Liquid crystal mixture and liquid crystal intelligent window

Abstract

The invention belongs to the technical field of liquid crystal, and particularly relates to a liquid crystal mixture and a liquid crystal intelligent window. The liquid crystal mixture comprises nematic phase liquid crystal and a chiral agent, the nematic phase liquid crystal comprises a bent monomer, and the reflection wavelength of the liquid crystal mixture is 0.3-4 microns. According to the liquid crystal mixture disclosed by the invention, the existence of a shortened transition plane state (b) can be realized by adding the bent monomer, and a spiral removal state (d) is switched to a reflection state (e) of a plane texture state. Meanwhile, by utilizing the principle that liquid crystals are cholesteric liquid crystals and can reflect specific wavelengths, the wavelengths are set to be visible light and infrared light areas, and the effect of adjusting the temperature is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of liquid crystal technology, and specifically relates to a liquid crystal mixture and a liquid crystal smart window, and relates to applications including indoor and outdoor smart dimming glass (including film systems) for buildings, and has applications in front windshields, rearview mirrors, side windows and skylights of mobile devices such as airplanes and cars. It has functions such as privacy protection, infrared radiation protection, and image display. Background Art

[0002] The existing energy-saving dimming glass used in buildings or smart glass for transportation mainly adopts glass technologies such as PDLC (polymer dispersed liquid crystal), SPD (suspended particles) and EC (electrochromic). Among them, the transparency and fogging of PDLC dimming glass are determined by the liquid crystal molecules inside it. After the alternating current is applied, the liquid crystal molecules are arranged in order, the incident light can pass directly through, and the glass is transparent; when the power is not applied, the liquid crystal molecules are arranged in disorder, the incident light is scattered and passed through, and the glass is fogged and opaque. The principle of SPD dimming glass is to disperse particles with oriented light absorption characteristics in the suspension. When the power is not applied, the particles in Brownian motion are randomly arranged and can absorb more than 99% of visible light. When an AC voltage of 110V is applied, the particles are oriented and arranged, and light can pass through. EC dimming glass uses redox reaction to achieve the dimming of glass. The commonly used electrochromic material is tungsten trioxide. Usually the glass is transparent. Under the drive of +3V DC voltage, the glass will slowly turn black and opaque.

[0003] Most of the liquid crystal formulas in this field use liquid crystals with dyes to achieve energy saving. Some of them use cholesteric liquid crystals (CLC) with dyes as the basis. Figure 1 As shown, when the adjustable cholesteric liquid crystal device is used to quickly switch the liquid crystal state between the reflective state (planar), focal-conic and homeotropic states, the recovery speed of the cholesteric liquid crystal from the vertical state (a) to the planar state (c) is slow and the planar state easily passes through a transitional unstable planar state (b). Although it is a planar state, it has oil streak defects, which will affect the transmittance of the reflective state. It often takes tens of minutes to recover to the reflective state (c) (planar) with high transmittance.

[0004] To solve this problem, the currently common technology is to formulate a cholesteric liquid crystal formulation with a positive nematic liquid crystal and a chiral agent. Select an appropriate liquid crystal cell thickness, configure a phase-matching layer, or add a polymer to form a polymer by heating or light irradiation to improve the switching response speed between the three states of recovery. Or by adding a specific bent monomer structure to improve it. For example, the invention patent with the application number 202210548415.7 discloses a preparation method of a defect-free and fast-switching dye-doped cholesteric liquid crystal smart window, and the specific steps are as follows: Step 1, select a liquid crystal, a bent liquid crystal, a chiral agent, and a dichroic dye, and mix the above raw materials according to a ratio to form a mixture; Step 2, place the mixture on a hot stage and stir at a certain temperature, and then use a pipette to take a small amount of the mixture; Step 3, use ODF or capillary action to inject the mixture into a liquid crystal cell with a cell thickness of 10 microns through a liquid crystal injection port at a temperature of 90-110 °C, and seal it after cooling to obtain a dye-doped cholesteric liquid crystal smart window, which also relies on the dichroic dye to achieve temperature regulation.

[0005] Therefore, a new method is needed to quickly switch the liquid crystal state between the reflective state (planar), the focal-conic texture state, and the de-twisted state (homeotropic alignment). Summary of the Invention

[0006] The present invention aims to solve the above problems and provides a liquid crystal mixture and a liquid crystal smart window, which apply the reflection wavelength to the visible light and infrared light sections, can quickly modulate the liquid crystal state, and shorten the reaction time, and are particularly suitable for a liquid crystal element system with a high cell thickness.

[0007] According to the technical solution of the present invention, the liquid crystal mixture includes a nematic liquid crystal and a chiral agent, and the nematic liquid crystal includes a bent monomer, and the structure of the bent monomer is as follows:

[0008]

[0009] Among them, n = 7, 9, 11;

[0010] R1 is selected from C1-C9 alkyl or substituted alkyl, C1-C9 alkoxy, -C≡N, -N = C = S, -F, -Cl, -CFH2, -CF2H, -CF3, -OCFH2, -OCF2H, -OCF3, -C≡C-H, or -C≡C-C≡N, and the substitution mode of the C1-C9 substituted alkyl is that a single -CH2- is substituted by -CH = CH- or -C≡C-;

[0011] The reflection wavelength of the liquid crystal mixture is 0.3 μm to 4 μm.

[0012] Such asFigure 1 As shown, by adding a bent monomer to the liquid crystal mixture of the present invention, the existence of the transitional planar state (b) can be shortened, and the reflective state (e) of the planar texture state can be switched from the dehelical state (d). At the same time, by utilizing the principle that a cholesteric liquid crystal can reflect a specific wavelength, the wavelength is set in the visible light and infrared light regions to achieve the effect of temperature regulation, and it can be used for building glass or fast-moving transport carriers.

[0013] Specifically, the R1 can be the following chemical groups:

[0014] -n-C n H 2n+1 , (n = 1 - 9);

[0015] -nO-O-C n H 2n +1, (n = 1 - 9);

[0016] -V-CH=CH2;

[0017] -nV-C n H 2n -CH=CH2, (n = 1 - 8);

[0018] -Vn-CH=CH-C n H 2n +1, (n = 1 - 8);

[0019] -nVm-C n H 2n -CH=CH-C m H 2m+1 , (n + m = 2 - 8);

[0020] -N-C≡N;

[0021] -S-N=C=S;

[0022] -F-F;

[0023] -CL-Cl;

[0024] -M-CFH2;

[0025] -D-CF2H;

[0026] -T-CF3;

[0027] -OM-OCFH2;

[0028] -OD-OCF2H;

[0029] -OT-OCF3;

[0030] -A-C≡C-H;

[0031] -An-C≡C-C n H 2n+1 , (n = 0 - 8);

[0032] -AN-C≡C-C≡N.

[0033] In one embodiment of the present invention, the content of the chiral agent in the liquid crystal mixture is 0.1 - 50 wt%, and the cholesteric phase is induced to form by adding the chiral agent to the nematic phase.

[0034] In a specific embodiment, the chiral agent includes one or several of bis[4-(4-pentylcyclohexyl)benzoic acid]1-phenyl-1,2-ethanediyl ester, 2-octyl 4-(4-hexyloxybenzoyloxy)benzoate, 4'-(2-methylbutyl)-4-biphenylcarbonitrile, isosorbide, binaphthol and its derivatives.

[0035] In one embodiment of the present invention, the content of the nematic liquid crystal in the liquid crystal mixture is 10 - 99 wt%, and for example, it can be 10 wt%, 30 wt%, 50 wt%, 70 wt%, 90 wt%, 99 wt%, etc.

[0036] In one embodiment of the present invention, in the nematic liquid crystal, the mass ratio of the bent monomer is 10% - 100%, and for example, it can be 10%, 30%, 50%, 70%, 90%, 100%, etc.

[0037] In one embodiment of the present invention, the birefringence of the nematic liquid crystal is 0.05 - 0.5.

[0038] In one embodiment of the present invention, the liquid crystal mixture further includes a dichroic dye. By adding the dichroic dye, the alignment of the liquid crystal is manipulated by an electrostatic field, so that the hue changes with the electrostatic field, and then color display is completed, which has advantages such as a larger viewing angle, a brighter screen, less radiation, a wider range of uses, bright and comfortable colors, and hue diversity.

[0039] In a specific embodiment, the dichroic dye can be an azo dichroic dye or a naphthalimide dichroic dye. Among them, the N=N bond of the azo dichroic dye can conjugate with the benzene ring, generating a large π bond, thereby reducing the transition electron energy level of the molecular structure to produce dichroism. After doping it into the liquid crystal, the liquid crystal will exhibit many unique optical characteristics; after doping it into the liquid crystal, the liquid crystal will exhibit many unique optical characteristics, and the utilization of these optical characteristics is beneficial to improving the quality of liquid crystal display. The dye molecular structure shows excellent characteristics, such as excellent optical properties, heat resistance, and solubility.

[0040] In one embodiment of the present invention, the concentration of the dichroic dye is 10 ppm to 50%.

[0041] In one embodiment of the present invention, the liquid crystal mixture further comprises one or more of a liquid crystal polymerizable monomer, a non-liquid crystal polymerizable monomer, and a photoinitiator.

[0042] In one embodiment of the present invention, by mass fraction, in the liquid crystal mixture, the content of the liquid crystal polymerizable monomer is 0.1 - 30%, the content of the non-liquid crystal polymerizable monomer is 0.1 - 40%, and the content of the photoinitiator is 0.01 - 1%.

[0043] In a specific embodiment, the liquid crystal polymerizable monomer is a free radical photo-curable monomer, including one or several of acrylate, methacrylate, styryl, and diacetyl, and the number of active functional groups is 1 - 5;

[0044] The non-liquid crystal polymerizable monomer is a cationic photo-curable monomer, including epoxy monomers, vinyl ether monomers, and oxetane monomers, and the number of active functional groups is 1 - 5;

[0045] The photoinitiator can be a free radical photoinitiator and / or a cationic photoinitiator. Under the irradiation of ultraviolet light, visible light, or infrared light, the photoinitiator generates free radicals to cause the reaction to occur, and forms a surface polymer, a polymer network, or a cholesteric liquid crystal polymer droplet. The free radical photoinitiator includes benzil dimethyl ketal or aromatic ketones; the cationic photoinitiator includes diazonium salts, diaryliodonium salts, triaryliodonium salts, alkylsulfonium salts, iron arene salts, sulfonyloxy ketones, and their triarylsilyl ethers.

[0046] The second aspect of the present invention provides a method for preparing a liquid crystal smart window, comprising the following steps,

[0047] Step 1: Provide the above liquid crystal mixture;

[0048] Step 2: Heat and stir the liquid crystal mixture;

[0049] Step 3: Inject the liquid crystal mixture after heating and stirring in Step 2 into a liquid crystal cell to obtain the liquid crystal smart window.

[0050] Further, in Step 2, the temperature of heating and stirring is 100 - 120 °C, for example, it can be 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, etc.; the time is 25 - 40 h, for example, it can be 25 h, 30 h, 35 h, 40 h, etc.

[0051] In an embodiment of the present invention, in step S3, the liquid crystal mixture obtained in step 2 is injected into the liquid crystal cell by using ODF or capillary action.

[0052] Preferably, the ODF process is adopted. Specifically, a liquid crystal dropping machine is used to drop the liquid crystal, and a uniform liquid crystal screen can be formed. After dropping the liquid crystal, in a vacuum, the substrate coated with the frame sealant, the substrate with a high-precision amount of liquid crystal dropped thereon, and the substrate with spacers evenly dispersed are aligned accurately and then bonded together. Then, through processes such as UV irradiation and heating to cure the frame sealant and liquid crystal reorientation, a liquid crystal screen is formed. The method of liquid crystal drop filling in this process has a short time and high efficiency; it is not heated during vacuum cell assembly. The compression ratio of the liquid crystal screen mainly depends on the amount of liquid crystal drops. The spacers can deform accordingly, but the reaction force on the glass substrate is large; the liquid crystal dropping method does not require an injection port, and the frame sealant is hot-pressed directly to seal the liquid crystal in the liquid crystal screen. The hot curing process of the frame sealant also plays a role in reorientation at the same time.

[0053] In an embodiment of the present invention, in step S3, the cell gap of the liquid crystal cell is 3.5 microns, and conductive layers are provided on the inner sides of both ends of the glass.

[0054] In an embodiment of the present invention, in the liquid crystal smart window, the number of helical layers of the cholesteric liquid crystal in the liquid crystal layer is 0.5 to 200 layers.

[0055] In a specific embodiment, the preparation method of the liquid crystal smart window may be as follows:

[0056] Step 1: Provide a liquid crystal mixture, which includes a nematic liquid crystal and a chiral agent. The nematic liquid crystal includes 10% to 100% of a bent monomer, and the structure of the bent monomer is as follows:

[0057]

[0058] Among them, n = 7, 9, 11;

[0059] R1 is selected from C1-C9 alkyl or substituted alkyl, C1-C9 alkoxy, -C≡N, -N=C=S, -F, -Cl, -CFH2, -CF2H, -CF3, -OCFH2, -OCF2H, -OCF3, -C≡C-H, or -C≡C-C≡N. The substitution mode of the C1-C9 substituted alkyl is that a single -CH2- is substituted by -CH=CH- or -C≡C-.

[0060] Step 2: Place the liquid crystal mixture on a hot stage, heat it and stir at a certain temperature so that the liquid crystal mixture dissolves and mixes evenly.

[0061] Step 3: Inject the liquid crystal mixture after heating and stirring in Step 2 into the liquid crystal cell by using ODF or capillary action to obtain a cholesteric liquid crystal smart window.

[0062] The third aspect of the present invention provides a liquid crystal smart window prepared by the above preparation method.

[0063] The technical solution of the present invention has the following advantages compared with the prior art:

[0064] The present invention provides a specific liquid crystal formulation of bistable liquid crystals, combined with a special bent monomer, which eliminates the over-polarized state in the planar state and quickly returns the liquid crystal element from the dehelical state to the reflective state of the planar texture state, and the two are quickly switched; and the reflection wavelength is applied to the visible light and infrared regions, without relying on dichroic dyes. By switching among the planar texture state, the focal conic texture state, and the dehelical state, the switching of light absorption and light scattering is carried out to control the solar radiation flux, thereby reducing the indoor temperature and protecting privacy. Description of the Drawings

[0065] Figure 1 Comparison of the driving paths for quickly returning to the P state.

[0066] Figure 2 Microscopic magnified view of the liquid crystal mixture in Example 1. Detailed Description of the Invention

[0067] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments given are not intended to limit the present invention.

[0068] The present invention provides a liquid crystal mixture, which includes a nematic liquid crystal and a chiral agent. Based on the total weight of the liquid crystal mixture, the proportions of the nematic liquid crystal and the chiral agent are 10-99% and 0.1-50% respectively.

[0069] Among them, the nematic liquid crystal includes a bent monomer (Compound A), and the structure of the bent monomer is as follows:

[0070]

[0071] Among them, n = 7, 9, 11;

[0072] R1 is selected from C1-C9 alkyl or substituted alkyl, C1-C9 alkoxy, -C≡N, -N=C=S, -F, -Cl, -CFH2, -CF2H, -CF3, -OCFH2, -OCF2H, -OCF3, -C≡C-H, or -C≡C-C≡N, and the substitution mode of the C1-C9 substituted alkyl is that a single -CH2- is substituted by -CH=CH- or -C≡C-.

[0073] Specifically, the chiral agent includes one or more of bis[4-(4-pentylcyclohexyl)benzoic acid]1-phenyl-1,2-ethanediyl ester, 2-octyl 4-(4-hexyloxybenzoyloxy)benzoate, 4'-(2-methylbutyl)-4-biphenylcarbonitrile, isosorbide, binaphthol and its derivatives.

[0074] The birefringence of the nematic liquid crystal is 0.05 to 0.5.

[0075] The liquid crystal mixture may further include a dichroic dye with a concentration of 10 ppm to 50%, which may be an azo dichroic dye or a naphthalimide dichroic dye.

[0076] Specifically, the liquid crystal mixture further includes one or more of a liquid crystal polymerizable monomer, a non-liquid crystal polymerizable monomer, and a photoinitiator.

[0077] Among them, the liquid crystal polymerizable monomer is a free radical photocurable monomer, including one or more of acrylates, methacrylates, styryl compounds, and diacetyl compounds, and the number of active functional groups is 1 to 5; the non-liquid crystal polymerizable monomer is a cationic photocurable monomer, including epoxy monomers, vinyl ether monomers, and oxetane monomers, and the number of active functional groups is 1 to 5; the photoinitiator may be a free radical photoinitiator and / or a cationic photoinitiator. The free radical photoinitiator includes benzil dimethyl ketal or aromatic ketones, and the cationic photoinitiator includes diazonium salts, diaryliodonium salts, triaryliodonium salts, alkylsulfonium salts, iron arene salts, sulfonyloxy ketones and their triarylsilyl ethers.

[0078] Using the above liquid crystal mixture to prepare a liquid crystal smart window, the preparation method includes the following steps

[0079] Step 1: Provide the above liquid crystal mixture;

[0080] Step 2: Place the liquid crystal mixture on a hot stage, heat and stir at a temperature of 100 - 120 °C for 25 - 40 h to dissolve and mix the liquid crystal mixture evenly;

[0081] Step 3: Inject the liquid crystal mixture obtained in Step 2 into the liquid crystal cell by ODF or capillary action to obtain a cholesteric liquid crystal smart window.

[0082] Example 1

[0083] This example provides a preparation method for a fast-switching cholesteric liquid crystal smart window, and the specific steps are as follows:

[0084] Step 1, mixing a bending monomer, a liquid crystal polymerizable monomer, a non-liquid crystal polymerizable monomer, a photoinitiator and a chiral agent in a mass ratio of 32.7:27:38:0.5:1.8 to form a liquid crystal mixture C, whose birefringence is 0.3; wherein the bending monomer is compound B, whose structure is as follows, the liquid crystal polymerizable monomer is 2-methyl-1,4-bis(4-(6'-propyleneoxyhexyloxy)benzoyloxy)benzene, the non-liquid crystal polymerizable monomer is 1,4-cyclohexyl dimethanol divinyl ether, the photoinitiator is benzoin dimethyl ether, and the chiral agent is 4-(4-hexyloxybenzoyloxy)benzoic acid-2-octyl ester;

[0085]

[0086] Step 2: Place the liquid crystal mixture C on a hot plate, heat and stir at 110° C. for 30 h to dissolve and mix evenly;

[0087] Step 3: Use the ODF process to inject the liquid crystal mixture C into a liquid crystal box with a cell thickness of 3.5 microns to form a liquid crystal layer. The inner sides of both ends of the liquid crystal box glass are provided with a conductive layer to obtain a cholesteric liquid crystal smart window.

[0088] like Figure 2 As shown, liquid crystal mixture C shows its bending properties under a microscope.

[0089] A voltage was applied to the obtained cholesteric liquid crystal smart window, and the results were as follows:

[0090] When a voltage E = 25 V, 60 Hz is directly applied, the texture switches from the reflective state (a) (planar) or the vertical state (c) (homeotropic) of the planar texture state to the focal-conic texture state.

[0091] When a voltage Ec=65V, 60Hz is directly applied, the reflective state (a) of the planar texture state or the focal-conic texture state (b) switches to the homeotropic state (c).

[0092] In the homeotropic state (c), the original voltage can be maintained, but after switching the low frequency to the high frequency (50KHz), the liquid crystal will instantly convert from the reflective state (a) (planar) state to the planar texture state. After releasing the voltage, it maintains the steady state and its transmittance. Unlike ordinary cholesteric liquid crystal materials, when switching at a fast speed, the recovery speed of cholesteric liquid crystal from the homeotropic state to the planar state is slow and the planar state is prone to oil streak defects, which affects the transmittance of the reflective state.

[0093] The proposed cholesteric liquid crystal can shorten the existence of the transitional planar state (b) and switch from the de-twisted state (homeotropic alignment) (d) to the reflective state of the planar texture state (e) by adding Compound A, and the reaction time is shortened from dozens of minutes to the second level. For the application of smart windows with a thick liquid crystal cell thickness, the reflection wavelength is defined as the visible light and infrared regions. By switching among the planar texture state, the focal conic texture state, and the de-twisted state, the switching between light absorption and light scattering is carried out to control the solar radiation flux and thus reduce the indoor temperature and protect privacy.

[0094] Example 2

[0095] This example provides a preparation method for a fast-switching cholesteric liquid crystal smart window, and the specific steps are as follows:

[0096] Step 1: Mix a bent monomer, a liquid crystalline polymerizable monomer, a non-liquid crystalline polymerizable monomer, a photoinitiator, and a chiral agent in a mass ratio of 41:22:34.7:0.5:1.8 to form a liquid crystal mixture C, and its birefringence is 0.34; among them, the bent monomer is Compound B, the liquid crystalline polymerizable monomer is 2-methyl-1,4-bis(4-(6'-acryloyloxyhexyloxy)benzoyloxy)benzene, the non-liquid crystalline polymerizable monomer is 1,4-cyclohexanedimethanol divinyl ether, the photoinitiator is benzoin dimethyl ether, and the chiral agent is 2-octyl 4-(4-hexyloxybenzoyloxy)benzoate;

[0097] Step 2: Place the liquid crystal mixture C on a hot stage, heat and stir at 110 °C for 30 h to dissolve and mix evenly;

[0098] Step 3: Inject the liquid crystal mixture C into a liquid crystal cell with a cell thickness of 3.5 microns by the ODF process to form a liquid crystal layer, and there are conductive layers on the inner sides of both ends of the liquid crystal cell glass to obtain a cholesteric liquid crystal smart window.

[0099] Example 3

[0100] This example provides a preparation method for a fast-switching cholesteric liquid crystal smart window, and the specific steps are as follows:

[0101] Step 1: Mix a bent monomer, a liquid-crystalline polymerizable monomer, a non-liquid-crystalline polymerizable monomer, a photoinitiator, and a chiral agent in a mass ratio of 32.7:27:38:0.5:1.8 to form a liquid crystal mixture C with a birefringence of 0.34. Among them, the bent monomer is compound D with the following structure, the liquid-crystalline polymerizable monomer is 2-methyl-1,4-bis(4-(6'-acryloyloxyhexyloxy)benzoyloxy)benzene, the non-liquid-crystalline polymerizable monomer is 1,4-cyclohexanedimethanol divinyl ether, the photoinitiator is benzoin dimethyl ether, and the chiral agent is 2-octyl 4-(4-hexyloxybenzoyloxy)benzoate;

[0102]

[0103] Step 2: Place the liquid crystal mixture C on a hot stage, heat it, and stir it at 110 °C for 30 h to dissolve and mix it evenly;

[0104] Step 3: Inject the liquid crystal mixture C into a liquid crystal cell with a cell thickness of 3.5 μm using the ODF process to form a liquid crystal layer. Conductive layers are provided on the inner sides of both ends of the liquid crystal cell glass to obtain a cholesteric liquid crystal smart window.

[0105] Example 4

[0106] This example provides a method for preparing a fast-switching cholesteric liquid crystal smart window, and the specific steps are as follows:

[0107] Step 1: Mix a bent monomer, a liquid-crystalline polymerizable monomer, a non-liquid-crystalline polymerizable monomer, a photoinitiator, a chiral agent, and a dichroic dye in a mass ratio of 32.6:27:38:0.5:1.8:0.1 to form a liquid crystal mixture C with a birefringence of 0.3. Among them, the bent monomer is compound B, the liquid-crystalline polymerizable monomer is 2-methyl-1,4-bis(4-(6'-acryloyloxyhexyloxy)benzoyloxy)benzene, the non-liquid-crystalline polymerizable monomer is 1,4-cyclohexanedimethanol divinyl ether, the photoinitiator is benzoin dimethyl ether, the chiral agent is 2-octyl 4-(4-hexyloxybenzoyloxy)benzoate, and the dichroic dye is an azo dichroic dye;

[0108] Step 2: Place the liquid crystal mixture C on a hot stage, heat it, and stir it at 110 °C for 30 h to dissolve and mix it evenly;

[0109] Step 3: Inject the liquid crystal mixture C into a liquid crystal cell with a cell thickness of 3.5 μm using the ODF process to form a liquid crystal layer. Conductive layers are provided on the inner sides of both ends of the liquid crystal cell glass to obtain a cholesteric liquid crystal smart window.

[0110] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A liquid crystal mixture, characterized in that, Comprising a nematic liquid crystal and a chiral agent, the nematic liquid crystal comprising a bent monomer, the structure of the bent monomer being as follows: wherein, n = 7, 9, 11; R1 is selected from C1-C9 alkyl or substituted alkyl, C1-C9 alkoxy, -C≡N, -N=C=S, -F, -Cl, -CFH2, -CF2H, -CF3, -OCFH2, -OCF2H, -OCF3, -C≡C-H, or -C≡C-C≡N, and the substitution mode of the C1-C9 substituted alkyl is that a single -CH2- is substituted by -CH=CH- or -C≡C-; The reflection wavelength of the liquid crystal mixture is 0.3 μm to 4 μm.

2. The liquid crystal mixture according to claim 1, characterized in that, The content of the chiral agent in the liquid crystal mixture is 0.1 to 50 wt%.

3. The liquid crystal mixture according to claim 1, characterized in that, The content of the nematic liquid crystal in the liquid crystal mixture is 10 to 99 wt%.

4. The liquid crystal mixture according to claim 1, characterized in that, In the nematic liquid crystal, the mass ratio of the bent monomer is 10% to 100%.

5. The liquid crystal mixture according to claim 1, 3 or 4, characterized in that, The birefringence of the nematic liquid crystal is 0.05 to 0.

5.

6. The liquid crystal mixture according to claim 1, characterized in that, The liquid crystal mixture further comprises a dichroic dye.

7. The liquid crystal mixture according to claim 6, characterized in that, The concentration of the dichroic dye is 10 ppm to 50%.

8. The liquid crystal mixture according to claim 1, characterized in that, The liquid crystal mixture further comprises one or more of a liquid crystalline polymerizable monomer, a non-liquid crystalline polymerizable monomer, and a photoinitiator.

9. A preparation method of a liquid crystal smart window, characterized in that, Comprising the following steps, Step 1: Provide the liquid crystal mixture according to any one of claims 1-8; Step 2: Heat and stir the liquid crystal mixture; Step 3: Inject the liquid crystal mixture after heating and stirring in Step 2 into a liquid crystal cell to obtain the liquid crystal smart window.

10. A liquid crystal smart window prepared by the preparation method according to claim 9.

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