Double-shell liquid crystal microcapsule and method for preparing the same

Abstract

This application relates to the field of microcapsule materials technology, and more particularly to a double-shell liquid crystal microcapsule and its preparation method. The double-shell liquid crystal microcapsule provided in this application includes a core material, a first outer shell layer covering the outer surface of the core material, and a second outer shell layer covering the surface of the first outer shell layer; wherein the core material is liquid crystal, the first outer shell layer is porous hollow glass microspheres, and the second outer shell layer is an acrylic polymer material. The formed liquid crystal core material can flow fully inside the porous hollow glass microspheres and can be deflected with voltage changes, achieving ideal photoelectric performance; the porous hollow glass microspheres have high strength, good transparency, and can produce a pressure-resistant effect; using an acrylic polymer material as the second outer shell layer, the refractive index of the acrylic polymer shell is adjustable, highly flexible, and allows the refractive index of the shell material to match that of the liquid crystal material itself, thereby effectively eliminating haze generated at the interface.

Description

Technical Field

[0001] This application belongs to the field of microcapsule material technology, and in particular relates to a double-shell liquid crystal microcapsule and its preparation method. Background Technology

[0002] Simple liquid crystals have a certain flow rate. Due to its inherent rigidity, liquid crystals twist when bent or compressed, preventing the fabrication of flexible devices. Later research revealed that adding polymers to liquid crystals to create polymer-dispersed liquid crystal displays (PDLCs) and polymer-stabilized crystal textiles (PSCTs) partially overcame this problem and led to their widespread application in rigid display devices. However, particle size and distribution significantly influence the electro-optical performance of these devices, and pressure resistance remains a bottleneck for achieving flexible displays. Microencapsulation of liquid crystals can address these issues; therefore, the research and development of liquid crystal microcapsules with high core material content and high deformability for device fabrication has become a current research hotspot and challenge.

[0003] On the one hand, encapsulation achieves the dispersion, protection, and stabilization of liquid crystals, preventing their flow during device flexing and thus ensuring the feasibility of flexible liquid crystal displays. On the other hand, controlling the size and distribution of microcapsules adjusts the size of liquid crystal droplets in the system, thereby improving the electro-optical performance of the device. However, to date, reports on liquid crystal microencapsulation have mainly focused on a few regions and companies. This is primarily because the doping of organic solvents and additives will lead to the loss of the intrinsic properties of liquid crystal materials, making the process more complex.

[0004] Currently, the commonly used method involves using epoxy resin liquid crystal microcapsules, comprising a core material (liquid crystal) and a wall material (epoxy resin). Preparation methods for epoxy resin liquid crystal microcapsules include: oil-phase preparation, aqueous-phase preparation, oil-in-water emulsion preparation, liquid crystal microcapsule preparation, filtration, and centrifugal washing. However, the raw materials for the two reactants used in producing the wall material have high requirements; they must have high reactivity to ensure the feasibility of the polycondensation reaction. This method is prone to incomplete reactions, leaving a small amount of unreacted monomers in the product. The resulting wall membrane has high permeability, making it unsuitable for encapsulating cores requiring airtight seals. Furthermore, it requires the use of large amounts of organic solvents, resulting in high costs.

[0005] Therefore, there is an urgent need to provide a simple and rapid method for preparing liquid crystal microcapsules to ensure that liquid crystal microcapsules can be widely used in industrial fields. Summary of the Invention

[0006] The purpose of this application is to provide a double-shell liquid crystal microcapsule and its preparation method, which aims to solve the problems of existing methods for preparing liquid crystal microcapsules, such as high requirements for the activity of raw materials, harsh reaction conditions, low success rate, and limited applicability.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0008] In a first aspect, this application provides a double-shell liquid crystal microcapsule, which includes a core material, a first outer shell layer covering the outer surface of the core material, and a second outer shell layer covering the surface of the first outer shell layer; wherein the core material is liquid crystal, the first outer shell layer is porous hollow glass microspheres, and the second outer shell layer is an acrylic polymer material.

[0009] Secondly, this application provides a method for preparing double-shell liquid crystal microcapsules, comprising the following steps:

[0010] Hollow glass microspheres are perforated to obtain porous hollow glass microspheres. Liquid crystal is injected into the cavity of the porous hollow glass microspheres to obtain liquid crystal-porous hollow glass microspheres.

[0011] Acrylic acid prepolymer, acrylic acid monomer, photoinitiator and liquid crystal-porous hollow glass microspheres were mixed to obtain an oil phase component, and emulsifier and deionized water were mixed to obtain an aqueous phase component.

[0012] The oil phase component and the aqueous phase component are mixed and then subjected to emulsification and equilibration treatment in sequence to obtain an O / W type emulsion.

[0013] Under water bath conditions, ultraviolet light irradiation was used to initiate the curing and polymerization of O / W type emulsions to form a coated emulsion containing porous hollow glass microspheres. Then, centrifugation was performed to break the emulsion, resulting in double-shell liquid crystal microcapsules.

[0014] The first aspect of this application provides a double-shell liquid crystal microcapsule, comprising a liquid crystal core material, a first outer shell layer of porous hollow glass microspheres covering the outer surface of the liquid crystal core material, and a second outer shell layer of acrylic polymer material covering the surface of the first outer shell layer. The liquid crystal core material can flow fully within the porous hollow glass microspheres and can deflect with voltage changes, achieving ideal photoelectric performance. Using porous hollow glass microspheres as the first outer shell layer provides high strength, good transparency, and adjustable shell thickness, which can restrict the flow of the liquid crystal material, creating a pressure-resistant effect and solving the problem of water ripples when the liquid crystal is pressed. Furthermore, using acrylic polymer material as the second outer shell layer allows for adjustable refractive index and high flexibility, enabling the refractive index of the shell material to match that of the liquid crystal material itself, thereby effectively eliminating haze generated at the interface.

[0015] The second aspect of this application provides a method for preparing double-shell liquid crystal microcapsules. This method involves first infusing liquid crystal core material into porous hollow glass microspheres, then providing an emulsion containing acrylic acid material, and finally sealing the liquid crystal-porous hollow glass microspheres with a surface-curing emulsion to obtain double-shell liquid crystal microcapsules. This method offers high production efficiency and effectively controls the liquid crystal coverage rate, residual impurities, and reduces adhesion between microcapsules. Furthermore, since the provided porous hollow glass microspheres are rigid materials, the second shell can be precisely controlled after the material is formed, thus ensuring that a lower second shell content can be used in the preparation process, which is beneficial for process control. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the double-shell liquid crystal microcapsule provided in the embodiments of this application.

[0018] Figure 2 This is a flowchart illustrating the preparation process of the double-shell liquid crystal microcapsules provided in the embodiments of this application.

[0019] Figure 3 This is a particle size analysis diagram of the double-shell liquid crystal microcapsules provided in the embodiments of this application.

[0020] Figure 4 These are SEM and TEM images of the double-shell liquid crystal microcapsule provided in Example 1 of this application. Detailed Implementation

[0021] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0023] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0024] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. 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 this application.

[0025] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0026] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as μg, mg, g, or kg.

[0027] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0028] The first aspect of this application provides a double-shell liquid crystal microcapsule, such as... Figure 1 As shown, the double-shell liquid crystal microcapsule includes a core material 1, a first outer shell layer 2 covering the outer surface of the core material 1, and a second outer shell layer 3 covering the surface of the first outer shell layer 2; wherein, the core material 1 is liquid crystal, the first outer shell layer 2 is porous hollow glass microspheres, and the second outer shell layer 3 is an acrylic polymer material.

[0029] The first aspect of this application provides a double-shell liquid crystal microcapsule, comprising a liquid crystal core material, a first outer shell layer of porous hollow glass microspheres covering the outer surface of the liquid crystal core material, and a second outer shell layer of acrylic polymer material covering the surface of the first outer shell layer. The liquid crystal core material can flow fully within the porous hollow glass microspheres and can deflect with voltage changes, achieving ideal photoelectric performance. Using porous hollow glass microspheres as the first outer shell layer provides high strength, good transparency, and adjustable shell thickness, which can restrict the flow of the liquid crystal material, creating a pressure-resistant effect and solving the problem of water ripples when the liquid crystal is pressed. Furthermore, using acrylic polymer material as the second outer shell layer allows for adjustable refractive index and high flexibility, enabling the refractive index of the shell material to match that of the liquid crystal material itself, thereby effectively eliminating haze generated at the interface.

[0030] In some embodiments, the core material of the double-shell liquid crystal microcapsule is liquid crystal, which is selected from at least one of bistable liquid crystal, namely, cholesteric liquid crystal, chiral nematic liquid crystal, and smectic A-phase liquid crystal.

[0031] In the process of using the formed liquid crystal microcapsules, the threshold voltage of the liquid crystal is related to the thickness of the liquid crystal layer in the device. Therefore, controlling the thickness of the shell layer covering the liquid crystal core material is particularly important.

[0032] Furthermore, using porous hollow glass microspheres as the first outer shell layer of the liquid crystal core material, the diameter and wall thickness of the porous hollow glass microspheres are adjustable. Moreover, the rigidity of the hollow glass microspheres can protect the liquid crystal material adsorbed inside the microspheres from external pressure. This also gives the bistable liquid crystal the ability to resist the influence of the external environment, so no color change occurs during bending. The photoelectric properties are inherent to the liquid crystal itself, which not only helps protect the liquid crystal core material but also facilitates its widespread application.

[0033] In some embodiments, the thickness of the first outer shell layer is 1–2 μm. If the first outer shell layer is too thick, the liquid crystal loading will be insufficient, thus affecting the subsequent display effect; if the first shell layer is too thin, the compressive strength will be insufficient. In some specific embodiments, the thickness of the first outer shell layer includes, but is not limited to, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, and 2.0 μm.

[0034] Furthermore, an acrylic polymer material is used as the second outer shell layer covering the surface of the first outer shell layer. Since the glass microspheres are porous, further encapsulation is required to obtain microcapsules for use. However, because porous hollow glass microspheres are rigid materials, only a small amount of acrylic polymer material is needed to achieve complete encapsulation, ensuring the display effect of the resulting double-shell liquid crystal microcapsules, the refractive index control of the encapsulated shell material, and the refractive index matching between the liquid crystal and the hollow glass microspheres.

[0035] In some embodiments, the thickness of the second outer shell layer is 1–2 μm. If the second outer shell layer is too thick, it will lead to an increase in the interlayer spacing during use, resulting in a higher driving voltage applied to the liquid crystal flipping; if the second outer shell layer is too thin, it will result in insufficient coverage and is prone to leakage. In some specific embodiments, the thickness of the second outer shell layer includes, but is not limited to, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, and 2.0 μm.

[0036] In some embodiments, the particle size of the double-shell liquid crystal is 10–12 μm. In some specific embodiments, the particle size of the double-shell liquid crystal includes, but is not limited to, 10 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11.0 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.8 μm, 11.9 μm, and 12.0 μm.

[0037] The second aspect of this application provides a method for preparing double-shell liquid crystal microcapsules, such as... Figure 2 As shown, it includes the following steps:

[0038] S01. Hollow glass microspheres are perforated to obtain porous hollow glass microspheres, and liquid crystal is injected into the cavity of the porous hollow glass microspheres to obtain liquid crystal-porous hollow glass microspheres.

[0039] S02. The acrylic prepolymer, acrylic monomer, photoinitiator and liquid crystal-porous hollow glass microspheres are mixed to obtain the oil phase component, and the emulsifier and deionized water are mixed to obtain the aqueous phase component.

[0040] S03. After mixing the oil phase component and the aqueous phase component, emulsification and equilibration treatments are performed sequentially to obtain an O / W type emulsion;

[0041] S04. Under water bath conditions, O / W type emulsion is solidified and polymerized by ultraviolet light irradiation to form a coated emulsion containing porous hollow glass microspheres. Then, centrifugation is performed to break the emulsion and obtain double-shell liquid crystal microcapsules.

[0042] The second aspect of this application provides a method for preparing double-shell liquid crystal microcapsules. This method involves first infusing liquid crystal core material into porous hollow glass microspheres, then providing an emulsion containing acrylic acid material, and finally sealing the liquid crystal-porous hollow glass microspheres with a surface-curing emulsion to obtain double-shell liquid crystal microcapsules. This method offers high production efficiency and effectively controls the liquid crystal coverage rate, residual impurities, and reduces adhesion between microcapsules. Furthermore, since the porous hollow glass microspheres are rigid materials, precise control can be achieved by molding the material before preparing the second shell, thus ensuring that a lower second shell content can be used in the preparation process, which is beneficial for process control.

[0043] In step S01, hollow glass microspheres are perforated to obtain porous hollow glass microspheres, and liquid crystal is injected into the cavity of the porous hollow glass microspheres to obtain liquid crystal-porous hollow glass microspheres.

[0044] In some embodiments, hollow glass microspheres are perforated to obtain porous hollow glass microspheres. The perforation process includes: stirring the hollow glass microspheres with an acidic solution until the hollow glass microspheres completely sink to the bottom, followed by washing, filtering, and drying.

[0045] In some embodiments, the acidic solution is selected from hydrofluoric acid solutions with a concentration of 0.1–1 mol / L. When glass microspheres are treated with hydrofluoric acid, the hydrofluoric acid reacts with silicate substances to generate gaseous silicon tetrafluoride, resulting in a porous structure on the surface of the hollow glass microspheres. In some specific embodiments, the concentration of the hydrofluoric acid solution includes, but is not limited to, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, and 1.0 mol / L.

[0046] In some embodiments, the hollow glass microspheres in the acidic solution comprise 1 wt% to 5 wt% by mass, ensuring that the acidic solution completely treats the hollow glass microspheres. In some specific embodiments, the mass percentage of hollow glass microspheres in the acidic solution includes, but is not limited to, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%.

[0047] In some embodiments, the stirring speed is 100–300 rpm, and the time is 10–15 minutes. Stirring ensures that the hollow glass microspheres are uniformly perforated, guaranteeing the formation of porous hollow glass microspheres and ensuring the orderly infusion of liquid crystal into the inner cavity of the porous hollow glass microspheres. In some specific embodiments, the stirring speed includes, but is not limited to, 100 rpm, 150 rpm, 200 rpm, 250 rpm, and 300 rpm; the time includes, but is not limited to, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, and 15 minutes.

[0048] Furthermore, liquid crystal is injected into the cavity of porous hollow glass microspheres to obtain liquid crystal-porous hollow glass microspheres.

[0049] In some embodiments, the step of injecting liquid crystal into the cavity of porous hollow glass microspheres includes: mixing porous hollow glass microspheres and liquid crystal, performing heat treatment under vacuum conditions to obtain a first mixture; stopping the vacuum conditions, allowing the first mixture to stand, and then centrifuging it to obtain liquid crystal-porous hollow glass microspheres.

[0050] In some embodiments, during the mixing of porous hollow glass microspheres and liquid crystal, the volume ratio of porous hollow glass microspheres to liquid crystal is 3 to 5:1, which ensures that the liquid crystal is completely injected into the porous hollow glass microspheres to form microcapsules.

[0051] Furthermore, the mixture of porous hollow glass microspheres and liquid crystal is placed in a vacuum drying oven and heat-treated under vacuum conditions to obtain the first mixture.

[0052] In some embodiments, the vacuum level is ≤1 Pa. Providing a vacuum environment is mainly to remove the air inside the porous glass microspheres so that the liquid crystal can completely fill the interior of the glass microspheres.

[0053] In some embodiments, the heat treatment temperature is 50–80°C, and the time is 30–90 minutes. The heating process aims to reduce the viscosity of the liquid crystal and improve its fluidity, which facilitates the filling of the glass microspheres by the liquid crystal. In some specific embodiments, the heat treatment temperature is 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C; the time includes, but is not limited to, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, or 90 minutes.

[0054] Furthermore, the vacuum condition is stopped, the first mixture is allowed to stand, and then centrifuged to obtain liquid crystal-porous hollow glass microspheres. By stopping the vacuum condition, the liquid crystal is allowed to flow into the hollow glass microspheres under the drive of pressure difference and capillary action.

[0055] In some embodiments, the first mixture is allowed to stand for 20 to 60 minutes to stabilize the liquid crystal-glass microsphere mixture. When the glass microspheres settle to the bottom, the loading is considered complete. In some specific embodiments, the standing time includes, but is not limited to, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, and 60 minutes.

[0056] Further, centrifugation is performed to remove excess liquid crystal material. In some embodiments, the centrifugation speed is 4000–12000 rpm, and the time is 20–40 minutes. In some specific embodiments, the centrifugation speed includes, but is not limited to, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, and 12000 rpm; and the time includes, but is not limited to, 20 minutes, 25 minutes, 30 minutes, 35 minutes, and 40 minutes.

[0057] After centrifugation to remove excess liquid crystal material, liquid crystal-porous glass microsphere material is obtained.

[0058] In step S02, the acrylic prepolymer, acrylic monomer, photoinitiator and liquid crystal-porous hollow glass microspheres are mixed to obtain the oil phase component, and the emulsifier and deionized water are mixed to obtain the aqueous phase component.

[0059] Furthermore, the acrylic prepolymer, acrylic monomer, photoinitiator, and liquid crystal-porous hollow glass microspheres are mixed to obtain the oil phase component.

[0060] Since the prepared oil phase component will immediately undergo a polymerization reaction under ultraviolet light, the reaction should be controlled under yellow light conditions when preparing the oil phase component.

[0061] In some embodiments, the acrylic prepolymer is selected from at least one of difunctional or polyfunctional polyurethane acrylates, polyester acrylates, polyether acrylates, epoxy acrylates, and unsaturated polyesters.

[0062] In some embodiments, the acrylic monomer includes at least one of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, isocyanurate triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate ethoxylate.

[0063] In some embodiments, the photoinitiator includes at least one of photoinitiator 907, photoinitiator 1173, photoinitiator MBF, and photoinitiator TPO-L.

[0064] In some embodiments, the mass ratio of acrylic prepolymer, acrylic monomer, and photoinitiator is 3–6:1:0.01–0.03. Controlling the mass ratio of acrylic prepolymer, acrylic monomer, and photoinitiator facilitates the reaction to obtain acrylic polymer materials through photocuring, ensuring the encapsulation of glass microspheres.

[0065] In some embodiments, the mass ratio of acrylic polymer material to liquid crystal-porous hollow glass microspheres is 0.5–0.8:1. Controlling this mass ratio effectively controls the liquid crystal encapsulation rate, the amount of residual impurities, and reduces the adhesion problem between microcapsules. In some specific embodiments, the mass ratio of acrylic polymer material to liquid crystal-porous hollow glass microspheres includes, but is not limited to, 0.5:1, 0.6:1, 0.7:1, and 0.8:1.

[0066] In some embodiments, the mixing speed is 500–1500 rpm, and the time is 0.5–3 hours. In some specific embodiments, the mixing speed includes, but is not limited to, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, and 1500 rpm; and the time includes, but is not limited to, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, and 3 hours.

[0067] Furthermore, the emulsifier and deionized water are mixed to obtain an aqueous phase component.

[0068] In some embodiments, the emulsifier includes, but is not limited to, at least one of sorbitan stearate, sorbitan sesquioleate, dehydrated sorbitan fatty acid ester, alkylphenol polyoxyethylene ether, polydimethylsiloxane, and fatty alcohol polyoxyethylene ether.

[0069] In some embodiments, the mixing speed is 500–1500 rpm, and the time is 0.5–3 hours. In some specific embodiments, the mixing speed includes, but is not limited to, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, and 1500 rpm; and the time includes, but is not limited to, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, and 3 hours.

[0070] In step S03, the oil phase component and the aqueous phase component are mixed and then subjected to emulsification and equilibration treatment in sequence to obtain an O / W type emulsion.

[0071] In some embodiments, the oil phase component is slowly added to the aqueous phase component for emulsification at room temperature. The emulsification rotation speed is 6000–12000 rpm, and the time is 3–7 minutes to ensure complete emulsification of the oil and aqueous phase components. In some specific embodiments, the emulsification rotation speed includes, but is not limited to, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, and 12000 rpm; the time includes, but is not limited to, 3 minutes, 4 minutes, 5 minutes, 6 minutes, and 7 minutes.

[0072] Furthermore, the emulsion after high-speed emulsification is subjected to equilibration treatment, wherein the stirring speed during equilibration treatment is 600-1400 rpm and the time is 30-150 minutes, resulting in an O / W type emulsion. In some specific embodiments, the stirring speed during equilibration treatment includes, but is not limited to, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, and 1400 rpm; and the time includes, but is not limited to, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes, 130 minutes, 140 minutes, and 150 minutes.

[0073] In step S04, under water bath conditions, ultraviolet light is used to initiate the curing and polymerization of O / W type emulsion to form a coated emulsion containing porous hollow glass microspheres. Then, centrifugation is performed to break the emulsion and obtain double-shell liquid crystal microcapsules.

[0074] In some embodiments, the water bath temperature is 35–45°C. Under this temperature condition, the polymerization reaction rate can be increased, and the UV-cured acrylate can play a better encapsulation role.

[0075] In some embodiments, the curing light intensity of the polymer is 10–100 mW / cm². 2 The curing time is 5 to 30 minutes. If the curing light intensity is too low or the curing time is too short, the emulsion will not cure completely, which is not conducive to the formation of a complete encapsulation layer. If the curing light intensity is too high or the curing time is too long, it will easily lead to material aging, which is not conducive to use.

[0076] In some specific embodiments, the curing light intensity includes, but is not limited to, 10 mW / cm². 2 20mW / cm 2 30mW / cm 2 40mW / cm 2 50mW / cm 2 60mW / cm 2 70mW / cm 2 80mW / cm2 90mW / cm 2 100mW / cm 2 .

[0077] In some specific embodiments, the curing time includes, but is not limited to, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes.

[0078] Furthermore, after photocuring, a coated emulsion containing porous hollow glass microspheres is formed, which is then centrifuged to break the emulsion, resulting in double-shell liquid crystal microcapsules.

[0079] In some embodiments, the centrifugation speed for demulsification is 10,000-15,000 rpm, and the time is 10-15 minutes. In some specific embodiments, the centrifugation speed for demulsification includes, but is not limited to, 10,000 rpm, 11,000 rpm, 12,000 rpm, 13,000 rpm, 14,000 rpm, and 15,000 rpm; and the time includes, but is not limited to, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, and 15 minutes.

[0080] Furthermore, after demulsification, the process further includes repeated washing and drying to obtain the desired double-layer pressure-resistant liquid crystal microcapsules. In some embodiments, the washing solvent is selected from organic alcohol solvents such as ethanol and methanol.

[0081] The following description is based on specific embodiments.

[0082] Example 1

[0083] Double-shell liquid crystal microcapsules and their preparation method

[0084] The double-shell liquid crystal microcapsule includes a core material, a first outer shell layer covering the outer surface of the core material, and a second outer shell layer covering the surface of the first outer shell layer; wherein, the core material is liquid crystal, the first outer shell layer is porous hollow glass microspheres, and the second outer shell layer is an acrylic polymer material; the particle size of the double-shell liquid crystal is 11 μm; the thickness of the first outer shell layer is 2 μm; and the thickness of the second outer shell layer is 2 μm.

[0085] The preparation method of double-shell liquid crystal microcapsules includes the following steps:

[0086] 1) Soak hollow glass microspheres in hydrofluoric acid solution and stir intermittently at 150 rpm for 15 min. After most of the hollow glass microspheres sink to the bottom of the beaker, wash them repeatedly with water, filter, wash, and dry at 100℃ for 12 h to obtain porous hollow glass microspheres with micro / nano-scale pores in the shell.

[0087] 2) Pour the porous hollow glass microspheres and liquid crystal into an Erlenmeyer flask at a mass ratio of 3:1, place it in a vacuum drying oven, evacuate for 30 minutes to defoam, maintain a vacuum degree ≤1pa, and heat to 70℃; stop the vacuum operation, let the liquid crystal flow into the hollow glass microspheres, let it stand for 30 minutes, when the glass microspheres settle at the bottom, centrifuge the hollow glass microspheres at a speed of 12000rpm for 30 minutes;

[0088] 3) Under yellow light conditions, a certain amount of difunctional polyurethane acrylate, difunctional polyester acrylate, and triacrylate isocyanurate were taken, and photoinitiator 1173 was added. The ratio of acrylate prepolymer, polyfunctional acrylate monomer, and initiator was 2:1:0.02. The mixture was stirred at 1000 rpm for 30 min, and porous glass microspheres filled with liquid crystal were poured into the inner cavity. The ratio between the acrylic mixture and the porous glass microspheres filled with liquid crystal was 0.6:1. The mixture was stirred for another 30 min until it was uniformly mixed to prepare the oil phase. The emulsifier and deionized water were added to a beaker and mechanically stirred at 1000 rpm for 30 min to prepare the aqueous phase. At room temperature, the oil phase was slowly added to the aqueous phase and emulsified using a high-speed emulsifier. The emulsifier speed was set to 10000 rpm and the emulsification time was 5 min. The emulsion after high-speed emulsification was then transferred to a beaker, heated to 40℃, stirred at 1000 rpm, and equilibrated for 30 min to obtain an O / W type emulsion.

[0089] 4) Under water bath conditions, the temperature is raised to 40℃ at a rate of 80mW / cm². 2 Irradiation with ultraviolet light for 20 minutes initiates O / W type emulsion polymerization to form an emulsion containing porous hollow glass microspheres and microcapsules. After the curing reaction is completed, the emulsion is placed in a centrifuge and centrifuged at 10,000 rpm for 10 minutes to break the emulsion. The emulsion is repeatedly washed with ethanol and dried to obtain double-shell liquid crystal microcapsules.

[0090] Example 2

[0091] Double-shell liquid crystal microcapsules and their preparation method

[0092] The double-shell liquid crystal microcapsule includes a core material, a first outer shell layer covering the outer surface of the core material, and a second outer shell layer covering the surface of the first outer shell layer; wherein, the core material is liquid crystal, the first outer shell layer is porous hollow glass microspheres, and the second outer shell layer is an acrylic polymer material; the particle size of the double-shell liquid crystal is 11 μm; the thickness of the first outer shell layer is 1 μm; and the thickness of the second outer shell layer is 1 μm.

[0093] The preparation method of double-shell liquid crystal microcapsules includes the following steps:

[0094] 1) Soak hollow glass microspheres in hydrofluoric acid solution and stir intermittently at 200 rpm for 12 min to ensure that perforation is completed. Wash repeatedly with water, filter, wash, and dry at 100℃ for 12 h to obtain porous hollow glass microspheres with micro / nano-scale pores in the shell.

[0095] 2) Pour the porous hollow glass microspheres and liquid crystal into an Erlenmeyer flask at a mass ratio of 4:1, place it in a vacuum drying oven, evacuate for 30 minutes to defoam, maintain a vacuum degree ≤1pa, remove the air inside the hollow glass microspheres, and heat to 60℃; stop the vacuum operation, let stand for 40 minutes, and centrifuge the hollow glass microspheres at a speed of 10000rpm for 30 minutes.

[0096] 3) Under yellow light conditions, a certain amount of bifunctional polyurethane acrylate and trihydroxypropane triacrylate were taken, and photoinitiator TPO was added. The ratio of acrylate prepolymer, polyfunctional acrylate monomer and initiator was 3:1:0.03. The mixture was stirred at 1000 rpm for 30 min. The ratio between the acrylic mixture and the porous glass microspheres filled with liquid crystal was 0.5:1. The mixture was stirred for another 30 min until it was uniformly mixed to prepare the oil phase. The emulsifier and deionized water were added to a beaker and mechanically stirred at 1000 rpm for 30 min to prepare the aqueous phase. At room temperature, the oil phase was slowly added to the aqueous phase and emulsified using a high-speed emulsifier. The emulsifier speed was set to 10000 rpm and the emulsification time was 5 min. The emulsion after high-speed emulsification was then transferred to a beaker, heated to 40℃, stirred at 1000 rpm, and equilibrated for 30 min to obtain an O / W type emulsion.

[0097] 4) Under water bath conditions, the temperature is raised to 40℃ at a rate of 50mW / cm². 2 Irradiation with ultraviolet light for 20 minutes initiates O / W type emulsion polymerization to form an emulsion containing porous hollow glass microspheres and microcapsules. After the curing reaction is completed, the emulsion is placed in a centrifuge and centrifuged at 10,000 rpm for 10 minutes to break the emulsion. The emulsion is repeatedly washed with ethanol and dried to obtain double-shell liquid crystal microcapsules.

[0098] Performance testing and results analysis

[0099] (I) Particle Size Analysis

[0100] The particle size of the double-shell liquid crystal microcapsules obtained in Example 1 was analyzed, such as... Figure 3 As shown, Figure 3 (A) is a particle size distribution diagram of the glass microspheres before coating; Figure 3 (B) is a particle size distribution diagram of the coated glass microspheres.

[0101] (II) SEM and TEM analysis of the double-shell liquid crystal microcapsules obtained in Example 1

[0102] From the appendix Figure 4 As shown in (A), the prepared MC-DDLC-Ms microcapsules have a spherical structure, a smooth surface, and a particle size of approximately 11 μm. Figure 3 The particle size is consistent with (B). TEM was used to characterize the microcapsule microstructure (e.g., Figure 4 (As shown in (B)), the results show that the double-shell liquid crystal microcapsules prepared in the first step have an obvious double-layer pressure-resistant structure. The thickness of the polyacrylate shell was measured to be about 1-2 μm, and the core diameter was about 7 μm, which shows extremely high loading capacity and encapsulation efficiency.

[0103] The dual-shell liquid crystal microcapsule provided in this application includes a liquid crystal core material, a first outer shell layer of porous hollow glass microspheres covering the outer surface of the liquid crystal core material, and a second outer shell layer of acrylic polymer material covering the surface of the first outer shell layer. The liquid crystal core material can flow freely within the porous hollow glass microspheres and deflect with voltage changes, achieving ideal photoelectric performance. Using porous hollow glass microspheres as the first outer shell layer provides high strength, good transparency, and adjustable shell thickness, which restricts the flow of the liquid crystal material, creating a pressure-resistant effect and solving the problem of water ripples when the liquid crystal is pressed. Furthermore, using acrylic polymer material as the second outer shell layer allows for adjustable refractive index and high flexibility, enabling the refractive index of the shell material to match that of the liquid crystal material itself, thereby effectively eliminating haze at the interface.

[0104] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a double-shell liquid crystal microcapsule, characterized in that, Includes the following steps: Hollow glass microspheres are perforated to obtain porous hollow glass microspheres, and liquid crystal is injected into the inner cavity of the porous hollow glass microspheres to obtain liquid crystal-porous hollow glass microspheres. The acrylic prepolymer, acrylic monomer, photoinitiator and the liquid crystal-porous hollow glass microspheres are mixed to obtain an oil phase component, and the emulsifier and deionized water are mixed to obtain an aqueous phase component. The oil phase component and the aqueous phase component are mixed and then subjected to emulsification and equilibration treatment in sequence to obtain an O / W type emulsion. Under water bath conditions, the O / W type emulsion is solidified and polymerized by ultraviolet light irradiation to form a coated emulsion containing porous hollow glass microspheres. Then, centrifugation is performed to break the emulsion and obtain double-shell liquid crystal microcapsules.

2. The method for preparing double-shell liquid crystal microcapsules according to claim 1, characterized in that, The perforation process includes: stirring the hollow glass microspheres with an acidic solution until the hollow glass microspheres completely sink to the bottom, followed by washing, filtering, and drying.

3. The method for preparing double-shell liquid crystal microcapsules according to claim 2, characterized in that, The acidic solution is selected from hydrofluoric acid solutions with a concentration of 0.1~1 mol / L; And / or, The hollow glass microspheres are present in the acidic solution at a mass percentage of 1 wt% to 5 wt%; and / or, The stirring speed is 100~300 rpm and the time is 10~15 minutes.

4. The method for preparing double-shell liquid crystal microcapsules according to claim 1, characterized in that, The step of injecting liquid crystal into the cavity of the porous hollow glass microspheres includes: mixing the porous hollow glass microspheres and liquid crystal, and heat-treating under vacuum conditions to obtain a first mixture; stopping the vacuum conditions, allowing the first mixture to stand, and then centrifuging to obtain liquid crystal-porous hollow glass microspheres.

5. The method for preparing double-shell liquid crystal microcapsules according to claim 4, characterized in that, The volume ratio of the porous hollow glass microspheres to the liquid crystal is 3~5:1; and / or, The vacuum level of the vacuum condition is ≤1 Pa; and / or, The heat treatment is performed at a temperature of 50-80°C for a time of 30-90 minutes; and / or, The settling time is 20-60 minutes; and / or, The centrifugation process is carried out at a speed of 4000~12000 rpm for 20~40 minutes.

6. The method for preparing double-shell liquid crystal microcapsules according to claim 1, characterized in that, The liquid crystal is selected from at least one of bistable liquid crystals, namely, cholesteric liquid crystals, chiral nematic liquid crystals, and smectic A-phase liquid crystals; and / or, The acrylic prepolymer is selected from at least one of difunctional or polyfunctional polyurethane acrylates, polyester acrylates, polyether acrylates, and epoxy acrylates; and / or, The acrylic monomer comprises at least one of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, isocyanurate triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate ethoxylate; and / or, The photoinitiator includes at least one of photoinitiator 907, photoinitiator 1173, photoinitiator MBF, and photoinitiator TPO-L; and / or, The mass ratio of the acrylic acid prepolymer, the acrylic acid monomer, and the photoinitiator is 3~6:1:0.01~0.

03.

7. The method for preparing double-shell liquid crystal microcapsules according to claim 1, characterized in that, The mixing process is carried out at a speed of 500~1500 rpm for a time of 0.5~3 hours; and / or, The emulsification process is carried out at a rotation speed of 6000~12000 rpm for 3~7 minutes; and / or, The stirring speed for the balancing process is 600~1400 rpm, and the time is 30~150 minutes.

8. The method for preparing double-shell liquid crystal microcapsules according to claim 1, characterized in that, The curing light intensity of the polymer is 10~100 mW / cm². 2 The curing time is 5-30 minutes; and / or, The centrifugal demulsification process is carried out at a speed of 10,000-15,000 rpm for 10-15 minutes.

9. A double-shell liquid crystal microcapsule prepared by the method for preparing double-shell liquid crystal microcapsules according to any one of claims 1-8, characterized in that, The dual-shell liquid crystal microcapsule includes a core material, a first outer shell layer covering the outer surface of the core material, and a second outer shell layer covering the surface of the first outer shell layer; wherein, the core material is liquid crystal, the first outer shell layer is porous hollow glass microspheres, and the second outer shell layer is an acrylic polymer material.

10. The double-shell liquid crystal microcapsule according to claim 9, characterized in that, The particle size of the double-shell liquid crystal is 10~12 μm; and / or, The thickness of the first outer shell layer is 1~2 μm; and / or, The thickness of the second outer shell layer is 1~2μm.

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