Preparation method of transmissive liquid crystal dimming glass based on liquid crystal physical gel

Abstract

The application discloses a preparation method of a trans-liquid crystal dimming glass based on a liquid crystal physical gel. A nematic liquid crystal is mixed with a physical gel, and the nematic liquid crystal is heated to a clearing point T IN The nematic liquid crystal physical gel is heated again to a clearing point T IN The solution is slowly cooled to a white and flowing liquid, a chiral compound is added, and magnetic stirring is performed, the white liquid with flowability is filled into a glass interlayer, and is cooled to room temperature to obtain the trans-liquid crystal dimming glass. The material used in the application needs to have both a light transparent state and a light scattering state. A cholesteric phase liquid crystal (Ch liquid crystal, hereinafter referred to as Ch) is selected as a basic material, the Ch is a mother liquid crystal of a nematic liquid crystal and is realized by doping a certain proportion of a chiral compound in the nematic liquid crystal. A planar texture of the Ch is a light transparent state, and a focal conic texture is a light scattering state, i.e. an opaque state.

Description

Technical Field

[0001] This invention relates to liquid crystal display devices, and more specifically to a method for preparing inverted liquid crystal dimming glass based on liquid crystal physical gel. Background Technology

[0002] Liquid crystal (LC) materials are special substances whose molecular polarity allows their molecular orientation to change under the influence of an applied electric field. In other words, the optical properties of liquid crystals can be controlled by an electric field. A typical example is the use of electro-controlled liquid crystal dimming glass. Due to its advantage of adjustable transmittance, electro-controlled liquid crystal dimming glass has been widely used in automotive windows and interior partitions.

[0003] Currently, the main mechanism of commercially available electro-optical dimming glass is based on formal electro-optical dimming using polymer-dispersed liquid crystals (PDLCs). These products are normally in a light-scattering state, i.e., opaque; they only remain transparent when an external electric field is applied and maintained. However, in practical applications, some situations require windows to be light-transmitting most of the time, and only opaque for a few hours. Using formal electro-optical dimming glass in these situations would inevitably lead to unnecessary energy consumption. In contrast, the electro-optical properties of inverted electro-optical liquid crystal dimming glass are exactly the opposite of formal electro-optical dimming: it is transparent when no electric field is applied, and exhibits strong light scattering when an electric field is applied. Therefore, inverted electro-optical dimming glass better meets the energy-saving and environmental protection requirements of these applications, giving it a broader range of application prospects.

[0004] Another problem with electrically controlled dimming glass currently used in daily life is that it cannot be used under direct current. Because it is made of PDLC, and the content of prepolymer in this material is roughly the same as that in LC, there are many more impurities around the LC molecules (for LC, prepolymer is an impurity), which makes the product unable to be driven by direct current. This undoubtedly reduces the portability and mobility of the device.

[0005] Therefore, there is an urgent need to develop a new material and manufacturing process for electronically controlled dimming glass to solve the problems of reverse modulation and DC drive of the device. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a transverse liquid crystal dimming glass based on a liquid crystal physical gel, which is capable of inverse modulation and DC drive.

[0007] To achieve the above objectives, the preparation method of the present invention is as follows:

[0008] Step 1: Mix 0.08–0.16% by mass of oriented liquid crystal and physical gel with nematic liquid crystal. Then, place the mixed nematic liquid crystal and physical gel at a clearing point T of the nematic liquid crystal. IN The above heating and magnetic stirring process is used to fully and uniformly mix the nematic liquid crystal and the physical gel to obtain a mixed solution. After cooling to room temperature, a non-flowing milky white nematic liquid crystal physical gel is obtained.

[0009] Step 2: Reheat the nematic liquid crystal physical gel to its cooling point T. IN The above process makes the nematic liquid crystal physical gel transparent and highly fluid. The temperature is gradually reduced until the substance becomes a fluid, milky white liquid. While maintaining this temperature, 1-7% of the chiral compound by mass of the nematic liquid crystal is added and the mixture is magnetically stirred until homogeneous to obtain a fluid white liquid.

[0010] Step 3: At the temperature at which the chiral compound is added, a free-flowing white liquid is filled into the glass interlayer and cooled to room temperature to obtain a reverse liquid crystal dimming glass.

[0011] The nematic liquid crystal in step one is SLC-1717, HTG135200-100, SLC-9023, C5 or XH154T7023-000.

[0012] The physical gel in step one is benzyl sorbitol, di(p-methylbenzyl)sorbitol, or di(3,4-dimethylbenzyl)sorbitol.

[0013] The chiral compound in step two is R5011, S811, R811, R1011, or CB15.

[0014] The temperature control rate for step two, in which the temperature is gradually reduced, is 1–4 °C / min.

[0015] The glass interlayer in step three is made of transparent glass with one side coated with indium tin oxide.

[0016] The materials used in this invention need to possess both a light-transparent state and a light-scattering state. Cholesteric liquid crystal (Ch-phase liquid crystal, hereinafter referred to as Ch) is chosen as the basic material. Ch is achieved by doping a certain proportion of chiral compounds into a nematic liquid crystal matrix. The planar texture of Ch represents the light-transparent state, while the focal conic texture represents the light-scattering state, i.e., the opaque state.

[0017] This invention uses a liquid crystal physical gel system as the material. Liquid crystal physical gel (LCPG) is obtained by doping small-molecule physical gelling agents into liquid crystals and utilizing the self-assembly behavior between these agents. An applied electric field provides the force for Ch to transition from a transparent state to a scattering state. However, since the energy of a planar texture is greater than that of a focal conic texture, Ch in the focal conic texture cannot spontaneously revert to a planar texture. The self-assembly behavior of the gelling agents forms a three-dimensional (3D) fiber network that binds LC molecules within it. The anchoring energy between the fiber network and the LC molecules provides the force to restore Ch to its optically transparent state. Unlike PDLC, this invention requires only a very small amount of physical gelling agents, less than 0.50% of the liquid crystal mass. This is negligible, and the system is very close to pure LC (i.e., free of impurities), thus allowing it to be driven under direct current.

[0018] The glass used in this invention is a transparent glass with one side coated with indium tin oxide (ITO, a conductive material) and the other side uncoated. Two such pieces of glass are used to form a liquid crystal cell using two 56μm thick polyethylene gaskets. The material used is then filled into the liquid crystal cell to prepare the desired electrically tunable glass. Attached Figure Description

[0019] Figure 1 This refers to the transmittance of Ch in the visible light band when no physical gel DMDBS is added in Embodiment 1 of the present invention. The transmittance is 100% when the empty liquid crystal cell is used as a reference.

[0020] Figure 2 These are images of LCPG in different states. (a) is the anisotropic-gel state, where the substance is non-flowing and white; (b) is the isotropic-sol state, where the substance is flowing and colorless and transparent; (c) is the anisotropic-sol state, where the substance is flowing and white.

[0021] Figure 3 The transmittance of the inventive product in this embodiment to visible light under normal conditions (when not powered on) can reach a maximum of over 80%. Measurements are taken with an empty liquid crystal cell as a reference, i.e., a transmittance of 100%.

[0022] Figure 4 This is the electro-optic curve of the product in the example, that is, the relationship between transmittance and voltage. During the test, the maximum transmittance was 100%, and the wavelength of the light source was 625nm.

[0023] Figure 5This is a response time test of the product in the example. The "on" time in the response time refers to the time it takes for the product to change from a transparent state to a fully scattering state after being powered on; the "off" time refers to the time it takes for the product to change back to a transparent state after the electric field is removed. Here, the fully scattering state refers to the state with the lowest transmittance. The wavelength of the light source used in the test is 625 nm.

[0024] Figure 6 These are physical images of the product in the embodiments. (a) is a physical image of the product in its normal state; (b) is a physical image of the product becoming transparent after being energized; (c) is a physical image of the product returning to a light-transparent state after the electric field is removed.

[0025] Figure 7 These are images of the examples under a polarizing microscope. (a) is Ch, which is a mixture of 96% SLC-1717 and 4% S811 by mass; (b) is an LCPG image after adding DMDBS to the above Ch, and the black filamentous material in the image is the gel formed by DMDBS.

[0026] Figure 8 This is a structural diagram of the product in the embodiment. The main structure of the product consists of a sandwich layer composed of two pieces of glass, one side of which is coated with ITO (conductive) and the other side is non-conductive. The product is completed after LCPG is filled into the sandwich layer.

[0027] Figure 9 This is a schematic diagram showing the changes in the arrangement of liquid crystal molecules when energized and de-energized. (a) shows Ch in a planar texture, i.e., transparent state, when no energization is applied; (b) shows Ch in a focal conic texture, i.e., scattering state, when an electric field is applied; (c) shows Ch returning to a planar texture under the anchoring energy of the physical gel after the electric field is removed. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. All raw materials used in the following embodiments are commercially available. The room temperature mentioned in the following embodiments is 25℃±3℃.

[0029] The nematic liquid crystal used in this invention is as follows:

[0030]

[0031] The physical gel is as follows:

[0032]

[0033]

[0034] Usable chiral compounds:

[0035]

[0036] Before the actual fabrication, a liquid crystal cell needs to be prepared. Take two pieces of conductive glass, one side of which is coated with ITO to conduct electricity, and the other side is non-conductive. Place the two conductive sides "face to face" and use two 56μm thick spacers to form a 56μm thick interlayer between the two pieces of glass.

[0037] Example 1:

[0038] The following examples used compounds as shown in Table 1: In this example, the total mass fraction of SLC-1717 and S811 is recorded as 100%, that is, the mass fraction of Ch formed by the two is 100%.

[0039] Table 1:

[0040]

[0041] The compounds named SLC-1717, DMDBS, and S811 used in the examples are all publicly available compounds that can be obtained by those skilled in the art through publicly available literature or by purchasing them.

[0042] The specific preparation steps in this embodiment are as follows:

[0043] Step 1: The product of this invention needs to possess both a light-transparent state and a light-scattering state. For the light-transparent state, the higher the transmittance in the visible light band, the better. In this embodiment, the transparent state is achieved by mixing SLC-1717 and S811 to form a planar texture of cholesteric liquid crystal. Different mass fractions of S811 will produce different transmission bands and transmittances. In this embodiment, when the mass fraction ratio of SLC-1717 to S811 is 96:4, its transmission effect to visible light is optimal, and the maximum transmittance can reach over 80%. The transmittance in the visible light band is as follows: Figure 1 As shown.

[0044] Step 2: Prepare the materials according to the proportions shown in Table 1. Place SLC-1717 and DMDBS into a glass bottle, then add an appropriately sized magnetic stirrer. Heat and stir on a magnetic stirrer for approximately 15 minutes. The heating and stirring temperature must be within the clearing point T of the liquid crystal. IN To ensure that the liquid crystal and physical gelling agent can be fully and uniformly mixed, the heating and stirring temperature in this embodiment is maintained at 120°C.

[0045] Step 3: After stirring SLC-1717 and DMDBS, cool the solution to room temperature. At room temperature, if the substance in the glass bottle is milky white and does not flow when the bottle is inverted, this state is also called anisotropic gel state. A sample image is shown below. Figure 2 As shown in (a), it indicates that SCL-1717 and DMDBS have formed an LCPG.

[0046] Step 4: Reheat the LCPG to 120°C. The substance in the bottle will once again exhibit a free-flowing, colorless, and transparent solution (also known as an isotropic sol state). See the image below. Figure 2 (b) At this point, the cooling rate is controlled at 2°C / min to ensure that the substance in the bottle remains a free-flowing white liquid (also known as anisotropic sol state) and that the solution in the bottle is maintained in this state. Too high a temperature will cause the solution to revert to a transparent state, while too low a temperature will cause the sol to lose its fluidity and become a gel. Therefore, this step requires temperature control within a certain range. In this embodiment, the temperature is controlled and maintained at 76°C ± 1.5°C.

[0047] Step 5: In anisotropic sol-sol solutions, i.e. Figure 2 (c) Add pre-weighed S811 to the solution as shown in diagram (c), and stir at this temperature for approximately 15 minutes to ensure uniform mixing of S811 and SLC-1717. After adding S811, the Tc of the liquid crystal... IN The temperature will decrease. If, during this step, the liquid crystal reverts to a colorless and transparent state, the process needs to be restarted from step two. In this embodiment, the temperature is maintained at 76℃±1.5℃. This temperature ensures that the substance inside the bottle remains a highly fluid white liquid, allowing for successful production.

[0048] Step Six: At this temperature, fill the prepared glass interlayer with the solution and cool to room temperature. The reverse electro-optical dimming glass is now complete. Figure 8 The material inside the interlayer is LCPG.

[0049] The performance of this embodiment was tested, and the product of this embodiment achieved a visible light transmittance of over 80%. The test results are as follows: Figure 3 As shown; the transmittance versus voltage curve and response time curve were measured using a liquid crystal comprehensive parameter meter, and the results are as follows. Figure 4 and Figure 5 As shown, the product in this example exhibits a contrast ratio greater than 30, a response time of approximately 30ms, and a maximum drive voltage not exceeding 30V. Its response time is less than the human eye's reaction time (approximately 40ms), and the maximum drive voltage is below the safe voltage for the human body (36V).

[0050] See Figure 6 (a) is a physical image of this embodiment under normal conditions; (b) is a physical image of this embodiment after being energized and becoming transparent; (c) is a physical image of this embodiment after the electric field is removed and it returns to a light-transparent state.

[0051] Figure 7(a) is Ch, which is a mixture of 96% SLC-1717 and 4% S811 by mass in this embodiment; (b) is an LCPG image of Ch after adding DMDBS, and the black filamentous substance in the image is the gel formed by DMDBS.

[0052] Figure 9 (a) is when Ch is in a planar texture, i.e., transparent state, without electricity in this embodiment; (b) is when Ch is in a focal cone texture, i.e., scattering state, with electricity applied in this embodiment; (c) is when Ch returns to a planar texture after the electric field is removed in this embodiment, under the anchoring energy of the physical gel.

[0053] Table 2 shows the performance test results of the products in the embodiments of the present invention:

[0054] Table 2:

[0055]

[0056] In reverse-type electronically controlled dimming glass, the maximum driving voltage, also known as the minimum transmittance voltage, is the voltage at which the product becomes opaque after being powered on and has the lowest transmittance; the threshold voltage is the voltage at which the transmittance decreases by 10%.

[0057] Example 2:

[0058] Step 1: Mix the nematic liquid crystal HTG135200-100 with 0.08% (by mass) of the physical gel DMDBS. Then, place the mixed nematic liquid crystal and physical gel at the clearing point T of the nematic liquid crystal. IN The above heating and magnetic stirring process is used to fully and uniformly mix the nematic liquid crystal and the physical gel to obtain a mixed solution. In this embodiment, the heating and stirring temperature is maintained at 120°C. After cooling to room temperature, a non-flowing milky white nematic liquid crystal physical gel is obtained.

[0059] Step 2: Reheat the nematic liquid crystal physical gel to its cooling point T. IN The above describes the process of maintaining the temperature at 120°C to make the nematic liquid crystal physical gel transparent and highly fluid. The cooling rate is controlled at 2°C / min until the substance becomes a fluid, milky white liquid. In this embodiment, the temperature is controlled and maintained at 76°C ± 1.5°C. After maintaining this temperature, 2% (by mass) of the chiral compound R5011 of the nematic liquid crystal is added and magnetically stirred to mix evenly, resulting in a fluid white liquid.

[0060] Step 3: At the temperature at which the chiral compound is added, a free-flowing white liquid is filled into the glass interlayer and cooled to room temperature to obtain a reverse liquid crystal dimming glass.

[0061] Example 3:

[0062] Step 1: Mix 0.1% (by mass) of the nematic liquid crystal SLC-9023 with the physical gel DBS. Then, place the mixed nematic liquid crystal and physical gel at the clearing point T of the nematic liquid crystal. IN The above heating and magnetic stirring process is used to fully and uniformly mix the nematic liquid crystal and the physical gel to obtain a mixed solution. In this embodiment, the heating and stirring temperature is maintained at 135°C. After cooling to room temperature, a non-flowing milky white nematic liquid crystal physical gel is obtained.

[0063] Step 2: Reheat the nematic liquid crystal physical gel to its cooling point T. IN The above means that the temperature is maintained at 135℃, so that the nematic liquid crystal physical gel is transparent and has strong fluidity. The cooling rate is controlled at 3℃ / min until the substance becomes a fluid milky white liquid. In this embodiment, the temperature is controlled and maintained at 76℃±1.5℃. After adding 5% of the chiral compound R811 by mass of the nematic liquid crystal while keeping this temperature constant, the mixture is magnetically stirred and mixed evenly to obtain a fluid white liquid.

[0064] Step 3: At the temperature at which the chiral compound is added, a free-flowing white liquid is filled into the glass interlayer and cooled to room temperature to obtain a reverse liquid crystal dimming glass.

[0065] Example 4:

[0066] Step 1: Mix oriented liquid crystal C5 and 0.14% (by mass) of physical gel MDBS. Then, place the mixed nematic liquid crystal and physical gel at a clearing point T of the nematic liquid crystal. IN The above heating and magnetic stirring process is used to fully and uniformly mix the nematic liquid crystal and the physical gel to obtain a mixed solution. In this embodiment, the heating and stirring temperature is maintained at 100°C. After cooling to room temperature, a non-flowing milky white nematic liquid crystal physical gel is obtained.

[0067] Step 2: Reheat the nematic liquid crystal physical gel to its cooling point T. IN The above describes the process of maintaining the temperature at 100℃ to make the nematic liquid crystal physical gel transparent and highly fluid. The cooling rate is controlled at 1℃ / min until the substance becomes a fluid, milky white liquid. In this embodiment, the temperature is controlled and maintained at 72℃±1.5℃. While maintaining this temperature, 1% of the chiral compound R1011 by mass of the nematic liquid crystal is added and magnetically stirred to mix evenly, resulting in a fluid white liquid.

[0068] Step 3: At the temperature at which the chiral compound is added, a free-flowing white liquid is filled into the glass interlayer and cooled to room temperature to obtain a reverse liquid crystal dimming glass.

[0069] Example 5:

[0070] Step 1: Mix oriented nematic liquid crystal XH154T7023-000 with 0.16% (by mass) of MDSB physical gel. Then, place the mixed nematic liquid crystal and physical gel at the clearing point T of the nematic liquid crystal. IN The above heating and magnetic stirring process is used to fully and uniformly mix the nematic liquid crystal and the physical gel to obtain a mixed solution. In this embodiment, the heating and stirring temperature is maintained at 150°C. After cooling to room temperature, a non-flowing milky white nematic liquid crystal physical gel is obtained.

[0071] Step 2: Reheat the nematic liquid crystal physical gel to its cooling point T. IN The above describes the process of maintaining the temperature at 150°C to make the nematic liquid crystal physical gel transparent and highly fluid. The cooling rate is controlled at 4°C / min until the substance becomes a fluid, milky white liquid. In this embodiment, the temperature is controlled and maintained at 80°C ± 1.5°C. After adding 7% (by weight) of the chiral compound CB15 of the nematic liquid crystal while maintaining this temperature, the mixture is magnetically stirred until homogeneous to obtain a fluid white liquid.

[0072] Step 3: At the temperature at which the chiral compound is added, a free-flowing white liquid is filled into the glass interlayer and cooled to room temperature to obtain a reverse liquid crystal dimming glass.

Claims

1. A method for preparing inverted liquid crystal dimming glass based on liquid crystal physical gel, characterized in that: Step 1: Mix 0.08–0.16% by mass of oriented liquid crystal and physical gel with nematic liquid crystal. Then, place the mixed nematic liquid crystal and physical gel at a clearing point T of the nematic liquid crystal. IN The above heating and magnetic stirring process is used to fully and uniformly mix the nematic liquid crystal and the physical gel to obtain a mixed solution. After cooling to room temperature, a non-flowing milky white nematic liquid crystal physical gel is obtained. Step 2: Reheat the nematic liquid crystal physical gel to its cooling point T. IN The above process makes the nematic liquid crystal physical gel transparent and highly fluid. The temperature is gradually reduced until the substance becomes a fluid, milky white liquid. While keeping this temperature constant, 1-7% of the chiral compound by mass of the nematic liquid crystal is added and the mixture is magnetically stirred until homogeneous to obtain a fluid white liquid. Step 3: At the temperature at which the chiral compound was added, a free-flowing white liquid was filled into the glass interlayer and cooled to room temperature to obtain a reverse liquid crystal dimming glass; The glass interlayer is made of transparent glass with one side coated with indium tin oxide.

2. The method for preparing inverted liquid crystal dimming glass based on liquid crystal physical gel according to claim 1, characterized in that: The nematic liquid crystal in step one is SLC-1717, HTG135200-100, SLC-9023, C5 or XH154T7023-000.

3. The method for preparing inverted liquid crystal dimming glass based on liquid crystal physical gel according to claim 1, characterized in that: The physical gel in step one is benzyl sorbitol, di(p-methylbenzyl)sorbitol, or di(3,4-dimethylbenzyl)sorbitol.

4. The method for preparing inverted liquid crystal dimming glass based on liquid crystal physical gel according to claim 1, characterized in that: The chiral compound in step two is R5011, S811, R811, R1011, or CB15.

5. The method for preparing inverted liquid crystal dimming glass based on liquid crystal physical gel according to claim 1, characterized in that: The temperature control rate for step two, in which the temperature is gradually reduced, is 1–4 °C / min.

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