Multimode display layer and display application made with up-conversion liquid crystal microcapsules

Abstract

The application discloses a multi-mode display layer made of up-conversion liquid crystal microcapsules and display application, the display layer is coated by optical ink containing up-conversion liquid crystal microcapsules, the up-conversion liquid crystal microcapsules include core material, and the capsule wall covering the core material, the core material is cholesteric liquid crystal doped with photosensitizer and luminous agent, and the structural color of the cholesteric liquid crystal can be adjusted, and the capsule wall is synthetic polymer material or natural polymer material; the display layer has three display modes, namely, the reflection light mode under the bright field, the structural color of the cholesteric liquid crystal is presented; the fluorescent mode under UV, the fluorescent color of the luminous agent is presented; and the up-conversion luminescence mode under laser, the up-conversion luminescence color of the photosensitizer and the luminous agent being excited is presented. The multi-mode display layer made of up-conversion liquid crystal microcapsules can be applied in the field of anti-fake display and information encryption.

Description

Technical Field

[0001] This invention relates to the fields of fine chemicals and materials science, and in particular to a multi-mode display layer made using upconversion liquid crystal microcapsules and its display applications. Background Technology

[0002] Most luminescent materials absorb high-energy light and emit low-energy light, exhibiting a traditional downconversion luminescence process, a Stokes process. Photon upconversion, however, is an anti-Stokes shift process, where long-wavelength, low-energy light is absorbed and short-wavelength, high-energy light is emitted. Triplet-triplet annihilation upconversion (TTA-UC), as a novel photon upconversion technology, has received considerable attention and extensive research.

[0003] Triplet-triplet energy transfer processes require an anaerobic environment; otherwise, in the presence of oxygen, the energy of the triplet excited state will be captured by oxygen, leading to the failure of the energy transfer process. Traditional TTA upconversion processes mostly occur in organic solvents, typically using nitrogen / argon gas to remove oxygen from the system to ensure efficient TTA-UC processes. However, an anaerobic environment is itself a limitation; therefore, various methods have emerged in domestic and international literature to address the problem of oxygen quenching in TTA-UC. In summary, to ensure the effective occurrence of upconversion processes exposed to air, two approaches can be used: 1. Active deoxygenation through chemical reactions; 2. Passive physical resistance to oxygen.

[0004] The first method involves adding oxygen-scavenging molecules to the TTA-UC system, utilizing an antioxidant solution for active oxygen removal—that is, capturing reactive oxygen species that have acquired triplet energy—thereby reducing the oxygen content within the upconversion system. While this method temporarily alleviates the oxygen problem, it has significant drawbacks because it relies on a chemical reaction between the antioxidant and the oxygen in the system to ensure the TTA process. Once the antioxidant is depleted, external oxygen will continue to permeate, preventing the TTET process from occurring.

[0005] The second method is to passively resist oxygen intrusion, that is, to use oxygen barrier materials as a protective shell to prevent oxygen penetration. These materials can be inherently oxygen-impermeable host media or external encapsulation structures, such as silica, gels, and metal-organic frameworks. Although this type of method achieves better upconversion characteristics, it will encounter problems such as lower upconversion efficiency in solid-state systems. The main reasons are uneven distribution of dye molecules, slow molecular diffusion in the system, and oxygen quenching of triplet excited states.

[0006] Although TTA-UC has been widely applied through the development of various carriers, such as in environmental and energy applications, biomedicine, and sensing, research on display applications, especially in anti-counterfeiting displays and information encryption, is lacking. Therefore, from the perspective of upconversion carrier material preparation, how to ensure effective upconversion and high upconversion efficiency while realizing display applications in anti-counterfeiting and information encryption is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-mode display layer and display application made of upconversion liquid crystal microcapsules, which can be used in the fields of anti-counterfeiting display and information encryption.

[0008] The technical solution adopted by the present invention to solve its technical problem is: a multi-mode display layer made of upconversion liquid crystal microcapsules, the display layer being coated with optical ink containing upconversion liquid crystal microcapsules, the upconversion liquid crystal microcapsules comprising a core material and a capsule wall encapsulating the core material, the core material being a cholesteric liquid crystal doped with photosensitizers and luminescent agents, and the structural color of the cholesteric liquid crystal being adjustable, the capsule wall being a synthetic polymer material or a natural polymer material;

[0009] The display layer has three display modes: a bright field reflected light mode, which presents the structural color of the cholesteric liquid crystal; a UV fluorescence mode, which presents the fluorescence color of the luminescent agent; and a laser upconversion emission mode, which presents the upconversion emission color of the photosensitizer and the luminescent agent when excited.

[0010] As a further improvement of the present invention, the photosensitizer is a porphyrin, boron-fluorine compound, or phthalocyanine metal complex of ruthenium, iridium, palladium, or platinum; the luminescent agent is a biphenyl, benzo[a]phenyl compound or its derivative, or a boron-fluorine compound.

[0011] As a further improvement of the present invention, the cholesteric liquid crystal is prepared by mixing a nematic liquid crystal and a chiral agent in a certain proportion, or the cholesteric liquid crystal is prepared by chiral liquid crystal.

[0012] As a further improvement of the present invention, the chiral liquid crystal is at least two of the following: cholesterol acetate, cholesterol propionate, cholesterol butyrate, cholesterol nonanoate, cholesterol oleate, cholesterol linoleate, cholesterol benzoate, cholesterol cinnamate, cholesterol ethyl carbonate, cholesterol oleyl carbonate, cholesterol isostearyl carbonate, cholesterol butenoate, cholesterol ethyl carbonate, and cholesterol chloride.

[0013] The nematic liquid crystal is one or more of ethylbiphenyl nitrile, 4'-n-butyl-4-cyanobiphenyl, 4-propyl-4'-cyanobiphenyl, 4-cyano-4'-pentylbiphenyl, 4-heptyl-4'-cyanobiphenyl, and trans-4'-(4-pentylcyclohexyl)-[1,1'-biphenyl]-4-nitrile;

[0014] The chiral agent is one or more of S811, S1011, S5011 and their enantiomers.

[0015] As a further improvement of the present invention, the upconversion liquid crystal microcapsules are prepared by the following steps:

[0016] S2, take a certain amount of photosensitizer, add organic solvent to prepare a mother liquor, mix the mother liquor, luminescent agent, and synthetic polymer material or natural polymer material weighed in a certain proportion with cholesteric liquid crystal, then add organic solvent to completely dissolve it to obtain an organic mixed solution;

[0017] S3, add the organic mixed solution prepared by S2 dropwise to the emulsifier and perform emulsification treatment, so that the cholesteric liquid crystal doped with photosensitizer and luminescent agent is coated with synthetic polymer material or natural polymer material by physical or chemical methods;

[0018] S4. The product obtained in S3 is washed with water and concentrated by sedimentation to obtain upconversion liquid crystal microcapsules containing a two-component dye.

[0019] As a further improvement of the present invention, in S2, the mass ratio of the synthetic polymer material or the natural polymer material to the cholesteric liquid crystal is 1:(10-20).

[0020] As a further improvement of the present invention, the synthetic polymer material is one or more selected from polymethyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol formaldehyde, polyacrylic acid, urea-formaldehyde resin and melamine resin;

[0021] The natural polymer material is one or more of gelatin, gum arabic, and xanthan gum.

[0022] The present invention also provides a display application of a multi-mode display layer made of upconversion liquid crystal microcapsules, including: an optical pattern for information encryption or anti-counterfeiting display, the optical pattern being composed of the above-mentioned display layer and display substrate superimposed, wherein the display layer and the display substrate present the same reflected light under bright field, and thus the display layer is hidden in the display substrate; under UV or laser, the display substrate does not emit light, and thus the fluorescent color or upconversion luminescent color of the display layer is revealed.

[0023] As a further improvement of the present invention, the display substrate is coated with optical ink containing dye-free liquid crystal microcapsules, wherein the core material of the dye-free liquid crystal microcapsules is cholesteric liquid crystal with adjustable structural color.

[0024] As a further improvement of the present invention, the display substrate is coated with optical ink containing single-component dye liquid crystal microcapsules, wherein the core material of the single-component dye liquid crystal microcapsules is a cholesteric liquid crystal doped with a luminescent agent and whose structural color is adjustable.

[0025] The beneficial effects of this invention are: 1) This invention provides a multi-mode display layer and display application made using upconversion liquid crystal microcapsules. Cholesteric liquid crystal replaces conventional organic solvents, using cholesteric liquid crystal doped with a two-component dye photosensitizer and luminescent agent as the core material, polymethyl methacrylate as the capsule wall, and polyvinyl alcohol as the surfactant. The prepared upconversion liquid crystal microcapsules use cholesteric liquid crystal as the carrier of TTA-UC, which not only allows for the control of the size and particle size distribution of the upconversion liquid crystal microcapsules to obtain better performance, but also protects the core material from the influence of external factors, preserving the core material in the form of solid microparticles, ensuring effective upconversion and high upconversion efficiency; 2) Upconversion liquid crystal microcapsules can be used to prepare liquid crystals of different structural colors into dispersed optical inks. Display layers are created on surfaces such as glass, paper, and fabric through printing, spraying, etc., and the display layers have three modes: reflected light mode under bright field, fluorescent mode under UV, and upconversion luminescence mode under laser. In the display applications of anti-counterfeiting display and information encryption, the dual-mode display of TTA upconversion is introduced to display different information on the same pattern, thereby enhancing the level of anti-counterfeiting and information encryption; 3) The display layer and the display base layer are combined and superimposed to form an optical pattern. This method can design patterns without destroying the luminescence pattern, and hide the real information under UV and laser under the color information of liquid crystal reflected light, thereby realizing the multi-mode of hiding the real information under the surface pattern. This optical pattern has good application prospects in anti-counterfeiting display and information encryption. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the steps of the upconversion liquid crystal microcapsule preparation method in this invention;

[0027] Figure 2 This is a flowchart illustrating the specific steps of step S3 in the upconversion liquid crystal microcapsule preparation method of this invention;

[0028] Figure 3 This is a schematic diagram of the structure of the upconversion liquid crystal microcapsule in this invention;

[0029] Figure 4The images shown are polarized light microscope images of upconversion liquid crystal microcapsules prepared with different PMMA contents according to the present invention, and single-core ratio curves at different ratios.

[0030] Figure 5 The images shown are polarized light microscope images of upconversion liquid crystal microcapsules prepared by different emulsification stirring speeds according to the present invention, and curves showing the relationship between different emulsification stirring speeds and the particle size distribution of upconversion liquid crystal microcapsules.

[0031] Figure 6 The image shows a scanning electron microscope (SEM) image of the upconversion liquid crystal microcapsules prepared according to the present invention.

[0032] Figure 7 These are polarized light microscope images (a, b, c) of upconversion liquid crystal microcapsules made of cholesteric liquid crystals with different structural colors dispersed in an aqueous solution, and polarized light microscope images (a', b', c') of upconversion liquid crystal microcapsules made of cholesteric liquid crystals with different structural colors after being prepared into a film.

[0033] Figure 8 The images (a, a') of the upconversion liquid crystal microcapsules of the present invention under 532nm laser excitation and excitation and the upconversion emission spectrum (b) within the circled area of ​​the inset are shown.

[0034] Figure 9 This invention utilizes upconversion liquid crystal microcapsules to create a multi-mode display layer with three display modes;

[0035] Figure 10 This invention provides an embodiment of the display substrate and the display layer under bright field, UV and laser conditions (a), as well as another embodiment of the display substrate and the display of an optical pattern formed by combining and superimposing display layers under bright field, UV and laser conditions (b).

[0036] Referring to the accompanying drawings, the following explanations are provided:

[0037] 1. Core material; 2. Capsule wall. Detailed Implementation

[0038] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0039] This invention provides a multi-mode display layer made using upconversion liquid crystal microcapsules. The process of forming the display layer is as follows: the obtained upconversion liquid crystal microcapsules are dispersed in water to make optical ink, and then the display layer is made on the surface of glass, or even paper, cloth, etc. by printing, spraying, etc.

[0040] See Figure 3The upconversion liquid crystal microcapsule includes a core material 1 and a capsule wall 2 that encapsulates the core material 1. The core material 1 is a cholesteric liquid crystal doped with photosensitizers and luminescent agents, and the structural color of the cholesteric liquid crystal is adjustable. The capsule wall 2 is a synthetic polymer material or a natural polymer material.

[0041] The synthetic polymer material is one or more selected from polymethyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol formaldehyde, polyacrylic acid, urea-formaldehyde resin, and melamine resin; the natural polymer material is one or more selected from gelatin, gum arabic, and xanthan gum. Depending on the preparation process, the material used for the capsule wall 2 varies. For example, in this embodiment, the upconversion liquid crystal microcapsules are prepared using a solvent evaporation method, and the synthetic polymer material used is polymethyl methacrylate as its capsule wall 2. Alternatively, the upconversion liquid crystal microcapsules can also be prepared using a complex coagulation method, correspondingly using the natural polymer material gelatin as its capsule wall 2. Furthermore, the upconversion liquid crystal microcapsules can also be prepared using an in-situ polymerization method, correspondingly using natural polymer resins such as urea-formaldehyde resin or melamine resin as its capsule wall 2.

[0042] The display layer has three display modes: a bright field reflected light mode, which presents the structural color of the cholesteric liquid crystal; a UV fluorescence mode, which presents the fluorescence color of the luminescent agent; and a laser upconversion emission mode, which presents the upconversion emission color of the photosensitizer and luminescent agent when excited.

[0043] See Figure 1 and Figure 2 In this embodiment, the upconversion liquid crystal microcapsules are prepared using the following steps S1 to S4.

[0044] S1. Preparation of cholesteric liquid crystal, which is prepared by mixing nematic liquid crystal and chiral agent in a certain proportion, or by being prepared by chiral liquid crystal. In this embodiment, the former is specifically selected. The nematic liquid crystal and chiral agent are mixed in a certain proportion, and an organic solvent is added to completely dissolve them. Then, the mixture is heated to remove the organic solvent, thereby obtaining the cholesteric liquid crystal CLC with the desired structural color.

[0045] In S1 above, the organic solvent used is dichloromethane (the same below); the chiral liquid crystal is at least two of cholesterol acetate, cholesterol propionate, cholesterol butyrate, cholesterol nonanoate, cholesterol oleate, cholesterol linoleate, cholesterol benzoate, cholesterol cinnamate, cholesterol ethyl carbonate, cholesterol oleyl carbonate, cholesterol isostearyl carbonate, cholesterol butenoate, cholesterol carbonate, and cholesterol chloride; the nematic liquid crystal is one or more of ethylbiphenyl nitrile, 4'-n-butyl-4-cyanobiphenyl, 4-propyl-4'-cyanobiphenyl, 4-cyano-4'-pentylbiphenyl, 4-heptyl-4'-cyanobiphenyl, trans-4'-(4-pentylcyclohexyl)-[1,1'-biphenyl]-4-nitrile, and mixtures thereof E7; the chiral agent is one or more of S811, S1011, S5011 and their enantiomers.

[0046] The different ratios of nematic liquid crystal 5CB and chiral agent CD1 used in this invention directly affect the structural color of the final cholesteric liquid crystal CLC. Therefore, by changing the mass ratio of nematic liquid crystal 5CB to chiral agent CD1, cholesteric liquid crystals with different structural colors can be obtained. For example, a mass ratio of nematic liquid crystal 5CB to chiral agent CD1 of 44:1 is used. Specifically, 0.9777g of nematic liquid crystal 5CB and 0.0223g of chiral agent CD1 are taken, and an appropriate amount of dichloromethane is added to completely dissolve them. The solution is then placed on a heating stage at 60°C to remove the dichloromethane, resulting in a red cholesteric liquid crystal R-CLC.

[0047] Alternatively, the mass ratio of nematic liquid crystal 5CB to chiral agent CD1 can be set to 37:1. Specifically, 0.9736g of nematic liquid crystal 5CB and 0.0264g of chiral agent CD1 are taken, and an appropriate amount of dichloromethane is added to completely dissolve them. The solution is then placed on a heating stage at 60°C to remove the dichloromethane, resulting in the green cholesteric liquid crystal G-CLC.

[0048] Alternatively, the mass ratio of nematic liquid crystal 5CB to chiral agent CD1 can be set to 32:1. Specifically, 0.9696g of nematic liquid crystal 5CB and 0.0304g of chiral agent CD1 are taken, and an appropriate amount of dichloromethane is added to completely dissolve them. The solution is then placed on a heating stage at 60°C to remove the dichloromethane, resulting in the blue cholesteric liquid crystal B-CLC.

[0049] S2. Take a certain amount of photosensitizer and add an organic solvent to prepare a mother liquor. Place the mother liquor, luminescent agent, and polymethyl methacrylate (PMMA) weighed in a certain proportion and the cholesteric liquid crystal R / G / B-CLC prepared in S1 into a sample bottle. Then add dichloromethane and acetone to the sample bottle in sequence until they are completely dissolved to obtain an organic mixed solution.

[0050] The photosensitizer is a boron-fluorine compound, a porphyrin or phthalocyanine metal complex of ruthenium, iridium, palladium, or platinum; in this embodiment, octaethylporphyrin platinum is preferred. The luminescent agent is a biphenyl, a benzo[a]phenyl compound or its derivatives, or a boron-fluorine compound; in this embodiment, 9,10-diphenylanthracene is preferred. The mass ratio of polymethyl methacrylate (PMMA) to cholesteric liquid crystal CLC is 1:(10-20).

[0051] In S2 of this embodiment, specifically, the mother liquor is prepared by adding 0.001g of octaethylporphyrin platinum to 1ml of organic solvent (DMC), and the organic mixed solution is prepared by mixing 100μl of mother liquor, 0.005g of 9,10-diphenylanthracene, 0.1g of polymethyl methacrylate (PMMA) and 1g of cholesteric liquid crystal (CLC), and then adding 9ml of organic solvent (DMC) and 1ml of acetone in sequence.

[0052] S3 involves adding the organic mixed solution prepared by S2 dropwise to the emulsifier and performing emulsification treatment. This allows the cholesteric liquid crystal doped with photosensitizers and luminescent agents to be coated with synthetic or natural polymer materials using physical or chemical methods. The physical method utilizes solvent evaporation to remove the solvent, while the chemical method involves adjusting the pH to induce the polymerization reaction.

[0053] In this embodiment, the emulsifier used is a polyvinyl alcohol aqueous solution, and the specific steps of S3 above are as follows:

[0054] S31. Pour 40 ml of 2 wt% polyvinyl alcohol aqueous solution into a three-necked flask and control the water bath temperature at 20°C.

[0055] S32, at a stirring speed of 1500-2000 rpm, the organic mixed solution in the S2 sample vial is slowly and uniformly added dropwise to the three-necked flask using a syringe, and emulsification is maintained for 20 minutes; in this embodiment, the stirring speed is specifically 1500 rpm.

[0056] S33, adjust the stirring speed to 300 rpm, add 40 ml of 2 wt% polyvinyl alcohol aqueous solution again, and steadily and slowly increase the water bath temperature from 20°C to 35°C, with a heating time of 20-40 min; in this embodiment, the heating time is specifically 30 min.

[0057] S34, maintain a stirring speed of 300 rpm and a water bath temperature of 35°C, and continue stirring in an open environment for 8 to 12 hours. In this embodiment, the stirring time is specifically 10 hours.

[0058] In the solvent evaporation method described above, polyvinyl alcohol aqueous solution is used as the surfactant for upconversion liquid crystal microcapsules. The polyvinyl alcohol aqueous solution has a good barrier effect against oxygen, which is beneficial to the TTA-UC process.

[0059] S4. The product obtained in S3 is washed with water and concentrated by sedimentation to obtain upconversion liquid crystal microcapsules containing a two-component dye.

[0060] The following provides further explanation of the performance characterization and optical properties of the upconversion liquid crystal microcapsules prepared in this invention.

[0061] Figure 4 The images shown are polarized light microscope images of upconversion liquid crystal microcapsules prepared with different polymethyl methacrylate (PMMA) contents, and mononuclear ratio curves at different ratios. The PMMA / CLC ratios in the images are (a) 0.05 g / 1g, (b) 0.1 g / 1g, (c) 0.3 g / 1g, (d) 0.4 g / 1g, and (e) 0.5 g / 1g. By changing the PMMA / CLC ratio, maintaining an emulsification stirring speed of 1500 rpm, and keeping other preparation conditions constant, polarized light microscope images of the upconversion liquid crystal microcapsules at different ratios were obtained (e.g., ...). Figure 4 (As shown). As the PMMA / CLC ratio increases, the upconversion liquid crystal microcapsules gradually change from a mononuclear structure to a multinuclear structure. According to the phase volume effect, when the PMMA / CLC ratio decreases to 0.1 g / 1 g, the compatibility between the CLC-enriched phase and the PMMA-enriched phase decreases, the number of core material droplets in the upconversion liquid crystal microcapsules decreases, forming mononuclear upconversion liquid crystal microcapsules, as shown. Figure 4 As shown in (a) and (b), when the PMMA / CLC ratio is greater than 0.3 g / 1 g, the compatibility between the CLC-enriched phase and the PMMA-enriched phase is good during phase separation. The CLC-enriched phase is dispersed into a large number of small droplets, and the resulting upconversion liquid crystal microcapsules have a multinucleated structure, such as... Figure 4 As shown in (c) and (d), the structural color of the upconversion liquid crystal microcapsules was observed, and the proportions of single-core and multi-core microcapsules were statistically analyzed. The optimal ratio of PMMA / CLC was 0.05 g / 1 g and 0.1 g / 1 g.

[0062] Figure 5 These are polarized light microscope images of upconversion liquid crystal microcapsules prepared using different emulsification stirring speeds according to the present invention, as well as curves showing the relationship between different emulsification stirring speeds and the particle size distribution of the upconversion liquid crystal microcapsules. The upconversion liquid crystal microcapsules prepared by the solvent evaporation method can have particle sizes ranging from a few micrometers to several hundred micrometers. With a PMMA / CLC ratio of 0.1 g / 1 g and other conditions kept constant, varying the stirring speed during emulsification yielded polarized light microscope images of the microcapsules (e.g., [images of microcapsules]). Figure 5 (As shown). As the emulsification stirring speed decreases, the particle size of the upconversion liquid crystal microcapsules gradually increases. At emulsification stirring speeds of 2000 rpm / 1500 rpm, the prepared upconversion liquid crystal microcapsules have a relatively narrow particle size distribution and the best structural color effect.

[0063] After maintaining a PMMA / CLC ratio of 0.1 g / 1 g and an emulsification stirring speed of 1500 rpm, the scanning electron microscope images of the prepared upconversion liquid crystal microcapsules are as follows: Figure 5 As shown, its surface is smooth and the particle size is 6.79 μm.

[0064] Figure 7 These are polarized light microscope images (a, b, c) showing the dispersion of upconversion liquid crystal microcapsules made of cholesteric phase liquid crystals with different structural colors in aqueous solution, and polarized light microscope images (a', b', c') of the upconversion liquid crystal microcapsules made of cholesteric phase liquid crystals with different structural colors after film formation. Specifically, Figure 7 (a) is a polarized light microscope image of upconversion liquid crystal microcapsules made of red cholesteric liquid crystal R-CLC dispersed in aqueous solution; (b) is a polarized light microscope image of upconversion liquid crystal microcapsules made of green cholesteric liquid crystal G-CLC dispersed in aqueous solution; and (c) is a polarized light microscope image of upconversion liquid crystal microcapsules made of blue cholesteric liquid crystal B-CLC dispersed in aqueous solution. The structural colors of all prepared upconversion liquid crystal microcapsules were observed under a polarized light microscope. The refractive index of the capsule wall 2 (i.e., polymethyl methacrylate) of the upconversion liquid crystal microcapsules is close to that of the polyvinyl alcohol aqueous solution. When the corresponding upconversion liquid crystal microcapsules were dispersed in a small amount of polyvinyl alcohol aqueous solution, dried, and then formed into a film, the structural color observed under a polarized light microscope was not significantly different from that of the upconversion liquid crystal microcapsules dispersed in the polyvinyl alcohol aqueous solution.

[0065] Figure 8 Polarized light microscopy images were taken of R-CLC upconversion liquid crystal microcapsules without 532nm laser (a) and R-CLC upconversion liquid crystal microcapsules in upconversion emission mode under 532nm laser excitation (a'). Under 532nm laser irradiation, the upconversion liquid crystal microcapsules emitted upconverted blue light, and the corresponding upconversion emission spectrum is shown below. Figure 8 As shown in (b), the peak is at 438 nm.

[0066] like Figure 9As shown, the display layer and color obtained by the spraying method are relatively uniform. For example, the display layer prepared by selecting B-CLC upconversion liquid crystal microcapsules doped with two-component dyes exhibits a reflective light mode under bright field conditions, displaying green patterns of "hearts," "apples," and "ducks." The structural color of the reflective light mode is controlled by the pitch length of the upper helical structure in the cholesteric liquid crystal CLC. Under 365nm UV irradiation, it exhibits a fluorescent mode, displaying blue fluorescence. The fluorescence mode is determined by the molecular structure of the luminescent agent (i.e., 9,10-diphenylanthracene). Under 532nm laser excitation, it exhibits an upconversion luminescence mode, displaying upconversion blue light. The upconversion luminescence mode is obtained by the two-component dye photosensitizer (i.e., octaethylporphyrin platinum) and the luminescent agent (i.e., 9,10-diphenylanthracene) under 532nm laser excitation.

[0067] As can be seen, this invention uses cholesteric liquid crystal as the carrier for TTA-UC, which not only allows for the control of the size and particle size distribution of the upconversion liquid crystal microcapsules to achieve better performance, but also protects the core material 1 from the influence of external factors by preserving it in the form of solid microparticles, ensuring effective upconversion and high upconversion efficiency. Furthermore, in addition to the fluorescence of the luminescent agent (9,10-diphenylanthracene) and its ability to ensure the TTA-UC process, the structural color of the CLC is introduced, which can control the color and eliminate the influence of the dye molecules' own color. Moreover, the liquid crystal used has the property of undergoing a phase transition with temperature changes. Upconversion liquid crystal microcapsules can be used to prepare liquid crystals with different structural colors into dispersed optical inks. These inks can then be used to create display layers on surfaces such as glass, paper, and fabric through printing, spraying, etc. They can exhibit rich reflected light under bright field (depending on the structural color of the liquid crystal), fluorescent color under UV irradiation (depending on the fluorescence emission of the luminescent agent), and upconversion luminescent color under laser excitation (depending on the excitation of the photosensitizer and the luminescent agent). In anti-counterfeiting and information encryption applications, the introduction of TTA upconversion dual-mode display allows the same pattern to display different information, enhancing the level of anti-counterfeiting and information encryption.

[0068] This invention also provides a display application of a multi-mode display layer made using upconversion liquid crystal microcapsules, including: an optical pattern applied to information encryption or anti-counterfeiting displays, the optical pattern being composed of the aforementioned display layer and display substrate superimposed together. Under bright field conditions, the display layer and display substrate exhibit the same reflected light, thus the display layer is hidden within the display substrate. Under UV or laser conditions, the display substrate does not emit light, thus the fluorescent color or upconversion luminescent color of the display layer is revealed.

[0069] The display substrate has two specific implementation methods. The first method involves coating the display substrate with optical ink containing dye-free liquid crystal microcapsules, where the core material of the dye-free liquid crystal microcapsules is a cholesteric liquid crystal with tunable structural color. The second method involves coating the display substrate with optical ink containing monocomponent dye liquid crystal microcapsules, where the core material of the monocomponent dye liquid crystal microcapsules is a cholesteric liquid crystal doped with a luminescent agent and with tunable structural color.

[0070] The difference between the preparation methods of the aforementioned dye-free liquid crystal microcapsules and upconversion liquid crystal microcapsules lies in step S2. Specifically, the S2 process for dye-free liquid crystal microcapsules is as follows: 1g of cholesteric liquid crystal R / G / B-CLC prepared in step S1 and 0.1g of polymethyl methacrylate (PMMA) are placed in a 20ml sample vial, followed by the addition of 9.0ml of dichloromethane and 1.0ml of acetone, and then sonicated until completely dissolved. The remaining steps are the same, ultimately yielding dye-free liquid crystal microcapsules. The obtained dye-free liquid crystal microcapsules are dispersed in water to form optical ink, which is then used to create a display substrate on surfaces such as glass, paper, and fabric through printing, spraying, or other methods. This display substrate has only one display mode: a bright-field reflected light mode, exhibiting the structural color of its cholesteric liquid crystal.

[0071] The difference between the preparation methods of single-component dye liquid crystal microcapsules and upconversion liquid crystal microcapsules lies in the different steps of S2. Specifically, the S2 process for single-component liquid crystal microcapsules is as follows: 1g of cholesteric liquid crystal R / G / B-CLC prepared in S1, 0.1g of polymethyl methacrylate (PMMA), and 0.005g of 9,10-diphenylanthracene are placed in a 20ml sample vial, and 9.0ml of dichloromethane and 1.0ml of acetone are added sequentially, followed by sonication to completely dissolve the microcapsules. The remaining steps are the same, ultimately yielding single-component dye liquid crystal microcapsules. The prepared single-component dye liquid crystal microcapsules are dispersed in water to form optical ink, which is then used to create a display substrate on surfaces such as glass, paper, and fabric through printing, spraying, etc. This display substrate has two display modes: a bright-field reflected light mode, displaying the structural color of the cholesteric liquid crystal; and a UV-field fluorescent mode, displaying the fluorescent color of the luminescent agent (9,10-diphenylanthracene).

[0072] Figure 10In diagram (a), the display layer and the display substrate of the second embodiment are on the same surface and do not overlap. Specifically, the display substrate, coated with optical ink made from single-component dye liquid crystal microcapsules, forms an "apple" pattern, while the display layer, coated with upconversion liquid crystal microcapsules made from two-component dyes, forms a "duck" pattern. Both the single-component dye liquid crystal microcapsules and the upconversion liquid crystal microcapsules are prepared using cholesteric liquid crystals with a red structural color. Therefore, the "apple" and "duck" appear red under bright field. Under 365nm UV light, the luminescent agent (9,10-diphenylanthracene) is excited, resulting in blue "apples" and "ducks." Under 532nm laser light, only the "duck" pattern of the two-component dye liquid crystal microcapsules is excited, resulting in a blue upconversion light "duck" pattern.

[0073] Liquid crystal microcapsules with the same structural color can reduce color differences between patterns, and this structural color can hide upconversion within the colored microcapsules. For example... Figure 10 As shown in (b), the display layer is superimposed with the display substrate of the first embodiment. Specifically, the display layer coated with optical ink prepared from B-CLC upconversion liquid crystal microcapsules has a "butterfly" pattern, and the display substrate coated with optical ink prepared from B-CLC dye-free liquid crystal microcapsules has an irregular shape. The above-mentioned display layer and display substrate are combined and sprayed into an optical pattern. Under bright field, only half of the "butterfly" is seen, and the real information of the display layer is hidden in the display substrate. Under 365nm UV, the fluorescence color of the luminescent agent (9,10-diphenylanthracene) can be observed, presenting the overall "butterfly" pattern effect. Similarly, under 532nm laser irradiation, the overall "butterfly" pattern effect is also presented. That is to say, the real information of the display layer is revealed under UV and laser.

[0074] Similarly, the display layer can be combined and superimposed with the display base layer of the second implementation method, so that the upconversion luminous color of the display layer is only displayed under laser irradiation.

[0075] Under this strategy, dye-free liquid crystal microcapsules exhibit structural colors such as red, green, and blue; liquid crystal microcapsules containing only a luminescent agent (9,10-diphenylanthracene) exhibit a blue fluorescent pattern under UV (365nm); similarly, liquid crystal microcapsules containing only a photosensitizer (octaethylporphyrin platinum) can exhibit a red pattern under UV (365nm); and liquid crystal microcapsules doped with two-component dyes exhibit upconversion blue light under laser (532nm) or blue fluorescence under UV (365nm). Through various combinations, more complex encryption patterns can be formed. This method allows for pattern design without destroying the luminescent pattern, and hides the true information under UV and laser conditions within the color information of the liquid crystal reflected light. This optical pattern has certain application prospects in anti-counterfeiting displays and information encryption.

[0076] Therefore, this invention uses cholesteric liquid crystal doped with a two-component dye photosensitizer and luminescent agent as the core material 1, polymethyl methacrylate as the capsule wall 2, and polyvinyl alcohol as the surfactant to prepare R / G / B three-color liquid crystal microcapsules by solvent evaporation method. The structural color of the liquid crystal can effectively hide the color of the dye molecules themselves, and the structural color can be controlled. The display layer coated with optical ink made from the liquid crystal microcapsules has three modes: bright field reflected light mode, UV fluorescence mode, and laser upconversion luminescence mode, which enhances the anti-counterfeiting level. This multi-mode approach, which hides the real information under the surface pattern, has good application prospects in the field of anti-counterfeiting.

[0077] Many specific details have been set forth in the foregoing description to provide a thorough understanding of the present invention. However, the above description is merely a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed above. Furthermore, any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, using the methods and techniques disclosed above, without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A multi-mode display layer made using upconversion liquid crystal microcapsules, characterized in that: The display layer is coated with optical ink containing upconversion liquid crystal microcapsules. The upconversion liquid crystal microcapsules include a core material (1) and a capsule wall (2) covering the core material (1). The core material (1) is a cholesteric liquid crystal doped with photosensitizers and luminescent agents, and the structural color of the cholesteric liquid crystal is adjustable. The capsule wall (2) is a synthetic polymer material or a natural polymer material. The display layer has three display modes: a bright field reflected light mode, which presents the structural color of the cholesteric liquid crystal; a UV fluorescence mode, which presents the fluorescence color of the luminescent agent; and a laser upconversion emission mode, which presents the upconversion emission color of the photosensitizer and the luminescent agent when excited. The upconversion liquid crystal microcapsules were prepared using the following steps: S1, Prepare the cholesteric liquid crystal, wherein the cholesteric liquid crystal is prepared by mixing nematic liquid crystal and chiral agent in a certain proportion, or the cholesteric liquid crystal is prepared by chiral liquid crystal; S2, take a certain amount of photosensitizer, add organic solvent to prepare a mother liquor, mix the mother liquor, luminescent agent, and synthetic polymer material or natural polymer material weighed in a certain proportion with cholesteric liquid crystal, then add organic solvent to completely dissolve it to obtain an organic mixed solution; S3, add the organic mixed solution prepared by S2 dropwise to the emulsifier and perform emulsification treatment, so that the cholesteric liquid crystal doped with photosensitizer and luminescent agent is coated with synthetic polymer material or natural polymer material by physical or chemical methods; S4. The product obtained in S3 is washed with water and concentrated by sedimentation to obtain upconversion liquid crystal microcapsules containing a two-component dye.

2. The multi-mode display layer made using upconversion liquid crystal microcapsules according to claim 1, characterized in that: The photosensitizer is a porphyrin, boron-fluorine compound, or phthalocyanine metal complex of ruthenium, iridium, palladium, or platinum; The luminescent agent is biphenyl, benzobenzene compounds or their derivatives, or boron-fluorine compounds.

3. The multi-mode display layer made using upconversion liquid crystal microcapsules according to claim 1, characterized in that: The chiral liquid crystal is at least two of the following: cholesterol acetate, cholesterol propionate, cholesterol butyrate, cholesterol nonanoate, cholesterol oleate, cholesterol linoleate, cholesterol benzoate, cholesterol cinnamate, cholesterol ethyl carbonate, cholesterol oleyl carbonate, cholesterol isostearyl carbonate, cholesterol butenoate, cholesterol ethyl carbonate, and cholesterol chloride. The nematic liquid crystal is one or more of ethylbiphenyl nitrile, 4'-n-butyl-4-cyanobiphenyl, 4-propyl-4'-cyanobiphenyl, 4-cyano-4'-pentylbiphenyl, 4-heptyl-4'-cyanobiphenyl, and trans-4'-(4-pentylcyclohexyl)-[1,1'-biphenyl]-4-nitrile; The chiral agent is one or more of S811, S1011, S5011 and their enantiomers.

4. The multi-mode display layer made using upconversion liquid crystal microcapsules according to claim 1, characterized in that: In S2, the mass ratio of the synthetic polymer material or the natural polymer material to the cholesteric liquid crystal is 1:(10~20).

5. The multi-mode display layer made using upconversion liquid crystal microcapsules according to claim 1, characterized in that: The synthetic polymer material is one or more of the following: polymethyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol formaldehyde, polyacrylic acid, urea-formaldehyde resin, and melamine resin. The natural polymer material is one or more of gelatin, gum arabic, and xanthan gum.

6. A display application using a multi-mode display layer made of upconversion liquid crystal microcapsules, characterized in that, include: An optical pattern for information encryption or anti-counterfeiting display, wherein the optical pattern is formed by superimposing the display layer and the display substrate as described in any one of claims 1 to 5, wherein the display layer and the display substrate present the same reflected light under bright field, and thus the display layer is hidden in the display substrate; under UV or laser, the display substrate does not emit light, and thus the fluorescent color or upconversion luminous color of the display layer is revealed.

7. The display application of the multi-mode display layer made of upconversion liquid crystal microcapsules according to claim 6, characterized in that: The display substrate is coated with optical ink containing dye-free liquid crystal microcapsules, and the core material of the dye-free liquid crystal microcapsules is cholesteric liquid crystal with adjustable structural color.

8. The display application of the multi-mode display layer made of upconversion liquid crystal microcapsules according to claim 6, characterized in that: The display substrate is coated with optical ink containing single-component dye liquid crystal microcapsules, the core material of which is a cholesteric liquid crystal doped with a luminescent agent and with adjustable structural color.

Images