Polarization-independent liquid crystal lens, preparation method and application thereof

Abstract

The application belongs to the technical field of liquid crystal lens, and particularly relates to a polarization-independent liquid crystal lens and a preparation method thereof. The polarization-independent liquid crystal lens is prepared by using an orientation light path, and a polarization-independent liquid crystal body lens is prepared by using a washing-out and refilling method and superimposing a double-chirality polarization body lens template. The liquid crystal lens prepared by the method can converge left-handed and right-handed incident light to the same focus in a reflection mode, so that polarization-independent modulation is realized. The method has wavelength selectivity, and compared with other liquid crystal lenses, the method reduces the interference of stray light. Meanwhile, by using the geometric phase and the polarization-independent modulation performance, the diffraction efficiency of the obtained liquid crystal lens is greatly improved, and the liquid crystal lens can be widely applied in new display, imaging systems or optical communication systems.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal lens technology, specifically relating to a polarization-independent liquid crystal lens, its preparation method, and its application. Background Technology

[0002] Essentially, most liquid crystal lenses (LCDs) are based on the birefringence of liquid crystals, generating different phase modulations through the refractive index difference between the long and short axes of liquid crystal molecules. Therefore, LCDs are polarization-dependent in most cases. That is, for a specific polarized light, an LCD can achieve highly ideal modulation results, but for polarized light with orthogonal polarization, the LCD often cannot perform phase modulation. LCDs whose modulation is highly correlated with the polarization direction of the incident light are called polarization-dependent LCDs. In practical applications, they often require the use of polarization-inducing and polarization-analyzing devices. For example, in many existing twisted nematic liquid crystal displays, the light source passes through a polarizer before entering the liquid crystal layer as specifically polarized light, and then a polarizer is used to convert the phase to intensity. However, in other applications, filtering the polarization state of the incident light not only reduces the optical efficiency of the device but also limits its application in various scenarios, hindering its widespread development. Therefore, achieving polarization-independent modulation of liquid crystal lenses has become one of the important directions in the development of liquid crystal devices.

[0003] For polarization-independent liquid crystal lenses, current development mainly focuses on two directions. One is from the perspective of materials research and development, exploring novel liquid crystal materials with polarization-independent modulation properties. Blue phase liquid crystals do not exhibit birefringence like other liquid crystal phases, and macroscopically display thermodynamically stable optical isotropy, often used to fabricate polarization-independent liquid crystal lenses. However, their temperature range is much higher than room temperature and very narrow, thus severely limiting their practical applications.

[0004] Based on current polarization-dependent liquid crystal materials, a polarization-independent liquid crystal lens can also be realized by using different structural designs, such as dual-layer design and spatial multiplexing design, to equivalently modulate beams with orthogonal polarization states. However, the dual-layer design introduces additional crosstalk, and the spatial multiplexing design has low light energy utilization efficiency, making it difficult to widely apply in practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide a polarization-independent liquid crystal lens and its preparation method. The polarization-independent liquid crystal lens provided by this invention achieves co-modulation of left and right chiral incident light, thereby realizing polarization-independent beam convergence. At the same time, the polarization-independent liquid crystal lens provided by this invention can use polarization-dependent liquid crystal materials, has high diffraction efficiency, low stray light interference, and simple structure, and can be widely used in new display, imaging systems or optical communication systems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for fabricating a polarization-independent liquid crystal lens. The polarization-independent liquid crystal lens is fabricated using an orientation optical path. The orientation optical path, along the direction of the orientation light, includes a polarizer, a collimating beam expander, and a beam splitter. Along the direction of the first beam splitter obtained by the beam splitter, it includes a first quarter-wave plate and a first reflecting mirror. Along the direction of the second beam splitter obtained by the beam splitter, it includes a second quarter-wave plate and a second reflecting mirror. A beam combiner is used to combine the first and second beam splitters. The method also includes a convex lens disposed between the first reflecting mirror and the beam combiner, or between the second reflecting mirror and the beam combiner. The major axis of the first quarter-wave plate forms an angle of 45° or -45° with the polarization direction of the polarizer, and the first and second quarter-wave plates are orthogonally arranged.

[0008] Includes the following steps:

[0009] A first alignment layer and a second alignment layer are respectively prepared on one surface of a first substrate and one surface of a second substrate to obtain a first substrate having a first alignment layer and a second substrate having a second alignment layer.

[0010] A liquid crystal cell is fabricated by means of a first substrate having a first alignment layer and a second substrate having a second alignment layer, wherein the first alignment layer and the second alignment layer are disposed opposite to each other inside the liquid crystal cell;

[0011] The liquid crystal cell is subjected to a first alignment process using an alignment optical path to obtain a first-aligned liquid crystal cell.

[0012] After injecting a first liquid crystal mixture into the first oriented liquid crystal cell, a first curing and a first rinsing are performed sequentially to obtain a liquid crystal cell with a single-chiral cholesteric polymer template. The first liquid crystal mixture includes a first nematic liquid crystal, a first chiral agent, a first polymer monomer, a first crosslinking agent, and a first photoinitiator.

[0013] The first 1 / 4 wave plate and the second 1 / 4 wave plate in the orientation optical path are rotated 90° in the same direction, and then the orientation optical path is used to perform a second orientation process on the liquid crystal cell with a single-chiral cholesteric polymer template to obtain a second-oriented liquid crystal cell.

[0014] After injecting a second liquid crystal mixture into the second oriented liquid crystal cell, a second curing and a second rinsing are performed sequentially to obtain a liquid crystal cell with a bipolar cholesteric polymer template. The second liquid crystal mixture includes a second nematic liquid crystal, a second chiral agent, a second polymer monomer, a second crosslinking agent, and a second photoinitiator. Therefore, the second chiral agent and the first chiral agent have opposite chirality.

[0015] The polarization-independent liquid crystal lens is obtained by injecting a third-nematic liquid crystal into a liquid crystal cell with a bipolar cholesteric polymer template.

[0016] Preferably, during the first and second orientation processes, the distance between the convex lens in the orientation optical path and the liquid crystal cell is twice the focal length of the convex lens.

[0017] Preferably, the method for preparing the first orientation layer and the second orientation layer includes the following steps:

[0018] A photoalignment material solution is coated onto one surface of a first substrate and one surface of a second substrate, and then dried to obtain the first alignment layer and the second alignment layer; the photoalignment material solution includes a photoalignment material and an organic solvent.

[0019] Preferably, the photo-alignment material comprises SD1 material; the mass content of the photo-alignment material solution is 0.1-0.5%.

[0020] Preferably, the coating is spin coating, which includes performing a first spin coating and a second spin coating in sequence. The first spin coating has a rotation speed of 300-500 r / min and a time of 5-10 s, and the second spin coating has a rotation speed of 2500-3000 r / min and a time of 20-25 s.

[0021] The drying temperature is 180–200°C, and the time is 2–3 hours.

[0022] Preferably, the method for preparing the liquid crystal cell includes the following steps:

[0023] The first substrate having a first orientation layer and the second substrate having a second orientation layer are arranged opposite each other and assembled into a box using UV-curable adhesive under ultraviolet light conditions.

[0024] The distance between the first substrate having a first orientation layer and the second substrate having a second orientation layer is 2 to 10 μm.

[0025] Preferably, the first chiral agent includes R5011 chiral agent or S5011 chiral agent;

[0026] The first nematic liquid crystal, the second nematic liquid crystal, and the third nematic liquid crystal include BPH006 liquid crystal;

[0027] The first and second polymer monomers include TMPTA polymer monomers;

[0028] The first and second crosslinking agents include C3M crosslinking agent;

[0029] The first and second photoinitiators include IRG184 photoinitiator.

[0030] Preferably, the mass ratio of the first nematic liquid crystal, the first chiral agent, the first polymer monomer, the first crosslinking agent, and the first photoinitiator is 82.9:2:6.7:8.3:0.1;

[0031] The mass ratio of the second nematic liquid crystal, the second chiral agent, the second polymer monomer, the second crosslinking agent, and the second photoinitiator is 82.9:2:6.7:8.3:0.1.

[0032] Preferably, the orientation light used in the first and second orientation processes is blue-violet light with a wavelength of 405 nm; the total irradiation energy of the orientation light during the first and second orientation processes is 4 J / cm². 2 ;

[0033] The focal length of the convex lens is 10cm.

[0034] The present invention provides a polarization-independent liquid crystal lens prepared by the preparation method described in the above technical solution.

[0035] This invention provides the application of the polarization-independent liquid crystal lens described above in display, imaging systems, or optical communication systems.

[0036] This invention provides a method for fabricating a polarization-independent liquid crystal lens. The invention employs an alignment optical path to fabricate the polarization-independent liquid crystal lens. In this invention, since the orientation of the cholesteric liquid crystal determines its geometric phase modulation, the alignment optical path is used to write a fixed orientation pattern on the light-aligning materials in the first and second alignment layers, allowing for flexible control of the geometric phase modulation of the cholesteric liquid crystal. However, the same geometric phase modulation results in conjugate modulation for left- and right-handed cholesteric liquid crystals. That is, the same phase change distribution produces opposite modulation results for left-handed and right-handed polarized incident light. Therefore, this invention employs a two-stage alignment fabrication method using an alignment optical path, ensuring the coexistence of the two orientation results through cholesteric liquid crystal template formation. Thus, this invention utilizes an alignment optical path for two-stage alignment processing to obtain a liquid crystal cell (i.e., a second-aligned liquid crystal cell) with a two-handed polarizing lens template. Simultaneously, a wash-refill method is used to obtain the polarization-independent liquid crystal lens. Specifically, the structure of the alignment optical path used in this invention is as follows: Figure 2As shown, the orientation light path, after passing through a beam splitter, is divided into two beams with the same polarization direction and intensity. Quarter-wave plates (first and second) and mirrors (second and second mirrors) are placed in the two beam paths respectively. This invention achieves the conversion of linearly polarized light into left- and right-handedly polarized light by controlling the angle between the major axes of the two quarter-wave plates and the polarization direction of the polarizer. Simultaneously, a convex lens is placed in either of the beam paths, and finally, a beam combiner is used to combine the two beams, ultimately illuminating the first and second orientation layers inside the liquid crystal cell, forming a lens-shaped circular interference pattern. This achieves the template processing of the bipolar polarizing body lens of the light orientation material in the first and second orientation layers. Therefore, the method provided by this invention performs template processing of the light orientation material in the first and second orientation layers through two orientation processes, realizing the co-modulation of left- and right-handed incident light within a single device layer. Meanwhile, by maintaining complete conjugation of the two orientations, the liquid crystal lens achieved by this invention can converge incident light of both left and right chirality to the same focal point through reflection, thereby realizing polarization-independent modulation. The polarization-independent liquid crystal lens prepared by this invention has wavelength selectivity and reduces stray light interference compared with other liquid crystal lenses. Furthermore, due to the application of geometric phase and polarization-independent modulation performance, the diffraction efficiency of the polarization-independent liquid crystal lens prepared by this invention is greatly improved, and it can be widely used in new display, imaging systems, or optical communication systems.

[0037] This invention provides a polarization-independent liquid crystal lens prepared by the method described above. The polarization-independent liquid crystal lens provided by this invention includes a first substrate and a second substrate, which are disposed opposite to each other to form a liquid crystal cell. A liquid crystal layer is disposed between the first substrate and the second substrate. A first alignment layer is disposed on one surface of the first substrate, and a second alignment layer is disposed on one surface of the second substrate. The first and second alignment layers are disposed opposite to each other inside the liquid crystal cell. The liquid crystal layer is provided with two cholesteric polymer templates with opposite chirality, which enable the liquid crystal in the liquid crystal layer to form a polarization-independent Fresnel liquid crystal lens. A schematic diagram of the structure of the polarization-independent liquid crystal lens provided by this invention is shown below. Figure 1 As shown. The polarization-independent liquid crystal lens provided by the present invention includes two cholesteric polymer templates with opposite chirality integrated on a single layer (i.e., liquid crystal layer), corresponding to left-handed and right-handed liquid crystals of the desired wavelength, respectively. Under the combined action of the two cholesteric polymer templates with opposite chirality, the co-modulation of left-handed and right-handed incident light is achieved, thereby realizing polarization-independent beam focusing.

[0038] Compared with existing technologies, the polarization-independent liquid crystal lens provided by this invention has the following technical advantages:

[0039] The polarization-independent liquid crystal lens provided by this invention has wavelength selectivity and high diffraction efficiency.

[0040] The polarization-independent liquid crystal lens provided by this invention utilizes the Bragg reflection property of cholesteric liquid crystals, and its reflected light has wavelength selectivity, that is, it only diffracts for specific wavelengths, thereby reducing the interference of stray light.

[0041] The polarization-independent liquid crystal lens provided by this invention utilizes the geometric phase modulation characteristics of cholesteric liquid crystals, which allows for flexible phase modulation and enables beam focusing at different focal lengths. At the same time, it facilitates the addition of lens functions and can achieve off-axis beam focusing relatively easily.

[0042] The polarization-independent liquid crystal lens provided by this invention uses a template technique to superimpose left- and right-handed polarized liquid crystal lenses, so that it has the same control effect on beams of all polarization states, which greatly improves the diffraction efficiency.

[0043] The results from the examples show that the reflectivity and polarization of linearly polarized light at the target wavelength (532 nm) were tested for both the single-chiral cholesteric liquid crystal lens and the polarization-independent liquid crystal lens provided in this invention. The test results indicate that the reflectivities of the left-handed and right-handed cholesteric liquid crystal lenses at 532 nm are 41.5% and 40.6%, respectively, while the proposed polarization-independent liquid crystal lens has a reflectivity as high as 74.1%, significantly improving diffraction efficiency. Furthermore, the polarization correlations of the left-handed and right-handed cholesteric liquid crystal lenses at 532 nm are 89.3% and 81.0%, respectively, while the polarization correlation of the proposed polarization-independent liquid crystal lens is only 8.6%, demonstrating excellent polarization independence.

[0044] Furthermore, in this invention, during the first and second orientation processes, the distance between the convex lens in the orientation optical path and the liquid crystal cell is twice the focal length of the lens, to ensure that the two beams have the same spot size. The focal length of the polarization-independent liquid crystal lens is determined by the lens used. Attached Figure Description

[0045] Figure 1 A schematic diagram of the structure of the polarization-independent liquid crystal lens provided by the present invention;

[0046] Figure 2 This is a schematic diagram of the orientation optical path provided by the present invention;

[0047] Figure 3 Transmittance spectra of left- and right-handed cholesteric liquid crystal lenses prepared for comparative examples and polarization-independent lenses provided in Example 1;

[0048] Figure 4The polarization independence of the left-handed and right-handed cholesteric liquid crystal lenses prepared in the comparative example and the polarization-independent lens provided in Example 1 are compared.

[0049] In the figure: 101 is the first substrate, 102 is the second substrate, 103 is the liquid crystal layer; 201 is the alignment laser, 202 is the polarizer, 203 is the collimating beam expander, 204 is the beam splitter, 205 is the first quarter wave plate, 206 is the first reflecting mirror, 207 is the second quarter wave plate, 208 is the second reflecting mirror, 209 is the convex lens, 210 is the beam combiner, and 211 is the liquid crystal cell. Detailed Implementation

[0050] This invention provides a method for fabricating a polarization-independent liquid crystal lens. The polarization-independent liquid crystal lens is fabricated using an orientation optical path. The orientation optical path, along the direction of the orientation light, includes a polarizer, a collimating beam expander, and a beam splitter. Along the direction of the first beam splitter obtained by the beam splitter, it includes a first quarter-wave plate and a first reflecting mirror. Along the direction of the second beam splitter obtained by the beam splitter, it includes a second quarter-wave plate and a second reflecting mirror. A beam combiner is used to combine the first and second beam splitters. The method also includes a convex lens disposed between the first reflecting mirror and the beam combiner, or between the second reflecting mirror and the beam combiner. The major axis of the first quarter-wave plate forms an angle of 45° or -45° with the polarization direction of the polarizer, and the first and second quarter-wave plates are orthogonally arranged.

[0051] Includes the following steps:

[0052] A first alignment layer and a second alignment layer are respectively prepared on one surface of a first substrate and one surface of a second substrate to obtain a first substrate having a first alignment layer and a second substrate having a second alignment layer.

[0053] A liquid crystal cell is fabricated by means of a first substrate having a first alignment layer and a second substrate having a second alignment layer, wherein the first alignment layer and the second alignment layer are disposed opposite to each other inside the liquid crystal cell;

[0054] The liquid crystal cell is subjected to a first alignment process using an alignment optical path to obtain a first-aligned liquid crystal cell.

[0055] After injecting a first liquid crystal mixture into the first oriented liquid crystal cell, a first curing and a first rinsing are performed sequentially to obtain a liquid crystal cell with a single-chiral cholesteric polymer template. The first liquid crystal mixture includes a first nematic liquid crystal, a first chiral agent, a first polymer monomer, a first crosslinking agent, and a first photoinitiator.

[0056] The first 1 / 4 wave plate and the second 1 / 4 wave plate in the orientation optical path are rotated 90° in the same direction, and then the orientation optical path is used to perform a second orientation process on the liquid crystal cell with a single-chiral cholesteric polymer template to obtain a second-oriented liquid crystal cell.

[0057] After injecting a second liquid crystal mixture into the second oriented liquid crystal cell, a second curing and a second rinsing are performed sequentially to obtain a liquid crystal cell with a bipolar cholesteric polymer template. The second liquid crystal mixture includes a second nematic liquid crystal, a second chiral agent, a second polymer monomer, a second crosslinking agent, and a second photoinitiator. Therefore, the second chiral agent and the first chiral agent have opposite chirality.

[0058] The polarization-independent liquid crystal lens is obtained by injecting a third-nematic liquid crystal into a liquid crystal cell with a bipolar cholesteric polymer template.

[0059] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0060] In this invention, the liquid crystal cell with a single-chiral cholesteric phase polymer template is a liquid crystal cell with an S-chiral cholesteric phase polymer template or a liquid crystal cell with an R-chiral cholesteric phase polymer template.

[0061] In this invention, the liquid crystal cell with bichiral cholesteric polymer template is a liquid crystal cell that simultaneously has an S-chiral cholesteric polymer template and an R-chiral cholesteric polymer template.

[0062] This invention employs an alignment optical path to fabricate the polarization-independent liquid crystal lens. A schematic diagram of the alignment optical path is shown below. Figure 2 As shown below, in conjunction with Figure 2 The orientation optical path provided by the present invention will be described in detail.

[0063] The orientation optical path provided by the present invention preferably further includes an orientation laser 201 along the optical path direction of the orientation light. In the present invention, the orientation laser 201 is used to emit orientation light.

[0064] The orientation optical path provided by this invention includes a polarizer 202 along the optical path direction of the orientation light. In this invention, the polarizer 202 is used to obtain polarized light.

[0065] The orientation optical path provided by this invention includes a collimating beam expander 203 along the optical path direction of the orientation light. In this invention, the collimating beam expander 203 is used for laser focusing.

[0066] The orientation optical path provided by the present invention includes a beam splitter 204 along the optical path direction of the orientation light. In the present invention, the beam splitter 204 is used to split the polarized orientation light (an incident beam) passing through the collimating beam expander 203 into two linearly polarized beams with the same polarization direction in an equal proportion.

[0067] The orientation optical path provided by the present invention includes a first quarter-wave plate 205 and a first reflecting mirror 206 along the optical path direction of the first beam obtained by the beam splitter prism.

[0068] The orientation optical path provided by the present invention includes a second quarter-wave plate 207 and a second reflecting mirror 208 along the optical path direction of the second beam obtained by the beam splitter prism.

[0069] In this invention, the major axis of the first quarter wave plate 205 makes an angle of 45° or -45° with the polarization direction of the polarizer 202, and the first quarter wave plate 205 and the second quarter wave plate 207 are orthogonally arranged.

[0070] The orientation optical path provided by the present invention includes a beam combiner 210 that combines the first beam splitter and the second beam splitter.

[0071] The orientation optical path provided by this invention further includes a convex lens 209 disposed between the first reflector and the beam combiner or between the second reflector and the beam combiner. In this invention, the function of the convex lens 209 is to form a specific interference pattern on the first and second orientation layers of the liquid crystal cell. Without the lens, the two optical paths are identical, and the interference is a planar pattern; with the addition of the lens, a lens-shaped circular interference pattern appears.

[0072] In this invention, during the first and second orientation processes, the distance between the convex lens in the orientation optical path and the liquid crystal cell is preferably twice the focal length of the convex lens.

[0073] In this invention, during the first and second orientation processes, it is preferable to ensure that the optical path centers of the first and second orientation processes are aligned to ensure that the focal points of the left-hand and right-hand reflected light are located at the same position, thereby achieving polarization-independent beam convergence.

[0074] This invention involves fabricating a first alignment layer and a second alignment layer on one surface of a first substrate and a second substrate, respectively, to obtain a first substrate having the first alignment layer and a second substrate having the second alignment layer. In this invention, the first substrate and the second substrate are preferably glass substrates. The method for fabricating the first alignment layer and the second alignment layer preferably includes the following steps:

[0075] A photoalignment material solution is coated onto one surface of a first substrate and one surface of a second substrate, respectively, and then dried to obtain a first alignment layer and a second alignment layer. The photoalignment material solution comprises a photoalignment material and an organic solvent. In this invention, the photoalignment material preferably comprises SD1 material. The organic solvent preferably comprises dimethylxylene. The mass content of the photoalignment material in the photoalignment material solution is preferably 0.1% to 0.5%, and in the examples it can be 0.3%. In this invention, the coating is preferably spin-coating, and the spin-coating preferably includes sequentially performing a first spin-coating and a second spin-coating. The rotation speed of the first spin-coating is preferably 300 to 500 r / min, and the time is preferably 5 to 10 s. The rotation speed of the second spin-coating is preferably 2500 to 3000 r / min, and the time is preferably 20 to 25 s. The drying is preferably oven-drying. The drying temperature is preferably 180 to 200°C, and the drying time is preferably 2 to 3 hours.

[0076] After obtaining a first substrate having a first alignment layer and a second substrate having a second alignment layer, the present invention fabricates a liquid crystal cell using the first substrate having the first alignment layer and the second substrate having the second alignment layer, wherein the first alignment layer and the second alignment layer are disposed opposite to each other inside the liquid crystal cell. In the present invention, the fabrication method of the liquid crystal cell preferably includes the following steps:

[0077] The first substrate having a first alignment layer and the second substrate having a second alignment layer are arranged opposite each other, and a box is formed using UV-cured adhesive under ultraviolet light conditions. In this invention, the distance between the first substrate and the second substrate is preferably 2 to 10 μm, more preferably 8 μm. The box is preferably formed by staggering the top and bottom layers by 2 mm.

[0078] In embodiments of the present invention, the method for preparing the liquid crystal cell may include the following steps: applying adhesive to both sides of a first substrate having a first alignment layer and a second substrate having a second alignment layer using a dispensing machine to form a cell; the dispensing uses a UV-curable adhesive, which preferably contains spacers, the diameter of which is preferably 2–10 μm, more preferably 8 μm. The present invention preferably controls the cell thickness by controlling the diameter of the spacers in the UV-curable adhesive. The cell is preferably formed by staggering the vertical spacing by 2 mm; then, it is fully cured under ultraviolet light to obtain the liquid crystal cell.

[0079] After obtaining the liquid crystal cell, the present invention performs a first alignment process on the liquid crystal cell using an alignment optical path to obtain a first-aligned liquid crystal cell. In the present invention, during the first alignment process, the liquid crystal cell is located downstream of the light beam obtained by the beam combiner. During the first alignment process, the distance between the convex lens in the alignment optical path and the liquid crystal cell is preferably twice the focal length of the lens. In the present invention, the alignment light preferably used in the first alignment process is blue-violet light, and the wavelength of the blue-violet light is preferably 405 nm. The total irradiation energy of the alignment light during the first alignment process is preferably 4 J / cm². 2 The focal length of the lens is 10cm.

[0080] After obtaining the first oriented liquid crystal cell, the present invention injects a first liquid crystal mixture into the first oriented liquid crystal cell and then performs a first curing and a first washing process sequentially to obtain a liquid crystal cell with a single-chiral cholesteric polymer template. The first liquid crystal mixture includes a first nematic liquid crystal, a first chiral agent, a first polymer monomer, a first crosslinking agent, and a first photoinitiator. In the present invention, the first chiral agent preferably includes R5011 chiral agent or S5011 chiral agent. The first nematic liquid crystal preferably includes BPH006 liquid crystal. The first polymer monomer preferably includes TMPTA polymer monomer. The first crosslinking agent preferably includes C3M crosslinking agent. The first photoinitiator preferably includes IRG184 photoinitiator. The mass ratio of the first nematic liquid crystal, the first chiral agent, the first polymer monomer, the first crosslinking agent, and the first photoinitiator is preferably 82.9:2:6.7:8.3:0.1. The preferred method for preparing the first liquid crystal mixture includes: mixing the first nematic liquid crystal, the first chiral agent, the first polymer monomer, the first crosslinking agent, and the first photoinitiator to obtain the first liquid crystal mixture. The mixing temperature is preferably 60–80°C, and the mixing time is preferably 5–10 min. The first mixing is carried out under stirring conditions. The injection is preferably perfusion, and the perfusion is preferably performed using a capillary tube. The first curing is preferably carried out under ultraviolet light conditions, the wavelength of which is preferably 388 nm, and the ultraviolet light conditions are preferably provided by an ultraviolet lamp. The first curing time is preferably 5–10 min, and the first curing temperature is preferably room temperature. The first rinsing is carried out in an organic solvent, preferably acetone, and the first rinsing preferably includes: immersing the first cured sample in the organic solvent for the first rinsing. The first rinsing time is preferably 12–24 h. The first rinsing is preferably used to thoroughly clean the residual first liquid crystal mixture in the liquid crystal cell. Preferably, the sample after the first rinsing is dried, the drying temperature is preferably 60–80°C, and the first drying is carried out on a hot plate. The first drying time is preferably 5–10 min.

[0081] In this invention, when the first chiral agent is R5011 chiral agent, the resulting liquid crystal cell with a single-chiral cholesteric phase polymer template is a liquid crystal cell with an R-chiral cholesteric phase polymer template.

[0082] In this invention, when the first chiral agent is S5011 chiral agent, the resulting liquid crystal cell with a single-chiral cholesteric polymer template is a liquid crystal cell with an S-chiral cholesteric polymer template.

[0083] In this invention, when the first chiral agent is R5011 chiral agent, the second chiral agent is S5011 chiral agent.

[0084] In this invention, when the first chiral agent is S5011 chiral agent, the second chiral agent is R5011 chiral agent.

[0085] After obtaining a liquid crystal cell with a single-chiral cholesteric polymer template, the present invention rotates the first and second quarter-wave plates in the orientation optical path by 90° in the same direction, and then performs a second orientation treatment on the liquid crystal cell with the single-chiral cholesteric polymer template using the orientation optical path to obtain a second-oriented liquid crystal cell. In the present invention, during the second orientation treatment, the liquid crystal cell is located downstream of the light obtained by the beam combiner. During the second orientation treatment, the distance between the convex lens in the orientation optical path and the liquid crystal cell is preferably twice the focal length of the lens. In the present invention, the orientation light preferably used in the second orientation treatment is blue-violet light, and the wavelength of the blue-violet light is preferably 405 nm. The total irradiation energy of the orientation light during the second orientation treatment is preferably 4 J / cm². 2 The focal length of the lens is 10cm.

[0086] After obtaining the second-oriented liquid crystal cell, the present invention injects a second liquid crystal mixture into the second-oriented liquid crystal cell and then performs a second curing and a second rinsing sequentially to obtain a liquid crystal cell with a bipolar cholesteric polymer template. The second liquid crystal mixture includes a second nematic liquid crystal, a second chiral agent, a second polymer monomer, a second crosslinking agent, and a second photoinitiator, so the second chiral agent is the opposite of the first chiral agent. In the present invention, the second chiral agent preferably includes R5011 chiral agent or S5011 chiral agent. The second nematic liquid crystal preferably includes BPH006 liquid crystal. The second polymer monomer preferably includes TMPTA polymer monomer. The second crosslinking agent preferably includes C3M crosslinking agent. The second photoinitiator preferably includes IRG184 photoinitiator. The mass ratio of the second nematic liquid crystal, the second chiral agent, the second polymer monomer, the second crosslinking agent, and the second photoinitiator is preferably 82.9:2:6.7:8.3:0.1. The preparation method of the second liquid crystal mixture preferably includes: mixing the second nematic liquid crystal, the second chiral agent, the second polymer monomer, the second crosslinking agent, and the second photoinitiator to obtain the second liquid crystal mixture. The mixing temperature is preferably 60–80°C, and the mixing time is preferably 5–10 min. The mixing is carried out under stirring. The injection is preferably perfusion, and the perfusion is preferably performed using a capillary tube. The second curing is preferably carried out under ultraviolet light, the wavelength of which is preferably 388 nm, and the ultraviolet light is preferably provided by an ultraviolet lamp. The first curing time is preferably 5–10 min, and the second curing temperature is preferably room temperature. The second elution is carried out in an organic solvent, preferably acetone, and the second elution preferably includes: immersing the second-cured sample in the organic solvent for a second elution. The second elution time is preferably 12–24 h. The second elution is preferably used to thoroughly clean the residual second liquid crystal mixture in the liquid crystal cell. Preferably, the sample after the second elution is subjected to a second drying, the drying temperature is preferably 60–80°C, and the second drying is carried out on a hot plate. The second drying time is preferably 5–10 min.

[0087] After obtaining a liquid crystal cell with a bipolar cholesteric polymer template, the present invention injects a third-nematic liquid crystal into the liquid crystal cell with the bipolar cholesteric polymer template to obtain the polarization-independent liquid crystal lens. In the present invention, the third-nematic liquid crystal preferably includes BPH006 liquid crystal. The injection is preferably perfusion, and the perfusion is preferably performed using a capillary.

[0088] The focal length of the polarization-independent liquid crystal lens prepared by the present invention is preferably composed of... Figure 2 The orientation of the optical path is determined by the convex lens shown.

[0089] The present invention provides a polarization-independent liquid crystal lens prepared by the preparation method described in the above technical solution. Figure 1 This is a schematic diagram of the polarization-independent liquid crystal lens provided by the present invention. The following is in conjunction with... Figure 1 The structure of the polarization-independent liquid crystal lens provided by the present invention will be described in detail.

[0090] The polarization-independent liquid crystal lens provided by the present invention includes a first substrate 101.

[0091] The polarization-independent liquid crystal lens provided by the present invention includes a second substrate and a liquid crystal layer 102.

[0092] In this invention, a liquid crystal cell is formed by the first substrate 101 and the second substrate 102 being disposed opposite to each other, and a liquid crystal layer 103 is disposed between the first substrate 101 and the second substrate 102.

[0093] In this invention, the first substrate 101 and the second substrate 102 are disposed opposite to each other, and the spacing between the first substrate 101 and the second substrate 102 is preferably 2 to 10 μm, more preferably 8 μm. A first alignment layer is disposed on one surface of the first substrate 101, and a second alignment layer is disposed on one surface of the second substrate 102. The first alignment layer and the second alignment layer are disposed opposite to each other inside the liquid crystal cell.

[0094] The polarization-independent liquid crystal lens provided by the present invention includes a liquid crystal layer 103. The liquid crystal layer is encapsulated between a first substrate and a second substrate. The liquid crystal layer 103 is provided with two cholesteric polymer templates with opposite chirality, which enables the liquid crystal in the liquid crystal layer to form a polarization-independent Fresnel liquid crystal lens.

[0095] The polarization-independent liquid crystal lens provided by this invention uses a template technique to superimpose left- and right-handed polarized liquid crystal lenses, so that it has the same control effect on beams of all polarization states, which greatly improves the diffraction efficiency.

[0096] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0097] Example 1

[0098] This embodiment provides a method for fabricating a polarization-independent liquid crystal lens. The polarization-independent liquid crystal lens fabricated by this invention is a liquid crystal polarization-independent lens with a red, green, and blue wavelength of 532nm and a focal length of 7.6cm. Specifically, it includes the following steps:

[0099] Step 1: Select R5011 chiral agent as the right-handed chiral agent and S5011 chiral agent as the left-handed chiral agent. Prepare a first liquid crystal mixture and a second liquid crystal mixture by mixing BPH006 liquid crystal, chiral agent (R5011 or S5011 chiral agent), TMPTA polymer monomer, C3M crosslinking agent, and IRG184 photoinitiator in a mass ratio of 82.9:2.0:6.7:8.3:0.1, respectively. Name them RCLC and LCLC, respectively, with a reflection band covering 532nm. Stir the prepared cholesteric phase liquid crystals on a hot plate at 80°C for 10 minutes to ensure thorough mixing, then cool to room temperature for later use.

[0100] Step 2: Prepare an SD1 solution at a ratio of 0.3 wt%, using dimethylxylene as the solvent. Drop the SD1 solution onto a cleaned glass substrate and spin coat it at 300 rpm for 10 s, then at 2500 rpm for 25 s. Finally, dry it at 200°C for 2 hours to form a robust SD1 alignment layer.

[0101] Step 3: Using a dispensing machine, apply adhesive to both sides of two glass substrates spin-coated with SD1 alignment layers. The UV-curable adhesive contains 8μm spacers to control the thickness of the liquid crystal cell. The cells are formed by alternating 2mm vertically and fully curing under UV light to prepare the liquid crystal cell.

[0102] Step 4: Use Figure 2 The optical path in the process is oriented. First, a template for a right-handed chiral lens is prepared. Blue-violet light with a wavelength of 405nm is used as the orientation light in the orientation optical path. The lens focal length is selected as 10cm, and the total irradiation energy is 4J / cm². 2 After the alignment process is completed, the liquid crystal cell is placed on a hot stage at a temperature above 80°C, and the prepared RCLC is poured in using a capillary tube and then slowly cooled to room temperature.

[0103] Step 5: Place the liquid crystal cell cooled to room temperature under a 388nm ultraviolet lamp for 10 minutes to cure it, so as to form a right-handed chiral cholesteric phase polymer template.

[0104] Step 6: Place the cured liquid crystal cell from Step 5 in acetone and let it stand for 24 hours to thoroughly clean the residual cholesteric liquid crystal in the liquid crystal cell. Place the cleaned liquid crystal cell on a hot plate at 80°C and heat it for 10 minutes to remove the residual acetone. Thus, a liquid crystal cell with a right-handed cholesteric polymer template is prepared.

[0105] Step 7: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] Figure 2After rotating the two quarter-wave plates in the optical path by 90° in the same direction, LCLC is used to repeat steps 4 to 6 on the liquid crystal cell with the right-handed cholesteric polymer template obtained in step 6 to prepare a left-handed cholesteric polymer template, thus forming a liquid crystal cell with both left- and right-handed cholesteric polymer templates. During the preparation process, the orientation centers should be aligned during the first and second orientation processes to ensure that the focal points of the left- and right-handed reflected light are at the same position, achieving polarization-independent beam convergence.

[0106] Step 8: Fill the liquid crystal cell with the cholesteric polymer template with left and right bipolarity obtained in Step 7 with nematic liquid crystal (BPH006 liquid crystal) to obtain a polarization-independent liquid crystal lens.

[0107] Comparative Example 1

[0108] A liquid crystal cell with a right-handed cholesteric polymer template was obtained according to steps 1 to 6 in Example 1.

[0109] A right-handed cholesteric liquid crystal lens was obtained by filling a liquid crystal cell with a cholesteric polymer template having right-handed chirality into a nematic liquid crystal.

[0110] Comparative Example 2

[0111] The preparation method is basically the same as that in Example 1, except that RCLC in step 4 is replaced with LCLC, and a liquid crystal cell with a left-handed cholesteric polymer template is obtained in step 6.

[0112] A left-handed cholesteric liquid crystal lens was obtained by filling a liquid crystal cell with a cholesteric polymer template having left-handed chirality into a nematic liquid crystal.

[0113] In this embodiment, the target wavelength of the liquid crystal lens is determined by the refractive index n of the liquid crystal material, the concentration c of the chiral agent, and the torsional constant HTP of the chiral agent. The calculation formula for the target wavelength of the liquid crystal lens is shown in Formula 3:

[0114]

[0115] In Formula 3: λ is the target wavelength of the liquid crystal lens, n is the refractive index of the liquid crystal material in the liquid crystal layer, c is the chiral agent concentration, and HTP is the torsional constant of the chiral agent. The chiral agent concentration refers to the mass content of the first or second chiral agent in the first or second liquid crystal mixture.

[0116] The orientation of cholesteric liquid crystals determines their geometric phase modulation. Therefore, this invention uses an optically oriented material to write a fixed orientation pattern, allowing for flexible manipulation of the geometric phase modulation of the cholesteric liquid crystal. However, the same geometric phase modulation produces conjugate modulation results for both left- and right-handed cholesteric liquid crystals. That is, the same phase change distribution results in opposite modulation outcomes for left-handed and right-handed polarized incident light. Therefore, this embodiment proposes a two-stage orientation preparation method, and ensures the coexistence of the two orientation results through cholesteric liquid crystal templated fabrication. The orientation optical path used in this invention to prepare the polarization-independent liquid crystal lens is as follows: Figure 2 As shown, after passing through the beam splitter, the light path is divided into two beams with the same polarization direction and intensity. A quarter-wave plate and a mirror are placed in each of the two beam paths. The major axes of the two quarter-wave plates make angles of 45° and -45° with the polarization direction of the polarizer 202, respectively, to convert linearly polarized light into left- and right-handedly polarized light. A lens 209 is placed in one of the beam paths, and a beam combiner 210 combines the two beams, ultimately illuminating the inner surface of the liquid crystal cell sample 211. In this embodiment, the distance between the lens 209 and the liquid crystal cell sample 211 should be maintained at twice the lens focal length to ensure that the two beams have the same spot size. The focal length of the polarization-independent liquid crystal lens prepared in this embodiment is determined by the convex lens used.

[0117] The polarization-independent liquid crystal lens prepared in this embodiment was used to test the reflectivity and polarization of linearly polarized light at the target wavelength (532 nm) of both the single-chiral cholesteric liquid crystal lens and the proposed polarization-independent liquid crystal lens. Figure 3 The transmittance spectra of the left-handed cholesteric liquid crystal lens prepared in Comparative Example 2, the right-handed cholesteric liquid crystal lens prepared in Comparative Example 1, and the polarization-independent lens prepared in Example 1 are shown. Figure 3 The horizontal axis represents the wavelength of the incident light, and the vertical axis represents the transmittance. Figure 3 In this context, 301 represents the right-handed cholesteric liquid crystal lens prepared in Comparative Example 1. Figure 3 In this context, 302 represents the left-handed cholesteric liquid crystal lens prepared in Comparative Example 2. Figure 3 303 in the figure represents the transmittance spectrum of the polarization-independent lens prepared in Example 1.

[0118] Figure 4 The results show the comparison of polarization independence of the left-handed cholesteric liquid crystal lens prepared in Comparative Example 2, the right-handed cholesteric liquid crystal lens prepared in Comparative Example 1, and the polarization-independent lens prepared in Example 1. Figure 4 The horizontal axis represents the rotation angle of the incident light, and the vertical axis represents the transmittance. Figure 4 In the figure, 401 represents the transmittance curve of the right-handed cholesteric liquid crystal lens prepared in Comparative Example 1. Figure 4In the figure, 402 represents the transmittance curve of the left-handed cholesteric liquid crystal lens prepared in Comparative Example 2. Figure 4 403 in the figure represents the transmittance curve of the polarization-independent lens prepared in Example 1.

[0119] The transmittance can be directly calculated from the transmittance spectrum using Formula 1; polarization independence is calculated using Formula 2 based on the transmittance of linearly polarized incident light at different angles. Test results show that the reflectances of the left-handed and right-handed cholesteric liquid crystal lenses at 532 nm are 41.5% and 40.6%, respectively, while the polarization-independent liquid crystal lens proposed in Example 1 has a reflectance as high as 74.1%, significantly improving diffraction efficiency. The polarization correlations of the left-handed and right-handed cholesteric liquid crystal lenses at 532 nm are 89.3% and 81.0%, respectively, while the polarization correlation of the polarization-independent liquid crystal lens proposed in Example 1 is only 8.6%, demonstrating good polarization independence. The formulas for calculating reflectance are shown in Formula 1, and the formulas for calculating polarization independence are shown in Formula 2.

[0120]

[0121] In Formulas 1 and 2, R represents reflectivity, and I represents... reflect I represents the intensity of the reflected light. in I is the incident light intensity; P is the polarization correlation degree, I max I represents the maximum light intensity obtained by reflecting incident light with different polarization states. min This represents the minimum light intensity.

[0122] As can be seen from the above embodiments, the polarization-independent liquid crystal lens provided by the present invention has wavelength selectivity and high diffraction efficiency. The present invention utilizes the Bragg reflection property of cholesteric liquid crystals, whose reflected light exhibits wavelength selectivity, meaning it diffracts only for specific wavelengths, reducing stray light interference. The present invention also utilizes the geometric phase modulation characteristics of cholesteric liquid crystals, allowing for flexible phase modulation and enabling beam focusing at different focal lengths. Simultaneously, it facilitates the addition of lens functions, enabling relatively simple off-axis beam focusing. The present invention uses a template-based technique to superimpose left- and right-handed polarized liquid crystal lenses, giving them the same control effect on beams of all polarization states, greatly improving diffraction efficiency.

[0123] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for fabricating a polarization-independent liquid crystal lens, characterized in that, The polarization-independent liquid crystal lens is fabricated using an orientation optical path. The orientation optical path, along the direction of the orientation light, includes a polarizer, a collimating beam expander, and a beam splitter. Along the direction of the first beam splitter obtained by the beam splitter, it includes a first quarter-wave plate and a first reflecting mirror. Along the direction of the second beam splitter obtained by the beam splitter, it includes a second quarter-wave plate and a second reflecting mirror. A beam combiner is used to combine the first and second beam splitters. The lens also includes a convex lens disposed between the first reflecting mirror and the beam combiner, or between the second reflecting mirror and the beam combiner. The major axis of the first quarter-wave plate forms an angle of 45° or -45° with the polarization direction of the polarizer, and the first and second quarter-wave plates are orthogonally arranged. Includes the following steps: A first alignment layer and a second alignment layer are respectively prepared on one surface of a first substrate and one surface of a second substrate to obtain a first substrate having a first alignment layer and a second substrate having a second alignment layer. A liquid crystal cell is fabricated by means of a first substrate having a first alignment layer and a second substrate having a second alignment layer, wherein the first alignment layer and the second alignment layer are disposed opposite to each other inside the liquid crystal cell; The liquid crystal cell is subjected to a first alignment process using an alignment optical path to obtain a first-aligned liquid crystal cell. After injecting a first liquid crystal mixture into the first oriented liquid crystal cell, a first curing and a first rinsing are performed sequentially to obtain a liquid crystal cell with a single-chiral cholesteric polymer template. The first liquid crystal mixture includes a first nematic liquid crystal, a first chiral agent, a first polymer monomer, a first crosslinking agent, and a first photoinitiator. The first 1 / 4 wave plate and the second 1 / 4 wave plate in the orientation optical path are rotated 90° in the same direction, and then the orientation optical path is used to perform a second orientation process on the liquid crystal cell with a single-chiral cholesteric polymer template to obtain a second-oriented liquid crystal cell. After injecting a second liquid crystal mixture into the second oriented liquid crystal cell, a second curing and a second rinsing are performed sequentially to obtain a liquid crystal cell with a bipolar cholesteric polymer template. The second liquid crystal mixture includes a second nematic liquid crystal, a second chiral agent, a second polymer monomer, a second crosslinking agent, and a second photoinitiator. Therefore, the second chiral agent and the first chiral agent have opposite chirality. The polarization-independent liquid crystal lens is obtained by injecting a third-nematic liquid crystal into a liquid crystal cell with a bipolar cholesteric polymer template.

2. The preparation method according to claim 1, characterized in that, During the first and second orientation processes, the distance between the convex lens in the orientation optical path and the liquid crystal cell is twice the focal length of the convex lens.

3. The preparation method according to claim 1, characterized in that, The method for preparing the first orientation layer and the second orientation layer includes the following steps: A photoalignment material solution is coated onto one surface of a first substrate and one surface of a second substrate, and then dried to obtain the first alignment layer and the second alignment layer; the photoalignment material solution includes a photoalignment material and an organic solvent.

4. The preparation method according to claim 3, characterized in that, The photo-alignment material includes SD1 material; the mass content of the photo-alignment material solution is 0.1% to 0.5%.

5. The preparation method according to claim 3 or 4, characterized in that, The coating is spin coating, which includes performing a first spin coating and a second spin coating in sequence. The first spin coating has a rotation speed of 300-500 r / min and a time of 5-10 s, and the second spin coating has a rotation speed of 2500-3000 r / min and a time of 20-25 s. The drying temperature is 180–200°C, and the time is 2–3 hours.

6. The preparation method according to claim 1, characterized in that, The method for preparing the liquid crystal cell includes the following steps: The first substrate having a first orientation layer and the second substrate having a second orientation layer are arranged opposite each other and assembled into a box using UV-curable adhesive under ultraviolet light conditions. The distance between the first substrate having a first orientation layer and the second substrate having a second orientation layer is 2 to 10 μm.

7. The preparation method according to claim 1, characterized in that, The first chiral agent includes either R5011 chiral agent or S5011 chiral agent; The first nematic liquid crystal, the second nematic liquid crystal, and the third nematic liquid crystal include BPH006 liquid crystal; The first and second polymer monomers include TMPTA polymer monomers; The first and second crosslinking agents include C3M crosslinking agent; The first and second photosensitizers include IRG184 photosensitizer; The mass ratio of the first nematic liquid crystal, the first chiral agent, the first polymer monomer, the first crosslinking agent, and the first photoinitiator is 82.9:2:6.7:8.3:0.

1. The mass ratio of the second nematic liquid crystal, the second chiral agent, the second polymer monomer, the second crosslinking agent, and the second photoinitiator is 82.9:2:6.7:8.3:0.

1.

8. The preparation method according to claim 1 or 2, characterized in that, The orientation light used in the first and second orientation processes is blue-violet light with a wavelength of 405 nm; the total irradiation energy of the orientation light during the first and second orientation processes is 4 J / cm². 2 ; The focal length of the convex lens is 10cm.

9. A polarization-independent liquid crystal lens prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the polarization-independent liquid crystal lens of claim 9 in a display, imaging system or optical communication system.

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