Blue-phase liquid crystal quantum dot hybrid film and preparation method thereof

Abstract

The invention discloses a blue-phase liquid crystal quantum dot hybrid film and a preparation method thereof, and belongs to the technical field of flexible liquid crystal display, and a used liquid crystal composite system comprises micromolecular nematic liquid crystal, a chiral agent, a polymerizable liquid crystal monomer, a photoinitiator and quantum dots; the mass percent of the chiral agent is 3%, the mass percent of the polymerizable liquid crystal monomer is 20-30%, the mass percent of the photoinitiator is 1%, the mass percent of the cross-linking agent is 6%, the mass percent of the quantum dot is 0.1%, and the balance is the micromolecular nematic liquid crystal. According to the blue-phase liquid crystal quantum dot hybrid thin film, the performance of the hybrid thin film in the optical aspect is optimized through the twisting effect of a macromolecular network, and the blue-phase liquid crystal quantum dot hybrid thin film is suitable for flexible display.

Description

Technical Field

[0001] The present invention relates to a blue phase liquid crystal quantum dot hybrid film and a preparation method thereof, and in particular to a blue phase liquid crystal / quantum dot hybrid film with both super reflection and circular polarization and a preparation method thereof, belonging to the technical field of flexible liquid crystal display. Background Art

[0002] Blue phase liquid crystal was first discovered in the 1970s and initially appeared in the transition phase of cholesteric phase liquid crystal. Blue phase liquid crystal has three main structures: blue phase I, blue phase II (highly ordered three-dimensional crystal structure) and blue phase III (disordered structure). It has sensitive responsiveness in terms of electricity, light, magnetism, heat, mechanical force, solvent or humidity response.

[0003] Blue phase liquid crystals have several drawbacks: 1. They exist in a very narrow temperature range, typically only a few degrees. This is due to structural defects in the blue phase, which renders it highly unstable. 2. Blue phase liquid crystals typically have a multi-domain structure, consisting of multiple small domains. Because each domain reflects light based on its orientation and the randomly distributed lattice direction, this reduces the reflectivity of the blue phase liquid crystal. The reflectivity of single-domain blue phase liquid crystals is much higher than that of multi-domain blue phase liquid crystals. 3. Stimuli-responsive blue phase liquid crystals typically exhibit low sensitivity, poor stability, and incomplete reversibility, making them difficult to apply in a wider range of applications.

[0004] In order to make blue phase liquid crystal have better reflective properties and maintain its own properties at room temperature, photopolymerization is used to broaden the temperature range of blue phase liquid crystal, thereby maintaining its own properties and being applied in display, anti-counterfeiting, industrialization and other fields, which is of great significance. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a blue phase liquid crystal quantum dot hybrid film, which utilizes the circular polarization of blue phase liquid crystal-induced quantum dots to optimize its circular polarization performance and optical properties, improve the comprehensive performance of the hybrid film, and is used in the field of flexible liquid crystal displays.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0007] A blue phase liquid crystal quantum dot hybrid film, wherein the liquid crystal composite system comprises small molecule nematic liquid crystal, a chiral agent, a polymerizable liquid crystal monomer, a crosslinking agent, a photoinitiator and quantum dots; the mass percentage of the chiral agent is 3%, the mass percentage of the polymerizable liquid crystal monomer is 20%-30%, the mass percentage of the crosslinking agent is 6%, the mass percentage of the photoinitiator is 1%, the mass percentage of the quantum dots is 0.1%, and the balance is small molecule nematic liquid crystal.

[0008] Preferably, the small molecule nematic liquid crystal is HTG135200.

[0009] Preferably, the chiral agents are R5011 and S5011; and the polymerizable liquid crystal monomer is C6M.

[0010] Preferably, the photoinitiator is IRG651.

[0011] Preferably, the quantum dots are Q1525.

[0012] Preferably, the cross-linking agent is TMPTA.

[0013] Preferably, the mass percentage of the polymerizable liquid crystal monomer is 25%.

[0014] Preferably, the mass percentage of the small molecule nematic liquid crystal is 60%-70%.

[0015] The preparation method of the blue phase liquid crystal quantum dot hybrid film comprises the following steps:

[0016] (1) mixing a chiral agent, a cross-linking agent, a polymerizable small molecule liquid crystal, a small molecule nematic liquid crystal, and quantum dots in proportion, adding dichloromethane, heating in a water bath, and dissolving and mixing to obtain a liquid crystal polymer 1;

[0017] (2) mixing an opposite chiral agent, a cross-linking agent, a polymerizable small molecule liquid crystal, a small molecule nematic liquid crystal, and quantum dots, adding dichloromethane, heating in a water bath, dissolving and mixing, and obtaining liquid crystal polymer 2;

[0018] (3) Using a capillary glass, absorb the liquid crystal polymer 1 in step (1), drop it onto the opening end of the liquid crystal cell, and pour it into the liquid crystal cell through capillary action;

[0019] (4) Heating under a microscope until the isotropic state is completely dark in the viewing field, then cooling to the blue phase temperature range, i.e., green domains appear in the viewing field. This step needs to be repeated 2-3 times, and finally UV curing is performed under the blue phase to obtain a right-handed hybrid film;

[0020] (5) Soaking the right-handed hybrid film obtained in step (4) in n-hexane and waiting for one week to wash out the small molecule liquid crystal in the hybrid film in the liquid crystal cell, while retaining the polymer network twisted by the chiral agent, thereby obtaining a liquid crystal cell having only the polymer network;

[0021] (6) Using a capillary glass, absorb the liquid crystal polymer 2 obtained in step (2), drip it onto the opening end of the liquid crystal cell obtained in step (5), and pour it into the liquid crystal cell through capillary action;

[0022] (7) Repeat the operation of step (4) to finally obtain a hybrid film having both super reflectivity and circular polarization.

[0023] Preferably, in step (1), the mass percentage of the chiral agent is 3%, the mass percentage of the polymerizable liquid crystal monomer is 20%-30%, the mass percentage of the photoinitiator is 1%, the mass percentage of the cross-linking agent is 6%, the mass percentage of the quantum dots is 0.1%, and the remainder is small molecule nematic liquid crystal.

[0024] Preferably, in step (2), the mass percentage of the opposite chiral agent is 3%, the mass percentage of the polymerizable liquid crystal monomer is 20%-30%, the mass percentage of the photoinitiator is 1%, the mass percentage of the cross-linking agent is 6%, the mass percentage of the quantum dots is 0.1%, and the remainder is small molecule nematic liquid crystal.

[0025] Preferably, in step (4), the illumination intensity of the ultraviolet lamp is 80-100 mW / cm 2 .

[0026] Beneficial effects:

[0027] The blue phase liquid crystal quantum dot hybrid film of the present invention utilizes the polymer network inside the liquid crystal cell to optimize its reflective performance and circular polarization, thereby improving the comprehensive performance of the hybrid film and can be used in the field of flexible liquid crystal displays.

[0028] The specific beneficial effects are as follows:

[0029] 1. Different addition amounts of the polymerizable liquid crystal monomer C6M will result in different temperature ranges for the blue phase liquid crystal system. When the addition amount is 20wt%, the system's initial and final temperature range is 73.5℃-75.6℃, with a temperature range of 2.1℃; when the addition amount is 25wt%, the system's initial and final temperature range is 70.7℃-77.9℃, with a temperature range of 7.2℃; when the addition amount is 30wt%, the system's initial and final temperature range is 73.6℃-76.8℃, with a temperature range of 3.2℃. By adjusting the C6M content, it can be seen that the optimal proportion of C6M in this system is 25wt%;

[0030] 2. The polymerizable liquid crystal monomer C6M has a beneficial effect on blue phase liquid crystal quantum dot hybrid films. In the self-assembly of C6M and blue phase liquid crystals, its role is similar to that of small molecule nematic liquid crystals. Together with the nematic liquid crystals and chiral agents, it assembles into a blue phase periodic helical structure. After UV curing, the monomer forms a polymer network, which stabilizes the internal structure of the hybrid film.

[0031] 3. In terms of mechanical strength, the addition of polymerizable liquid crystal monomers improves the robustness of the hybrid film. In terms of optical properties, when the polymerizable liquid crystal monomers are added to a certain extent in the system, they will show their anchoring and orientation effect on the liquid crystal, thereby improving the reflectivity.

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not mean to limit the scope of protection of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1-1 This is a schematic diagram of the preparation process of the blue phase liquid crystal quantum dot hybrid film in Example 1 of the present invention;

[0034] Figure 1-2 This is a schematic diagram of the technical process for preparing a blue phase liquid crystal quantum dot hybrid film in Example 1 of the present invention;

[0035] Figure 2-1 is a polarized micrograph of the blue phase liquid crystal quantum dot hybrid film of Experimental Example 1 of the present invention;

[0036] Figure 2-2 is the Kossel polarization diagram of the blue phase liquid crystal quantum dot hybrid film in Example 1 of the present invention;

[0037] Figure 3 : are the reflection spectra of the blue phase liquid crystal / quantum dot hybrid film before and after washing in Example 1 of the present invention and that of Comparative Example 1 before and after washing;

[0038] Figure 4 The fluorescence spectra of the blue phase liquid crystal / quantum dot hybrid film before and after washing in Example 1 of the present invention and the fluorescence spectra of the comparative example 1 before and after washing;

[0039] Figure 5-1 is a comparison diagram of the circular polarization (CPL) intensity of Example 1 of the present invention and Comparative Example 1;

[0040] Figure 5-2 is the asymmetry factor (g lum ) comparison chart. DETAILED DESCRIPTION

[0041] Unless otherwise specified, in the following embodiments of the present invention, the required raw materials and auxiliary agents are conventional raw materials and auxiliary agents available on the market in this technical field, the required reaction equipment are conventional reaction equipment, the reaction conditions are conventional conditions, and the required testing equipment and methods are conventional testing equipment and methods.

[0042] Comparative Example 1

[0043] The steps for preparing a super reflective blue phase liquid crystal film are as follows:

[0044] (1) 0.06 g of chiral agent R5011, 0.12 g of crosslinking agent (TMPTA), 0.5 g of polymerizable small molecule liquid crystal (HTG135200), and 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60°C for 8 h to dissolve and mix, thereby obtaining liquid crystal polymer 1;

[0045] (2) 0.06 g of chiral agent S5011, 0.12 g of crosslinking agent (TMPTA), 0.5 g of polymerizable small molecule liquid crystal (HTG135200) and 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60 °C for 8 h to dissolve and mix, thereby obtaining liquid crystal polymer 2;

[0046] (3) Using a capillary glass, absorb the liquid crystal polymer 1 obtained in step (1), drip it onto the opening end of the liquid crystal cell, and pour it into the liquid crystal cell through capillary action;

[0047] (4) Heating is performed under a microscope. After the temperature is raised to the isotropic state and the field of view is pitch black, the temperature is lowered to the blue phase temperature range, that is, green domains appear in the field of view. This step needs to be repeated 2-3 times. Finally, ultraviolet curing is performed under the blue phase with a light intensity of 80mW / cm 2 , the illumination time is 120s, and a right-handed blue phase film is obtained;

[0048] (5) Soaking the blue phase film obtained in step (4) in n-hexane and waiting for one week, the purpose is to wash out the small molecule liquid crystal in the blue phase polymer film in the liquid crystal cell, while retaining the polymer network after the chiral agent twisting, to obtain a liquid crystal cell with only the polymer network;

[0049] (6) Using a capillary glass, absorb the liquid crystal polymer 2 obtained in step (2), drip it onto the open end of the liquid crystal box obtained in step (5), and pour it into the liquid crystal box through capillary action;

[0050] (7) Repeat the operation of step (4) to finally obtain a blue phase film with super reflection.

[0051] Example 1

[0052] like Figure 1-1 FIG. 1 is a schematic diagram of the preparation process of the blue phase liquid crystal quantum dot hybrid film in Example 1 of the present invention;

[0053] The preparation steps of blue phase liquid crystal quantum dot hybrid film are as follows:

[0054] (1) 0.06 g of chiral agent R5011, 0.12 g of crosslinking agent (TMPTA), 0.4 g of polymerizable small molecule liquid crystal (C6M), 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.), and 0.002 g of green quantum dots Q1525 (Wuhan Jiayuan Quantum Dot Technology Development Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60 °C for 8 h to dissolve and mix, thereby obtaining liquid crystal polymer 1;

[0055] (2) 0.06 g of chiral agent S5011, 0.12 g of crosslinking agent (TMPTA), 0.4 g of polymerizable small molecule liquid crystal (C6M), 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.) and 0.002 g of quantum dot Q1525 (Wuhan Jiayuan Quantum Dot Technology Development Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60 ° C for 8 h to dissolve and mix to obtain liquid crystal polymer 2;

[0056] (3) Using a capillary glass, absorb the liquid crystal polymer 1 in step (1), drop it onto the opening end of the liquid crystal cell, and pour it into the liquid crystal cell through capillary action;

[0057] (4) Heating is performed under a microscope. After the temperature is raised to the isotropic state and the field of view is pitch black, the temperature is lowered to the blue phase temperature range, that is, green domains appear in the field of view. This step needs to be repeated 2-3 times. Finally, ultraviolet curing is performed under the blue phase with a light intensity of 80mW / cm 2 , the illumination time is 120s, and a right-handed hybrid film is obtained;

[0058] (5) Soaking the right-handed hybrid film obtained in step (4) in n-hexane and waiting for one week to wash out the small molecule liquid crystal in the hybrid film in the liquid crystal cell, while retaining the polymer network twisted by the chiral agent, thereby obtaining a liquid crystal cell having only the polymer network;

[0059] (6) Using a capillary glass, absorb the liquid crystal polymer 2 obtained in step (2), drip it onto the opening end of the liquid crystal cell obtained in step (5), and pour it into the liquid crystal cell through capillary action;

[0060] (7) Repeat the operation of step (4) to finally obtain a hybrid film 1 having both super reflectivity and circular polarization.

[0061] Example 2

[0062] The preparation steps of blue phase liquid crystal quantum dot hybrid film are as follows:

[0063] (1) 0.06 g of chiral agent R5011, 0.12 g of crosslinking agent (TMPTA), 0.5 g of polymerizable small molecule liquid crystal (C6M), 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.), and 0.002 g of quantum dot Q1525 (Wuhan Jiayuan Quantum Dot Technology Development Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60 ° C for 8 h to dissolve and mix to obtain liquid crystal polymer 1;

[0064] (2) 0.06 g of chiral agent S5011, 0.12 g of crosslinking agent (TMPTA), 0.5 g of polymerizable small molecule liquid crystal (C6M), 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.) and 0.002 g of quantum dot Q1525 (Wuhan Jiayuan Quantum Dot Technology Development Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60 ° C for 8 h to dissolve and mix to obtain liquid crystal polymer 2;

[0065] (3) Using a capillary glass to absorb the liquid crystal polymer in step (1), drip it onto the opening end of the liquid crystal box, and pour it into the liquid crystal box through capillary action;

[0066] (4) Heating is performed under a microscope. After the temperature is raised to the isotropic state and the field of view is pitch black, the temperature is lowered to the blue phase temperature range, that is, green domains appear in the field of view. This step needs to be repeated 2-3 times. Finally, ultraviolet curing is performed under the blue phase with a light intensity of 80mW / cm 2 , the illumination time is 120s, and a right-handed hybrid film is obtained;

[0067] (5) Soaking the right-handed hybrid film obtained in step (4) in n-hexane and waiting for one week to wash out the small molecule liquid crystal in the hybrid film in the liquid crystal cell, while retaining the polymer network twisted by the chiral agent, thereby obtaining a liquid crystal cell having only the polymer network;

[0068] (6) Using a capillary glass to absorb the liquid crystal polymer 2 in step (2), drip it onto the open end of the liquid crystal box obtained in step (5), and pour it into the liquid crystal box through capillary action;

[0069] (7) Repeat the operation of step (4) to finally obtain a hybrid film 2 having both super reflectivity and circular polarization.

[0070] Example 3

[0071] The preparation steps of blue phase liquid crystal quantum dot hybrid film are as follows:

[0072] (1) 0.06 g of chiral agent R5011, 0.12 g of crosslinking agent (TMPTA), 0.6 g of polymerizable small molecule liquid crystal (C6M), 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.), and 0.002 g of quantum dot Q1525 (Wuhan Jiayuan Quantum Dot Technology Development Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60 ° C for 8 h to dissolve and mix to obtain liquid crystal polymer 1;

[0073] (2) 0.06 g of chiral agent S5011, 0.12 g of crosslinking agent (TMPTA), 0.6 g of polymerizable small molecule liquid crystal (C6M), 1.3 g of small molecule nematic liquid crystal HTG135200 (Jiangsu Hecheng Display Materials Co., Ltd.) and 0.002 g of quantum dot Q1525 (Wuhan Jiayuan Quantum Dot Technology Development Co., Ltd.) were mixed, 1 ml of dichloromethane was added, and the mixture was heated in a water bath at 60 ° C for 8 h to dissolve and mix to obtain liquid crystal polymer 2;

[0074] (3) Using a capillary glass to absorb the liquid crystal polymer in step (1), drip it onto the opening end of the liquid crystal box, and pour it into the liquid crystal box through capillary action;

[0075] (4) Heating is performed under a microscope. After the temperature is raised to the isotropic state and the field of view is pitch black, the temperature is lowered to the blue phase temperature range, that is, green domains appear in the field of view. This step needs to be repeated 2-3 times. Finally, ultraviolet curing is performed under the blue phase with a light intensity of 80mW / cm 2 , the illumination time is 120s, and a right-handed hybrid film is obtained;

[0076] (5) Soaking the right-handed hybrid film obtained in step (4) in n-hexane and waiting for one week, the purpose is to wash out the small molecule liquid crystal in the hybrid film in the liquid crystal cell, while retaining the polymer network after the chiral agent twisting, to obtain a liquid crystal cell with only the polymer network;

[0077] (6) Using a capillary glass, absorb the liquid crystal polymer 2 obtained in step (2), drip it onto the opening end of the liquid crystal cell obtained in step (5), and pour it into the liquid crystal cell through capillary action;

[0078] (7) Repeat the operation of step (4) to finally obtain a hybrid film 3 having both super reflectivity and circular polarization.

[0079] The present invention adopts a mixing method with quantum dots to make it have super reflection, circular polarization and fluorescence properties coexisting, and prepares a blue phase liquid crystal quantum dot hybrid film.

[0080] Quantum dots are extremely small semiconductor nanocrystals, approximately 2-10 nanometers in diameter, that exhibit unique quantum effects. By adjusting the size of quantum dots, their emission color can be controlled. Their high brightness, tunable emission wavelength, and excellent stability give them great potential in displays and biomarkers.

[0081] The present invention studies hybrid films: 1. By combining blue phase liquid crystal with quantum dots, the temperature range of the blue phase liquid crystal is increased by 1.9°C, and an electric field is applied to align the liquid crystal molecules in an orderly manner, thereby reducing the voltage required to convert the blue phase liquid crystal into a negative charge state by 57%; 2. By doping red, green, and blue quantum dots (QDs) into a reconfigurable blue phase liquid crystal elastomer (BPLCE), visualized full-color circular polarization (CPL) is achieved.

[0082] The present invention studies the circular polarization property (CPL) of blue phase liquid crystals as follows: 1. By doping green quantum dots (QDs) into a polymerizable blue phase liquid crystal (BPLC) film, a higher value of circular polarization property (CPL) and an adjustable circular polarization property (CPL) with a relatively large asymmetry factor (glum) of up to -0.846 are achieved through the superposition of peak positions.

[0083] The present invention studies the wash-out and refill method: a CLC mixture with abnormal reflectivity and heat-induced helicity inversion is prepared. When the helicity becomes right-handed at high temperature, the polymerizable monomer is cured under ultraviolet irradiation. Due to the memory effect of the polymer network, when the temperature is reduced to the same pitch, the reflectivity of the blend system exceeds 50%. However, before the polymer network reacts, the reflectivity of the blend system is left-handed. The invention is carried out by injecting right-handed (left-handed) cholesteric liquid crystal into a liquid crystal cell and polymerizing the polymerizable liquid crystal monomer using ultraviolet light; then, the right-handed (left-handed) liquid crystal is washed away, leaving the right-handed (left-handed) polymer network; and then, the left-handed (right-handed) cholesteric liquid crystal is re-injected, finally obtaining a left-handed (right-handed) liquid crystal system with a right-handed (left-handed) polymer network, thereby achieving the purpose of super reflection.

[0084] Since blue phase liquid crystal has its own temperature range, the present invention configures a blue phase liquid crystal polymer with two chiral agents. In addition, after the liquid crystal cell is parallel oriented, the liquid crystal molecules can form a planar texture in the cell, making the cholesteric liquid crystal film performance better; one side of the liquid crystal cell is lipophilic treated to enhance the adhesion of the liquid crystal molecules on this side, avoiding the tearing of the polymer network after the small liquid crystal molecules are removed.

[0085] In the present invention, the cutting and cleaning of the glass substrate are as follows: indium tin oxide conductive glass (ITO glass) is cut into small glass pieces of 2.5 cm × 2 cm using a glass cutter, the cut glass pieces are placed in a dyeing jar filled with detergent, ultrasonically cleaned for 30 minutes, repeated twice, the wastewater is discarded, deionized water is added again, ultrasonically cleaned for 30 minutes, repeated twice, the wastewater is discarded again, anhydrous ethanol is added again, ultrasonically cleaned for 30 minutes, and finally placed in an oven for drying to obtain clean small glass pieces.

[0086] In the present invention, the lipophilic treatment of the glass substrate involves dissolving the silane coupling agent KH-570 in a 1:1 volume ratio of deionized water to isopropyl alcohol to create a 1% by weight lipophilic solution. This solution is then spin-coated onto a clean, dry glass sheet using a benchtop spin coater at a speed of 2000 rpm for 60 seconds. The coated glass sheet is then heated in a 100°C oven for 20 minutes to form an lipophilic layer.

[0087] In the present invention, the orientation treatment of the glass substrate is as follows: the orientation surface is spin-coated on a clean and dry glass sheet using a 3% by mass polyvinyl alcohol (PVA) aqueous solution using a desktop coater at a spin coating speed of 2500 r / min for 30 seconds. The spin-coated glass sheet is placed in a 100°C oven and heated for 1 hour. Then, the PVA-coated side is rubbed 30 times in the same direction with a clean flannel cloth to obtain a parallel orientation surface.

[0088] In the present invention, the treated upper and lower glass slides and 36 μm thick polyethylene terephthalate (PET) film are used as spacers. Figure 1-2 Assemble them together as shown, then heat the prepared liquid crystal to 60℃ and pour it into the liquid crystal box. After heating to 70℃, cool it down to the blue phase temperature range and keep it warm for half an hour. Then use 80mW / cm 2 The sample was irradiated with ultraviolet light for 120 seconds, and the polymerized sample was immersed in n-hexane solution for more than 7 days (the solution was changed every two days) to obtain a polymer network, which was then filled with blue phase liquid crystals of opposite chirality, ultimately obtaining a blue phase liquid crystal filter with super reflection, circular polarization and fluorescence effects.

[0089] In the present invention, after a liquid crystal box is manufactured, a polymer of any chiral agent is filled into the liquid crystal box, and the polymer is photocured by heating and cooling to a blue phase liquid crystal to form a hybrid film. The cured polymer hybrid film is immersed in n-hexane to wash out the small molecule liquid crystal in the hybrid film while maintaining the polymer texture. After washing out, a polymer of an opposite chiral agent is filled into the liquid crystal box. Under the action of the previous polymer texture, the liquid crystal polymer is physically twisted, thereby achieving super-reflective properties.

[0090] Product performance test:

[0091] The samples were characterized using a LEICADM2700M polarizing optical microscope at room temperature. Figure 2-1 As shown in the figure, it is the polarization diagram under the blue phase I state; Figure 2-2 As shown, it is the Kossel polarization diagram of the blue phase liquid crystal / quantum dot hybrid film in Example 1 of the present invention; when quantum dots are not added to the polymer, the film does not produce a fluorescent effect under fluorescence, and it can be seen that the domains of the blue phase are smaller and denser. After adding quantum dots, it is found that the domains of the blue phase liquid crystal become larger, indicating that the quantum dots are filled into the disclination lines of the blue phase liquid crystal, playing a supporting role, making the blue phase liquid crystal more stable within the temperature range.

[0092] The samples of Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention were tested using an AvaSpec-2048FT-SPU fiber optic spectrometer. Figure 3 As shown, the reflectance spectra of Example 1 of the present invention and Comparative Example 1 before washing, after washing, and after refilling are shown. It can be seen from the reflectance spectra that the reflectance of the film is improved by the washing and refilling process. This is because the polymer network after washing also has an orientation effect on the liquid crystal molecules. On the basis of the chiral agent, the blue phase liquid crystal is twisted in the opposite direction, which greatly improves the reflectance of the film. However, if the amount of chiral agent added is too high, the chiral agent itself has the effect of twisting the liquid crystal molecules, which offsets the twisting force of the polymer network and reduces the reflectance.

[0093] The samples of Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention were tested using an F4700 fluorescence spectrometer. Figure 4 As shown in the figure, it is the fluorescence spectra of Example 1 of the present invention and Comparative Example 1 before washing out and after refilling; it can be seen from the fluorescence spectra that the fluorescence intensity of the film is improved by the washing out and refilling process. This is because the polymer network after washing out has a limiting effect on the liquid crystal molecules, which increases the density of the domain and thus improves the stability. On the basis of the cross-linking agent, it plays a microscopic and stabilizing role on the blue phase liquid crystal, so that the fluorescence intensity of the film is greatly improved.

[0094] Use circular polarization test instrument to characterize the sample under test at room temperature: Figure 5-1 As shown, it is a comparison diagram of the circular polarization (CPL) intensity of Example 1 of the present invention and Comparative Example 1, that is, a comparison diagram of the CPL before and after washing; Figure 5-2 The asymmetric factors (g lum ) comparison chart, that is, g before and after washing lumValue comparison chart; when quantum dots are not added to the polymer, under fluorescence, the film has basically no circular polarization effect, and it can be seen that the domain of the blue phase is smaller and denser. After adding quantum dots, it is found that the domain of the blue phase liquid crystal becomes larger, indicating that the quantum dots are filled into the disclination lines of the blue phase liquid crystal, playing a supporting role, making the blue phase liquid crystal more stable in the temperature range, and the circular polarization of the hybrid film becomes larger, and the asymmetry factor, i.e. g lum The larger the value, the stronger the circular polarization of the hybrid film is through the wash-out and refilling method and the addition of quantum dots.

[0095] Application Example 1

[0096] Application of blue phase liquid crystal quantum dot hybrid films in flexible display devices

[0097] The blue phase liquid crystal quantum dot hybrid film in Example 1 of the present invention has good reflective properties and can be sprayed on a flexible substrate for use, or sprayed on a PET film or other flexible substrate to be cured into a liquid crystal film. Based on the unique optical properties of the blue phase liquid crystal, it can realize reflective, bistable color display, and has broad application prospects in flexible displays.

[0098] Application Example 2

[0099] Application of blue phase liquid crystal quantum dot hybrid films in anti-counterfeiting inks

[0100] Liquid crystal inks are the basis of anti-counterfeiting inks and can be used for packaging, document security, advertising brochures, and more. The blue-phase liquid crystal quantum dot hybrid film of Example 1 of the present invention can be used to manufacture inks or optically variable pigments with circular polarization effects. By adding an ink binder, a high-quality ink that is stable at room temperature, has a bright color, and exhibits special anti-counterfeiting properties can be produced.

[0101] The blue phase liquid crystal quantum dot hybrid film of the present invention adds quantum dots to a blue phase liquid crystal polymer to form a liquid crystal composite system, which is then solidified into a liquid crystal cell by a wash-out and refill method. Since the blue phase liquid crystal can induce circular polarization in the quantum dots, the inventors designed to collaboratively incorporate the quantum dots and polymerizable blue phase liquid crystal into the liquid crystal cell. Without changing its internal structure and reflection band, a blue phase liquid crystal quantum dot hybrid film with both super reflection and circular polarization is prepared.

[0102] The present invention prepares a blue phase liquid crystal quantum dot hybrid film by a wash-out and refilling method, thereby improving the optical performance of the film.

[0103] The main innovation of the present invention is to introduce quantum dots into blue phase liquid crystal polymers, and use the wash-out and refill method to use the prepared liquid crystal box as a storage device. The polymer is solidified into a hybrid film through ultraviolet free radical polymerization, and the mass percentage of polymerizable monomers in the hybrid film is regulated to improve its optical reflectivity, circular polarization and the polymerization temperature range of the blue phase. Finally, a blue phase liquid crystal quantum dot hybrid film with both high reflectivity and circular polarization performance is obtained. This material can be used in reflective liquid crystal displays, anti-counterfeiting fields, color filters, etc.

[0104] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail, but do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A blue phase liquid crystal quantum dot hybrid film, wherein the liquid crystal composite system used comprises a small molecule nematic phase liquid crystal, a chiral agent, a polymerizable liquid crystal monomer, a photoinitiator, and quantum dots; the mass percentage of the chiral agent is 3%, the mass percentage of the polymerizable liquid crystal monomer is 20%-30%, the mass percentage of the photoinitiator is 1%, the mass percentage of the cross-linking agent is 6%, the mass percentage of the quantum dots is 0.1%, and the balance is small molecule nematic phase liquid crystal.

2. The blue phase liquid crystal quantum dot hybrid film according to claim 1, characterized in that: The small molecule nematic liquid crystal is HTG135200; the chiral agents are R5011 and S5011; the polymerizable liquid crystal monomer is C6M; the photoinitiator is IRG651; and the quantum dot is Q1525.

3. The blue phase liquid crystal quantum dot hybrid film according to claim 1, characterized in that: The mass percentage of the polymerizable liquid crystal monomer is 25%.

4. The blue phase liquid crystal quantum dot hybrid film according to claim 1, characterized in that: The mass percentage of the small molecule nematic liquid crystal is 60%-70%.

5. A method for preparing the blue phase liquid crystal quantum dot hybrid film according to any one of claims 1 to 4, comprising the following steps: (1) mixing a chiral agent, a cross-linking agent, a polymerizable small molecule liquid crystal, a small molecule nematic liquid crystal, and quantum dots in proportion, adding dichloromethane, heating in a water bath, and dissolving and mixing to obtain a liquid crystal polymer 1; (2) mixing an opposite chiral agent, a cross-linking agent, a polymerizable small molecule liquid crystal, a small molecule nematic liquid crystal, and quantum dots, adding dichloromethane, heating in a water bath, dissolving and mixing, and obtaining liquid crystal polymer 2; (3) Using a capillary glass, absorb the liquid crystal polymer 1 in step (1), drop it onto the opening end of the liquid crystal cell, and pour it into the liquid crystal cell through capillary action; (4) Heating under a microscope until the isotropic state is completely dark in the viewing field, then cooling to the blue phase temperature range, i.e., green domains appear in the viewing field. This step needs to be repeated 2-3 times, and finally UV curing is performed under the blue phase to obtain a right-handed hybrid film; (5) Soaking the right-handed hybrid film obtained in step (4) in n-hexane and waiting for one week to wash out the small molecule liquid crystal in the hybrid film in the liquid crystal cell, while retaining the polymer network twisted by the chiral agent, thereby obtaining a liquid crystal cell having only the polymer network; (6) Using a capillary glass, absorb the liquid crystal polymer 2 obtained in step (2), drip it onto the opening end of the liquid crystal cell obtained in step (5), and pour it into the liquid crystal cell through capillary action; (7) Repeat the operation of step (4) to finally obtain a hybrid film having both super reflectivity and circular polarization.

6. The method for preparing a blue phase liquid crystal quantum dot hybrid film according to claim 5, characterized in that: In step (1), the mass percentage of the chiral agent is 3%, the mass percentage of the polymerizable liquid crystal monomer is 20%-30%, the mass percentage of the photoinitiator is 1%, the mass percentage of the cross-linking agent is 6%, the mass percentage of the quantum dots is 0.1%, and the remainder is small molecule nematic liquid crystal.

7. The method for preparing a blue phase liquid crystal quantum dot hybrid film according to claim 5, characterized in that: In step (2), the mass percentage of the opposite chiral agent is 3%, the mass percentage of the polymerizable liquid crystal monomer is 20%-30%, the mass percentage of the photoinitiator is 1%, the mass percentage of the cross-linking agent is 6%, the mass percentage of the quantum dots is 0.1%, and the remainder is small molecule nematic liquid crystal.

8. The method for preparing a blue phase liquid crystal quantum dot hybrid film according to claim 5, characterized in that: In step (4), the illumination intensity of the ultraviolet lamp is 80-100 mW / cm 2 .

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