Multifunctional liquid crystal element, preparation method and application thereof

Abstract

The invention discloses a multifunctional liquid crystal element as well as a preparation method and application thereof. The multifunctional liquid crystal element comprises a first ITO glass substrate, a first light-operated orientation layer, a second ITO glass substrate, a second light-operated orientation layer and a liquid crystal layer, the first light-operated orientation layer is coated on the first ITO glass substrate through spin coating, the second light-operated orientation layer is coated on the second ITO glass substrate through spin coating, and the first light-operated orientation layer surface of the first ITO glass substrate and the second light-operated orientation layer surface of the second ITO glass substrate are oppositely arranged. The first ITO glass substrate and the second ITO glass substrate are bonded with each other through microspheres arranged on the two sides, so that a liquid crystal layer is formed between the microspheres on the two sides, and the distance between the first light-operated orientation layer and the second light-operated orientation layer is controlled through the microspheres; the prepared liquid crystal element can realize generation of a vector light array and imaging of a microlens array, is low in manufacturing cost and easy to prepare, and can be widely applied to the fields of optical micromachining, precision measurement and optical traps.

Description

Technical Field

[0001] The present invention relates to the field of liquid crystal photoelectric elements, vector structured light arrays, and microlens array imaging technology, and in particular to a multifunctional liquid crystal element, a preparation method, and an application thereof. Background Art

[0002] Vector light is a special structured light field, and its polarization state is non-uniformly distributed in space. With this special polarization state, it has shown great application value in many fields such as super-resolution imaging, optical communication, and laser processing. With the in-depth study of vector light fields, the generation of vector light field arrays with multiple singularities of different numbers and positions in the same light field has been favored by researchers. This has enriched the application of vector light fields to a certain extent, and will have greater value in capturing and observing multiple particles, realizing multi-channel fiber-optic communications, and multi-position laser processing. How to generate vector structured light arrays has always been a research focus. At present, methods such as Dammann gratings, spatial light modulators, and metasurfaces have emerged. However, the above methods have the disadvantages of huge size, high price, and cumbersome preparation. Therefore, a simpler and more flexible method for generating vector light field arrays is expected to be proposed.

[0003] Liquid crystal is an excellent electro-optical material whose optical properties can be regulated by an external field, thereby modulating the polarization and phase of light. Using liquid crystal elements to control light fields has many advantages, such as simple configuration, easy use, low cost, and high conversion efficiency. The smectic phase liquid crystal in liquid crystal, especially the torus focal cone domain structure (TFCD) formed by its self-assembly, provides a new idea for the generation of vector light arrays. At present, people can use nematic liquid crystal and cholesteric liquid crystal microstructures to stably and efficiently generate vector light arrays, but these microstructures often have a single function and lack multifunctionality. Summary of the invention

[0004] The present invention aims to solve the problems of complex manufacturing process, high manufacturing cost and single function of current vector light generation technology, and provides a multifunctional liquid crystal element, a preparation method and its application. The prepared liquid crystal element can realize the generation of vector light array and microlens array imaging, and has low manufacturing cost and is easy to prepare, and can be widely used in optical micromachining, precision measurement, optical traps and other fields.

[0005] To achieve the above object, the present invention provides the following technical solution: a multifunctional liquid crystal element, comprising a first ITO glass substrate, a first light-controlled alignment layer, a second ITO glass substrate, a second light-controlled alignment layer and a liquid crystal layer;

[0006] The first photo-controlled alignment layer is coated on the first ITO glass substrate by spin coating, and the second photo-controlled alignment layer is coated on the second ITO glass substrate by spin coating. The first photo-controlled alignment layer of the first ITO glass substrate and the second photo-controlled alignment layer of the second ITO glass substrate are placed opposite to each other. The first ITO glass substrate and the second ITO glass substrate are bonded to each other through microspheres provided on both sides, and a liquid crystal layer is formed between the microspheres on both sides. The liquid crystal layer is located between the first photo-controlled alignment layer and the second photo-controlled alignment layer, and the distance between the first photo-controlled alignment layer and the second photo-controlled alignment layer is controlled by the microspheres.

[0007] Preferably, the material of the photo-controlled alignment layer includes one of a surfactant, a rubbing alignment agent, a photo-crosslinking material, a photo-degradable material and a photoinduced cis-trans isomerization material.

[0008] Preferably, the orientation agents of the photo-controlled orientation layer are respectively an azo photo-controlled orientation material SD1 and a polyamic acid solution with stable viscosity and excellent performance. The liquid crystal molecules are vertically oriented by the orientation agent. Under the irradiation of linear polarized light, the SD1 molecules will be arranged in a direction perpendicular to the direction of the linear polarized light, and the liquid crystal molecules will form an orderly orientation through the interaction with the liquid crystal molecules, thereby realizing the manipulation of the orientation of the liquid crystal molecules; in actual operation, it is not limited to these two materials.

[0009] Preferably, the microspheres are spacer particles made of silicon spheres or silicon dioxide spheres. The spacer particles are mixed with UV curing glue by oscillation and evenly applied to the edges of the first ITO glass substrate and the second ITO glass substrate. The upper and lower glass substrates are staggered and bonded, and cured by UV light to form a liquid crystal layer.

[0010] Preferably, the material of the liquid crystal layer includes smectic liquid crystal, and the self-assembly of the toroidal focal cone domain array is achieved by slowly cooling the temperature from the nematic phase to the smectic phase.

[0011] The present invention also provides a method for preparing a multifunctional liquid crystal element, comprising the following steps:

[0012] S1, using ITO cleaning solution to ultrasonically clean the ITO glass substrate; then repeatedly using ultrapure water to ultrasonically clean it twice; putting the cleaned ITO glass substrate into a drying oven; finally, performing ultraviolet ozone cleaning on the ITO glass substrate;

[0013] S2, spin coating the photo-alignment agent SD1 on the ITO glass substrate, and spin coating the photo-alignment film prepared by the selected SD1 material on the ITO glass substrate by spin coating, and after spin coating the alignment agent, annealing the glass substrate spin coated with the photo-alignment agent SD1;

[0014] S3, spin coating a vertical alignment agent on the ITO glass substrate and annealing;

[0015] S4. Mix the spacer particles and the UV curing adhesive by oscillation, evenly apply them on the edge of the ITO glass substrate, bond the upper and lower substrates in an offset manner, and irradiate them with UV light to cure the UV curing adhesive, thereby placing the spacer particles between the two substrates to form a liquid crystal layer.

[0016] Preferably, in step S2, the spin coating method includes:

[0017] The first step was spin coating at 800 rpm for 8 seconds;

[0018] The second step was spin coating at 3000 rpm for 40 seconds.

[0019] The present invention also provides an application of a multifunctional liquid crystal element, and the prepared multifunctional liquid crystal element realizes the generation of a vector light array and TFCD microlens array imaging.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. In the present invention, the smectic phase liquid crystal is precisely self-assembled to form a toroidal focal cone domain array that can exist stably at room temperature through the photo-controlled orientation and thermal annealing treatment scheme. The director field of the domain structure unit has a gradual change in the direction of the director from the bottom horizontal to the top vertical in the z-axis direction; the in-plane component in the xy plane continuously changes along the angular direction around the central singular point. This array can not only introduce specific geometric and optical phase changes in the light field to produce a vector light array, but also realize microlens imaging through the gradient refractive index distribution of its director.

[0022] 2. The TFCD microlens array in the multifunctional liquid crystal element prepared by the present invention has good imaging quality, and the vector light field generated by the TFCD array in the multifunctional liquid crystal element prepared by the present invention at room temperature also has good stability.

[0023] 3. The liquid crystal element prepared by the present invention can realize the generation of vector light array and microlens array imaging. It has low production cost and is easy to prepare, and can be widely used in optical micromachining, precision measurement, optical traps and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0025] In the attached picture:

[0026] Figure 1 It is a structural diagram of a liquid crystal element prepared by the present invention;

[0027] Figure 2 It is a comparison diagram of microstructures of the multifunctional liquid crystal element prepared by the present invention at different temperatures;

[0028] Figure 3 It is a light path design diagram of the multifunctional liquid crystal element prepared by the present invention;

[0029] Figure 4 It is a light field diagram generated by the multifunctional liquid crystal element prepared by the present invention;

[0030] Figure 5 This is a microlens imaging diagram of the multifunctional liquid crystal element prepared by the present invention. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0032] Example: Figure 1 As shown, a multifunctional liquid crystal element comprises a first ITO glass substrate, a first photo-control alignment layer, a second ITO glass substrate, a second photo-control alignment layer and a liquid crystal layer;

[0033] The first photo-controlled alignment layer is coated on the first ITO glass substrate by spin coating, and the second photo-controlled alignment layer is coated on the second ITO glass substrate by spin coating. The first photo-controlled alignment layer of the first ITO glass substrate and the second photo-controlled alignment layer of the second ITO glass substrate are placed opposite to each other. The first ITO glass substrate and the second ITO glass substrate are bonded to each other through microspheres provided on both sides, and a liquid crystal layer is formed between the microspheres on both sides. The liquid crystal layer is located between the first photo-controlled alignment layer and the second photo-controlled alignment layer, and the distance between the first photo-controlled alignment layer and the second photo-controlled alignment layer is controlled by the microspheres.

[0034] Furthermore, the material of the photo-controlled alignment layer includes one of a surfactant, a rubbing alignment agent, a photo-crosslinking material, a photo-degradable material and a photoinduced cis-trans isomerization material.

[0035] Furthermore, the orientation agents of the photo-controlled orientation layer are respectively an azo photo-controlled orientation material SD1 and a polyamic acid solution with stable viscosity and excellent performance. The liquid crystal molecules are vertically oriented by the orientation agent. Under the irradiation of linear polarized light, the SD1 molecules will be arranged in a direction perpendicular to the direction of the linear polarized light, and through the interaction with the liquid crystal molecules, the liquid crystal molecules form an orderly orientation, thereby realizing the manipulation of the orientation of the liquid crystal molecules; in actual operation, it is not limited to these two materials.

[0036] Furthermore, the microspheres are spacer particles made of silicon spheres or silicon dioxide spheres with a diameter of 9 μm. The spacer particles are mixed with UV curing glue by vibration and evenly applied to the edges of the first ITO glass substrate and the second ITO glass substrate. The upper and lower glass substrates are staggered and bonded, and cured by UV light to form a liquid crystal box.

[0037] Furthermore, the material of the liquid crystal layer includes smectic phase liquid crystal, and the self-assembly of the toroidal focal cone domain array is achieved by slowly cooling from the nematic phase to the smectic phase; due to the special director distribution of the toroidal focal cone domain structure, each focal cone domain structure can not only generate vector light of specific topological charge under the incidence of linear polarized light, but also act as a microlens to achieve light convergence. The multifunctional liquid crystal element described in the present invention uses smectic phase liquid crystal 8CB, but is not limited to these materials.

[0038] The present invention also provides a method for preparing a multifunctional liquid crystal element, comprising the following steps:

[0039] S1. Use ITO washing solution to ultrasonically clean the ITO glass substrate for 30 minutes; then repeat ultrasonic cleaning with ultrapure water twice, each cleaning time is 10 minutes; put the cleaned ITO glass substrate into a drying oven, adjust the temperature of the drying oven to 120°C, and dry it for 40 minutes; finally, perform ultraviolet ozone cleaning on the ITO glass substrate for 30 minutes;

[0040] S2, spin coating the photo-alignment agent SD1 on the ITO glass substrate, and spin coating the photo-alignment film prepared by the selected SD1 material on the ITO glass substrate by spin coating, wherein the spin coating method includes:

[0041] The first step was spin coating at 800 rpm for 8 seconds;

[0042] The second step was spin coating at 3000 rpm for 40 seconds;

[0043] After the orientation agent is spin-coated, the glass substrate spin-coated with the light-controlled orientation agent SD1 is annealed at a temperature of 100° C. for 10 minutes;

[0044] S3, spin coating a vertical alignment agent 4070 on the ITO glass substrate and annealing the substrate at a temperature of 230° C. for 30 minutes;

[0045] S4. Select silicon balls or silicon dioxide balls with a diameter of 9μm, oscillate and mix the spacer particles with UV curing glue, evenly apply them on the edge of the ITO glass substrate, glue the upper and lower substrates together, and use UV light to cure the UV curing glue, so as to place the spacer particles between the two substrates to form a liquid crystal layer.

[0046] The present invention also provides an application of a multifunctional liquid crystal element, and the prepared multifunctional liquid crystal element realizes the generation of a vector light array and TFCD microlens array imaging. The present invention uses a light-controlled orientation and thermal annealing treatment scheme to enable the smectic phase liquid crystal to accurately self-assemble into a toroidal focal cone domain array that can exist stably at room temperature, and the director field of the domain structure unit has a gradual change in the direction of the director from the bottom horizontal to the top vertical in the z-axis direction; the in-plane component in the xy plane continuously changes in the angular direction around the central singular point. The array can not only introduce specific geometric and optical phase changes in the light field to generate a vector light array, but also realize microlens imaging through the gradual change in the refractive index distribution of its director.

[0047] In order to achieve a structure that conforms to the orientation of the torus focal cone domain of the smectic phase liquid crystal, a multi-step partially overlapping exposure was performed using a micro-projection exposure system based on a digital micromirror device. The light beam reflected by each micromirror in the system is given a specific polarization state after passing through an electrically controlled polarizer, and then irradiated on the surface of the liquid crystal box. After a certain dose of light, the photo-controlled orientation agent molecules on the exposure area will be arranged in a graphical manner. By rotating the polarizer in the system, different positions of the exposure pattern can correspond to polarized light in different directions, so that the photo-controlled orientation agent molecules have different orientations.

[0048] Figure 2 The microtexture comparison diagram of the multifunctional liquid crystal element prepared by the present invention at different temperatures. Since the present invention expects to use the TFCD array in the liquid crystal element to generate a vector light field at room temperature, the stability of the TFCD array at room temperature is verified. Figure 2 As shown in the figure, a TFCD array with a diameter of 15 μm and a diameter of 21.6 μm was prepared in a liquid crystal cell and its microtexture was recorded at 33.2°C. Then, the cell was slowly cooled to room temperature and stored away from light. Two days later, the microtexture of the TFCD array was characterized under a crossed polarizing microscope at room temperature. The results fully proved that the TFCD array had good stability at room temperature.

[0049] Figure 3 This is the optical path design diagram of the multifunctional liquid crystal element prepared by the present invention. In order to generate a vector beam array, a linear polarizer is added after the 633nm laser source as a polarizer to ensure that the incident light is linearly polarized light. If necessary, a polarizer is placed behind the sample to analyze the outgoing structured light to verify that each structured light unit in the array is a cylindrical vector light. Finally, the outgoing light is collected by a CCD camera and imaged on a computer.

[0050] Figure 4 The light field generated by the multifunctional liquid crystal element prepared by the present invention. Figure 3The designed optical path verifies the ability of the TFCD array in the liquid crystal element prepared by the present invention to generate a vector light array. When no polarizer is added to the optical path, a donut intensity distribution array is observed on the CCD camera, such as Figure 4 As shown in (a), this is consistent with the characteristic that there is a polarization singularity at the center of the vector beam. When a polarizer is added to the optical path, a petal-shaped intensity distribution array is observed on the CCD camera, as shown in Figure 4 As shown in (b), it is further verified that the TFCD array in the liquid crystal element prepared by the present invention generates a vector light array with a polarization order P=2.

[0051] Figure 5 In order to verify the imaging effect of the TFCD array in the liquid crystal element prepared by the present invention as a microlens array, a beam of linearly polarized light was used as the incident light based on the polarizing microscope experimental platform. Figure 5 The homemade simple mask shown in the first row is imaged above each focal cone after passing through the TFCD microlens array. The imaging result is recorded by the CCD installed in the microscope, as shown in Figure 5 As shown in the second row, it can be clearly seen from the figure that the image focused by the TFCD microlens array has a higher resolution and clarity, indicating that the TFCD microlens array in the liquid crystal element prepared by the present invention has a better imaging quality.

[0052] Finally, it should be noted that the above description is only a preferred example of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multifunctional liquid crystal element, characterized in that: It includes a first ITO glass substrate, a first photo-controlled alignment layer, a second ITO glass substrate, a second photo-controlled alignment layer and a liquid crystal layer; The first photo-controlled alignment layer is coated on the first ITO glass substrate by spin coating, and the second photo-controlled alignment layer is coated on the second ITO glass substrate by spin coating. The first photo-controlled alignment layer of the first ITO glass substrate and the second photo-controlled alignment layer of the second ITO glass substrate are placed opposite to each other. The first ITO glass substrate and the second ITO glass substrate are bonded to each other through microspheres provided on both sides, and a liquid crystal layer is formed between the microspheres on both sides. The liquid crystal layer is located between the first photo-controlled alignment layer and the second photo-controlled alignment layer, and the distance between the first photo-controlled alignment layer and the second photo-controlled alignment layer is controlled by the microspheres.

2. A multifunctional liquid crystal element according to claim 1, characterized in that: in, The material of the photo-controlled alignment layer includes one of a surfactant, a rubbing alignment agent, a photo-crosslinking material, a photo-degradable material and a photo-induced cis-trans isomerization material.

3. A multifunctional liquid crystal element according to claim 2, characterized in that: in, The orientation agents of the photo-controlled orientation layer are azo photo-controlled orientation material SD1 and polyamic acid solution, respectively. The liquid crystal molecules are vertically oriented by the orientation agents. Under the irradiation of linear polarized light, the SD1 molecules will be arranged in a direction perpendicular to the direction of the linear polarized light, and through the interaction with the liquid crystal molecules, the liquid crystal molecules are formed into an orderly orientation, thereby realizing the manipulation of the orientation of the liquid crystal molecules.

4. A multifunctional liquid crystal element according to claim 1, characterized in that: The microspheres are spacer particles including silicon spheres or silicon dioxide spheres. The spacer particles are mixed with ultraviolet curing glue by vibration and evenly smeared on the edges of the first ITO glass substrate and the second ITO glass substrate. The upper and lower glass substrates are staggered and bonded, and cured by ultraviolet light to form a liquid crystal layer.

5. A multifunctional liquid crystal element according to claim 4, characterized in that: The material of the liquid crystal layer includes smectic phase liquid crystal, and the self-assembly of the toroidal focal cone domain array is achieved by slowly cooling the temperature from the nematic phase to the smectic phase.

6. A method for preparing a multifunctional liquid crystal element, characterized in that: The following steps are involved: S1, using an ITO cleaning solution to ultrasonically clean the ITO glass substrate, and then repeatedly using ultrapure water to ultrasonically clean it twice; putting the cleaned ITO glass substrate into a drying oven; and finally performing ultraviolet ozone cleaning on the ITO glass substrate; S2, spin coating the photo-alignment agent SD1 on the ITO glass substrate, and spin coating the photo-alignment film prepared by the selected SD1 material on the ITO glass substrate by spin coating, and after spin coating the alignment agent, annealing the glass substrate spin coated with the photo-alignment agent SD1; S3, spin coating a vertical alignment agent on the ITO glass substrate and annealing; S4. Mix the spacer particles and the UV curing adhesive by oscillation, evenly apply them on the edge of the ITO glass substrate, bond the upper and lower substrates in an offset manner, and irradiate them with UV light to cure the UV curing adhesive, thereby placing the spacer particles between the two substrates to form a liquid crystal layer.

7. The method for preparing a multifunctional liquid crystal element according to claim 6, characterized in that: In step S2, the spin coating method includes: The first step was spin coating at 800 rpm for 8 seconds; The second step was spin coating at 3000 rpm for 40 seconds.

8. An application of a multifunctional liquid crystal element, characterized in that: The prepared multifunctional liquid crystal element realizes the generation of vector light array and TFCD microlens array imaging.

Images