterfeiting label, characterized in that: The preparation method thereof comprises: S1, cutting the circularly polarized light-emitting film according to claim 7 into a suitable shape; S2, using an acid solution or an alkaline solution as ink to write anti-counterfeiting information on the surface of the circularly polarized luminescent film; S3, drying the circularly polarized luminescent film with anti-counterfeiting information to obtain an anti-counterfeiting label; The anti-counterfeiting label has high humidity and luminous wavelength response characteristics.

10. The anti-counterfeiting label according to claim 9, characterized in that: The high humidity refers to a relative humidity of 80-100%.

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