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

Abstract

The invention belongs to the technical field of liquid crystal lenses, and particularly relates to a polarization-independent liquid crystal lens and a preparation method thereof. The polarization-independent liquid crystal lens is prepared by adopting an orientation light path, and the polarization-independent liquid crystal lens which is formed by superposing a double-chiral polarizer lens template by utilizing a washing-refilling method is provided. The liquid crystal lens prepared by the method provided by the invention can converge left-handed and right-handed incident light to the same focus in a reflection manner, so that polarization-independent modulation is realized. The method provided by the invention has wavelength selectivity, and compared with other liquid crystal lenses, the interference of stray light is reduced. Meanwhile, the diffraction efficiency of the obtained liquid crystal lens is greatly improved through application of geometric phases and polarization-independent modulation performance, and the liquid crystal lens can be widely applied to novel display and imaging systems or optical communication systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid crystal lenses, and in particular relates to a polarization-independent liquid crystal lens and a preparation method and application thereof. Background Art

[0002] In essence, most liquid crystal lenses are based on the birefringence phenomenon of liquid crystals, and different phase modulations are produced through the refractive index difference between the long axis and the short axis of the liquid crystal molecules. Therefore, in most cases, liquid crystal lenses are polarization-dependent. That is to say, for a certain polarized light, the liquid crystal lens can achieve an extremely ideal modulation result, but for polarized light with polarization states in orthogonal directions, the liquid crystal lens often cannot perform phase modulation. This kind of liquid crystal lens whose modulation is highly related to the polarization direction of the incident light is called a polarization-dependent liquid crystal lens. In practical applications, it is often necessary to cooperate with certain polarizing and analyzing devices. For example, in many existing twisted nematic mode liquid crystal displays, the light source will pass through a layer of polarizer and then be incident on the liquid crystal layer in the form of specific polarized light, and the analyzer will be used again to achieve phase-to-intensity conversion. However, in other applications, the screening of the polarization state of the incident light will not only reduce the optical utilization efficiency of the device, but also limit the multi-scenario application of the device to a certain extent, which is not conducive to the widespread development of the device. Therefore, realizing polarization-independent modulation of liquid crystal lenses has become one of the important directions for the development of liquid crystal devices.

[0003] There are two main directions for the development of polarization-independent liquid crystal lenses. One is to explore new liquid crystal materials with polarization-independent modulation properties from the perspective of material research and development. Blue phase liquid crystal does not have the birefringence phenomenon of other liquid crystal phases. It presents thermodynamically stable optical isotropy on a macroscopic scale and is often used to prepare polarization-independent liquid crystal lenses. However, its temperature range is much higher than room temperature and very narrow, so it is very limited in practical applications.

[0004] Based on the current polarization-dependent liquid crystal materials, through different structural designs, such as double-layer design and spatial multiplexing design, the orthogonal polarization state light beams can be modulated equivalently, and an overall polarization-independent liquid crystal lens can also be realized. However, the double-layer design will introduce additional crosstalk, and the spatial multiplexing design has low light energy utilization efficiency, making it difficult to be widely used in practical applications. Summary of the invention

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

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a polarization-independent liquid crystal lens. The polarization-independent liquid crystal lens is prepared by adopting an oriented light path. The oriented light path includes a polarizer, a collimating beam expander, and a beam splitter along the light path direction of the oriented light; the light path direction of a first split light beam obtained by the beam splitter includes a first 1 / 4 wave plate and a first reflector; the light path direction of a second split light beam obtained by the beam splitter includes a second 1 / 4 wave plate and a second reflector; a beam combiner for combining the first split light beam and the second split light beam; and a convex lens arranged between the first reflector and the beam combiner or between the second reflector and the beam combiner; the angle between the major axis of the first 1 / 4 wave plate and the polarization direction of the polarizer is 45° or -45°, and the first 1 / 4 wave plate and the second 1 / 4 wave plate are arranged orthogonally;

[0008] The following steps are involved:

[0009] Prepare a first alignment layer and a second alignment layer on one surface of the first substrate and one surface of the second substrate, respectively, to obtain a first substrate having the first alignment layer and a second substrate having the second alignment layer;

[0010] The first substrate having the first alignment layer and the second substrate having the second alignment layer are used to prepare a liquid crystal box, wherein the first alignment layer and the second alignment layer are arranged opposite to each other inside the liquid crystal box;

[0011] Performing a first alignment treatment on the liquid crystal cell using an alignment light path to obtain a first-aligned liquid crystal cell;

[0012] After injecting a first liquid crystal mixture into the first orientation liquid crystal box, first curing and first washing are sequentially performed to obtain a liquid crystal box having a single-chiral cholesteric polymer template, wherein the first liquid crystal mixture includes a first nematic liquid crystal, a first chiral agent, a first polymer monomer, a first cross-linking agent and a first photosensitive initiator;

[0013] The first 1 / 4 wave plate and the second 1 / 4 wave plate in the alignment light path are rotated 90 degrees in the same direction, and then the alignment light path is used to perform a second alignment treatment on the liquid crystal box having a single-chiral cholesteric polymer template to obtain a second alignment liquid crystal cell;

[0014] After injecting a second liquid crystal mixture into the second orientation liquid crystal box, a second curing and a second washing are sequentially performed to obtain a liquid crystal box having a two-handed cholesteric polymer template, wherein the second liquid crystal mixture includes a second nematic liquid crystal, a second chiral agent, a second polymer monomer, a second cross-linking agent, and a second photoinitiator, so that the second chiral agent and the first chiral agent have opposite chirality;

[0015] The third nematic phase liquid crystal is injected into the liquid crystal box having the chiral cholesteric polymer template to obtain the polarization-independent liquid crystal lens.

[0016] Preferably, during the first alignment treatment and the second alignment treatment, the distance between the convex lens in the alignment light path and the liquid crystal box is twice the focal length of the convex lens.

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

[0018] The photo-alignment material solution is coated on one surface of the first substrate and one surface of the second substrate respectively, and then dried to obtain the first alignment layer and the second alignment layer; the photo-alignment material solution includes a photo-alignment material and an organic solvent.

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

[0020] Preferably, the coating is spin coating, and the spin coating includes sequentially performing a first spin coating and a second spin coating, wherein the first spin coating has a rotation speed of 300 to 500 r / min and a time of 5 to 10 s, and the second spin coating has a rotation speed of 2500 to 3000 r / min and a time of 20 to 25 s;

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

[0022] Preferably, the method for preparing the liquid crystal box comprises the following steps:

[0023] The first substrate with the first alignment layer and the second substrate with the second alignment layer are arranged opposite to each other, and are formed into a box by using ultraviolet curing glue under ultraviolet conditions;

[0024] The distance between the first substrate having the first alignment layer and the second substrate having the second alignment layer is 2-10 μm.

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

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

[0027] The first polymer monomer and the second polymer monomer include a TMPTA polymer monomer;

[0028] The first cross-linking agent and the second cross-linking agent include a C3M cross-linking agent;

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

[0030] Preferably, the mass ratio of the first nematic liquid crystal, the first chiral agent, the first polymer monomer, the first cross-linking 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 cross-linking agent and the second photoinitiator is 82.9:2:6.7:8.3:0.1.

[0032] Preferably, the alignment light used in the first alignment treatment and the second alignment treatment is blue-violet light, and the wavelength of the blue-violet light is 405nm; the total irradiation energy of the alignment light during the first alignment treatment and the second alignment treatment is 4J / cm 2 ;

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

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

[0035] The present invention provides the application of the polarization-independent liquid crystal lens described in the above technical solution in a display, imaging system or optical communication system.

[0036] The present invention provides a method for preparing a polarization-independent liquid crystal lens. The present invention adopts an orientation light path to prepare the polarization-independent liquid crystal lens. In the present invention, since the orientation of the cholesteric liquid crystal determines the geometric phase modulation of the cholesteric liquid crystal, the present invention uses an orientation light path to write a fixed orientation pattern on the light orientation material in the first orientation layer and the second orientation layer, and the geometric phase modulation of the cholesteric liquid crystal can be flexibly controlled. However, the same geometric phase modulation has a conjugated modulation result for left-handed and right-handed cholesteric liquid crystals. That is, for the same phase change distribution, the modulation results for left-handed polarized incident light and right-handed polarized incident light are opposite. Therefore, the present invention adopts an orientation light path to perform a preparation method of two orientations, and ensures the coexistence of the two orientation results by template-based cholesteric liquid crystal. Therefore, the present invention uses an orientation light path to perform two orientation processes to obtain a liquid crystal box (i.e., a second orientation liquid crystal box) having a two-handed polarizer lens template. At the same time, a wash-out-refilling method is used to obtain a polarization-independent liquid crystal lens. Specifically, the structure of the orientation light path used in the present invention is as follows Figure 2As shown, after the orientation light path passes through the beam splitter, it is divided into two beams of light with the same polarization direction and the same intensity. A quarter wave plate (a first quarter wave plate and a second quarter wave plate) and a reflector (a second reflector and a second reflector) are placed in the two light paths respectively. The present invention realizes the conversion of linear polarized light into left-handed and right-handed polarized light by controlling the angle between the long axis of the two quarter wave plates and the polarization direction of the polarizer; at the same time, the present invention places a convex lens in any one of the light paths, and finally uses a beam combiner to combine the two light paths, and finally irradiates the first orientation layer and the second orientation layer inside the liquid crystal box to form a lens-shaped circular interference pattern, thereby realizing the template processing of the bimanual polarizer lens of the light orientation material in the first orientation layer and the second orientation layer. Therefore, the method provided by the present invention performs template processing on the light orientation material in the first orientation layer and the second orientation layer through two orientation processes, and realizes the common modulation of left and right chiral incident light in one layer of the device. At the same time, the liquid crystal lens realized by the present invention can converge the incident light of left and right hands to the same focus by reflection while maintaining the two orientations completely conjugated, thereby realizing polarization-independent modulation. The polarization-independent liquid crystal lens prepared by the present invention has wavelength selectivity and reduces the interference of stray light compared with other liquid crystal lenses. At the same time, due to the application of geometric phase and polarization-independent modulation performance, the diffraction efficiency of the polarization-independent liquid crystal lens prepared by the present invention is greatly improved, and can be widely used in new display, imaging systems or optical communication systems.

[0037] The present invention provides a polarization-independent liquid crystal lens prepared by the preparation method described in the above technical solution. The polarization-independent liquid crystal lens provided by the present invention comprises a first substrate and a second substrate, the first substrate and the second substrate are arranged relative to each other to form a liquid crystal box, a liquid crystal layer is arranged between the first substrate and the second substrate; a first orientation layer is arranged on one surface of the first substrate, a second orientation layer is arranged on one surface of the second substrate, the first orientation layer and the second orientation layer are arranged relative to each other inside the liquid crystal box; the liquid crystal layer is provided with two cholesteric polymer templates with opposite chirality, and the two cholesteric polymer templates with opposite chirality can make the liquid crystal in the liquid crystal layer form a polarization-independent Fresnel liquid crystal lens. The structural schematic diagram of the polarization-independent liquid crystal lens provided by the present invention is shown as follows. Figure 1 The polarization-independent liquid crystal lens provided by the present invention comprises two cholesteric polymer templates with opposite chirality integrated on a layer (i.e., liquid crystal layer), which correspond to left-handed and right-handed liquid crystals of required wavelengths respectively. Under the joint action of the two cholesteric polymer templates with opposite chirality, the joint modulation of the left-handed and right-handed incident light is achieved, thereby achieving polarization-independent light beam convergence.

[0038] Compared with the prior art, the polarization-independent liquid crystal lens provided by the present invention has the following technical effects:

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

[0040] The polarization-independent liquid crystal lens provided by the present invention utilizes the Bragg reflection property of cholesteric liquid crystal, and its reflected light has wavelength selectivity, that is, it only plays a diffraction role on a specific wavelength, thereby reducing the interference of stray light.

[0041] The polarization-independent liquid crystal lens provided by the present invention utilizes the geometric phase modulation characteristics of cholesteric liquid crystal, and has flexible phase modulation, and can realize light beam convergence of different focal lengths; at the same time, it is beneficial to add lens functions, and can realize off-axis light beam convergence relatively simply.

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

[0043] It can be seen from the results of the embodiment that the reflectivity and polarization of linearly polarized light of the single-handed cholesteric liquid crystal lens and the polarization-independent liquid crystal lens provided by the present invention are tested at the target wavelength (532nm). The test results show that the reflectivities of the left-handed and right-handed cholesteric liquid crystal lenses at 532nm are 41.5% and 40.6% respectively, and the reflectivity of the proposed polarization-independent liquid crystal lens is as high as 74.1%, which greatly improves the diffraction efficiency; the polarization correlations of the left-handed and right-handed cholesteric liquid crystal lenses at 532nm are 89.3% and 81.0% respectively, and the polarization correlation of the proposed polarization-independent liquid crystal lens is only 8.6%, which has good polarization independence.

[0044] Furthermore, in the present invention, during the first alignment treatment and the second alignment treatment, the distance between the convex lens in the alignment light path and the liquid crystal box is twice the focal length of the lens to ensure that the two light beams have the same spot size. The focal length of the prepared polarization-independent liquid crystal lens is determined by the lens used. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0046] Figure 2 A schematic diagram of the structure of the orientation light path provided by the present invention;

[0047] Figure 3 The transmittance spectra 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;

[0048] Figure 4The polarization independence comparison results 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 shown;

[0049] In the figure: 101 is the first substrate, 102 is the second substrate, 103 is the liquid crystal layer; 201 is the orientation laser, 202 is the polarizer, 203 is the collimating beam expander, 204 is the beam splitter, 205 is the first 1 / 4 wave plate, 206 is the first reflector, 207 is the second 1 / 4 wave plate, 208 is the second reflector, 209 is the convex lens, 210 is the beam combiner, and 211 is the liquid crystal box. DETAILED DESCRIPTION

[0050] The present invention provides a method for preparing a polarization-independent liquid crystal lens. The polarization-independent liquid crystal lens is prepared by adopting an oriented light path. The oriented light path includes a polarizer, a collimating beam expander, and a beam splitter along the light path direction of the oriented light; the light path direction of a first split light beam obtained by the beam splitter includes a first 1 / 4 wave plate and a first reflector; the light path direction of a second split light beam obtained by the beam splitter includes a second 1 / 4 wave plate and a second reflector; a beam combiner for combining the first split light beam and the second split light beam; and a convex lens arranged between the first reflector and the beam combiner or between the second reflector and the beam combiner; the angle between the major axis of the first 1 / 4 wave plate and the polarization direction of the polarizer is 45° or -45°, and the first 1 / 4 wave plate and the second 1 / 4 wave plate are arranged orthogonally;

[0051] The following steps are involved:

[0052] Prepare a first alignment layer and a second alignment layer on one surface of the first substrate and one surface of the second substrate, respectively, to obtain a first substrate having the first alignment layer and a second substrate having the second alignment layer;

[0053] The first substrate having the first alignment layer and the second substrate having the second alignment layer are used to prepare a liquid crystal box, wherein the first alignment layer and the second alignment layer are arranged opposite to each other inside the liquid crystal box;

[0054] Performing a first alignment treatment on the liquid crystal cell using an alignment light path to obtain a first-aligned liquid crystal cell;

[0055] After injecting a first liquid crystal mixture into the first orientation liquid crystal box, first curing and first washing are sequentially performed to obtain a liquid crystal box having a single-chiral cholesteric polymer template, wherein the first liquid crystal mixture includes a first nematic liquid crystal, a first chiral agent, a first polymer monomer, a first cross-linking agent and a first photosensitive initiator;

[0056] The first 1 / 4 wave plate and the second 1 / 4 wave plate in the alignment light path are rotated 90 degrees in the same direction, and then the alignment light path is used to perform a second alignment treatment on the liquid crystal box having a single-chiral cholesteric polymer template to obtain a second alignment liquid crystal cell;

[0057] After injecting a second liquid crystal mixture into the second orientation liquid crystal box, a second curing and a second washing are sequentially performed to obtain a liquid crystal box having a two-handed cholesteric polymer template, wherein the second liquid crystal mixture includes a second nematic liquid crystal, a second chiral agent, a second polymer monomer, a second cross-linking agent, and a second photoinitiator, so that the second chiral agent and the first chiral agent have opposite chirality;

[0058] The third nematic phase liquid crystal is injected into the liquid crystal box having the chiral cholesteric polymer template to obtain the polarization-independent liquid crystal lens.

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

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

[0061] In the present invention, the liquid crystal cell having a chiral cholesteric polymer template is a liquid crystal cell having both an S-chiral cholesteric polymer template and an R-chiral cholesteric polymer template.

[0062] The present invention adopts an oriented light path to prepare the polarization-independent liquid crystal lens. The structural schematic diagram of the oriented light path is as follows Figure 2 As shown below, combined Figure 2 The orientation optical path provided by the present invention is described in detail.

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

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

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

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

[0067] The oriented light path provided by the present invention includes a first quarter wave plate 205 and a first reflector 206 along the light path direction of the first split light beam obtained by the splitter prism.

[0068] The oriented light path provided by the present invention includes a second quarter wave plate 207 and a second reflector 208 along the light path direction of the second split light beam obtained by the splitter prism.

[0069] In the present invention, the angle between the major axis of the first quarter wave plate 205 and the polarization direction of the polarizer 202 is 45° or −45°, and the first quarter wave plate 205 and the second quarter wave plate 207 are arranged orthogonally.

[0070] The oriented optical path provided by the present invention comprises a beam combiner 210 for combining the first split light beam and the second split light beam.

[0071] The alignment optical path provided by the present 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 the present invention, the convex lens 209 is used to form a specific interference pattern on the first alignment layer and the second alignment layer of the liquid crystal box. When the lens is not used, the two optical paths are exactly the same, and the interference is a plane pattern; after adding the lens, a lens-shaped circular interference pattern appears.

[0072] In the present invention, during the first alignment treatment and the second alignment treatment, the distance between the convex lens in the alignment light path and the liquid crystal box is preferably twice the focal length of the convex lens.

[0073] In the present invention, during the first alignment treatment and the second alignment treatment, the present invention preferably ensures that the optical path centers of the first alignment treatment and the second alignment treatment are aligned to ensure that the foci of the left-handed and right-handed reflected light are located at the same position to achieve polarization-independent beam convergence.

[0074] In the present invention, a first alignment layer and a second alignment layer are prepared on one surface of a first substrate and one surface of a second substrate, respectively, to obtain a first substrate having a first alignment layer and a second substrate having a second alignment layer. In the present invention, the first substrate and the second substrate are preferably glass substrates. The method for preparing the first alignment layer and the second alignment layer preferably comprises the following steps:

[0075] The photo-orientation material solution is applied to one surface of the first substrate and one surface of the second substrate respectively, and then dried to obtain the first orientation layer and the second orientation layer; the photo-orientation material solution includes a photo-orientation material and an organic solvent. In the present invention, the photo-orientation material preferably includes SD1 material. The organic solvent preferably includes dimethyl xylene. The mass content of the photo-orientation material in the photo-orientation material solution is preferably 0.1-0.5%, and can be 0.3% in the embodiment. In the present invention, the coating is preferably spin coating, and the spin coating preferably includes sequentially performing the first spin coating and the second spin coating, the rotation speed of the first spin coating is preferably 300-500r / min, the time is preferably 5-10s, and the rotation speed of the second spin coating is preferably 2500-3000r / min, and the time is preferably 20-25s. The drying is preferably baking. The drying temperature is preferably 180-200°C, and the time is preferably 2-3h.

[0076] After obtaining a first substrate having a first alignment layer and a second substrate having a second alignment layer, the present invention prepares a liquid crystal box by 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 arranged relatively inside the liquid crystal box. In the present invention, the preparation method of the liquid crystal box preferably includes the following steps:

[0077] The first substrate with the first alignment layer and the second substrate with the second alignment layer are arranged opposite to each other, and are formed into a box using ultraviolet curing glue under ultraviolet conditions. In the present 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 in a staggered manner of 2 mm up and down.

[0078] In an embodiment of the present invention, the preparation method of the liquid crystal box may include the following steps: using a glue dispenser to dispense glue on the left and right sides of a first substrate having a first orientation layer and a second substrate having a second orientation layer to form a box, the dispensing uses ultraviolet curing glue, the ultraviolet curing glue is preferably mixed with spacers, and the diameter of the spacers is preferably 2 to 10 μm, more preferably 8 μm. The present invention preferably controls the thickness of the liquid crystal box by the diameter of the spacers in the ultraviolet curing glue. The box formation is preferably formed in a staggered manner of 2 mm up and down; then fully cured under the action of ultraviolet rays to prepare a liquid crystal box.

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

[0080] After obtaining the first oriented liquid crystal box, the present invention injects the first liquid crystal mixture into the first oriented liquid crystal box and then performs the first curing and the first washing out in sequence to obtain a liquid crystal box with a single-chiral cholesteric phase polymer template, wherein the first liquid crystal mixture includes a first nematic phase liquid crystal, a first chiral agent, a first polymer monomer, a first cross-linking agent and a first photoinitiator. In the present invention, the first chiral agent preferably includes an R5011 chiral agent or an S5011 chiral agent. The first nematic phase liquid crystal preferably includes a BPH006 liquid crystal. The first polymer monomer preferably includes a TMPTA polymer monomer. The first cross-linking agent preferably includes a C3M cross-linking agent. The first photoinitiator preferably includes an IRG184 photoinitiator. The mass ratio of the first nematic phase liquid crystal, the first chiral agent, the first polymer monomer, the first cross-linking agent and the first photoinitiator is preferably 82.9:2:6.7:8.3:0.1. The preparation method of the first liquid crystal mixture preferably includes: first mixing the first nematic liquid crystal, the first chiral agent, the first polymer monomer, the first cross-linking agent and the first photosensitive initiator to obtain the first liquid crystal mixture. The temperature of the first mixing is preferably 60-80°C, and the time is preferably 5-10 minutes. The first mixing is performed under stirring. The injection is preferably perfusion, and the perfusion is preferably performed using a capillary. The first curing is preferably performed under ultraviolet conditions, the wavelength of the ultraviolet conditions is preferably 388nm, and the ultraviolet conditions are preferably provided by an ultraviolet lamp. The time of the first curing is preferably 5-10 minutes, and the temperature of the first curing is preferably room temperature. The first washing out is performed in an organic solvent, and the organic solvent is preferably acetone. The first washing out preferably includes: immersing the first cured sample in an organic solvent for the first washing out. The time of the first washing out is preferably 12-24 hours. The first washing out is preferably used to fully clean the first liquid crystal mixture remaining in the liquid crystal box. The present invention preferably dries the sample after the first washing out, and the drying temperature is preferably 60-80°C, and the first drying is performed on a hot stage. The time of the first drying is preferably 5-10 minutes.

[0081] In the present invention, when the first chiral agent is R5011 chiral agent, the obtained liquid crystal cell having a single-chiral cholesteric polymer template is a liquid crystal cell having an R-chiral cholesteric polymer template.

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

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

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

[0085] After obtaining the liquid crystal box with a unichiral cholesteric polymer template, the present invention rotates the first 1 / 4 wave plate and the second 1 / 4 wave plate in the orientation light path by 90° in the same direction, and then uses the orientation light path to perform a second orientation treatment on the liquid crystal box with a unichiral cholesteric polymer template to obtain a second oriented liquid crystal liquid box. In the present invention, during the second orientation treatment, the liquid crystal box 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 light path and the liquid crystal box 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 405nm. The total irradiation energy of the orientation light during the second orientation treatment is preferably 4J / cm 2 The focal length of the lens is 10 cm.

[0086] After obtaining the second orientation liquid crystal box, the present invention injects the second liquid crystal mixture into the second orientation liquid crystal box and then performs the second curing and the second washing in sequence to obtain a liquid crystal box with a two-handed cholesteric polymer template, wherein 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 opposite to the first chiral agent. In the present invention, the second chiral agent preferably includes an R5011 chiral agent or an S5011 chiral agent. The second nematic liquid crystal preferably includes a BPH006 liquid crystal. The second polymer monomer preferably includes a TMPTA polymer monomer. The second crosslinking agent preferably includes a C3M crosslinking agent. The second photoinitiator preferably includes an 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 comprises: second mixing the second nematic liquid crystal, the second chiral agent, the second polymer monomer, the second cross-linking agent and the second photosensitive initiator to obtain the second liquid crystal mixture. The temperature of the second mixing is preferably 60-80°C, and the time is preferably 5-10 minutes. The second mixing is performed under stirring. The injection is preferably perfusion, and the perfusion is preferably performed by a capillary. The second curing is preferably performed under ultraviolet conditions, the wavelength of the ultraviolet conditions is preferably 388nm, and the ultraviolet conditions are preferably provided by an ultraviolet lamp. The time of the first curing is preferably 5-10 minutes, and the temperature of the second curing is preferably room temperature. The second washing out is performed in an organic solvent, and the organic solvent is preferably acetone. The second washing out preferably comprises: immersing the second cured sample in an organic solvent for the second washing out. The time of the second washing out is preferably 12-24 hours. The second washing out is preferably used to fully clean the residual second liquid crystal mixture in the liquid crystal box. The present invention preferably performs a second drying on the sample after the second washing out, and the drying temperature is preferably 60-80°C, and the second drying is performed on a hot stage. The time of the second drying is preferably 5-10 minutes.

[0087] After obtaining a liquid crystal box having a chiral cholesteric polymer template, the present invention injects a third nematic phase liquid crystal into the liquid crystal box having a chiral cholesteric polymer template to obtain the polarization-independent liquid crystal lens. In the present invention, the third nematic phase 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 Figure 2 The orientation shown is determined by the convex lens in the light path.

[0089] The present invention provides a polarization-independent liquid crystal lens prepared by the preparation method described in the above technical solution. Figure 1 The schematic diagram of the structure of the polarization-independent liquid crystal lens provided by the present invention is shown below. Figure 1 The structure of the polarization-independent liquid crystal lens provided by the present invention is 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 the present invention, the first substrate 101 and the second substrate 102 are arranged opposite to each other to form a liquid crystal box, and a liquid crystal layer 103 is arranged between the first substrate 101 and the second substrate 102 .

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

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

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

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

[0097] Example 1

[0098] This embodiment provides a method for preparing a polarization-independent liquid crystal lens. The polarization-independent liquid crystal lens prepared by the present invention is a liquid crystal polarization-independent lens with a red, green and blue band of 532nm respectively and a focal length of 7.6cm. Specifically, the method comprises the following steps:

[0099] Step 1, select R5011 chiral agent as right-handed chiral agent, S5011 chiral agent as left-handed chiral agent. BPH006 liquid crystal, chiral agent (R5011 chiral agent or S5011 chiral agent), TMPTA polymer monomer, C3M crosslinker and IRG184 photoinitiator are respectively configured into a first liquid crystal mixture and a second liquid crystal mixture in a mass ratio of 82.9:2.0:6.7:8.3:0.1, and are named RCLC and LCLC respectively, and their reflection bands cover 532nm respectively. Stir the prepared cholesteric phase liquid crystals at 80°C for 10 minutes on a hot stage to fully mix them, and then cool them to room temperature for use.

[0100] Step 2: Prepare SD1 solution at a ratio of 0.3wt%, and choose dimethylbenzene as the solvent. Drop the SD1 solution on the cleaned glass substrate, and spin-coat it at a speed of 300r / min for 10s, 2500r / min for 25s, and then dry it at 200℃ for 2 hours to form a firm SD1 alignment layer.

[0101] Step 3: Use a glue dispenser to dispense glue on the left and right sides of two glass substrates spin-coated with SD1 orientation layers. The UV curing glue used is mixed with 8μm spacers to control the thickness of the liquid crystal box. The boxes are formed in a 2mm staggered manner and fully cured under the action of ultraviolet light to prepare a liquid crystal box.

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

[0103] Step 5: Place the liquid crystal box cooled to room temperature under a 388 nm ultraviolet lamp for 10 minutes for curing to form a right-handed cholesteric polymer template.

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

[0105] Step 7: Figure 2After the two 1 / 4 wave plates in the optical path are rotated 90° in the same direction, the LCLC is used to repeat the work of steps 4 to 6 for the liquid crystal box with a right-handed cholesteric polymer template obtained in step 6 to prepare a left-handed cholesteric polymer template, thereby forming a liquid crystal box with left-handed and right-handed cholesteric polymer templates. During the preparation process, the first orientation treatment and the second orientation treatment should ensure that the two orientation centers are aligned to ensure that the focus of the left-handed and right-handed reflected light is located at the same position to achieve polarization-independent beam convergence.

[0106] Step 8: Nematic liquid crystal (BPH006 liquid crystal) is poured into the liquid crystal cell with the cholesteric polymer template having left-handed and right-handed chirality obtained in step 7 to obtain a polarization-independent liquid crystal lens.

[0107] Comparative Example 1

[0108] According to steps 1 to 6 in Example 1, a liquid crystal cell having a cholesteric polymer template with right-handed chirality is obtained.

[0109] A right-handed cholesteric liquid crystal lens was obtained by pouring nematic liquid crystal (BPH006 liquid crystal) into a liquid crystal cell having a right-handed cholesteric polymer template.

[0110] Comparative Example 2

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

[0112] Nematic liquid crystal (BPH006 liquid crystal) was poured into a liquid crystal cell having a left-handed cholesteric polymer template to obtain a left-handed cholesteric liquid crystal lens.

[0113] In this embodiment, the target wavelength of the liquid crystal lens is determined by the refractive index n of the liquid crystal material used, the concentration c of the chiral agent, and the twisting force constant HTP of the chiral agent. The calculation formula of 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 concentration of the chiral agent, and HTP is the twisting force constant of the chiral agent. The concentration of the chiral agent is the mass content of the first chiral agent or the second chiral agent in the first liquid crystal mixture or the second liquid crystal mixture.

[0116] The orientation of cholesteric liquid crystal determines the geometric phase modulation of cholesteric liquid crystal. Therefore, the present invention uses a light-oriented material to write a fixed orientation pattern, and the geometric phase modulation of the cholesteric liquid crystal can be flexibly controlled. However, the same geometric phase modulation has conjugated modulation results for left-handed and right-handed cholesteric liquid crystals. That is, for the same phase change distribution, the modulation results for left-handed polarized incident light and right-handed polarized incident light are opposite. Therefore, this embodiment proposes a two-orientation preparation method, and through the cholesteric liquid crystal template method, the coexistence of the two orientation results is ensured. The orientation light path used in the preparation of the polarization-independent liquid crystal lens of the present invention is as follows Figure 2 As shown. After passing through the beam splitter, the light path is divided into two beams of light with the same polarization direction and the same intensity. A quarter wave plate and a reflector are placed in the two light paths respectively. The angles between the long axes of the two quarter wave plates and the polarization direction of the polarizer 202 are 45° and -45° respectively, so as to realize the conversion of linear polarized light into left-handed and right-handed polarized light. In one of the light paths, a lens 209 is placed, and a beam combiner 210 is used to combine the two light paths, and finally irradiate the inner surface of the liquid crystal box sample 211. In this embodiment, the spacing between the lens 209 and the liquid crystal box sample 211 should be maintained at twice the focal length of the lens to ensure that the two light 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 is used to test the reflectivity and polarization of linearly polarized light at a target wavelength (532 nm) for 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, Figure 3 The horizontal axis is the wavelength of the incident light, and the vertical axis is the transmittance; Figure 3 301 in the figure represents the right-handed cholesteric liquid crystal lens prepared in Comparative Example 1, Figure 3 302 in the figure represents the left-handed cholesteric liquid crystal lens prepared in Comparative Example 2, Figure 3 303 in FIG. 1 represents the transmittance spectrum of the polarization-independent lens prepared in Example 1.

[0118] Figure 4 The polarization independence comparison results 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 in FIG. Figure 4 The horizontal axis is the rotation angle of the incident light, and the vertical axis is the transmittance; Figure 4 401 in the figure represents the transmittance curve of the right-handed cholesteric liquid crystal lens prepared in Comparative Example 1, Figure 4402 in FIG. 4 represents the transmittance curve of the left-handed cholesteric liquid crystal lens prepared in Comparative Example 2. Figure 4 403 in FIG. 1 represents the transmittance curve of the polarization-independent lens prepared in Example 1.

[0119] The transmittance can be directly calculated from the transmittance spectrum through Formula 1; the polarization independence is calculated through the transmittance of linearly polarized incident light at different angles through Formula 2. The test results show that the reflectances of left-handed and right-handed cholesteric liquid crystal lenses at 532nm are 41.5% and 40.6% respectively, and the reflectance of the polarization-independent liquid crystal lens proposed in Example 1 is as high as 74.1%, which greatly improves the diffraction efficiency; the polarization correlations of left-handed and right-handed cholesteric liquid crystal lenses at 532nm are 89.3% and 81.0% respectively, and the polarization correlation of the polarization-independent liquid crystal lens proposed in Example 1 is only 8.6%, which has good polarization independence. The calculation formula for the reflectance used is shown in Formula 1, and the calculation formula for polarization independence is shown in Formula 2:

[0120]

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

[0122] From the above embodiments, it can be seen that the polarization-independent liquid crystal lens provided by the present invention has wavelength selection characteristics and high diffraction efficiency. The present invention utilizes the Bragg reflection property of cholesteric liquid crystal, and its reflected light has wavelength selectivity, that is, it only diffracts a specific wavelength, reducing the interference of stray light. The present invention utilizes the geometric phase modulation characteristics of cholesteric liquid crystal, and the phase modulation is flexible, which can realize the convergence of light beams with different focal lengths; at the same time, it is conducive to the addition of lens functions, and can relatively simply realize off-axis light beam convergence. The present invention uses template technology to superimpose left and right chiral polarized liquid crystal lenses, so that it has the same control effect on light beams of all polarization states, greatly improving the diffraction efficiency.

[0123] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a polarization-independent liquid crystal lens, characterized in that: The polarization-independent liquid crystal lens is prepared by using an oriented light path, wherein the oriented light path includes a polarizer, a collimating beam expander, and a beam splitter along the light path direction of the oriented light; the light path direction of the first split light beam obtained by the beam splitter includes a first 1 / 4 wave plate and a first reflector; the light path direction of the second split light beam obtained by the beam splitter includes a second 1 / 4 wave plate and a second reflector; a beam combiner for combining the first split light beam and the second split light beam; and a convex lens arranged between the first reflector and the beam combiner or between the second reflector and the beam combiner; the angle between the major axis of the first 1 / 4 wave plate and the polarization direction of the polarizer is 45° or -45°, and the first 1 / 4 wave plate and the second 1 / 4 wave plate are arranged orthogonally; The following steps are involved: Prepare a first alignment layer and a second alignment layer on one surface of the first substrate and one surface of the second substrate, respectively, to obtain a first substrate having the first alignment layer and a second substrate having the second alignment layer; The first substrate having the first alignment layer and the second substrate having the second alignment layer are used to prepare a liquid crystal box, wherein the first alignment layer and the second alignment layer are arranged opposite to each other inside the liquid crystal box; Performing a first alignment treatment on the liquid crystal cell using an alignment light path to obtain a first-aligned liquid crystal cell; After injecting a first liquid crystal mixture into the first orientation liquid crystal box, first curing and first washing are sequentially performed to obtain a liquid crystal box having a single-chiral cholesteric polymer template, wherein the first liquid crystal mixture includes a first nematic liquid crystal, a first chiral agent, a first polymer monomer, a first cross-linking agent and a first photosensitive initiator; The first 1 / 4 wave plate and the second 1 / 4 wave plate in the alignment light path are rotated 90 degrees in the same direction, and then the alignment light path is used to perform a second alignment treatment on the liquid crystal box having a single-chiral cholesteric polymer template to obtain a second alignment liquid crystal cell; After injecting a second liquid crystal mixture into the second orientation liquid crystal box, a second curing and a second washing are sequentially performed to obtain a liquid crystal box having a two-handed cholesteric polymer template, wherein the second liquid crystal mixture includes a second nematic liquid crystal, a second chiral agent, a second polymer monomer, a second cross-linking agent, and a second photoinitiator, so that the second chiral agent and the first chiral agent have opposite chirality; The third nematic phase liquid crystal is injected into the liquid crystal box having the chiral cholesteric polymer template to obtain the polarization-independent liquid crystal lens.

2. The preparation method according to claim 1, characterized in that: During the first alignment treatment and the second alignment treatment, the distance between the convex lens in the alignment light path and the liquid crystal box 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 alignment layer and the second alignment layer comprises the following steps: The photo-alignment material solution is coated on one surface of the first substrate and one surface of the second substrate respectively, and then dried to obtain the first alignment layer and the second alignment layer; the photo-alignment material solution includes a photo-alignment 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 0.1-0.5%.

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

6. The preparation method according to claim 1, characterized in that: The method for preparing the liquid crystal cell comprises the following steps: The first substrate with the first alignment layer and the second substrate with the second alignment layer are arranged opposite to each other, and are formed into a box by using ultraviolet curing glue under ultraviolet conditions; The distance between the first substrate having the first alignment layer and the second substrate having the second alignment layer is 2-10 μm.

7. The preparation method according to claim 1, characterized in that: The first chiral agent includes R5011 chiral agent or S5011 chiral agent; The first nematic phase liquid crystal, the second nematic phase liquid crystal and the third nematic phase liquid crystal include BPH006 liquid crystal; The first polymer monomer and the second polymer monomer include a TMPTA polymer monomer; The first cross-linking agent and the second cross-linking agent include a C3M cross-linking agent; The first photoinitiator and the second photoinitiator include IRG184 photoinitiator; The mass ratio of the first nematic liquid crystal, the first chiral agent, the first polymer monomer, the first cross-linking 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 cross-linking 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 alignment light used in the first alignment treatment and the second alignment treatment is blue-violet light, and the wavelength of the blue-violet light is 405nm; the total irradiation energy of the alignment light during the first alignment treatment and the second alignment treatment is 4J / cm 2 ; The focal length of the convex lens is 10 cm.

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

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

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