Cholesteric liquid crystal microcapsule as well as preparation method and application thereof

Abstract

The invention discloses a preparation method of a cholesteric liquid crystal microcapsule with a core-shell structure. The cholesteric liquid crystal microcapsule with a core-shell structure, which is composed of a core material cholesteric liquid crystal and a shell phase melamine resin, is prepared by taking a Pickering emulsion with stable cellulose nanocrystals as a template and taking melamine formaldehyde resin as a shell material through an in-situ polymerization method. The liquid crystal display device solves the problems that in an existing liquid crystal display device, liquid crystal flows, is prone to pollution and is unstable. The preparation method of the liquid crystal microcapsule is simple and convenient, short in time consumption, uniform in particle size distribution and low in production cost. The cholesteric liquid crystal in the liquid crystal microcapsule prepared by the invention can display different colors according to different screw pitches when being stimulated by the outside, and the cholesteric liquid crystal is separated from the external environment, so that the core material in the shell is not invaded by the external environment and does not overflow to the outside, and the display effect is greatly improved; therefore, more stable and long-term display is realized on the basis of original color display.

Description

Technical Field

[0001] The present invention relates to the technical field of microcapsules, and particularly relates to a cholesteric liquid crystal microcapsule, a preparation method thereof and an application thereof. Background Art

[0002] Matter is divided into three states: liquid, solid, and gas. Solids are further divided into two forms: crystals and amorphous substances. When matter changes from one phase state to another, it is said that the matter has undergone a phase change. Generally, the phase change of matter occurs directly without a process, that is, its form and internal molecular structure change instantaneously. However, there is a form of matter that lies between the crystalline state and the liquid state. This phase state of matter that simultaneously has the flowing form of a liquid and the spatially ordered arrangement structure of crystal molecules is called the liquid crystal state, and substances with this property are called liquid crystals.

[0003] Cholesteric liquid crystal is different from other liquid crystal materials due to its unique helical structure. It selectively reflects the light irradiated on its surface. The selective reflection of cholesteric liquid crystal follows Bragg's reflection law. The reflection wavelength can be controlled by changing the molecular pitch (P), and different colors of reflected light can be displayed accordingly. P can also be adjusted by external stimuli such as temperature, light, electric field, magnetic field, mechanical stress, and chemical reaction conditions, which thus endows it with color-changing properties and enables its application in many aspects.

[0004] Although cholesteric liquid crystal is deeply favored by people due to its excellent color-changing properties, it has the following problems in practical applications. For example: (1) The inherent fluid characteristics of liquid crystal cause it to flow in display devices and are not easy to store, and it is prone to non-uniform distribution, affecting display stability; (2) Liquid crystal is easily damaged by external pollutants or mechanical stress, resulting in deterioration of the liquid crystal molecular arrangement and display performance degradation. The above problems can be solved by optimizing or improving its structure or existence mode. Making it into a liquid crystal microcapsule structure is a feasible optimization method. Take the flexible display, which is one of the many applications of liquid crystal microcapsules, for example. In 1975, Sheridon, a researcher at PARC of Xerox, first proposed the concept of electronic paper. The main part of this electronic paper display is electronic ink, which is composed of many tiny electronic ink capsules. The capsules contain black and white charged particles with positive and negative charges. Then, electrophoresis technology is used to control the movement of the charged particles in the capsules to achieve the purpose of display. With the development and progress of technology, this kind of electronic paper has been eliminated because of its disadvantages such as slow response speed, slow conversion speed, complex manufacturing process, and only black and white display, which cannot meet people's needs. Therefore, color display and high response speed have become the focus of people's research. Since the discovery of liquid crystal, it has become a well-known display material. Therefore, people use cholesteric liquid crystal to replace the black and white charged particles and store it in the microcapsules with a core-shell structure to make it the core material of flexible displays.

[0005] The proposal of liquid crystal microcapsules has a certain improvement effect on many problems existing in liquid crystal displays. However, there are still corresponding problems in the preparation of current liquid crystal microcapsules. The preparation methods of liquid crystal microcapsules are generally divided into two categories. One is the traditional method, such as in-situ polymerization method, interfacial polymerization method, complex coacervation method, solvent evaporation method, etc. The other preparation method is the microfluidic method. Both of these two methods have room for improvement. The microcapsules prepared by the traditional method have problems such as uneven particle size, polydispersity, and more impurities, which affect their application effects. The microfluidic method has problems such as uneven particle size distribution of the prepared microcapsules, high equipment cost, insufficient wall material sealing, resulting in easy leakage of liquid crystal, and thus poor flexible color display performance. Summary of the Invention

[0006] To overcome the above problems in the prior art, the purpose of the present invention is to provide a preparation method of cholesteric liquid crystal microcapsules with a core-shell structure. The present invention selects the in-situ polymerization method to prepare cholesteric liquid crystal microcapsules. Generally, the preparation of microcapsules is based on the emulsion formed by traditional emulsifiers, and then shell polymerization is carried out. This research abandons ordinary emulsions and innovatively selects CNC-stabilized Pickering emulsions, and then uses melamine formaldehyde resin for shell polymerization to encapsulate cholesteric liquid crystals to form cholesteric liquid crystal microcapsules. CNC-stabilized Pickering emulsions are more stable than traditional emulsions. Taking Pickering emulsions as templates, the emulsion interface has a better fitting effect during shell polymerization. At the same time, compared with the existing preparation methods, the preparation cycle of the method of the present invention is shorter, the cost of experimental materials required is smaller, and the cost is low. It encapsulates cholesteric liquid crystal (CLC) / melamine-formaldehyde (MF) microcapsules in a polymer shell. Without changing its properties, the liquid crystal is separated from the external environment, enabling it to exhibit stable and efficient performance.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] On the one hand, the present invention provides a preparation method of cholesteric liquid crystal microcapsules with a core-shell structure, which includes the following steps:

[0009] S1: Mix a nematic liquid crystal and a chiral dopant evenly to obtain a cholesteric liquid crystal solution;

[0010] S2: Add a formaldehyde solution and melamine to deionized water, and use an alkaline solution to adjust the pH to 8-9 to obtain a melamine formaldehyde prepolymer solution;

[0011] S3: Mix the solid particle cellulose nanocrystal-stabilized Pickering emulsion with deionized water uniformly to obtain a 0.5 wt% mixture, and then add deionized water for dilution to obtain a 0.3 wt% mixture;

[0012] S4: Mix the cholesteric liquid crystal solution obtained in step S1 with the mixture obtained in step S3 uniformly, and adjust the pH of the resulting solution to 4 - 5;

[0013] S5: Drop the melamine formaldehyde prepolymer solution obtained in step S2 into the solution with a pH of 4 - 5 obtained in step S4, and stir at 60 - 80 °C to obtain a mixture;

[0014] S6: Wash, filter, and dry the mixture obtained in step S5 to obtain cholesteric liquid crystal microcapsule powder.

[0015] Further, in step S1, the nematic liquid crystal is E7 or SLC-1717, and the chiral dopant is R6N, R811, or chiral dopant Q.

[0016] Further, in step S1, the nematic liquid crystal is SLC-1717, and the chiral dopant is R6N, wherein the mass ratio of SLC-1717 to R6N is 15:1.

[0017] Further, in step S1, the nematic liquid crystal is E7, and the chiral dopant is R811, wherein the mass ratio of E7 to R811 is 3.3:1.

[0018] Further, in step S1, the nematic liquid crystal is SLC-1717, and the chiral dopant is chiral dopant Q, wherein the mass ratio of SLC-1717 to chiral dopant Q is 20:1.

[0019] Further, in step S2, the mass ratio of the formaldehyde solution, melamine, and deionized water is (0.1 - 0.4):(0.05 - 0.1):(2 - 3).

[0020] Further, in step S5, a syringe is used for dropping, the dropping rate is 1 - 3 mL / min, and the stirring speed of the mixture of the melamine formaldehyde prepolymer solution obtained in step S2 and the emulsion obtained in step S4 at 60 - 80 °C is 300 - 1000 rpm.

[0021] Further, in step S6, after allowing the mixture obtained in step S5 to stand and cool, it is washed multiple times with deionized water and then filtered, and dried overnight in a 40 °C vacuum drying oven, and then dispersed in a centrifuge tube filled with alcohol, and the aggregated microcapsules are dispersed by ultrasonic treatment to obtain cholesteric liquid crystal microcapsule powder.

[0022] On the other hand, the present invention provides a cholesteric liquid crystal microcapsule prepared by the above method, characterized in that the core material of the cholesteric liquid crystal microcapsule is a cholesteric liquid crystal composed of a nematic liquid crystal and a chiral dopant, and the shell material is melamine formaldehyde resin.

[0023] Another invention of the present invention provides an application of the cholesteric liquid crystal microcapsule in a flexible display.

[0024] Compared with the prior art, the preparation method of the present invention has the following beneficial effects:

[0025] 1) In the present invention, shell polymerization is carried out by in-situ polymerization method, and then cholesteric liquid crystal microcapsules with a core-shell structure are prepared through washing, filtering, drying and ultrasonic dispersion, and microcapsules with uniform dispersion and good morphology are obtained.

[0026] 2) The reaction conditions of the present invention are mild, the preparation process is simple, the morphology of the product is uniform, and the reaction process is easy to control. The particle size of the microcapsules can be controlled by controlling the stirring speed and the content of the emulsifier. The selected shell material MF has good stability and can encapsulate the inner liquid crystal under normal environment without affecting its performance.

[0027] 3) The cholesteric liquid crystal microcapsule with a core-shell structure of the present invention realizes the application of a flexible film display with thermochromism, and it has good application in a flexible display.

[0028] 4) Compared with the preparation of other liquid crystal microcapsules, the method of the present invention abandons ordinary emulsions and innovatively selects a Pickering emulsion stabilized by CNC with high stability, low demulsification rate and small stratification rate, and then the cholesteric liquid crystal is encapsulated by shell polymerization with melamine formaldehyde resin to form cholesteric liquid crystal microcapsules.

[0029] 5) The preparation method of the present invention has process economy, and the production cycle is shortened to 3 hours. Compared with the microfluidic method, the equipment investment cost is reduced by more than 80%.

[0030] 6) The preparation method of the present invention provides coating performance. The MF shell layer fits tightly with the Pickering emulsion interface, and the demulsification rate is lower than 1%, which is significantly better than the traditional emulsifier system (demulsification rate > 5%); BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 SEM image of the cholesteric liquid crystal microcapsules with a core - shell structure prepared in Example 1 of the present invention.

[0033] Figure 2 POM image of the cholesteric liquid crystal microcapsules with a core - shell structure prepared in Example 1 of the present invention.

[0034] Figure 3 IR image of the cholesteric liquid crystal microcapsules with a core - shell structure prepared in Examples 1 - 3 of the present invention.

[0035] Figure 4 Physical image of the powder of the cholesteric liquid crystal microcapsules with a core - shell structure prepared in Example 1 of the present invention.

[0036] Figure 5 Physical image of the color change of the film of the cholesteric liquid crystal microcapsules with a core - shell structure prepared in Examples 1 - 3 of the present invention.

[0037] Figure 6 Particle size image of the cholesteric liquid crystal microcapsules with chiral agents R6N, R811, and Q prepared in Examples 1 - 3 of the present invention.

[0038] Figure 7 SEM image of the cholesteric liquid crystal microcapsules with a core - shell structure prepared in Example 1 and Comparative Example 1 of the present invention.

[0039] Figure 8 Particle size image of the liquid crystal microcapsules with gradually increasing CNC concentration prepared in the present invention example (increasing from left to right). Detailed implementation manners

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0041] The present invention provides a method for preparing cholesteric liquid crystal microcapsules with a core-shell structure. By encapsulating CLC / MF microcapsules in a polymer shell, the liquid crystal can be separated from the external environment without changing its properties, enabling it to exhibit stable and efficient performance. The present invention uses an in-situ polymerization method to prepare cholesteric liquid crystal microcapsules with a core-shell structure (CLC / MF). This method is simple, the prepared microspheres have good stability and uniform particle size. Compared with other traditional methods, the CNC-stabilized Pickering used in the preparation method of this study is more stable than traditional emulsions. Using Pickering emulsion as a template, the shell has a better fitting effect during interfacial polymerization of the emulsion. At the same time, it has a shorter preparation cycle and lower cost of experimental materials compared with other preparation methods. The present invention uses a CNC-stabilized Pickering emulsion as a template and melamine formaldehyde resin (MF) as the shell material to prepare cholesteric liquid crystal microcapsules with a particle size of about 1-5 μm. The prepared cholesteric liquid crystal microcapsules have excellent properties such as good dispersibility, high stability, and good color display performance.

[0042] The following specific examples are used to further illustrate the present invention. The experimental methods used in the following examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used in the following examples can all be obtained from commercial channels unless otherwise specified.

[0043] Example 1

[0044] This example provides a method for preparing cholesteric liquid crystal microcapsules, which includes the following steps:

[0045] S1: 0.5 g of nematic liquid crystal SLC-1717 (purchased from Shandong Xianhua Technology Co., Ltd.) and 0.0335 g of chiral dopant R6N (purchased from Shandong Binlai Technology Co., Ltd.) are mixed in a beaker and ultrasonically dispersed to obtain a uniform cholesteric liquid crystal solution A.

[0046] S2: 0.16875 g of formaldehyde solution (37 wt%) and 0.0875 g of melamine are mixed and added to 2 g of deionized water, and the pH is adjusted to 8-9 with triethanolamine (1 mol / L) to obtain a melamine formaldehyde prepolymer solution B.

[0047] S3: The solid particle CNC-stabilized Pickering emulsion is mixed with deionized water and ultrasonically treated for 2-3 h to obtain a solution C (0.5 wt%), and then diluted with 6 g of deionized water to obtain a solution D (0.3 wt%).

[0048] S4: The solution A prepared in step S1 is mixed with the solution D prepared in step S3, stirred at a speed of 8000 rpm for 20 min, and its pH is adjusted to 4.5, and then left standing for a period of time to obtain a solution E.

[0049] S5: Add the solution B prepared in step S2 dropwise into the solution E prepared in step S5 at a dropping rate of 1 mL / min, and stir at a speed of 1000 rpm for 3 h at 70 °C to obtain solution F.

[0050] S6: After allowing the solution F prepared in step S5 to stand and cool, wash it several times with deionized water, filter it, and dry it overnight in a vacuum drying oven at 40 °C. Finally, take a small amount and disperse it in a centrifuge tube filled with alcohol, and disperse the aggregated microcapsules by ultrasonic treatment to obtain white monodisperse liquid crystal microcapsule powder.

[0051] Example 2

[0052] This example provides a method for preparing cholesteric liquid crystal microcapsules, which includes the following steps:

[0053] S1: Mix 0.5 g of nematic liquid crystal E7 (purchased from Shandong Xianhua Technology Co., Ltd.) and 0.15 g of chiral dopant R811 (purchased from Beijing Bayi Space-Time Liquid Crystal Technology Co., Ltd.) in a beaker, and disperse them by ultrasonic treatment to obtain a uniform cholesteric liquid crystal solution A.

[0054] S2: Mix 0.25 g of formaldehyde solution (37 wt%) and 0.08 g of melamine, add them to 2.5 g of deionized water, and adjust the pH to 8 - 9 with triethanolamine (1 mol / L) to obtain a melamine formaldehyde prepolymer solution B.

[0055] S3: Mix the solid particle CNC-stabilized Pickering emulsion with deionized water, and ultrasonically treat it for 2 - 3 h to obtain solution C (0.5 wt%), and then dilute it by adding 6 g of deionized water to obtain solution D (0.3 wt%).

[0056] S4: Mix the solution A prepared in step S1 and the solution D prepared in step S3, stir at a speed of 8000 rpm for 20 min, adjust its pH to 4.5, and let it stand for a period of time to obtain solution E.

[0057] S5: Add the solution B prepared in step S2 dropwise into the solution E prepared in step S5 at a dropping rate of 2 mL / min, and stir at a speed of 700 rpm for 3 h at 60 °C to obtain solution F.

[0058] S6: After allowing the solution F prepared in step S5 to stand and cool, wash it several times with deionized water, filter it, and dry it overnight in a vacuum drying oven at 40 °C. Finally, take a small amount and disperse it in a centrifuge tube filled with alcohol, and disperse the aggregated microcapsules by ultrasonic treatment to obtain white monodisperse liquid crystal microcapsule powder.

[0059] Example 3

[0060] This example provides a method for preparing cholesteric liquid crystal microcapsules, which includes the following steps:

[0061] S1: Mix 0.5 g of nematic liquid crystal SLC-1717 (purchased from Shandong Xianhua Technology Co., Ltd.) and 0.0235 g of chiral dopant Q (purchased from Beijing Bayi Space-Time Liquid Crystal Technology Co., Ltd.) in a beaker, and disperse them by ultrasonic wave to obtain a uniform cholesteric liquid crystal solution A.

[0062] S2: Mix 0.4 g of formaldehyde solution (37 wt%) and 0.1 g of melamine, add them to 3 g of deionized water, and adjust the pH to 8 - 9 with triethanolamine (1 mol / L) to obtain a melamine formaldehyde prepolymer solution B.

[0063] S3: Mix the solid particle CNC-stabilized Pickering emulsion with deionized water, and ultrasonicate for 2 - 3 h to obtain a solution C (0.5 wt%), and then dilute it by adding 6 g of deionized water to obtain a solution D (0.3 wt%).

[0064] S4: Mix the solution A prepared in step S1 with the solution D prepared in step S3, stir at a speed of 8000 rpm for 20 min, adjust its pH to 4.5, and let it stand for a period of time to obtain a solution E.

[0065] S5: Drop the solution B prepared in step S2 into the solution E prepared in step S5 through a syringe at a dropping speed of 3 mL / min, and stir at a speed of 300 rpm at 60 °C for 3 h to obtain a solution F.

[0066] S6: After the solution F prepared in step S5 is allowed to stand and cool, wash it with deionized water multiple times, filter it, and dry it overnight in a vacuum drying oven at 40 °C. Finally, take a small amount and disperse it in a centrifuge tube filled with alcohol, and ultrasonicate to disperse the aggregated microcapsules to obtain white monodisperse liquid crystal microcapsule powder.

[0067] Figure 1 and Figure 2 Respectively show the SEM image and POM image of the cholesteric liquid crystal microcapsule powder with a core-shell structure prepared in Example 1. As can be seen from the figure, the prepared liquid crystal microcapsules have a complete structure and good morphology. We respectively carried out infrared characterization on the obtained microcapsule powder, microcapsule shell material, core material, and crushed ones. Figure 3 (a) to (c) respectively show the infrared spectroscopy (IR) images of the liquid crystal microcapsules prepared in Examples 1 to 3, which can confirm the successful coating of the liquid crystal microcapsules. Figure 6(a) to (c) respectively show the liquid crystal microcapsules prepared in Examples 1 to 3. As can be seen from the figure, the particle size distribution of the prepared liquid crystal microcapsules is uniform.

[0068] Comparative Example 1

[0069] Compared with Example 1, the preparation method of Comparative Example 1 is the same as that of Example 1 in all steps except for the core-shell ratio. We obtained different core-shell ratios by changing the mass of melamine formaldehyde in step S2. Figure 7 (a) and (b) respectively show the SEM images of the liquid crystal microcapsules prepared in Example 1 and Comparative Example 1 with core-shell ratios of 1:2 and 1:1. In Example 1, the core-shell ratio (the mass ratio of the shell material melamine resin to the core material cholesteric liquid crystal) in step S2 is 1:2. As Figure 7 (a) shows, the cholesteric liquid crystal microcapsules with a core-shell ratio of 1:2 prepared in Example 1 have a complete structure and good morphology. In Comparative Example 1, we used a core-shell ratio of 1:1. As Figure 7 (b) shows, the white powder of the cholesteric liquid crystal microcapsules prepared in Comparative Example 1 shows extensive adhesion due to too much shell material.

[0070] Comparative Example 2

[0071] Compared with Example 1, the preparation method of Comparative Example 2 is the same as that of Example 1 in all steps except for the core-shell ratio. The core-shell ratio used in this comparative example is 1:3, and most of the prepared liquid crystal microcapsules are damaged and it is impossible to successfully prepare liquid crystal microcapsule powder.

[0072] Comparative Example 3

[0073] By changing the CNC concentration in the CNC suspension, it was found that as the concentration increased, the particle size of the liquid crystal microcapsules also decreased. As Figure 8 shown, the particle size of the microcapsules is inversely proportional to the CNC concentration. When the CNC concentration in the CNC suspension before dilution is 0.5 wt%, the particle size of the prepared microcapsules is about 0 - 5 μm, which is the best.

[0074] We mixed the microcapsule powder obtained after drying, as Figure 4 shown, with transparent PVA glue and coated it on a black film. By heating the microcapsule layer on the black film, different colors changing with temperature were shown, as Figure 5 shown. Thus, it can be seen that for the cholesteric liquid crystal in the liquid crystal microcapsules prepared by the present invention, the selective reflection of the cholesteric liquid crystal complies with the compound Bragg reflection law as shown in formula (1). When subjected to external stimuli, different colors can be shown according to the different pitch (P) sizes.

[0075] λ = 2nPsinφ

[0076] Where n is the average refractive index, p is the pitch of the cholesteric liquid crystal, φ is the angle between the incident light and the liquid crystal surface, and λ is the wavelength of the reflected light. Therefore, the cholesteric liquid crystal microcapsules prepared by the present invention can be applied to flexible displays. Due to reasons such as its flexibility, if the liquid crystal is not encapsulated in a flexible display, problems such as uneven distribution and flow of the liquid crystal will occur during the bending process of the display. The liquid crystal microcapsules prepared by the present invention solve this series of problems, greatly improving the display effect, and thus achieving a more stable and long-lasting display on the basis of the original color display.

[0077] In this paper, the in-situ polymerization method is selected to prepare cholesteric liquid crystal microcapsules. The preparation of general microcapsules is based on the emulsion formed by traditional emulsifiers, and then shell polymerization is carried out. This study abandons the ordinary emulsion and innovatively selects the CNC-stabilized Pickering emulsion. Then, shell polymerization is carried out through melamine formaldehyde resin to encapsulate the cholesteric liquid crystal, forming cholesteric liquid crystal microcapsules. The CNC-stabilized Pickering emulsion is more stable than the traditional emulsion. Taking the Pickering emulsion as a template, the emulsion interface has a better fitting effect during shell polymerization. At the same time, it has a shorter preparation cycle than other preparation methods and requires less cost for experimental materials.

[0078] A cholesteric liquid crystal microcapsule with a core-shell structure and a preparation method thereof according to the present invention solve the problems existing in the existing liquid crystal microcapsules, such as low encapsulation rate, uneven particle size and complex process, by innovatively combining the Pickering emulsion template and the in-situ polymerization technology. At the same time, the stability and color display performance of the microcapsules in flexible displays are improved. It is a liquid crystal microcapsule with simple process, low cost, controllable and uniform particle size, and good encapsulation.

[0079] The microcapsules prepared by the method of the present invention are composed of a core material of cholesteric liquid crystal and a shell material of melamine resin. The particle size of this microcapsule is controlled below 5 μm, and the shell thickness is about 100 nm or less. The present invention solves the problems of liquid crystal flow, easy contamination and instability in existing liquid crystal display devices. The microcapsule preparation method adopted in the present invention is simple, time-consuming short, has a relatively uniform particle size distribution and low production cost. The cholesteric liquid crystal in the microcapsule can display different colors according to the different sizes of the pitch (P) when stimulated by the outside world. The microcapsules prepared in the present invention separate the cholesteric liquid crystal from the external environment, so that the core material in the shell is neither invaded by the external environment nor overflows to the outside, greatly improving the display effect, and thus achieving a more stable and long-lasting display on the basis of the original color display.

[0080] It should be noted that the above-described embodiments are only the preferred embodiments of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several modifications, improvements, and equivalent substitutions can be made to the present invention, and these modifications, improvements, and equivalent substitutions are also considered to fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing cholesteric liquid crystal microcapsules with a core-shell structure, characterized in that: The steps include: S1: uniformly mixing the nematic liquid crystal and the chiral dopant to obtain a cholesteric liquid crystal solution; S2: Mixing the formaldehyde solution and melamine, adding them into deionized water, and adjusting the pH to 8-9 with an alkaline solution to obtain a melamine formaldehyde prepolymer solution; S3: mixing the solid particulate cellulose nanocrystal stabilized Pickering emulsion with deionized water to obtain a 0.5 wt % mixed solution, and then adding deionized water to dilute to obtain a 0.3 wt % mixed solution; S4: uniformly mixing the cholesteric liquid crystal solution obtained in step S1 and the mixed solution obtained in step S3, and adjusting the pH of the obtained solution to 4-5; S5: adding the melamine formaldehyde prepolymer solution obtained in step S2 dropwise to the solution with a pH of 4 to 5 obtained in step S4, and stirring at 60 to 80° C. to obtain a mixed solution; S6: washing, filtering and drying the mixed solution obtained in step S5 to obtain cholesteric liquid crystal microcapsule powder.

2. The method for preparing cholesteric liquid crystal microcapsules with a core-shell structure according to claim 1, characterized in that: In step S1, the nematic liquid crystal is E7 or SLC-1717, and the chiral dopant is R6N, R811 or chiral dopant Q.

3. The method for preparing cholesteric liquid crystal microcapsules with a core-shell structure according to claim 1 or 2, characterized in that: In step S1, the nematic liquid crystal is SLC-1717, and the chiral dopant is R6N, wherein the mass ratio of SLC-1717 to R6N is 15:

1.

4. The method for preparing cholesteric liquid crystal microcapsules with a core-shell structure according to claim 1 or 2, characterized in that: In step S1, the nematic liquid crystal is E7, and the chiral dopant is R811, wherein the mass ratio of E7 to R811 is 3.3:

1.

5. The method for preparing cholesteric liquid crystal microcapsules with a core-shell structure according to claim 1 or 2, characterized in that: In step S1, the nematic liquid crystal is SLC-1717, and the chiral dopant is chiral dopant Q, wherein the mass ratio of SLC-1717 to chiral dopant Q is 20:

1.

6. The method for preparing cholesteric liquid crystal microcapsules with a core-shell structure according to claim 1, characterized in that: In step S2, the mass ratio of the formaldehyde solution, melamine and deionized water is (0.1-0.4):(0.05-0.1):(2-3).

7. The method for preparing cholesteric liquid crystal microcapsules with a core-shell structure according to claim 1, characterized in that: In step S5, dropwise addition is performed using a syringe at a dropping speed of 1 to 3 mL / min, and the mixed solution of the melamine formaldehyde prepolymer solution obtained in step S2 and the emulsion obtained in step S4 is stirred at a speed of 300 to 1000 rpm at 60 to 80°C.

8. The method for preparing cholesteric liquid crystal microcapsules with a core-shell structure according to claim 1, characterized in that: In step S6, the mixed solution obtained in step S5 is allowed to stand and cool, washed with deionized water for multiple times, filtered, and dried in a vacuum drying oven at 40° C. overnight. Thereafter, the mixed solution is dispersed in a centrifuge tube filled with alcohol, and the agglomerated microcapsules are dispersed by ultrasound to obtain cholesteric liquid crystal microcapsule powder.

9. A cholesteric liquid crystal microcapsule prepared by the method according to any one of claims 1 to 8, characterized in that: The core material of the cholesteric liquid crystal microcapsule is a cholesteric liquid crystal composed of a nematic liquid crystal and a chiral dopant, and the shell material is a melamine formaldehyde resin.

10. Use of the cholesteric liquid crystal microcapsule according to claim 9 in a flexible display.

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