A liquid crystal intelligent window capable of self-adapting to light intensity, its preparation method and application

Abstract

The present invention discloses a liquid crystal smart window capable of self - adapting to light intensity, which comprises a first substrate, a second substrate and a liquid crystal layer; the material of the liquid crystal layer includes a host liquid crystal, a chiral dopant and an infrared absorption material; wherein, the host liquid crystal has at least two liquid crystal phases, namely a smectic phase and a nematic phase. After the infrared absorption material in the liquid crystal smart window absorbs sunlight, it provides energy for the phase transition of the host liquid crystal, so that the liquid crystal smart window self - adapts to the sunlight intensity and presents a transparent state or a scattering state, and the transparency changes with the sunlight intensity. This liquid crystal window that changes intelligently with light intensity is more energy - saving and environmentally friendly and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent materials. More specifically, it relates to a liquid crystal intelligent window capable of self - adapting to light intensity and a preparation method thereof. Background Art

[0002] Liquid crystal is a state of matter between solid and liquid. Small - molecule organic liquid crystal materials have been widely studied and used in the optoelectronic field due to their simultaneous characteristics of liquid fluidity and anisotropy of optoelectronic properties. Common achiral rod - shaped liquid crystal molecules usually have smectic phase, nematic phase, isotropic phase, etc. above the melting point.

[0003] Rod - shaped molecules in the nematic phase are prone to maintaining a consistent orientation under the action of external forces. When the rod - shaped liquid crystal molecules in the system are arranged uniformly, the light scattering in the liquid crystal system is minimized and the macroscopic manifestation is a transparent state; when a suitable chiral dopant is added to the liquid crystal molecules or the liquid crystal molecules themselves are chiral, the nematic liquid crystal will self - assemble into a cholesteric liquid crystal with a layered helical structure. Since the orientation of the liquid crystal molecules changes continuously between layers, the refractive index of the liquid crystal also changes periodically. It is a typical photonic crystal material, and its photonic band gap is related to the action effect of the chiral dopant in the liquid crystal system and can reflect specific wavelengths. When the chiral agent in the liquid crystal system reaches a certain amount, the cholesteric liquid crystal will present a scattering focal conic state and prevent light from passing through.

[0004] Generally, when the rod - shaped liquid crystal molecules in the smectic phase are arranged orderly, the macroscopic state can also be transparent, and it is not easy to change their arrangement when a chiral agent is added. However, when a chiral agent is added to the nematic liquid crystal, it can be transformed into the cholesteric phase, and at the same time, the optical characteristics change from a transparent state to a reflective or scattering state.

[0005] In solar radiation, infrared light is the main source of solar heat. If this part of energy can be well regulated and utilized, it is of great significance for energy conservation and utilization.

[0006] Therefore, it is necessary to provide a liquid crystal intelligent window capable of self - adapting to light intensity, which can adjust the light transmittance by using sunlight. Summary of the Invention

[0007] An object of the present invention is to provide a liquid crystal intelligent window capable of self - adapting to light intensity, the transparency of which changes with the light intensity. When the light is strong, the transparency decreases, and after the light intensity decreases, the transparency is restored.

[0008] Another object of the present invention is to provide a preparation method of a liquid crystal intelligent window capable of self - adapting to light intensity.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A liquid crystal smart window capable of adapting to light intensity, characterized in that it comprises a first substrate, a second substrate and a liquid crystal layer; the material of the liquid crystal layer comprises a host liquid crystal, a chiral dopant and an infrared absorbing material;

[0011] Wherein, the host liquid crystal has at least two liquid crystal phases, namely a smectic phase and a nematic phase.

[0012] The host liquid crystal in the liquid crystal layer material of the liquid crystal smart window provided by the present invention has at least two liquid crystal phases, namely a smectic phase and a nematic phase. At different temperatures, the host liquid crystal presents a smectic phase or a nematic phase. When the host liquid crystal is in the smectic phase, the liquid crystal molecules are arranged orderly, and the chiral dopant cannot change its arrangement state, and the smart window is in a transparent state; when the host liquid crystal is in the nematic phase, adding a chiral dopant can make it transform into a cholesteric phase, presenting a scattered focal conic state, preventing light from passing through, and the transparency of the smart window decreases. The near-infrared absorbing material can absorb light in the near-infrared band, provide energy for the phase transition of the host liquid crystal, and make the liquid crystal smart window adapt to the sunlight intensity and present a transparent state or a scattered state.

[0013] After the infrared absorbing material in the present invention absorbs sunlight, it causes the temperature of the liquid crystal layer material to rise. After reaching the phase transition temperature, the liquid crystal phase changes from the smectic phase to the cholesteric phase of the focal conic state. When the heat that the infrared absorbing material can provide matches the liquid crystal phase transition temperature, the liquid crystal smart window has a higher sensitivity to the light intensity, and the change in transparency is more sensitive to the change in light. In some preferred embodiments of the present invention, the temperature at which the liquid crystal layer material changes from the smectic phase to the nematic phase is 26-32 °C.

[0014] The doping amount of the chiral dopant will affect the phase transition temperature of the liquid crystal, and thus affect the sensitivity of the liquid crystal smart window to the self-adaptation of light. In some preferred embodiments, the weight ratio of the chiral dopant to the host liquid crystal is 1 wt% to 8 wt%. Further preferably, the weight ratio of the chiral dopant to the host liquid crystal includes but is not limited to 2 wt% to 7 wt%, 3 wt% to 6 wt%, or 4 wt% to 5 wt%, etc.

[0015] The self-adaptation of the liquid crystal smart window to sunlight can be adjusted by changing the type of the host liquid crystal, the content of the chiral dopant, and the doping amount of the infrared absorbing material. In some preferred embodiments, the weight ratio of the infrared absorbing material to the host liquid crystal is 0.5 wt% to 3.5 wt. Further preferably, the weight ratio of the infrared absorbing material to the host liquid crystal includes but is not limited to 1 wt% to 3 wt%, 1.5 wt% to 2.5 wt%, or 2 wt%, etc.

[0016] In some embodiments of the present invention, the host liquid crystal is in a liquid crystal state at 20°C to 50°C. When the temperature is lower than 20°C, the host liquid crystal is in a crystalline state. When the temperature is higher than 50°C, the host liquid crystal will transform into a liquid state.

[0017] In some preferred embodiments, the host liquid crystal includes, but is not limited to, a mixed liquid crystal composed of 10CB, 12CB, 8OCB, and 8CB, or 8CB, or 5CB.

[0018] Liquid crystal 8CB is initially in a smectic phase with a vertical alignment. Due to the consistency of the optical axis orientation, its macroscopic manifestation is a transmissive state. Due to the addition of a chiral dopant, when the system temperature rises to reach the transition temperature between the smectic phase and the nematic phase, the liquid crystal molecules will transform from the vertically aligned smectic phase into a cholesteric phase liquid crystal with a disordered focal conic state. Since the optical axis orientations of the rod-shaped liquid crystal molecules are inconsistent, they will strongly scatter the incident light and prevent the sunlight from passing through.

[0019] In some preferred embodiments, the absorption band of the infrared absorption material is 800 - 1200 nm.

[0020] More preferably, the infrared absorption material can be isobutyl-substituted diimmonium with borate anion (IDI), and its structural formula is shown as follows:

[0021]

[0022] The photothermal conversion material IDI with infrared absorption characteristics is a diammonium borate salt. It has a strong absorption characteristic for near-infrared light in the 800 - 1200 nm band. The heat generated by its absorption of the near-infrared band can raise the temperature of the entire liquid crystal smart window by 5 - 8°C. At the same time, IDI also has a good absorption of ultraviolet light near 380 nm, and in the visible light band of 400 - 800 nm, its absorption is small. Therefore, when mixed with the liquid crystal, it has little influence on the transparency of the liquid crystal material. And under the irradiation of 50 mW / cm 2 , 380 nm ultraviolet light for 2 hours, its absorption characteristics do not show an obvious decline, and it has good ultraviolet tolerance. It is an infrared absorption material with excellent performance. The diammonium borate salt IDI with good infrared absorption characteristics is mainly prepared by the method of normal temperature reflux. The specific preparation steps are as follows:

[0023] Add N,N,N′,N′-tetrakis[4-(diisobutylamino)phenyl]-1,4-benzenediamine (IPA) (1.0 g, 1.08 mmol) and lithium diborate (0.5 g, 2.58 mmol) into a two-necked flask. Then, add 5.0 g of dichloromethane and 2.0 g of ethanol, and reflux for 2 h. When the solution turns dark green after 2 h, add sodium persulfate (0.35 g, 1.47 mmol) and 8.0 g of water, and reflux for 2 h. The reaction is terminated by adding a large amount of water and dichloromethane, and washed several times with water to remove unreacted materials and impurities. The combined organic layer is subjected to vacuum distillation to obtain a black solid (1.1 g, 78.6%).

[0024] In some preferred embodiments, the chiral dopant is selected from one or more of S811, S5011, and R5011.

[0025] Wherein R5011 refers to

[0026]

[0027] S5011 refers to

[0028]

[0029] S811 refers to

[0030]

[0031] Preferably, the thickness of the liquid crystal layer is 4 - 20 μm.

[0032] The thickness of the liquid crystal layer can regulate the sensitivity of the liquid crystal smart window to the adaptability of light. The thickness of the liquid crystal layer of the liquid crystal smart window provided by the present invention is determined by the interval between the first substrate and the second substrate, and the interval size is determined by the silica glass microspheres in the interval, that is, the size of the glass microsphere diameter is the interval size between the two glass sheets.

[0033] In a preferred embodiment, the particle size range of the spacer silica glass microspheres is 4 - 20 μm. Using silica microspheres in this particle size range can make the vertical alignment agent on the substrate surface play a role within the entire liquid crystal smart window range, so that the liquid crystal layer material in the entire liquid crystal smart window initially maintains a vertical alignment. At the same time, a thickness of 4 - 20 μm does not affect the initial light transmission performance. If the particle size of the microspheres is too large or too small, it will not only affect the light transmission performance, but also affect the magnitude of the capillary force received by the liquid crystal layer and the amount of liquid crystal layer content, thereby affecting the light response performance of the liquid crystal layer and the stability of the entire system. Therefore, the optimal size of the glass microsphere spacer used in the liquid crystal smart window is 4 - 20 μm.

[0034] In a preferred embodiment, a vertical liquid crystal alignment agent is spin-coated on the surfaces of the first substrate and the second substrate that are in contact with the liquid crystal layer. The inner surfaces of the upper and lower substrates are both treated with the vertical liquid crystal alignment agent, so that the long axes of the rod-shaped liquid crystal molecules in the liquid crystal smart window will be arranged in a direction perpendicular to the two substrates, thereby maintaining the initial transparent state of the liquid crystal smart window. There are silica glass microspheres for controlling the spacing between the two substrates, which are fixed at the four corners of the glass sheet by ultraviolet curable glue. After that, the liquid crystal layer material is filled between the glass sheets. Through capillary action, the liquid crystal layer material is confined between the two glass sheets, enabling the entire system to exist stably.

[0035] Of course, those skilled in the art can choose other vertical liquid crystal alignment agents when modifying the substrate surface according to needs, and it is not necessarily necessary to use polyimide. It can be understood that such improvements in technical solutions do not require creative labor and are all within the protection scope of the present invention.

[0036] A method for preparing a liquid crystal smart window that can adapt to light as described above includes the following steps:

[0037] Dissolve the liquid crystal, chiral dopant, and infrared absorbing material in dichloromethane, and pour it between the first substrate and the second substrate at 50 - 110 °C, then cool down to obtain a liquid crystal smart window that can adapt to light.

[0038] The first substrate and the second substrate need to go through a pretreatment process before use, including: spin-coating a vertical liquid crystal alignment agent on the substrate surface and fixing the spacing between the two substrates. Specifically: spin-coat the vertical liquid crystal alignment agent that can make the rod-shaped liquid crystal molecules align vertically on the substrate surface, then apply silica glass microspheres mixed with ultraviolet curable glue between the four corners of the substrate, and cure it with an ultraviolet lamp to obtain an empty liquid crystal smart window with a fixed spacing.

[0039] The process of filling the empty liquid crystal smart window with the liquid crystal layer is as follows: Mix a quantitative amount of host liquid crystal, chiral dopant, and infrared absorbing material evenly in a dichloromethane solution, and after ultrasonic treatment for 24 h, dry the dichloromethane solution to obtain the liquid crystal layer material; on a hot stage at 40 - 80 °C, fill the liquid crystal mixture into the empty liquid crystal smart window through capillary suction, and then slowly cool down the hot stage to obtain the liquid crystal smart window.

[0040] In some preferred examples, the material of the substrate is ordinary glass, quartz wafer, or silicon wafer.

[0041] The present invention provides a method for preparing a liquid crystal smart window that can adapt to the light intensity here. The specific preparation process includes:

[0042] 1) Ultrasonic clean the glass sheets with dishwashing liquid for 30 min, rinse with running water for 15 min, ultrasonic clean with ethanol for 30 min, and then dry for later use;

[0043] 2) Spin-coat a 5% polyimide aqueous solution on a glass substrate, then volatilize the water at 80 °C for 15 s, keep it in an incubator at 80 °C for 15 min, at 110 °C for 30 min, and at 230 °C for 2 h;

[0044] 3) Dot-apply ultraviolet curable glue and glass microbead spacers at the four corners of the inner surfaces of two glass slides (the side with polyimide modification), after slight extrusion, irradiate with an ultraviolet lamp for 10 s to cure the ultraviolet glue and make an empty liquid crystal cell;

[0045] 4) Dissolve 8CB, a chiral dopant, and IDI in dichloromethane, ultrasonicate for 24 h, and then dry the dichloromethane to obtain a liquid crystal layer material;

[0046] 5) Use capillary action on a hot stage at 80 °C to fill the empty liquid crystal cell with the liquid crystal layer material, and slowly cool it to room temperature to obtain a liquid crystal smart window that can adapt to light illumination.

[0047] An application of a liquid crystal smart window that can adapt to the light intensity as described above in adjusting the solar transmittance.

[0048] When the liquid crystal smart window that can adapt to the light intensity provided by the present invention is irradiated by strong sunlight or the light of a solar simulator, the transparency of the liquid crystal smart window decreases and the light transmission reduces. Specifically, when the liquid crystal layer material is irradiated by a solar simulator (100 mW / cm 2 ) for 1 min, an opaque scattering region starts to appear at the edge of the transparent liquid crystal smart window, and as the irradiation time increases, the scattering region slowly expands. By about 2 min, the haze region covers the entire liquid crystal smart window region, and the pattern at the bottom side of the liquid crystal smart window will become unclear due to scattering. After turning off the solar simulator and in the dark condition, in about 30 s, the haze region on the liquid crystal smart window will slowly disappear, and the pattern placed at the bottom side of the liquid crystal smart window can become clearly visible again. The present invention will be further described by way of examples below, but the protection scope of the present invention is not limited to these embodiments.

[0049] The beneficial effects of the present invention are as follows:

[0050] The present invention provides a liquid crystal smart window that can adapt to the light intensity. The material of the liquid crystal layer of the liquid crystal smart window includes a host liquid crystal, a chiral dopant, and an infrared absorption material, wherein the host liquid crystal has at least two liquid crystal phases, namely the smectic phase and the nematic phase. After the infrared absorption material absorbs sunlight, it provides energy for the liquid crystal phase transition, enabling the liquid crystal smart window to adapt to the sunlight intensity and present a transmissive state or a scattering state, and the transparency changes with the sunlight intensity. This liquid crystal window that changes intelligently with the light intensity is more energy-saving and environmentally friendly and has a wide application prospect. Description of the Drawings

[0051] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0052] Figure 1 Show the absorption spectrum results of the prepared infrared absorption material IDI.

[0053] Figure 2 Show the test results of the temperature change of the liquid crystal smart window in Example 1 under the irradiation of a solar simulator.

[0054] Figure 3 Show the macroscopic transparency and POM characterization results of the liquid crystal smart window in Test Example 1 under light irradiation.

[0055] Figure 4 Show the test results of the temperature change with time of the liquid crystal smart window in Test Example 2 under a solar simulator.

[0056] Figure 5 Show the POM characterization results of the texture change with temperature of the liquid crystal smart window in Test Example 3.

[0057] Figure 6 Show the test results of the transmittance change of the liquid crystal smart window in Test Example 4 at different temperatures.

[0058] Figure 7 Show the change of the macroscopic transparency of the liquid crystal smart window in Example 3 with light irradiation.

[0059] Figure 8 Show the change of the macroscopic transparency of the liquid crystal smart window in Example 4 with light irradiation.

[0060] Figure 9 Show the change of the macroscopic transparency of the liquid crystal smart window in Example 5 with light irradiation.

[0061] Figure 10 Show the change of the macroscopic transparency of the liquid crystal smart window in Example 6 with light irradiation. Detailed implementation manners

[0062] To more clearly illustrate the present invention, the present invention will be further described below in conjunction with preferred embodiments and the accompanying drawings. Similar components in the drawings are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0063] Preparation of the infrared light-absorbing and photothermal conversion material IDI

[0064] Add N,N,N′,N′-tetrakis[4-(diisobutylamino)phenyl]-1,4-phenylenediamine (IPA) (1.0 g, 1.08 mmol) and lithium diborate (0.5 g, 2.58 mmol) into a two-necked flask. Then, add 5.0 g of dichloromethane and 2.0 g of ethanol, and reflux for 2 h. When the solution turns dark green after 2 h, add sodium persulfate (0.35 g, 1.47 mmol) and 8.0 g of water, and reflux for 2 h. The reaction is terminated by adding a large amount of water and dichloromethane, and washed several times with water to remove unreacted materials and impurities. The combined organic layer is subjected to vacuum distillation to obtain a black solid (1.1 g, 78.6%).

[0065] Dissolve the synthesized infrared absorption material IDI at 1 wt% in the small molecule liquid crystal 5CB and dichloromethane solution, and perform absorption tests using ultraviolet-visible-near-infrared spectroscopy, as Figure 1 shown. It can be found that the main absorption peaks of IDI in both solutions are in the near-infrared band of 800 - 1200 nm and the ultraviolet region around 380 nm. After normalizing the absorption rate, the transmittance in the 800 - 1200 nm band does not exceed 10%, and the transmittance in the visible light range of 400 - 800 nm is not less than 80%. This indicates that the synthesized ammonium diborate IDI is a photothermal conversion material with high transparency in the visible light region and good near-infrared light absorption performance.

[0066] Example

[0067] Example 1

[0068] After spin-coating a polyimide with vertical alignment function on the surface of a clean glass slide, pre-bake it on a hot plate at 80 °C for 15 s, pre-bake it in an oven at 80 °C for 15 min, cure it in the oven at 110 °C for 30 min, and keep it in the oven at 230 °C for 1.5 - 2 h to obtain a glass slide with a vertically aligned liquid crystal aligning agent on its inner surface. Place the inner surfaces of two vertically aligned glass slides opposite to each other, and coat 20-μm silica glass microbead spacers mixed with ultraviolet-curable glue at the four corners in the middle of the two slides. Then, cure the glue with ultraviolet light to make an empty liquid crystal cell that can vertically align the liquid crystal.

[0069] Dissolve the host liquid crystal 5CB and IDI (with a weight ratio of 1 wt% to the host liquid crystal 5CB) together in dichloromethane, stir ultrasonically for 24 h, and pour the mixture into the empty liquid crystal cell by capillary action on a hot stage at 80 °C. Then, slowly cool the system to obtain a liquid crystal smart window that can adapt to light.

[0070] Place this liquid crystal smart window under a solar simulator and irradiate the liquid crystal smart window at a power of 100 mW / cm 2 for 5 min. The temperature change is as Figure 2As shown, it can be found that the ambient temperature outside the light spot is 23 °C at this time, the ambient temperature without samples inside the light spot is 24.3 °C. As a control, the temperature of the sample containing only 5CB in the liquid crystal window is 25.5 °C, while the temperature of the liquid crystal smart window can reach 29 °C at this time. Compared with the liquid crystal window without the addition of the photothermal material IDI, the temperature has increased by 4.5 °C, indicating that IDI has a good photothermal effect when miscible with the liquid crystal.

[0071] Example 2

[0072] The preparation method of the empty liquid crystal cell is the same as that in Example 1.

[0073] The liquid crystal 8CB, the chiral dopant R5011 (weight ratio to the host liquid crystal 8CB is 1 wt%), and IDI (weight ratio to the host liquid crystal 8CB is 2.5 wt%) were dissolved in dichloromethane together, and ultrasonically stirred for 24 h. The mixture was poured into the empty liquid crystal cell by capillary action on a hot stage at 80 °C, and then the system was slowly cooled to obtain a liquid crystal smart window that can adapt to light illumination.

[0074] Example 3

[0075] The preparation method of the empty liquid crystal cell is the same as that in Example 1.

[0076] The liquid crystal 8CB, the chiral dopant R5011 (weight ratio to the host liquid crystal 8CB is 1.2 wt%), and IDI (weight ratio to the host liquid crystal 8CB is 2.5 wt%) were dissolved in dichloromethane together, and ultrasonically stirred for 24 h. The mixture was poured into the empty liquid crystal cell by capillary action on a hot stage at 80 °C, and then the system was slowly cooled to obtain a liquid crystal smart window that can adapt to light illumination. The change of its macroscopic transparency with time is as Figure 7 shown.

[0077] Example 4

[0078] The preparation method of the empty liquid crystal cell is the same as that in Example 1.

[0079] The liquid crystal 8CB, the chiral dopant R5011 (weight ratio to the host liquid crystal 8CB is 1.2 wt%), and IDI (weight ratio to the host liquid crystal 8CB is 2 wt%) were dissolved in dichloromethane together, and ultrasonically stirred for 24 h. The mixture was poured into the empty liquid crystal cell by capillary action on a hot stage at 80 °C, and then the system was slowly cooled to obtain a liquid crystal smart window that can adapt to light illumination. The change of its macroscopic transparency with time is as Figure 8 shown.

[0080] Example 5

[0081] The preparation method of the empty liquid crystal cell is the same as that in Example 1, except that the diameter of the spacer silica glass microbeads is modified from 20 μm to 10 μm.

[0082] The liquid crystal 8CB, chiral dopant R5011 (weight ratio to the host liquid crystal 8CB is 1.2 wt%), and IDI (weight ratio to the host liquid crystal 8CB is 2.5 wt%) were co-dissolved in dichloromethane, ultrasonic stirred for 24 h, and the mixture was filled into an empty liquid crystal cell by capillary action on a hot stage at 80 °C. Subsequently, the system was slowly cooled to obtain a liquid crystal smart window that can adapt to light. The variation of its macroscopic transparency with time is as Figure 9 shown.

[0083] Example 6

[0084] The preparation method of the empty liquid crystal cell is the same as that in Example 1, except that the diameter of the spacer silica glass microspheres is modified from 20 μm to 5 μm.

[0085] The liquid crystal 8CB, chiral dopant R5011 (weight ratio to the host liquid crystal 8CB is 1.0 wt%), and IDI (weight ratio to the host liquid crystal 8CB is 1.0 wt%) were co-dissolved in dichloromethane, ultrasonic stirred for 24 h, and the mixture was filled into an empty liquid crystal cell by capillary action on a hot stage at 80 °C. Subsequently, the system was slowly cooled to obtain a liquid crystal smart window that can adapt to light. The variation of its macroscopic transparency with time is as Figure 10 shown.

[0086] Test Example

[0087] Test Example 1 Variation of the transparency of the liquid crystal smart window with light

[0088] The liquid crystal smart window of Example 2 was placed under a solar simulator and irradiated with a power of 100 mW / cm 2 for 5 min. The macroscopic digital photo and polarized optical micrograph (POM) are as Figure 3 shown. It can be found that the sample was macroscopically transparent before solar irradiation. Compared with the control sample without IDI, it had a slight yellow color, and the color originated from the infrared absorption dye IDI. Even when the self-adaptive liquid crystal smart window was suspended 2 cm, the background text could still be clearly distinguished, indicating that the initial sample was macroscopically transparent and had a small light scattering effect. The POM image showed that the small particles of IDI were uniformly dispersed in the liquid crystal layer material, and there was no obvious texture in the liquid crystal, proving that it was in a good vertical orientation at this time, so it presented a pseudo-isotropic texture; after being irradiated by the solar simulator for 5 min, the color of the liquid crystal smart window became significantly darker. Compared with the control sample, the color became significantly darker. The background pattern could still be recognized when it was close to the background, but the background pattern was invisible when the liquid crystal smart window was suspended 2 cm. Under light, the liquid crystal smart window had a strong light scattering effect. From the POM image, it can be seen that the liquid crystal was in a focal conic cholesteric texture at this time, so it had a strong light scattering effect on light. When the solar simulator was turned off, the liquid crystal smart window could return to the initial transparent state within 2 min

[0089] Test Example 2: Variation of the temperature of the liquid crystal smart window with light illumination

[0090] Place the liquid crystal smart window prepared in Example 2 under a solar simulator and irradiate the liquid crystal smart window with a power of 100 mW / cm 2 . Continuously observe the temperature change on the surface of the liquid crystal smart window within 600 s using an infrared thermal imager, and collect data. Plot a temperature change curve with time as the horizontal axis and the surface temperature of the liquid crystal smart window as the vertical axis to obtain Figure 4 . It shows that when irradiated by the solar simulator, due to the action of the infrared absorption material IDI, the entire system can continuously heat up until around 300 s, when the temperature rise basically reaches equilibrium, proving that the temperature of the entire system is highly sensitive to sunlight.

[0091] Test Example 3: Variation of the liquid crystal material phase state and transmission spectrum with light illumination in the liquid crystal smart window

[0092] Place the liquid crystal smart window prepared in Example 2 on the hot stage of a polarized optical microscope equipped with an in-situ heating hot stage. Starting from room temperature of 25 °C, heat the liquid crystal smart window at a heating rate of 0.05 °C / min, and simultaneously collect POM images of the liquid crystal smart window at different temperatures to obtain Figure 5 . It can be seen that at 27.9 °C, small particles of IDI are dispersed in the liquid crystal smart window, but there is no texture, indicating that it is a smectic A phase liquid crystal with a vertical orientation at this time, thus presenting a pseudo-isotropic state; when the temperature rises to 28.1 °C, the texture of the cholesteric phase with a focal conic state begins to appear, and at 28.6 °C, the entire system is basically converted into a focal conic state cholesteric phase texture; at 37.9 °C, the isotropic phase transition point is reached, and the texture begins to disappear, and at 40 °C, the texture completely disappears. It shows that the current liquid crystal smart window system with 8CB as the liquid crystal has good temperature-sensitive characteristics in the range of 25 - 37 °C, and the liquid crystal texture will change significantly with the change of temperature.

[0093] At the same time, detect the transmission spectrum of the liquid crystal smart window when the liquid crystal is in different phase states, and the results are as Figure 6 shown. It can be seen that in the smectic A phase, taking 550 nm in the visible band as an example, the initial transmittance of the liquid crystal smart window can reach 80%. After the temperature rises and the phase of the liquid crystal smart window changes to the cholesteric phase texture with a focal conic state, the transmittance in the 550 nm band decreases to less than 20%. When the temperature continues to rise to reach the isotropic temperature of the liquid crystal, the transmittance at 550 nm rises to about 75%. It shows that when the liquid crystal smart window is in the cholesteric phase state, it has a strong modulation ability for sunlight, and within the temperature range from the smectic A phase to the cholesteric phase with a focal conic state, the liquid crystal smart window has good self-adaptability to sunlight.

[0094] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, based on the above description, other different forms of changes or variations can be made. It is impossible to enumerate all the implementation manners here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A liquid crystal smart window capable of self - adapting to light intensity, characterized in that, it includes a first substrate, a second substrate and a liquid crystal layer; the material of the liquid crystal layer includes a host liquid crystal, a chiral dopant and an infrared absorption material; wherein, the host liquid crystal has at least two liquid crystal phases: a smectic phase and a nematic phase; the temperature at which the host liquid crystal transforms from the smectic phase to the nematic phase is 26 - 32 °C; the weight ratio of the chiral dopant to the host liquid crystal is 1 wt% - 8 wt%; the weight ratio of the infrared absorption material to the host liquid crystal is 0.5 wt% - 3.5 wt%; the host liquid crystal is selected from 8CB or 5CB; the infrared absorption material is an isobutyl - substituted diammonium with a borate anion, and its structural formula is as follows: ； the chiral dopant is selected from R5011; the liquid crystal smart window is prepared according to the following steps: Dissolve the host liquid crystal, the chiral dopant and the infrared absorption material in dichloromethane, and pour it between the first substrate and the second substrate at 40 - 80 °C, then cool down to obtain the liquid crystal smart window capable of self - adapting to light intensity.

2. The liquid crystal smart window capable of self - adapting to light intensity according to claim 1, characterized in that, the thickness of the liquid crystal layer is 4 - 20 μm.

3. The liquid crystal smart window capable of self - adapting to light intensity according to claim 1, characterized in that, a vertical liquid crystal aligning agent is spin - coated on the surfaces of the first substrate and the second substrate that are in contact with the liquid crystal layer.

4. A preparation method of the liquid crystal smart window capable of self - adapting to light intensity according to any one of claims 1 - 3, characterized in that, it includes the following steps: Dissolve the host liquid crystal, the chiral dopant and the infrared absorption material in dichloromethane, and pour it between the first substrate and the second substrate at 40 - 80 °C, then cool down to obtain the liquid crystal smart window capable of self - adapting to light intensity.

5. An application of the liquid crystal smart window capable of self - adapting to light intensity according to any one of claims 1 - 3 in adjusting the solar transmittance.

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