Method for preparing blue phase liquid crystal microcosmic patterned array and application of blue phase liquid crystal microcosmic patterned array
By preparing grooves with the desired pattern on the polydimethylsiloxane film, applying liquid crystal solution under heating conditions and performing ultraviolet light polymerization, the problems of low resolution of blue phase liquid crystal micropatterned arrays in the prior art are solved, and high-quality micropatterning is achieved.
Patent Information
- Application Number
- CN202311539407.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-17
- Publication Date
- 2025-05-20
AI Technical Summary
In the prior art, when preparing a micropatterned array of blue phase liquid crystals, the resolution is low, and the single domain quality of blue phase liquid crystals is poor at micro-size.
By providing a polydimethylsiloxane film with a groove in a desired pattern, a liquid crystal solution is applied to the groove under heating conditions, cooling is reduced to form a stable BPI structure, and polymerization is performed by ultraviolet light to obtain a blue phase liquid crystal micropatterned array.
The high-quality patterning of blue-phase liquid crystals is realized, especially in the microscopic state, which improves the resolution of the microscopic patterned array. The influence of the domain-limiting structure makes the blue-phase liquid crystals self-generate into a uniform single-domain phase state at 50 μm.
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Figure CN120019938A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of blue phase liquid crystal materials. More specifically, it relates to a method for preparing a micro-patterned array of blue phase liquid crystals and its application. Background Art
[0002] Substances are generally divided into three phases: solid, liquid, and gas. Liquid crystal is a special phase between solid and liquid. The substances in this state have the characteristics of both the fluidity of liquid and the orderliness of crystal. Molecules with liquid crystal state are called liquid crystal molecules, and materials composed of liquid crystal molecules are called liquid crystal materials. Common liquid crystal materials can be classified into smectic phase, nematic phase, and cholesteric phase according to their structures in the liquid crystal state. Among them, due to the arrangement structure of molecular chirality can interact with light waves in the ultraviolet-visible-infrared band, the cholesteric phase has attracted extensive attention.
[0003] Blue phase liquid crystal is a special cholesteric liquid crystal, and its temperature range is often between chiral nematic phase and isotropic liquid phase. Because blue phase liquid crystal has a three-dimensional cubic structure with a lattice period of nanometer scale, it exhibits selective Bragg reflection in the visible light range corresponding to the cubic lattice. From the perspective of application, high-quality patterning of blue phase liquid crystal is very meaningful for fast light modulators or tunable photonic crystals.
[0004] The patterning methods are mainly divided into template-free methods and template-required methods. Among them, template-free methods mainly include direct writing and inkjet printing; template-required methods mainly include imprinting method, sandwich assembly method, and mask method. However, the above methods all have deficiencies: low resolution (pattern size ≥ 25 μm), and poor single domain quality of blue phase liquid crystal at micro scale. Summary of the Invention
[0005] Based on the above facts, the purpose of the present invention is to provide a method for preparing a micro-patterned array of blue phase liquid crystals and its application. Through this method, high-quality patterning of blue phase liquid crystal is achieved, especially high-quality patterning in the micro state.
[0006] To achieve the above purpose, the present invention adopts the following technical solutions:
[0007] On the one hand, the present invention provides a method for preparing a micro-patterned array of blue phase liquid crystals, the method comprising the following steps:
[0008] Providing a polydimethylsiloxane film with grooves of a desired pattern shape;
[0009] Under heating conditions, applying at least a liquid crystal solution into the grooves, and cooling to form a stable BPI structure;
[0010] Performing ultraviolet light polymerization to obtain the micro-patterned array of blue phase liquid crystals.
[0011] It can be understood that the shape of the groove is the shape of the desired pattern, and the size of the groove also corresponds to the size of the desired pattern. In addition, cooling to form a stable BPI structure also means cooling to form a stable blue phase I.
[0012] Furthermore, the length and width of the groove are both below 50 μm, and the height is below 20 μm.
[0013] Through the technical solution of the present invention, patterning of large-size and micro-size blue-phase liquid crystals can be achieved. Among them, exemplary micro-sizes include but are not limited to 5 - 30 μm, 5 - 15 μm, 5 - 10 μm, 50 μm, 30 μm, 15 μm, 10 μm, 5 μm, etc. In some examples, the pattern shapes include but are not limited to rectangles and / or frustum of a cone, etc.
[0014] In the technical solution of the present invention, the "size" mentioned refers to the length along the x-axis, y-axis, and / or z-axis directions. For example, when the pattern shape is a rectangle, the "size" refers to its length along the x-axis, y-axis, and z-axis directions; when the pattern shape is a frustum of a cone, the "size" refers to the diameter of its circular surface and the height.
[0015] Furthermore, the heating is carried out under closed conditions. Due to the poor heat transfer of the PDMS material, the phase change of the liquid crystal on the film shows a gradual change from the periphery to the central part; because the size of the micro-liquid crystal pattern is too small and is too sensitive to temperature, heating and cooling are carried out under closed conditions (such as using a closed hot stage) to prepare a uniform and stable blue-phase liquid crystal.
[0016] Furthermore, the heating temperature is 110 °C and the time is 15 min. Under this condition, further cooling is more likely to form a stable BPI structure.
[0017] Furthermore, the cooling rate is 0.01 - 0.2 °C / min. In the preparation method of the present invention, if the cooling rate is too high, the obtained pattern will be uneven; if the cooling rate is too low, a patterned array of a uniform phase state (blue phase) cannot be obtained. Preferably, the cooling rate is 0.01 - 0.1 °C / min or 0.1 - 0.2 °C / min.
[0018] Furthermore, during the cooling process, the surface of the groove in the polydimethylsiloxane film containing the liquid crystal solution faces the cooling source, and at this time, the phase change temperature can be controlled more precisely to obtain a larger area and more uniform blue-phase and liquid crystal patterned array.
[0019] Even further, a cover glass is covered on the surface of the groove in the polydimethylsiloxane film containing the liquid crystal solution, and then cooling is carried out. Furthermore, the conditions for ultraviolet light polymerization are: intensity is 50 mW / cm 2, irradiate with ultraviolet light with a wavelength of 365 nm for 5 min.
[0020] Furthermore, the preparation of the polydimethylsiloxane film with the required patterned grooves includes the following steps:
[0021] Perform surface hydrophobic treatment on the substrate with the required pattern;
[0022] Replicate the pattern onto the polydimethylsiloxane film.
[0023] Furthermore, the substrate is selected from silicon wafers.
[0024] Furthermore, the method of the surface hydrophobic treatment includes the following steps:
[0025] After the substrate is subjected to vacuum plasma cleaning, it is heat-treated with fluorosilane liquid after vacuum drying.
[0026] Furthermore, the method of the surface hydrophobic treatment includes the following steps:
[0027] Treat the substrate in a vacuum plasma cleaner at a strength of 200 W for 600 s, then put it into a vacuum dryer with fluorosilane liquid added and evacuate for 30 min. Then put the vacuum dryer into an oven for treatment, the treatment time is 8 h, and the treatment temperature is 80 °C.
[0028] Furthermore, the method of replicating the pattern onto the polydimethylsiloxane film includes the following steps:
[0029] Drop the solution obtained by mixing the monomer for forming polydimethylsiloxane and the initiator onto the substrate with the required pattern. After removing the bubbles, dry it to obtain the polydimethylsiloxane film with the required patterned grooves.
[0030] Furthermore, the mass ratio of the monomer to the initiator is 10:1.
[0031] Furthermore, the monomer includes but is not limited to dimethylsilanol.
[0032] Furthermore, the initiator includes but is not limited to silicate ester condensers.
[0033] Furthermore, by weight percentage, the liquid crystal solution contains:
[0034] 58 wt% of non-photopolymerizable nematic liquid crystal, 29 wt% of photopolymerizable nematic liquid crystal, 3.5 wt% of photopolymerizable chiral agent, 4 wt% of stabilizer, 2 wt% of photoinitiator and 2 wt% of photosensitizer.
[0035] Due to the confinement effect, it is more difficult for the microscale blue phase liquid crystal to polymerize compared to the macroscopic scale. In some preferred technical solutions of the present invention, the contents of photoinitiator and photosensitizer in the liquid crystal solution are increased, and then a blue phase liquid crystal micro-patterned array with high-quality micro-patterns is prepared.
[0036] Furthermore, the liquid crystal solution further contains 1.5 wt% of dye.
[0037] On the other hand, the present invention provides the application of the blue phase liquid crystal micro-patterned array prepared by the method as described above in the patterned display of blue phase liquid crystal and the preparation of microscale lasers.
[0038] Furthermore, according to different dyes, the obtained doped blue phase liquid crystal micro-patterned array can obtain blue phase liquid crystals that reflect light of different wavelengths. It can be used for pixel display and can be used to prepare microscale surface-emitting lasers.
[0039] The beneficial effects of the present invention are as follows:
[0040] In the preparation method provided by the present invention, a blue phase liquid crystal micro-pattern array is prepared by PDMS replication. The patterns can be designed as needed to meet diverse applications. The solution of the present invention improves the resolution of the micro-patterned array, and the minimum size can reach 2 μm or less. Due to the influence of the confinement structure, the blue phase liquid crystal can spontaneously generate a uniform single-domain phase state at 50 μm or less. Different from traditional liquid crystal cells, the growth environment of this blue phase liquid crystal can be an open system, and the growth does not require a liquid crystal cell, which is helpful for the preparation of three-dimensional blue phase liquid crystal devices. Different fluorescent dyes can be doped as needed to prepare microscale surface-emitting lasers. Since the PDMS film has a certain stretchability, it can be applied to stretchable devices such as bionic robots, broadening the bionic application field of blue phase liquid crystals. Description of the Drawings
[0041] The following further details the specific embodiments of the present invention with reference to the drawings.
[0042] Figure 1 Example 1 is shown: a) Schematic diagram of the polarized microscope observation of a blue phase liquid crystal rectangular patterned array with a side length of 50 μm; b) Reflection spectrum after polymerization.
[0043] Figure 2 The blue phase Kossel diagram of the liquid crystal polymer pattern array prepared in Example 1 is shown.
[0044] Figure 3 Example 2 is shown: a) Schematic diagram of the polarized microscope observation of a 30-μm blue phase liquid crystal patterned array; b) Reflection spectrum after polymerization.
[0045] Figure 4Example 3 is shown: a) Schematic diagram of polarized microscopy observation of a 10-μm blue phase liquid crystal patterned array; b) Reflection spectrum after polymerization.
[0046] Figure 5 Example 4 is shown: a) Schematic diagram of polarized microscopy observation of a blue phase liquid crystal circular pattern array with a diameter of 10 μm; b) Schematic diagram of polarized microscopy observation of a blue phase liquid crystal annular array with an outer diameter of 10 μm and an annular width of 2 μm. Detailed implementation manner
[0047] To illustrate the present invention more clearly, 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.
[0048] Example 1
[0049] A method for preparing a blue phase liquid crystal micro-patterned array, characterized by comprising the following steps:
[0050] 1) Preparation of blue phase liquid crystal mixture:
[0051] Weigh the polymerizable monomer C6M using a balance Non-polymerizable nematic commercial mixed liquid crystal HTG135200, polymerizable chiral agent R5011, stabilizer TMPTA, initiator I-651, photosensitizer and coumarin 6 (C6) are put into a container in mass percentages of 29%, 58%, 3.5%, 4%, 2%, 2%, and 1.5% respectively, and completely dissolved with 3 mL of dichloromethane, and then put into an oven to completely volatilize the dichloromethane to obtain a blue phase liquid crystal mixture.
[0052] 2) Preparation of PDMS template
[0053] Prepare a PDMS mixture solution: The monomer dimethylsilanol and the initiator silicate condensing agent are prepared into a solution according to a mass ratio of 10:1; the prepared solution is put into the refrigerator for 1 h (to remove bubbles); the refrigerated solution is dropped onto the patterned silicon wafer treated with surface hydrophobic treatment (the hydrophobic treatment method is: treating the patterned silicon wafer in a vacuum plasma cleaner at a strength of 200 W for 600 s, then putting it into a vacuum dryer dropwise added with fluorosilane liquid and evacuating for 30 min, then putting the vacuum dryer into an oven for treatment, the treatment time is 8 h, and the treatment temperature is 80 °C); the silicon wafer is put into a dryer and evacuated for 0.5 h (to remove bubbles); the silicon wafer is put into an oven at 120 °C and dried for 3 - 4 h; finally, the film is peeled off from the silicon wafer with pointed tweezers to complete the replication of the PDMS film, and the size of the silicon wafer template used is 50×50×20 μm.
[0054] 3) Spin-coating of blue phase liquid crystal:
[0055] Place the blue phase liquid crystal mixture prepared in step 1) and the PDMS template prepared in step 2) on a heating and stirring platform, keep it warm at 110 °C for 15 min. Under isotropic conditions, use a pipette to suck 2 μL of the liquid crystal solution and drop it onto the PDMS template, then use an ITO glass sheet for spin-coating. Finally, cover the ITO glass sheet on the PDMS template and press it firmly, and place it on the heating platform for cooling and observation.
[0056] 4) Slowly cool the PDMS liquid crystal cell at a rate of 0.1 °C / min until the BPI is formed and stabilized, and irradiate it with ultraviolet light with an intensity of 50 mW / cm 2 , a wavelength of 365 nm for 5 min for polymerization to obtain a blue phase liquid crystal polymer pattern array.
[0057] 5) Perform laser performance detection on the polymerized blue phase liquid crystal polymer pattern array, and observe the threshold of 0.22 μJ / pulse and lasing.
[0058] Figure 1 Among them, a) is a schematic diagram of the polarization microscope observation of the blue phase liquid crystal rectangular pattern array with a side length of 50 μm in Example 1; b) is the reflection spectrum after polymerization. The obtained reflection spectrum conforms to the reflection of the blue phase, and the domain blocks of the blue phase can be seen under the polarized light microscope. The measured blue phase Kossel diagram is as Figure 2 shown, this diagram characterizes the specular orientation of blue phase I and blue phase II, and proves that the obtained liquid crystal polymer pattern array is a blue phase liquid crystal polymer pattern array.
[0059] Example 2
[0060] The preparation steps are the same as those in Example 1, only changing the template pattern to a 30-μm rectangular pattern, and other parameters are the same. Finally, a blue phase liquid crystal rectangular array with a dot size of 30 μm is obtained.
[0061] Figure 3 Among them, a) is a schematic diagram of the polarization microscope observation of the 30-μm blue phase liquid crystal pattern array; b) is the reflection spectrum after polymerization. The obtained reflection spectrum conforms to the reflection of the blue phase, and the domain blocks of the blue phase can be seen under the polarized light microscope, and the Kossel of the blue phase is measured subsequently.
[0062] Example 3
[0063] The preparation steps are the same as those in Example 1, only changing the template pattern to a 10-μm rectangular pattern, and other parameters are the same. Finally, a blue phase liquid crystal rectangular array with a dot size of 10 μm is obtained.
[0064] Figure 4Among them, a) is a schematic diagram of the observation of a 10-μm blue phase liquid crystal patterned array by polarized light microscopy; b) is the reflection spectrum after polymerization. The obtained reflection spectrum conforms to that of the blue phase. Domains of the blue phase can be seen under a polarized light microscope, and the Kossel of the blue phase was measured subsequently.
[0065] Example 4
[0066] The preparation steps are the same as those in Example 1. In this method, the template pattern can also be changed to a 10-μm circular pattern and an annular pattern with an outer diameter of 10 μm and an annular width of 2 μm, and other parameters are the same. Finally, a blue phase liquid crystal annular array with a dot size of 10 μm and an annular pattern array with an outer diameter of 10 μm and an annular width of 2 μm are obtained.
[0067] Figure 5 Among them, a) is a schematic diagram of the observation of a blue phase liquid crystal pattern array with a circular pattern of 10-μm diameter by polarized light microscopy; b) is a schematic diagram of the observation of a blue phase liquid crystal annular array with an outer diameter of 10 μm and an annular width of 2 μm by polarized light microscopy.
[0068] Obviously, the above-mentioned embodiments of the present invention are only 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, other different forms of changes or modifications can be made based on the above description. It is impossible to enumerate all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.
Claims
1. A method for preparing a blue phase liquid crystal micro-patterned array, characterized in that: The steps include: providing a polydimethylsiloxane film having grooves in a desired pattern; Under heating conditions, applying a liquid crystal solution to at least the groove, and cooling the solution to form a stable BPI structure; Ultraviolet light polymerization is adopted to obtain the blue phase liquid crystal micro patterned array.
2. The method according to claim 1, characterized in that The length and width of the groove are both less than 50 μm; and the height is less than 20 μm.
3. The method according to claim 1, characterized in that The heating is carried out under closed conditions; and / or The heating temperature is 110° C. and the heating time is 15 min.
4. The method according to claim 1, characterized in that: The cooling rate is 0.01-0.2°C / min.
5. The method according to claim 1, characterized in that The conditions for the ultraviolet light polymerization are: intensity of 50 mW / cm 2 , irradiated with ultraviolet light of wavelength 365nm for 5min.
6. The method according to claim 1, characterized in that The preparation of the polydimethylsiloxane film having grooves in a desired pattern comprises the following steps: The substrate having the desired pattern is subjected to surface hydrophobic treatment; The pattern was replicated onto a polydimethylsiloxane film.
7. The method according to claim 6, characterized in that The substrate is selected from silicon wafer; and / or The method for surface hydrophobic treatment comprises the following steps: The substrate is cleaned by vacuum plasma, and then heat treated after vacuum drying with fluorosilane liquid.
8. The method according to claim 6, characterized in that The method for replicating the pattern onto a polydimethylsiloxane film comprises the following steps: A solution obtained by mixing a monomer for forming polydimethylsiloxane with an initiator is dripped onto a substrate having a desired pattern, and after eliminating bubbles, the solution is dried to obtain a polydimethylsiloxane film having grooves in the desired pattern.
9. The method according to claim 1, characterized in that: Measured by weight percentage, the liquid crystal solution comprises: 58 wt % of non-photopolymerizable nematic liquid crystal, 29 wt % of photopolymerizable nematic liquid crystal, 3.5 wt % of photopolymerizable chiral agent, 4 wt % of stabilizer, 2 wt % of photoinitiator and 2 wt % of photosensitizer; Preferably, the liquid crystal solution further comprises 1.5 wt % of a dye.
10. Application of the blue phase liquid crystal micro-patterned array prepared by the method according to any one of claims 1 to 9 in the patterned display of blue phase liquid crystal and the preparation of micro-area laser.