An electrically driven scattering state - wide spectrum reflective state - transparent state transition liquid crystal / polymer light modulation and display device

Abstract

The application belongs to the field of liquid crystal materials, and relates to a liquid crystal / polymer light-adjusting and display device capable of realizing scattering state-reflective state-transparent state transition under electric driving. The liquid crystal material comprises a bent liquid crystal molecule mixture with a twisted bent nematic phase, a nematic phase liquid crystal mixture and a chiral dopant, and the liquid crystal material can form an inclined helical arrangement under electric driving. The application provides a flexible liquid crystal / polymer composite device capable of realizing three-state transition of 'opaque state', 'wide-spectrum reflective state' and 'transparent state' under electric driving and a preparation method thereof by using an inclined helical cholesteric phase liquid crystal to replace traditional liquid crystal materials. The'reflective state' can realize dynamic regulation and control of selective reflection in a wide light spectrum range from full visible light to near infrared, and greatly expands the performance and application of a traditional liquid crystal / polymer composite device.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal materials, specifically relating to a tilted helical cholesteric liquid crystal material, and the liquid crystal / polymer composite material with electrically driven scattering state-broad spectrum reflective state-transparent state transition and liquid crystal / polymer dimming and display device obtained therefrom. Background Technology

[0002] De Gennes and Mayer theoretically predicted the twist-bending change in the cholesteric phase structure when molecules are arranged in a skewed helical pattern, based on the interaction laws between polar molecules. The dimer bent molecule CB7CB confirmed the existence of this change, and this new phase was named the twisted-bending nematic phase. It possesses a tilted helical structure with a nanoscale pitch and provides the first example in nature of a non-chiral molecule breaking mirror symmetry, attracting widespread attention from researchers. By doping bent liquid crystal molecules with a twisted-bending nematic phase into a nematic liquid crystal mixture to reduce its viscosity, and after the chiral dopant satisfies its chiral domain, a tilted helical cholesteric phase structure can be induced under an applied electric field. In the tilted helical cholesteric phase, the long axis of the molecule forms a constant angle with the helical axis, unlike the traditional cholesteric phase structure where the helical axis is perpendicular to the helical axis. Compared with traditional cholesteric liquid crystals, the biggest advantage of the tilted helical cholesteric liquid crystal is that it can change the pitch without altering the molecular orientation by applying an external electric field. Within a suitable voltage range, the pitch of the tilted helical cholesteric liquid crystal decreases with increasing voltage. Therefore, selective reflection dynamic control of light across a wide spectral range, from ultraviolet to visible light and then to near-infrared light, can be achieved through electric drive. This makes it promising for applications in information displays, smart windows, tunable filters, and other fields.

[0003] Although tilted helical cholesteric liquid crystals possess unique and excellent electro-optic properties and broad prospects for optical applications, it is generally difficult to fabricate bistable electro-optic devices by directly sandwiching liquid crystal materials between two substrates. This is because the different optical states of pure liquid crystal materials are easily disrupted by external interference, and their poor optical stability makes them unsuitable for long-term use. This is due to the poor mechanical strength and low viscosity of pure liquid crystal materials. To further improve the device performance of tilted helical cholesteric liquid crystals and expand their application scenarios, polymer networks can be introduced into the liquid crystal bulk to construct tilted helical cholesteric liquid crystal / polymer composite materials.

[0004] Liquid crystal / polymer composites constructed by introducing polymer networks into liquid crystal materials generally come in three forms: The first is polymer-stabilized liquid crystal. In this system, the liquid crystal is a continuous matrix, while a small amount of polymer network (usually a few percent by mass; otherwise, the stability of the oriented polymer network would be too strong, and the device could not be driven by an external field) is doped into the anisotropic fluid to stabilize the alignment of liquid crystal molecules under different optical states. Due to the low polymer concentration, smart windows based on polymer-stabilized liquid crystals exhibit high transparency and low driving voltage. However, under scattering conditions, the haze of the polymer-stabilized liquid crystal film is relatively weak, and its mechanical properties are poor.

[0005] The second type is polymer microsphere-filled liquid crystal. This system has an inverse phase separation structure, forming uniformly sized polymer microspheres in situ within the liquid crystal matrix. The microspheres have a very small specific surface area, thus greatly reducing the interaction at the liquid crystal / polymer interface. Due to the significant reduction in the polymer specific surface area and the spatial hindrance of the microspheres, both the planar state and the focal cone scattering state of the device are stable. Therefore, after removing the electric field, the transparent and opaque states of the prepared polymer microsphere-filled liquid crystal film can remain stable for at least one year, making repeated dynamic control difficult.

[0006] The third type is polymer-dispersed liquid crystal. It consists of liquid crystal droplets and a polymer matrix, with the liquid crystal dispersed within a continuous polymer matrix. Typically, after phase separation, a porous polymer structure is formed. Due to the high proportion of polymerizable monomers (usually above 30 wt%), it exhibits not only excellent mechanical strength and electro-optic properties, but also a certain degree of flexibility because the polymer network area is large enough to bond with the upper and lower substrates. The electro-optic properties of polymer-dispersed liquid crystal films depend on several factors: the shape of the liquid crystal domains and the droplet size, the density of the polymer network, etc. Therefore, selecting the optimal polymer matrix for polymer-dispersed liquid crystals has a significant impact on their optical properties.

[0007] Traditional liquid crystal / polymer composites can generally achieve dynamic switching between two states under electrical drive (such as the polymer-dispersed liquid crystal film described in CN113980274A). Without an applied electric field, the liquid crystal molecules are randomly oriented, and the liquid crystal / polymer composite is in a white scattering state. When an electric field is present, the liquid crystal molecules tend to align along the direction of the electric field, thus driving the composite to become transparent. With technological advancements, two-state transition liquid crystal / polymer composites can no longer meet the needs of certain fields. Liquid crystal / polymer composites capable of electrically driven reflection color modulation, even across the entire visible spectrum, have high research value. Tilted helical cholesteric phase liquid crystal materials offer a possibility for this idea.

[0008] The advantages of traditional polymer-dispersed liquid crystals, such as high haze, excellent electro-optic and mechanical properties, and ease of fabrication for large-area flexible displays, complement the characteristics of tilted helical cholesteric liquid crystal materials, which offer rapid dynamic control of reflected colors driven by external fields. This makes optical devices based on tilted helical cholesteric liquid crystal / polymer composites promising for broad applications. Therefore, it is necessary to find a method for preparing tilted helical liquid crystal / polymer composites that meets practical application requirements. Summary of the Invention

[0009] The purpose of this invention is to provide an optical device based on tilted spiral liquid crystal / polymer composite material and its fabrication method, which has a reasonable process design and can be applied to the electric field control of the three-state transition of "opaque state-broad spectrum reflective state-transparent state". The "broad spectrum reflective state" can achieve dynamic control of selective reflection in a wide spectrum from the visible light to the near-infrared light range.

[0010] To achieve the above objectives, a first aspect of the present invention provides a tilted helical cholesteric liquid crystal material, the liquid crystal material comprising: a mixture of bent liquid crystal molecules having a twisted nematic phase, a nematic liquid crystal mixture, and a chiral dopant, wherein the liquid crystal material is capable of forming a tilted helical arrangement under electrical drive.

[0011] According to a preferred embodiment of the present invention, the content of the curved liquid crystal molecule mixture is 46wt%-54wt% based on the total weight of the liquid crystal material, the content of the nematic liquid crystal mixture is 45wt%-49wt%, and the content of the chiral dopant is 1wt%-5wt%.

[0012] According to the present invention, preferably, the curved liquid crystal molecule mixture is obtained by mixing the curved liquid crystal molecule dimer shown in general formula I and the curved liquid crystal molecule trimer shown in general formula II, and the mixing ratio of the two is 15-20:1.

[0013] General Formula I

[0014] General Formula II

[0015] Wherein, n is a natural odd number of 5, 7, 9, or 11; m is a natural odd number of 5 or 7; X and X' are each independently selected from C1-C4 alkylene groups or oxygen atoms; F1, F2, F3, and F4 are the same or different and are each independently selected from hydrogen atoms or fluorine atoms; and M is a cyano group, a C2-C6 alkyl group, or a C2-C6 alkoxy group. This general formula is only an example and not an exhaustive one. The curved liquid crystal molecules with twisted nematic phases that can be used in actual curved liquid crystal molecule mixtures include, but are not limited to, the following general formula.

[0016] According to the present invention, preferably, the nematic liquid crystal mixture is a rod-shaped single-crystal molecule mixture, and the nematic liquid crystal used in the nematic liquid crystal mixture is selected from at least two of 5CB, E7, E8, E44, SLC-1717, SLC-1718 and TEB30A. The present invention does not particularly limit the proportion of various nematic liquid crystals in the mixture. According to a specific embodiment of the present invention, the nematic liquid crystal mixture is a mixture of 5CB and E7, and the mixing ratio of the two is 1-2:1.

[0017] According to the present invention, preferably, the chiral dopant (also referred to herein as chiral agent) includes, but is not limited to, at least one of CB15, S811, R811, S1011, R1011, S2011, R2011, S5011, and R5011:

[0018] CB15

[0019]

[0020] S811

[0021]

[0022] R811

[0023]

[0024] S1011

[0025]

[0026] R1011

[0027]

[0028] S2011

[0029]

[0030] R2011

[0031]

[0032] S5011

[0033]

[0034] R5011

[0035]

[0036] The preparation method of the tilted helical cholesteric liquid crystal material of the present invention may include the following steps:

[0037] In the presence of an organic solvent, the bent liquid crystal molecule mixture, the nematic liquid crystal mixture, and the chiral dopant are mixed uniformly, and then the organic solvent is evaporated to obtain the tilted helical cholesteric liquid crystal material; wherein the organic solvent is at least one of acetone, methanol, ethanol, tetrahydrofuran, dichloromethane, and trichloromethane.

[0038] A second aspect of the present invention provides a liquid crystal / polymer composite film material with an electrically driven scattering state-broad spectrum reflective state-transparent state transition, wherein the composite film material is a prepolymer of the above-mentioned tilted helical cholesteric liquid crystal material and polymerizable monomers, wherein the tilted helical cholesteric liquid crystal is dispersed in the polymer matrix in the form of liquid crystal droplets.

[0039] The composite film material of the present invention exhibits a scattering state, a broad-spectrum reflective state, and a transparent state under different electric field intensities, wherein the broad-spectrum reflective state refers to the reflective band being tunable within the spectral range from visible light to near-infrared light.

[0040] Furthermore, the composite film exhibits three states under different electric field intensities: a scattering state, a near-infrared reflection state in the 800-2000nm region, and a transparent state, corresponding to heat insulation and light insulation, heat insulation and light transmission, and complete light transmission, respectively.

[0041] According to the present invention, preferably, the polymerizable monomer is an acrylate monomer and / or a vinyl thiol monomer.

[0042] According to the present invention, preferably, the prepolymer comprises, by total weight, 80wt%-92wt% of a tilted helical cholesteric liquid crystal material, 8wt%-20wt% of a polymerizable monomer, and 0wt%-1wt% of a photoinitiator. When using acrylate polymerizable monomers, a small amount of photoinitiator needs to be added additionally. The photoinitiator can be any conventional photoinitiator in the art, and the present invention does not particularly limit it.

[0043] According to a preferred embodiment of the present invention, the prepolymer is prepared by a method comprising the following steps: mixing the tilted helical cholesteric liquid crystal material with a polymerizable monomer in the presence of an organic solvent, and then evaporating the organic solvent to obtain the prepolymer, wherein the organic solvent is at least one selected from acetone, methanol, ethanol, tetrahydrofuran, dichloromethane and trichloromethane.

[0044] To further improve the device performance of tilted helical cholesteric liquid crystals and expand their application scenarios, a third aspect of the present invention provides a liquid crystal / polymer dimming and display device with an electrically driven scattering state-broad spectrum reflective state-transparent state transition, wherein the liquid crystal / polymer dimming and display device is prepared by a method comprising the following steps:

[0045] Spacer balls are added to the molten prepolymer and stirred until homogeneous. The mixture is then dropped onto a flexible PET substrate coated with conductive ITO. The conductive surfaces of the two PET substrates are joined together, and after removing air bubbles, the mixture is slowly cooled to below room temperature. At 20-23°C, polymerization-induced phase separation occurs to obtain the liquid crystal / polymer dimming and display device. The conditions for polymerization-induced phase separation include: using 800-1200 μw / cm²... 2 Irradiate with ultraviolet light with a center wavelength of 365nm for 15-30 minutes.

[0046] The tilted spiral liquid crystal / polymer dimming and display device of the present invention exhibits an "opaque state" where no external electric field is applied; a "transparent state" where light is not transmitted when a large voltage is applied; and a "reflective state" when a suitable voltage is applied. Increasing the voltage can cause the reflected color to cover the entire visible spectrum from red to blue, while decreasing the voltage causes the reflected color to change from blue to red and finally to near-infrared light. This operation and its changes can be repeated multiple times. Furthermore, it can be used for display applications, as illustrated in the diagram below. Figure 9 As shown, the color in the broadband reflective state can be any RGB color; at the same time, switching between the scattering state and the transparent state on a black background can achieve black and white display.

[0047] Furthermore, spacer balls are added to the prepolymer in its molten state at 80-110°C.

[0048] Furthermore, the amount of the spacer spheres added is 0.2-0.8 wt% of the total weight of the prepolymer.

[0049] Furthermore, the size of the spacer sphere is 15-25 μm.

[0050] Furthermore, the rate of slow cooling is 0.8-1.2 °C / min.

[0051] According to a specific embodiment of the present invention, the liquid crystal / polymer dimming and display device is prepared by a method comprising the following steps: 0.5 wt% of 20 μm spacer balls are added to a prepolymer at 80°C, and the mixture is stirred uniformly in a molten state. Then, two transparent PET substrates with an ITO conductive layer and a thickness of 0.125 mm are taken, and the prepolymer is dropped onto the conductive surface of the PET substrates at 80°C using a dropper. The conductive surfaces of the two substrates are then joined together, and the two PET substrates are moved and rubbed to remove air bubbles. The substrates are then cooled uniformly at a cooling rate of 1°C / min until the temperature reaches 21°C. The utilization intensity is 800-2000 μw / cm. 2 Irradiation with ultraviolet light with a center wavelength of 365nm at 21℃ (below the liquid crystal clearing point) for 15-30 minutes causes the polymerizable monomers in the prepolymer to spontaneously polymerize, resulting in a flexible, tilted spiral liquid crystal / polymer composite material that can be bent.

[0052] Electrically controlled intelligent devices based on liquid crystal / polymer composite materials have wide applications in energy conservation and privacy protection due to their excellent optoelectronic properties. However, traditional liquid crystal / polymer composite devices can only switch between "transparent" and "opaque" states during electrical actuation. Tilted helical cholesteric liquid crystals possess the unique property of rapidly and dynamically adjustable reflective colors across a wide wavelength range and narrow bandwidth driven by an electric field, providing an effective means to adjust reflective colors. This invention provides a flexible liquid crystal / polymer composite device and its fabrication method that utilizes tilted helical cholesteric liquid crystals to replace traditional liquid crystal materials, enabling electrically driven transitions between "opaque," "reflective," and "transparent" states. The "reflective" state allows for dynamic control of selective reflection across a wide spectral range from the visible to the near-infrared, greatly expanding the performance and applications of traditional liquid crystal / polymer composite devices.

[0053] This invention provides a novel flexible liquid crystal / polymer composite device that combines the advantages of traditional liquid crystal / polymer composite devices, such as high haze, excellent electro-optic and mechanical properties, and ease of fabrication for large-area flexible displays, with the rapid dynamic control of reflective color of tilted helical cholesteric liquid crystal materials. Based on the electro-driven "opaque state" and "transparent state" of traditional liquid crystal / polymer composite materials, a "broad-spectrum reflective state" with electro-driven selective reflective dynamic control across the entire visible-near-infrared spectral range is added, simultaneously realizing a flexible display based on tilted helical cholesteric liquid crystal materials. This device is advantageous for applications in information display, energy conservation, and privacy protection.

[0054] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0055] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0056] Figure 1 This is a schematic diagram illustrating the three-state transition of a liquid crystal / polymer dimming device that achieves the electric-driven scattering state-broad-spectrum reflection state-transparency state transition according to the present invention.

[0057] Figure 2 This is a physical diagram of the dimming device based on the tilted spiral liquid crystal / polymer composite material of the present invention.

[0058] Figure 3 This is a physical image of the flexible display based on the tilted spiral liquid crystal / polymer composite material dimming device of the present invention.

[0059] Figure 4 This is a polarizing microscope texture image of the dimming device based on the tilted spiral liquid crystal / polymer composite material of the present invention.

[0060] Figure 5 This is a scanning electron microscope image of the dimming device based on the tilted spiral liquid crystal / polymer composite material of the present invention.

[0061] Figure 6 The results show the reflectance color test results of the dimming device based on the tilted spiral liquid crystal / polymer composite material of this invention.

[0062] Figure 7 The infrared reflection test results are for the dimming device based on the tilted spiral liquid crystal / polymer composite material of this invention.

[0063] Figure 8 The transmission test results are for the dimming device based on the tilted spiral liquid crystal / polymer composite material of this invention.

[0064] Figure 9 This invention is a schematic diagram of a display based on a tilted spiral liquid crystal / polymer composite material. Detailed Implementation

[0065] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0066] The present invention is further illustrated by the following examples:

[0067] This invention uses three types of bent liquid crystal molecules with twisted nematic phases as raw materials to prepare a dimming device based on a tilted helical cholesteric phase liquid crystal / polymer composite material. This example is merely illustrative; the bent liquid crystal molecules with twisted nematic phases used in practical applications of bent liquid crystal molecule mixtures include, but are not limited to, the following three types.

[0068] Formula 1

[0069] Formula 2

[0070] Formula 3

[0071] Example 1

[0072] In dichloromethane, bent liquid crystal molecules with twisted nematic phases as shown in Formulas 1, 2, and 3 are mixed to obtain the bent liquid crystal molecule mixture (based on the total weight of the bent liquid crystal molecule mixture, the content of the dimer of Formula 1 is 60 wt%, the content of the dimer of Formula 2 is 35 wt%, and the content of the trimer of Formula 3 is 5 wt%). 5CB and E7 are mixed to obtain the nematic liquid crystal mixture (based on the total weight of the nematic liquid crystal mixture, the content of 5CB is 60 wt% and the content of E7 is 40 wt%). The bent liquid crystal molecule mixture, the nematic liquid crystal mixture, and the chiral agent S811 are mixed at a mass ratio of 49:46:5. After evaporating the solvent, the tilted helical cholesteric liquid crystal material is obtained. The tilted helical cholesteric liquid crystal material is mixed with acrylate monomers in dichloromethane. After evaporating the solvent, a prepolymer is obtained (based on the total weight of the prepolymer, the content of the tilted helical cholesteric liquid crystal material is 85 wt% and the content of the acrylate monomers is 15 wt%). 0.5 wt% of 20 μm spacer balls were added to the molten prepolymer at 90 °C, stirred until homogeneous, and then dropped onto a conductive ITO-coated flexible PET substrate. The conductive surfaces of the two PET substrates were then bonded together. After removing air bubbles, the mixture was cooled to below room temperature at a rate of 1 °C / min. The sample was then tested at 21 °C and yielded a strength of 1200 μw / cm. 2 Irradiation with ultraviolet light with a center wavelength of 365nm for 20 minutes induces spontaneous polymerization and phase separation to obtain a dimming device, which is then tested.

[0073] Place the dimming device under a polarizing microscope. Figure 4 The image shows the polarizing microscope texture of the dimming device. Since the polymer network is optically isotropic, it appears dark under the polarizing microscope, while the liquid crystal molecules are optically anisotropic and appear bright under the polarizing microscope. The polarizing microscope shows that a dense polymer network is formed in the dimming device, which encapsulates the liquid crystal molecules in the form of microdroplets.

[0074] Further analysis of the polymer network formed in the dimming device using a scanning electron microscope (SEM) was conducted. The dimming device was immersed in anhydrous ethanol for three days until the small molecule liquid crystals were completely dissolved in the solution. After air drying, the sample was observed under a scanning electron microscope. Figure 5 The image shows a scanning electron microscope image of the dimming device, in which a dense white polymer network can be seen.

[0075] The dimming device was placed in a fiber optic spectrometer to test its reflectance spectrum. Figure 6The test results of the reflectance color of the dimming device are as follows: when the dimming device is driven by an electric field of 1.25V / micrometer, the dimming device shows a blue reflectance peak; when the dimming device is driven by an electric field of 1.08V / micrometer, the dimming device shows a green reflectance peak; and when the dimming device is driven by an electric field of 0.88V / micrometer, the dimming device shows a red reflectance peak. Figure 7 The dimming device is driven by an electric field of 0.75V / micrometer, and the dimming device exhibits a near-infrared light reflection peak (800-1250nm).

[0076] The transmission spectrum of the dimming device was further tested using a spectrophotometer. Figure 8 The transmission test results of the dimming device are as follows: the driving voltage starts from 0V and increases in increments of 7.5V. Initially, the transmittance of the dimming device is extremely low across the entire spectrum. At this time, the dimming device is in a focal cone scattering state. When the driving voltage is higher than a certain threshold, the dimming device generates a red reflection peak. As the voltage increases, the reflection peak continuously shifts to blue, eventually exhibiting a high transmittance across the entire visible light spectrum.

[0077] Comparative Example 1

[0078] 0.5 wt% of 20 μm spacer balls were added to the molten prepolymer of Example 1 at a higher temperature, stirred until homogeneous, and then dropped onto a conductive ITO-coated flexible PET substrate. The conductive surfaces of the two PET substrates were then bonded together. After removing air bubbles, the mixture was cooled to room temperature at a rate of 1 °C / min. The sample was then tested at 21 °C using a strength of 2000 μw / cm. 2 After being irradiated with ultraviolet light with a center wavelength of 365nm for 20 minutes to induce spontaneous polymerization and phase separation, the mixture was tested.

[0079] Comparative Example 2

[0080] 0.5 wt% of 20 μm spacer balls were added to the molten prepolymer of Example 1 at a higher temperature, stirred until homogeneous, and then dropped onto a conductive ITO-coated flexible PET substrate. The conductive surfaces of the two PET substrates were then bonded together. After removing air bubbles, the mixture was cooled to room temperature at a rate of 1 °C / min. The sample was then tested at 21 °C and yielded a strength of 460 μw / cm. 2 After being irradiated with ultraviolet light with a center wavelength of 365nm for 20 minutes to induce spontaneous polymerization and phase separation, the mixture was tested.

[0081] Comparative Example 3

[0082] 0.5 wt% of 20 μm spacer balls were added to the molten prepolymer of Example 1 at a higher temperature, stirred until homogeneous, and then dropped onto a flexible PET substrate coated with conductive ITO. The conductive surfaces of the two PET substrates were then bonded together. After removing air bubbles, the mixture was cooled to room temperature at a rate of 1 °C / min. The sample was then tested at 25 °C using a strength of 1200 μw / cm. 2 After being irradiated with ultraviolet light with a center wavelength of 365nm for 20 minutes to induce spontaneous polymerization and phase separation, the mixture was tested.

[0083] Test Example 1

[0084] An external electric field was used to drive the switching between three states of a flexible tilted spiral liquid crystal / polymer composite material: "opaque state," "reflective state," and "transparent state," and the change of reflected color in the reflective state was observed.

[0085] like Figure 2 , Figure 3 As shown, the optical device based on the tilted spiral liquid crystal / polymer composite material prepared in Example 1 can achieve dynamic reversible switching between "opaque state," "reflective state," and "transparent state" under electric field driving. The reflective state allows for selective dynamic control of reflective color across a wide spectral range of visible to near-infrared light, driven by electric drive. The flexible tilted spiral liquid crystal / polymer composite material prepared using a PET substrate can realize flexible displays. Figure 1 As shown, when no electric field is applied, the liquid crystal molecules exhibit a cholesteric focal conic scattering "opaque" state due to the presence of the chiral agent; when a large voltage is applied, the liquid crystal molecules are induced into a field-induced nematic state, and the device switches to a "transparent" state; when the voltage is adjusted, a tilted helical structure is formed, and the device switches to a "reflective" state. When the voltage is reduced, a change in the reflection peak from blue to green to red is observed, and finally it returns to the "opaque" state. This process is reversible and has good stability.

[0086] Comparative Test Example 1

[0087] Electrical drive can induce normal switching between "opaque state" and "transparent state", but the reflectivity of the "reflective state" induced by voltage adjustment is significantly lower than that of Example 1. The fiber optic spectrometer cannot measure the reflection spectrum, indicating that excessively strong polymerization light will lead to an overly dense polymer network, thereby affecting the formation of the tilted spiral structure of the bulk liquid crystal and thus affecting the normal operation of the reflective state.

[0088] Comparative Test Example 2

[0089] Electrical drive can induce normal switching between "opaque state" and "transparent state", but the reflectivity of the "reflective state" induced by voltage adjustment is significantly lower than that of Example 1. The fiber optic spectrometer cannot measure the reflection spectrum, indicating that if the polymerization light intensity is too weak, the polymer network will be too sparse, which will affect the normal operation of the reflective state.

[0090] Comparative Test Example 3

[0091] Electrical drive can induce normal switching between "opaque state" and "transparent state", but adjusting the voltage cannot induce "reflective state". This indicates that the polymerization temperature needs to be below the prepolymer clearing point to ensure that the flexible tilted spiral liquid crystal / polymer composite material works normally after polymerization.

[0092] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An electrically driven scattering- wide spectrum reflective- transparent state switching liquid crystal / polymer light modulating and display device, characterized in that, The liquid crystal / polymer light modulation and display device is prepared by a method comprising the following steps: The mixture is dropped onto the conductive ITO coated flexible PET substrate, the conductive surfaces of the two PET substrates are pasted together, and after removing the bubbles, it is slowly reduced to room temperature. At 20-23℃, the polymer-induced phase separation is carried out, and the liquid crystal / polymer light modulation and display device is obtained. The polymer-induced phase separation conditions include: using 800-1200 μw / cm 2 ultraviolet light with a central wavelength of 365 nm with an intensity of 15-30 min; the prepolymer is a pre-polymer of a tilted helical cholesteric phase liquid crystal material and a polymerizable monomer, wherein the tilted helical cholesteric phase liquid crystal is dispersed in the form of liquid crystal droplets in the polymer matrix; The tilted helical cholesteric phase liquid crystal material comprises a bent liquid crystal molecule mixture having a twisted bent nematic phase, a nematic phase liquid crystal mixture, and a chiral dopant, and the liquid crystal material can form a tilted helical arrangement under electric driving; The bent liquid crystal molecule mixture is obtained by mixing a bent liquid crystal molecule dimer represented by general formula I and a bent liquid crystal molecule trimer represented by general formula II, and the mixing ratio of the two is 15-20:

1. Formula I Formula II In the formula, n is a natural odd number of 5, 7, 9, or 11, m is a natural odd number of 5 or 7, X and X' are each independently selected from C1-C4 alkylene or an oxygen atom, F1, F2, F3, and F4 are the same or different and each independently selected from a hydrogen atom or a fluorine atom, and M is a cyano group, a C2-C6 alkyl group, or a C2-C6 alkoxy group.

2. The liquid crystal / polymer light modulating and display device of claim 1, wherein, The content of the bent liquid crystal molecule mixture is 46 wt%-54 wt%, the content of the nematic phase liquid crystal mixture is 45 wt%-49 wt%, and the content of the chiral dopant is 1 wt%-5 wt%, based on the total weight of the liquid crystal material.

3. The liquid crystal / polymer light modulation and display device according to claim 1, wherein The nematic phase liquid crystal mixture is a rod-like single crystal molecule mixture, and the nematic phase liquid crystal used in the nematic phase liquid crystal mixture is selected from at least two of 5CB, E7, E8, E44, SLC-1717, SLC-1718, and TEB30A; The chiral dopant is selected from at least one of CB15, S811, R811, S1011, R1011, S2011, R2011, S5011, and R5011: CB15 S811 R811 S1011 R1011 S2011 R2011 S5011 R5011 。 4. The liquid crystal / polymer light modulating and display device of claim 1, wherein, The preparation method of the tilted helical cholesteric phase liquid crystal material comprises the following steps: The bent liquid crystal molecule mixture, the nematic phase liquid crystal mixture, and the chiral dopant are mixed uniformly in the presence of an organic solvent, and then the organic solvent is evaporated to obtain the tilted helical cholesteric phase liquid crystal material; wherein the organic solvent is at least one of acetone, methanol, ethanol, tetrahydrofuran, dichloromethane, and trichloromethane.

5. The liquid crystal / polymer light modulating and display device of claim 1, wherein, The broad spectrum reflection state refers to that the reflection band can be controlled in the spectral range from visible light to near-infrared light.

6. The liquid crystal / polymer light modulating and display device of claim 1, wherein, The polymerizable monomer is an acrylate monomer and / or a vinyl thiol monomer; the prepolymer comprises 80 wt%-92 wt% of the tilted helical cholesteric phase liquid crystal material, 8 wt%-20 wt% of the polymerizable monomer, and 0 wt%-1 wt% of the photoinitiator, based on the total weight of the prepolymer.

7. The liquid crystal / polymer light modulating and display device of claim 1 wherein, The prepolymer is prepared by a method comprising the following steps: the tilted helical cholesteric phase liquid crystal material and the polymerizable monomer are mixed uniformly in the presence of an organic solvent, and then the organic solvent is evaporated to obtain the prepolymer, wherein the organic solvent is at least one of acetone, methanol, ethanol, tetrahydrofuran, dichloromethane, and trichloromethane.

8. The liquid crystal / polymer light modulating and display device of claim 1 wherein, A spacer ball is added to the prepolymer in a molten state at 80-110 ℃; The spacer balls are added in an amount of 0.2-0.8 wt% of the total weight of the prepolymer; The spacer balls have a size of 15-25 μm; The slow rate of decrease to below room temperature is 0.8-1.2 °C / min.

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