Liquid crystal microstructure modulation device and control method and preparation method thereof

Abstract

The invention relates to a liquid crystal microstructure modulation device and a control method and a preparation method thereof, the liquid crystal microstructure modulation device comprises a top substrate, a vertical alignment film, a liquid crystal layer, a parallel alignment film and a bottom substrate, and the bottom substrate and the top substrate are oppositely arranged; the vertical alignment film is arranged at the bottom of the top substrate, the parallel alignment film is arranged at the top of the bottom substrate, and the liquid crystal layer is located between the vertical alignment film and the parallel alignment film; one side of the parallel alignment film is provided with a square lattice alignment pattern, and the parallel alignment film and the vertical alignment film enable liquid crystal molecules in the liquid crystal layer to be self-assembled to form controllable nematic phase and smectic phase liquid crystal microstructures; the square lattice orientation pattern is provided with a preset initial azimuth orientation. By accurately controlling the liquid crystal microstructure, efficient and high-resolution spatial and dynamic modulation of the optical phase is achieved, and the problems of random contusion and form distortion in the liquid crystal self-assembly process are effectively solved.

Description

Technical Field

[0001] The present application relates to the technical field of liquid crystal microstructure modulation, and in particular to a liquid crystal microstructure modulation device and a control method and a preparation method thereof. Background Art

[0002] Liquid crystal is a unique functional material that has both the fluidity of liquid and the physical anisotropy of crystal. This property makes liquid crystal widely used as a large-scale parallel light valve in liquid crystal displays. Liquid crystal can also modulate the phase of light spatially and dynamically with high efficiency and high resolution, so it plays an indispensable role in all-optical interconnection, tunable lenses and lidar.

[0003] Recently, the self-assembly characteristics of liquid crystals have received great attention. The structure of liquid crystals determines their properties and applications. By creating more diverse, ordered, and complex liquid crystal microstructures, novel optical effects can be introduced and the application of advanced technologies can be promoted. For example, by precisely controlling the initial orientation of the helical arrangement of cholesteric liquid crystals, arbitrary modulation of the Bragg-Berry phase can be achieved, thereby achieving reflective phase modulation with specific circular polarization selectivity and a designable frequency range. In addition, by predefining the microstructure of double-helix blue phase liquid crystals, this regulation can even be extended to three-dimensional space. The controllable generation of liquid crystal microstructures provides an effective strategy for large-scale parallel and multi-dimensional optical operations, which is of great significance to cutting-edge technology fields such as high-capacity optical communications, optical neural networks, and augmented / virtual reality.

[0004] However, the self-assembly process of liquid crystals is often driven by entropy, which may lead to random setbacks and morphological distortions, making it challenging to precisely control the liquid crystal microstructure. Therefore, how to achieve flexible control and customized generation of liquid crystal microstructures in a low-cost and efficient manner remains an urgent problem to be solved. Summary of the invention

[0005] In order to solve the above-mentioned defects, the present application provides a liquid crystal microstructure modulation device and a control method and a preparation method thereof.

[0006] The above-mentioned invention objective of the present application is achieved through the following technical solutions:

[0007] A liquid crystal microstructure modulation device comprises a top substrate, a vertical alignment film, a liquid crystal layer, a parallel alignment film and a bottom substrate, wherein the bottom substrate is arranged opposite to the top substrate;

[0008] The vertical alignment film is disposed on the bottom of the top substrate by coating, the parallel alignment film is disposed on the top of the bottom substrate by coating, the liquid crystal layer is located between the vertical alignment film and the parallel alignment film, and spacer particles are disposed between the vertical alignment film and the parallel alignment film;

[0009] The vertical alignment film makes the molecular directors of the liquid crystal molecules in the liquid crystal layer adjacent to the vertical alignment film arranged perpendicular to the vertical alignment film, and the parallel alignment film has a square lattice alignment pattern with radially arranged molecular directors on one side close to the liquid crystal layer, so that the directors of the liquid crystal molecules in the liquid crystal layer adjacent to the parallel alignment film are arranged in the same manner as the molecular directors of the square lattice alignment pattern, and under the joint action of the vertical alignment film and the parallel alignment film, the liquid crystal molecules in the liquid crystal layer self-assemble to form controllable nematic and smectic liquid crystal microstructures;

[0010] Wherein, the square lattice orientation pattern is provided with a preset initial azimuth orientation.

[0011] By adopting the above technical scheme, the present application proposes a liquid crystal microstructure modulation device, which is provided with a vertical orientation film and a parallel orientation film with an orientation pattern of a square-arranged lattice, and introduces the azimuthal orientation of a preset initial azimuthal direction into the orientation pattern with a square-arranged lattice, effectively overcoming the uncontrollability of the microstructure in the process of liquid crystal entropy-driven self-assembly, so that the nematic phase liquid crystal molecules produce controllable distortion deformation, and realizes the control of the arrangement of liquid crystal molecules: the vertical orientation film makes the adjacent liquid crystal molecules in the liquid crystal layer arrange their directors vertically, while the square lattice orientation pattern with a preset initial azimuthal angle in the parallel orientation film , ensuring that the directors of the liquid crystal molecules are consistent with the directors of the graphic molecules, promoting the self-assembly of the liquid crystal molecules, and forming controllable nematic and smectic liquid crystal microstructures; at the same time, the uniformity and stability of the liquid crystal layer are ensured by the setting of spacer particles; the present application achieves efficient, high-resolution spatial and dynamic modulation of the optical phase through precise control of the liquid crystal microstructure, effectively solves the problems of random frustration and morphological distortion in the liquid crystal self-assembly process, and provides an effective strategy for large-scale parallel and multi-dimensional optical operations, which is of great significance to the progress of cutting-edge technology fields such as high-capacity optical communications, optical neural networks, and augmented / virtual reality.

[0012] In a preferred example, the present application can be further configured as follows: the square lattice orientation pattern is composed of square lattice sub-patterns that are closely arranged periodically along the row and column directions.

[0013] By adopting the above technical solution, the square lattice orientation pattern is composed of square lattice sub-patterns arranged closely and periodically along the row and column directions respectively. This arrangement provides a precise orientation template for the liquid crystal molecules, so that the liquid crystal molecules can be arranged according to the preset azimuth angles, thereby realizing precise control of the liquid crystal microstructure.

[0014] In a preferred example, the present application can be further configured as follows: the molecular directors of the square lattice orientation pattern are radially distributed from the center to the boundary along the radial direction.

[0015] By adopting the above technical scheme, the liquid crystal microstructure modulation device of the present invention adopts a special square lattice orientation pattern, which is characterized in that the molecular directors are radially distributed from the center to the boundary, providing clear orientation guidance for the liquid crystal molecules, so that the liquid crystal molecules can self-assemble according to a preset radial arrangement to form a highly ordered microstructure; this radially arranged square lattice orientation pattern can not only affect the orientation of the liquid crystal molecules, but also play a key role in the formation and phase change process of the liquid crystal layer.

[0016] In a preferred example, the present application can be further configured as follows: the center of the square lattice sub-pattern in the square lattice orientation pattern is a +1 topological singularity, the intersection points of four adjacent square lattice sub-patterns in the square lattice orientation pattern form a -1 topological singularity, and the molecules thereof are distributed in a hyperbolic shape.

[0017] By adopting the above technical scheme, in the liquid crystal microstructure modulation device of the present invention, the square lattice orientation pattern has a specific topological structural feature: the center of each square lattice sub-pattern is a +1 topological singularity, and a -1 topological singularity is formed at the intersection of four adjacent square lattice sub-patterns, and the layout of such topological singularities causes the molecular directors to present a hyperbolic distribution in the square lattice; such topological structural feature design utilizes the strong influence of topological singularities on the orientation of liquid crystal molecules, and can effectively guide the liquid crystal molecules to self-assemble according to a preset pattern.

[0018] In a preferred example, the present application can be further configured as follows: the side length of the square lattice sub-pattern in the square lattice orientation pattern is 30 μm.

[0019] By adopting the above-mentioned technical scheme, the liquid crystal microstructure modulation device of the present invention adopts a square lattice orientation pattern with a specific size, wherein the side length of each square lattice pattern is 30 μm. The side length of 30 μm provides an orientation unit of moderate size for the liquid crystal molecules, which not only ensures sufficient orientation accuracy, but also allows the microstructure to be controlled and optimized within a certain range.

[0020] In a preferred example, the present application can be further configured as follows: the thickness of the liquid crystal layer is 8.5 μm.

[0021] By adopting the above technical solution, the thickness of the liquid crystal layer in the liquid crystal microstructure modulation device of the present invention is 8.5 μm. The liquid crystal layer with this thickness ensures that the liquid crystal molecules have enough space for orientation and arrangement while also ensuring the stability and controllability of the microstructure.

[0022] The second object of the invention is achieved by the following technical solutions:

[0023] A control method for a liquid crystal microstructure modulation device comprises the following steps:

[0024] Introducing an azimuthal orientation into the square lattice orientation pattern, and presetting the initial azimuthal direction, so that the liquid crystal molecules adjacent to the parallel orientation film in the liquid crystal layer are twisted and deformed;

[0025] The liquid crystal microstructure modulation device is cooled to change the liquid crystal layer from an isotropic state to a nematic phase, and the arrangement of the liquid crystal molecules is controlled by the square lattice orientation pattern having a preset initial azimuth angle;

[0026] Further cooling to the smectic phase, due to the suppression of distortion and destruction of symmetry after the phase transition, a spiral toroidal focal cone domain array is formed;

[0027] By changing the direction of the initial azimuth angle, the toroidal focal cone domain array is degenerated from infinite rotational symmetry to four-fold rotational symmetry, thereby forming a controllable smectic microstructure.

[0028] By adopting the above technical scheme, the present invention proposes a control method for a liquid crystal microstructure modulation device, which realizes precise control of the arrangement of liquid crystal molecules by introducing azimuthal orientation into a square lattice orientation pattern and presetting the initial azimuthal direction; the method first causes the liquid crystal molecules adjacent to the parallel orientation film in the liquid crystal layer to produce twist deformation, and then transforms the liquid crystal layer from an isotropic state to a nematic phase by cooling, and uses the preset square lattice orientation pattern to accurately guide the arrangement of the liquid crystal molecules, and when further cooled to the smectic phase, the suppression of the twist deformation and the destruction of the symmetry during the phase change process lead to the formation of a spiral toroidal focal cone domain array, and at the same time, by further changing the initial azimuthal direction, the symmetry of the toroidal focal cone domain array is degraded from infinite rotational symmetry to four-fold rotational symmetry, thereby forming a controllable smectic phase microstructure; this control method not only realizes the high orderliness of the arrangement of liquid crystal molecules, but also enhances the optical performance and diversity of the liquid crystal microstructure by precisely controlling the phase change process and symmetry; the specific microstructure formed has unique optical properties and is suitable for cutting-edge technical fields such as high-capacity optical communications and optical neural networks.

[0029] The second object of the invention is achieved by the following technical solutions:

[0030] A method for preparing a liquid crystal microstructure modulation device comprises the steps of:

[0031] S1, forming the vertical alignment film on the bottom surface of the top substrate;

[0032] S2, forming the parallel alignment film on the top surface of the bottom substrate;

[0033] S3, performing an alignment treatment on a side of the parallel alignment film close to the liquid crystal layer to form a square lattice alignment pattern with molecular directors arranged radially;

[0034] S4, placing the vertical alignment film and the parallel alignment film obtained in S1 and S3 opposite to each other, separating them by the spacer particles, and packaging them into a box;

[0035] S5, forming the liquid crystal layer in an isotropic phase between the vertical alignment film and the parallel alignment film in the box obtained in S4, and obtaining a controllable nematic phase and smectic phase liquid crystal microstructure through multi-step temperature control treatment.

[0036] By adopting the above technical scheme, the present invention provides a preparation method of a liquid crystal microstructure modulation device, which realizes precise control of the arrangement of liquid crystal molecules, thereby preparing a liquid crystal microstructure with excellent performance; a vertical orientation film is formed on the bottom surface of the top substrate to provide a guide for the vertical arrangement of the liquid crystal molecules, and a parallel orientation film is formed on the top surface of the bottom substrate, and a square lattice orientation pattern with radially arranged molecular directors is formed on its surface through orientation treatment, so as to provide a specific arrangement mode for the liquid crystal molecules; the vertical orientation film and the parallel orientation film are arranged relative to each other, separated by spacer particles, and packaged into a box to ensure that the liquid crystal layer is formed in a preset space, and a liquid crystal layer in an isotropic phase is formed in the box, and a controllable transition between the nematic phase and the smectic phase liquid crystal microstructure is realized through multi-step temperature control treatment, which not only ensures the orderliness of the arrangement of the liquid crystal molecules, but also realizes the optimization of the optical performance and diversity of the microstructure through precise control of the phase change process; at the same time, the method simplifies the preparation process, reduces the manufacturing difficulty and cost, and is conducive to large-scale production and application.

[0037] In summary, the present application includes at least one of the following beneficial technical effects:

[0038] 1. This application achieves efficient, high-resolution spatial and dynamic modulation of the optical phase through precise control of the liquid crystal microstructure, effectively solves the problems of random frustration and morphological distortion in the liquid crystal self-assembly process, and provides an effective strategy for large-scale parallel and multi-dimensional optical operations. It is of great significance for the advancement of cutting-edge technology fields such as high-capacity optical communications, optical neural networks, and augmented / virtual reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of a liquid crystal microstructure modulation device of the present application;

[0040] Figure 2 It is a square lattice orientation pattern written in a parallel orientation film in an embodiment of a liquid crystal microstructure modulation device of the present application;

[0041] Figure 3 It is a flow chart of a control method of a liquid crystal microstructure modulation device of the present application;

[0042] Figure 4It is a cross-polarized light micrograph of a nematic phase microstructure generated when the azimuth angle α=0° in an embodiment of a control method for a liquid crystal microstructure modulation device of the present application;

[0043] Figure 5 It is a cross-polarized light micrograph of a smectic phase microstructure generated when the azimuth angle α=0° in an embodiment of a control method for a liquid crystal microstructure modulation device of the present application;

[0044] Figure 6 It is a square lattice orientation pattern with azimuth angles α=30°, α=60° and α=90° in an embodiment of a control method for a liquid crystal microstructure modulation device of the present application;

[0045] Figure 7 It is a cross-polarized light micrograph of a nematic phase microstructure generated at azimuth angles α=30°, α=60° and α=90° in an embodiment of a control method for a liquid crystal microstructure modulation device of the present application;

[0046] Figure 8 It is a cross-polarized light micrograph of a smectic phase microstructure produced at azimuth angles α=30°, α=60° and α=90° in an embodiment of a control method for a liquid crystal microstructure modulation device of the present application;

[0047] Fig. 9 This is a diagram showing changes in a mask pattern in an embodiment of a control method for a liquid crystal microstructure modulation device of the present application;

[0048] Fig.10 This is a preparation flow chart of a preparation method of a liquid crystal microstructure modulation device of the present application.

[0049] Explanation of the reference numerals: 1. top substrate; 2. vertical alignment film; 3. liquid crystal layer; 4. parallel alignment film; 5. bottom substrate; 6. +1 topological singularity; 7. -1 topological singularity. DETAILED DESCRIPTION

[0050] The following is combined with Figure 1-9 This application is described in further detail.

[0051] In one embodiment, if Figure 1As shown, the present application discloses a liquid crystal microstructure modulation device, comprising a top substrate, a vertical alignment film, a liquid crystal layer, a parallel alignment film and a bottom substrate, wherein the bottom substrate is arranged opposite to the top substrate; the vertical alignment film is arranged at the bottom of the top substrate by coating, and the parallel alignment film is arranged at the top of the bottom substrate by coating, the liquid crystal layer is located between the vertical alignment film and the parallel alignment film, and supporting spacer particles are arranged between the vertical alignment film and the parallel alignment film, so as to control the thickness of the liquid crystal layer, and the thickness is 8.5 μm; the vertical alignment film has a vertical anchoring effect on the liquid crystal molecules in the liquid crystal layer, so that the molecular directors of the liquid crystal molecules adjacent to the vertical alignment film in the liquid crystal layer are arranged perpendicular to the vertical alignment film, and the side of the parallel alignment film close to the liquid crystal layer has a direction in which the molecular directors are arranged radially The square lattice orientation pattern has an in-plane parallel anchoring effect on the liquid crystal layer, so that the directors of the liquid crystal molecules adjacent to the parallel orientation film in the liquid crystal layer are arranged in the same manner as the molecular directors of the square lattice orientation pattern, wherein the square lattice orientation pattern can be obtained by friction orientation or light-controlled orientation; under the joint action of the vertical orientation film and the parallel orientation film, the liquid crystal molecules in the liquid crystal layer self-assemble to form controllable nematic phase and smectic phase liquid crystal; wherein the square lattice orientation pattern is provided with a preset initial azimuthal orientation, and the azimuthal orientation in the preset initial azimuthal direction is introduced into the orientation pattern with the square arranged lattice, effectively overcoming the uncontrollability of the microstructure in the process of entropy-driven self-assembly of the liquid crystal, so that the nematic phase liquid crystal molecules produce controllable distortion deformation, thereby realizing the control of the arrangement of the liquid crystal molecules.

[0052] In this embodiment, if Figure 2 As shown, the square lattice orientation pattern of the parallel orientation film is formed by periodically and closely arranging square lattice sub-patterns along the row and column directions, wherein the side length of the square control pattern is 30 μm; the molecular directors of the square lattice orientation pattern are radially distributed from the center to the boundary along the radial direction; the center of the square lattice sub-pattern in the square lattice orientation pattern is the +1 topological singularity 6, that is, when rotating clockwise around the singularity center, the liquid crystal molecules on the path also rotate clockwise 360°; the four adjacent square lattice orientation patterns in the square lattice orientation pattern A -1 topological singularity 7 is formed at the intersection of the lattice patterns, that is, when rotating angularly clockwise around the center of the singularity, the liquid crystal molecules on the path rotate 360° counterclockwise, and the molecules are distributed in a hyperbolic shape; under the combined effect of boundary anchoring energy and liquid crystal elastic energy, the liquid crystal molecules in the liquid crystal film spontaneously nucleate and assemble around the +1 topological singularity 6 on the parallel orientation film and the boundary of the square lattice orientation pattern, forming a new controllable nematic and smectic liquid crystal microstructure that is periodically arranged in the row and column directions.

[0053] In one embodiment, a control method of a liquid crystal microstructure modulation device is disclosed, such as Figure 3 As shown, the steps include:

[0054] S10: introducing an azimuth angle orientation into the square lattice orientation pattern, and presetting the initial azimuth angle direction, so that the liquid crystal molecules adjacent to the parallel orientation film in the liquid crystal layer are twisted and deformed;

[0055] S20: Cooling the liquid crystal microstructure modulation device to transform the liquid crystal layer from an isotropic state to a nematic phase, and controlling the arrangement of the liquid crystal molecules by a square lattice orientation pattern with a preset initial azimuth angle;

[0056] S30: further cooling to the smectic phase, due to the suppression of distortion and symmetry destruction after the phase transition, a spiral toroidal focal cone domain array is formed;

[0057] S40: By changing the direction of the initial azimuth angle, the toroidal focal cone domain array is degenerated from infinite rotational symmetry to four-fold rotational symmetry, thereby forming a controllable smectic microstructure.

[0058] In this embodiment, if Figure 4 As shown, when the azimuth angle α = 0°, the liquid crystal layer is cooled from the isotropic state to the nematic phase at a cooling rate of 0.3°C / min through temperature control treatment, and the liquid crystal molecules will follow the guidance of the square lattice orientation pattern. The undefined orientation of the liquid crystal molecules at the orientation singularity will lead to the generation of ±1 point defects, thereby forming a structural array of ±1 point defects alternately arranged in a periodic and dense manner along the row and column directions. The point defect array formed completely follows the arrangement of the preset orientation singularity.

[0059] In this embodiment, if Figure 5 As shown in FIG. 1 , when the azimuth angle α is 0°, further cooling to the smectic phase will form an array of alternatingly arranged toroidal focal cone domains, in which the radius of a single toroidal focal cone domain is controlled by a single square lattice sub-pattern in the square lattice orientation pattern, which is

[0060] In this embodiment, if Figure 6 As shown, the azimuthal orientation is introduced into the square lattice orientation pattern, and by presetting the initial azimuthal angles of the orientation lattice to α=30°, α=60° and α=90°, the liquid crystal molecules are twisted and deformed, thereby effectively controlling the arrangement of the liquid crystal molecules.

[0061] In this embodiment, if Figure 7As shown, when the azimuth angles are α=30°, α=60° and α=90° respectively, the liquid crystal is cooled from the isotropic state to the nematic phase at a cooling rate of 0.3°C / min through temperature control treatment, and the liquid crystal molecules will follow the guidance of the patterned orientation substrate to form a structural array of ±1 point defects alternately arranged in a periodic and tight manner along the row and column directions. At this time, the arrangement of the liquid crystal molecules around the ±1 point defects changes significantly, and the point defect array formed completely follows the arrangement of the preset orientation singularity, thereby controllably generating a new nematic phase liquid crystal microstructure.

[0062] In this embodiment, if Figure 8 As shown, when the azimuth angles are α=30°, α=60° and α=90° respectively, the temperature is further lowered to the smectic phase, the suppression of distortion deformation and the unique symmetry destruction after the phase transition form a spiral toroidal focal cone domain array; by changing the direction of the initial azimuth angle, the toroidal focal cone domain degenerates from infinite rotational symmetry to four-fold rotational symmetry, thereby producing a controllable new smectic phase microstructure.

[0063] In this embodiment, if Fig. 9 As shown, the parallel alignment film is oriented to form a square lattice alignment pattern with a specific planar arrangement of liquid crystal molecules; there are 36 masks in total, and the black area in each mask is a non-exposure area, and the white area is an exposure area;

[0064] Select the first mask, set the polarization direction of the induced light to 90°, wherein the polarization direction of 90° here refers to the direction corresponding to rotating the row direction counterclockwise by 90°, and perform the first exposure; select the second mask, set the polarization direction of the induced light to 95°, and perform the second exposure; select masks in sequence according to the direction indicated by the arrows, and set the polarization direction of the induced light to increase by 5° each time the mask is changed, until the 36th mask is selected, and the polarization direction of the induced light is set to 265°, and perform the 36th exposure;

[0065] After the mask plate performs the above-mentioned orientation treatment on the orientation film, the parallel orientation film has a square lattice orientation pattern formed by square control patterns periodically arranged along the row and column directions, wherein the liquid crystal directors in a single square lattice sub-pattern are radially distributed from the center to the boundary, and work together with the vertical orientation film to make the liquid crystal molecules in the liquid crystal and polymer mixed layer self-assemble to form a liquid crystal toroidal focal cone domain microlens array. Those skilled in the art can select the pattern of the mask plate and the number of exposures according to actual conditions, as long as the liquid crystal directors of a single square control pattern in the orientation film can be radially distributed.

[0066] In one embodiment, a method for preparing a liquid crystal microstructure modulation device is disclosed, such as Fig.10 As shown, the steps include:

[0067] S1, forming the vertical alignment film on the bottom surface of the top substrate;

[0068] S2, forming the parallel alignment film on the top surface of the bottom substrate;

[0069] S3, performing an alignment treatment on a side of the parallel alignment film close to the liquid crystal layer to form a square lattice alignment pattern with molecular directors arranged radially;

[0070] S4, placing the vertical alignment film and the parallel alignment film obtained in S1 and S3 opposite to each other, separating them by the spacer particles, and packaging them into a box;

[0071] S5, forming the liquid crystal layer in an isotropic phase between the vertical alignment film and the parallel alignment film in the box obtained in S4, and obtaining a controllable nematic phase and smectic phase liquid crystal microstructure through multi-step temperature control treatment.

[0072] In this embodiment, the vertical alignment film is a polydimethylsiloxane film. Before forming the vertical alignment film, in order to increase the wettability and adhesion between the polydimethylsiloxane and the top substrate, ultrasonic cleaning is performed for 30 minutes using a mixed reagent such as acetone and alcohol, and ultrasonic cleaning is performed twice using ultrapure water, each time for 10 minutes, and then dried in a 120° C. oven for 40 minutes, and then UVO cleaning is performed for 30 minutes;

[0073] Specifically, the process of forming the polydimethylsiloxane film is as follows: spin-coating the polydimethylsiloxane material on one side of the top substrate, spinning at a low speed for 5 seconds, with a rotation speed of 800 r / min, and spinning at a high speed for 40 seconds, with a rotation speed of 8000 r / min; annealing the substrate spin-coated with the photo-controlled orientation material for 20 minutes, with an annealing temperature of 100° C., to form a vertical orientation film with a thickness of 100 nm to 200 nm.

[0074] In this embodiment, the parallel alignment film is a photo-controlled alignment film, and the material of the photo-controlled alignment film is an acidic azo dye 4,4'-di(4-hydroxy-3-carboxyl-phenylazo)benzidine-2,2'-disulfonic acid; before forming the photo-controlled alignment film, in order to increase the wettability and adhesion between the photo-controlled alignment film and the bottom substrate, ultrasonic cleaning is performed for 30 minutes using a mixed reagent such as acetone and alcohol, and then ultrasonic cleaning is performed twice with ultrapure water, each time for 10 minutes, and after drying in a 120° C. oven for 40 minutes, UVO cleaning is performed for 30 minutes;

[0075] Specifically, the photo-controlled orientation material is spin-coated on one side of the bottom substrate, with low-speed spin coating for 5 seconds and a rotation speed of 800 r / min, and high-speed spin coating for 40 seconds and a rotation speed of 3000 r / min; the bottom substrate spin-coated with the photo-controlled orientation material is annealed for 10 minutes at an annealing temperature of 100°C to form a photo-controlled orientation film with a thickness of 30nm to 50nm.

[0076] In this embodiment, the spacer particles are small silica balls. In order to prevent the silica balls from falling into the central area of ​​the liquid crystal box and affecting the assembly of the toroidal focal cone domain structure, the silica balls are mixed into the ultraviolet light curing glue and a small amount is coated on the inner edge of the substrate. After the top substrate and the bottom substrate are relatively arranged and packaged, ultraviolet light is used to irradiate the light curing glue coating area to achieve curing.

[0077] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0078] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A liquid crystal microstructure modulation device, characterized in that: It comprises a top substrate (1), a vertical alignment film (2), a liquid crystal layer (3), a parallel alignment film (4) and a bottom substrate (5), wherein the bottom substrate (5) is arranged opposite to the top substrate (1); The vertical alignment film (2) is disposed on the bottom of the top substrate (1) by coating, the parallel alignment film (4) is disposed on the top of the bottom substrate (5) by coating, the liquid crystal layer (3) is located between the vertical alignment film (2) and the parallel alignment film (4), and spacer particles are disposed between the vertical alignment film (2) and the parallel alignment film (4); The vertical alignment film (2) causes the molecular directors of the liquid crystal molecules in the liquid crystal layer (3) adjacent to the vertical alignment film (2) to be arranged perpendicular to the vertical alignment film (2); the parallel alignment film (4) has a square lattice alignment pattern with radially arranged molecular directors on one side close to the liquid crystal layer (3), causing the directors of the liquid crystal molecules in the liquid crystal layer (3) adjacent to the parallel alignment film (4) to be arranged in the same manner as the molecular directors of the square lattice alignment pattern; under the combined action of the vertical alignment film (2) and the parallel alignment film (4), the liquid crystal molecules in the liquid crystal layer (3) self-assemble to form controllable nematic and smectic liquid crystal microstructures; Wherein, the square lattice orientation pattern is provided with a preset initial azimuth orientation.

2. A liquid crystal microstructure modulation device according to claim 1, characterized in that: The square lattice orientation pattern is formed by periodically and closely arranging square lattice sub-patterns along the row and column directions.

3. The liquid crystal microstructure modulation device according to claim 1, characterized in that: The molecular directors of the square lattice orientation pattern are radially distributed from the center to the boundary.

4. A liquid crystal microstructure modulation device according to claim 3, characterized in that: The center of the square lattice sub-pattern in the square lattice orientation pattern is a +1 topological singular point (6), the intersection points of four adjacent square lattice sub-patterns in the square lattice orientation pattern form a -1 topological singular point (7), and the molecules thereof are distributed in a hyperbolic shape.

5. The liquid crystal microstructure modulation device according to claim 2, characterized in that: The side length of the square lattice sub-pattern in the square lattice orientation pattern is 30 μm.

6. The liquid crystal microstructure modulation device according to claim 1, characterized in that: The thickness of the liquid crystal layer (3) is 8.5 μm.

7. A control method for a liquid crystal microstructure modulation device according to any one of claims 1 to 6, characterized in that: Includes steps: Introducing an azimuthal orientation into the square lattice orientation pattern and presetting the initial azimuthal direction so that the liquid crystal molecules in the liquid crystal layer (3) adjacent to the parallel orientation film (4) are twisted and deformed; The liquid crystal microstructure modulation device is cooled to change the liquid crystal layer (3) from an isotropic state to a nematic phase, and the arrangement of the liquid crystal molecules is controlled by the square lattice orientation pattern having a preset initial azimuth angle; Further cooling to the smectic phase, due to the suppression of distortion and destruction of symmetry after the phase transition, a spiral toroidal focal cone domain array is formed; By changing the direction of the initial azimuth angle, the toroidal focal cone domain array is degenerated from infinite rotational symmetry to four-fold rotational symmetry, thereby forming a controllable smectic microstructure.

8. A method for preparing a liquid crystal microstructure modulation device according to any one of claims 1 to 6, characterized in that: Includes steps: S1, forming the vertical alignment film (2) on the bottom surface of the top substrate (1); S2, forming the parallel alignment film (4) on the top surface of the bottom substrate (5); S3, performing an alignment treatment on a side of the parallel alignment film (4) close to the liquid crystal layer (3) so as to form a square lattice alignment pattern with molecular directors arranged radially; S4, arranging the vertical alignment film (2) and the parallel alignment film (4) obtained in S1 and S3 opposite to each other, separating them by the spacer particles, and packaging them into a box; S5, forming the liquid crystal layer (3) in an isotropic phase between the vertically oriented film (2) and the parallel oriented film (4) in the box obtained in S4, and obtaining a controllable nematic phase and smectic phase liquid crystal microstructure through multi-step temperature control treatment.

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