Liquid crystal polymer geometric phase lens, preparation method and application thereof

Abstract

The present application relates to a kind of liquid crystal polymer geometric phase lens and its preparation method and application, wherein, liquid crystal polymer geometric phase lens, including transparent substrate, nanoimprint orientation layer, first liquid crystal polymer layer and second liquid crystal polymer layer from bottom to top are sequentially stacked;The nanoimprint orientation layer is used to control the orientation of first liquid crystal polymer layer and second liquid crystal polymer layer;The first liquid crystal polymer layer and the second liquid crystal polymer layer both have cholesteric phase liquid crystal helical structure, and the helical direction of the first liquid crystal polymer layer is opposite with the helical direction of the second liquid crystal polymer layer.It has beneficial effect, the preparation of the diffractive achromatic liquid crystal polymer geometric phase lens in visible light wave band is realized, while meeting the application requirement of high diffraction efficiency.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a liquid crystal polymer geometric phase lens, its preparation method, and its application. Background Technology

[0002] Liquid crystal polymer geometric phase lenses are lens elements that achieve optical focusing by relying on the pre-aligned structure or inherent physical properties of liquid crystal materials. The key lies in precisely controlling the orientation distribution of liquid crystal molecules to form a stable geometric phase arrangement, thereby achieving light refraction and focusing. These lenses can be made into planar lenses, offering advantages such as miniaturization, low power consumption, and easy integration. However, due to the diffraction characteristics of planar lenses, chromatic aberration is often more pronounced compared to traditional optical lenses. Current research on liquid crystal lenses largely focuses on single wavelengths, making it difficult to meet the performance requirement of maintaining high diffraction efficiency across a wide wavelength range.

[0003] In optical systems, achromatic technology plays a crucial role in improving image quality, enhancing system performance, and expanding application scenarios. It is widely used in fields such as photography, observation instruments, laser processing, photolithography, and fiber optic communication, enabling core functions such as high-quality imaging, precise beam control, and efficient signal transmission. Research on diffractive achromatic lenses has largely focused on metalens technology (Light: Science & Applications, 2025, 14(1), 75; Nature Communications, 2021, 12(1): 5560; Nature Nanotech, 2018, 13, 227–232.). This technology uses subwavelength artificial structures (i.e., metaatoms) to control the phase of light. The design is extremely difficult, and the process is extremely complex and expensive. Currently, it is still difficult to achieve full-color achromaticity while using large aperture and high numerical aperture (large aperture).

[0004] Currently, liquid crystal polymer lenses have significant limitations in diffraction achromatic lenses. Their efficiency and performance optimization are mostly limited to a single wavelength, and their adaptability across a wide wavelength range is poor. Achromatic metalenses require extremely high nanoscale fabrication precision, and their apertures are mostly at the micrometer level, making it difficult to achieve large-aperture fabrication and large-scale production. In addition, the phase modulation capability of meta-atoms has an upper limit, resulting in generally low diffraction efficiency. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a liquid crystal polymer geometric phase lens, its preparation method and application, which solves the technical problems of poor wide-band adaptability of existing diffractive achromatic lenses, difficulty in achieving the preparation of large-aperture lenses and the need for large-scale production, as well as the low diffraction efficiency outside the design wavelength.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, embodiments of the present invention provide a liquid crystal polymer geometric phase lens, comprising a transparent substrate, a nanoimprint alignment layer, a first liquid crystal polymer layer, and a second liquid crystal polymer layer stacked sequentially from bottom to top;

[0010] The nanoimprint alignment layer is used to control the orientation of the first liquid crystal polymer layer and the second liquid crystal polymer layer.

[0011] Both the first liquid crystal polymer layer and the second liquid crystal polymer layer have a cholesteric liquid crystal helical structure, and the helical direction of the first liquid crystal polymer layer is opposite to that of the second liquid crystal polymer layer.

[0012] The transparent substrate can be made of quartz, silicon carbide, polycarbonate (resin), or glass. The thicknesses of the first and second liquid crystal polymer layers range from 800 to 1700 nm.

[0013] It should be noted that, according to Bragg's law of reflexion The mass concentration of the chiral agent and the pitch of the liquid crystal polymer layer satisfy the following relationship: Where λ is the central reflection wavelength, p is the pitch of the liquid crystal polymer layer, HTP is the helical twisting force of the chiral agent, and c is the mass concentration of the chiral agent in the liquid crystal polymer layer. The average refractive index is denoted as .

[0014] In a preferred embodiment of the present invention, the liquid crystal polymer geometric phase lens has a nanoimprint alignment layer comprising a nanorod array with a period of 550-650 nm, wherein the nanorods in the array have a length of 390-410 nm, a width of 90-110 nm, and a height of 40-60 nm.

[0015] The nanoimprint alignment layer can be made of polymethyl methacrylate, wherein the nanorods have a rectangular cross-section and the orientation direction of the liquid crystal molecules is consistent with their length direction, which is used to achieve precise orientation control of the liquid crystal molecules.

[0016] In a preferred embodiment of the present invention, the liquid crystal polymer geometric phase lens wherein both the first liquid crystal polymer layer and the second liquid crystal polymer layer are formed by photopolymerization and curing of reactive mesocrystalline monomers;

[0017] The first liquid crystal polymer layer further includes a first chiral agent, and the second liquid crystal polymer layer further includes a second chiral agent, wherein the first chiral agent and the second chiral agent have opposite chirality;

[0018] The reactive mesocrystalline monomer is selected from at least one of RM257, RM82, RM105 and RM23.

[0019] The amount of chiral agent added is matched with the pitch of the liquid crystal polymer layer. The pitch of the cholesteric liquid crystal is controlled by adjusting the amount of chiral agent added to meet the requirements of color difference elimination.

[0020] In a preferred embodiment of the present invention, the first chiral agent (levorotatory chiral agent) of the liquid crystal polymer geometric phase lens is selected from one of S2011, S5011, S811 and S1011;

[0021] The second chiral agent (dextrorotatory chiral agent) is selected from one of CB-15, R5011, R811, and R1011. Among them, the preferred first chiral agent is S2011, and the preferred second chiral agent is CB-15.

[0022] As a preferred embodiment of the present invention, the liquid crystal polymer geometric phase lens,

[0023] By mass fractions: 20-32 parts of reactive mesocrystalline monomers forming the first liquid crystal polymer layer and the second liquid crystal polymer layer, and 0.05-0.5 parts of the first chiral agent and the second chiral agent.

[0024] Secondly, embodiments of the present invention provide a method for fabricating a liquid crystal polymer geometric phase lens, comprising the following steps:

[0025] S1. Prepare a nanoimprint alignment layer by placing the nanoimprint alignment layer on a glass substrate;

[0026] S2. A first liquid crystal polymer layer is prepared on the surface of the nanoimprint alignment layer, and then a second liquid crystal polymer layer is prepared on the surface of the first liquid crystal polymer layer to obtain the liquid crystal polymer geometric phase lens.

[0027] Wherein, both the first liquid crystal polymer layer and the second liquid crystal polymer layer have a cholesteric liquid crystal helical structure, and the helical direction of the first liquid crystal polymer layer is opposite to that of the second liquid crystal polymer layer;

[0028] In a preferred embodiment of the present invention, in the preparation method S2, when preparing the first liquid crystal polymer layer, a first solution is spin-coated and cured onto the nanoimprint alignment layer; the first solution includes a first chiral agent, a reactive mesocrystalline monomer, a photoinitiator, and a solvent;

[0029] When preparing the second liquid crystal polymer layer, a second solution is spin-coated and cured onto the first liquid crystal polymer layer; the second solution includes a second chiral agent, a reactive mesocrystalline monomer, a photoinitiator, and a solvent;

[0030] The first chiral agent and the second chiral agent have opposite chirality.

[0031] As a preferred embodiment of the present invention, in the preparation method S2, the spin coating process is as follows: the first solution or the second solution is rotated at 1500-2000 rpm for 40-100s to form a coating.

[0032] The curing process is as follows: heat the spin-coated coating at 80-100℃ for 120-350 seconds, and then cure it under UV light for 3-8 minutes.

[0033] As a preferred embodiment of the present invention, the preparation method, according to parts by mass:

[0034] The first solution consists of: 0.05-0.5 parts of a first chiral agent, 20-32 parts of a reactive mesocrystalline monomer, 2-3 parts of a photoinitiator, and 70-80 parts of a solvent;

[0035] The second solution consists of: 0.05-0.5 parts of a second chiral agent, 20-32 parts of a reactive mesocrystalline monomer, 2-3 parts of a photoinitiator, and 70-80 parts of a solvent;

[0036] Wherein, the first chiral agent is selected from one of S2011, S5011, S811 and S1011;

[0037] The second chiral agent is selected from one of CB-15, R5011, R811, and R1011;

[0038] The reactive mesocrystalline monomer is selected from at least one of RM257, RM82, RM105 and RM23;

[0039] The photoinitiator is selected from at least one of irgacure819, irgacure651 and irgacure184;

[0040] The solvent is selected from at least one of propylene glycol methyl ether acetate (PGMEA), ethylene glycol ethyl ether acetate (EEA), and propylene glycol methyl ether (PGME).

[0041] Thirdly, embodiments of the present invention provide a liquid crystal polymer geometric phase lens as described above, or the liquid crystal polymer geometric phase lens prepared by the preparation method described above can be applied to a diffraction achromatic imaging device in the visible light band.

[0042] Among them, visible light band diffraction achromatic imaging devices include vehicle-mounted imaging lenses and AR near-eye display optics.

[0043] (III) Beneficial Effects

[0044] The beneficial effects of this invention are as follows: This invention provides a liquid crystal polymer geometric phase lens, its fabrication method, and its application. Because the liquid crystal polymer geometric phase lens utilizes nanoimprint technology to construct an alignment layer, the orientation of two liquid crystal polymer layers with different rotational directions is controlled, forming a stable planar liquid crystal polymer lens. The diffraction achromatic function of this invention stems from the ingenious utilization of the birefringence characteristics of liquid crystals. By designing a bilayer liquid crystal arrangement with a chiral symmetry structure, the diffraction efficiency response of the lens is effectively broadened across the entire visible spectrum. This lens achieves high diffraction efficiency in the visible light band according to different wavelengths of incident light, with a diffraction efficiency exceeding 90%, breaking through the technical bottleneck of achieving high diffraction efficiency only for a single wavelength. The fabrication method of the liquid crystal polymer geometric phase lens does not require the construction of an optical path or the fabrication of a liquid crystal cell; only two spin-coating operations are needed to obtain a liquid crystal diffraction achromatic geometric phase lens with high diffraction efficiency in the visible light band. The process is simple, stable, and low-cost, making it suitable for widespread application. Compared to existing technologies, this invention significantly simplifies the fabrication process, improves production efficiency and repeatability, and maintains high stability in its key optical properties under a wide range of temperature and humidity variations, ensuring long-lasting and reliable performance in practical applications. It achieves the fabrication of diffractive achromatic liquid crystal polymer geometric phase lenses in the visible light band, while simultaneously meeting the requirements for high diffraction efficiency applications.

[0045] Nanoimprint lithography is used to fabricate low aspect ratio nanorods to construct alignment layers. This allows for orientation control of two liquid crystal layers with different rotational directions, thereby achieving achromatic diffraction and improving diffraction efficiency. Low aspect ratio nanorods typically exhibit better mechanical stability than high aspect ratio nanorods when constructing alignment layers, and are less prone to collapsing or entanglement. They are also more likely to form dense surface structures, providing uniform anchoring points for subsequent liquid crystal polymer layers or functional layers. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating the fabrication process of the liquid crystal polymer geometric phase lens in Embodiment 1 of the present invention;

[0047] Figure 2Design diagram for a 40mm diameter liquid crystal polymer geometric phase lens prepared in Example 1: where a is the phase distribution diagram; b is the nanorod rotation angle distribution diagram; c is the GDS design diagram;

[0048] Figure 3 SEM image of the surface of the nanoimprint alignment layer prepared in Example 1: where b is a locally enlarged schematic diagram of a;

[0049] Figure 4 This is a schematic diagram of the liquid crystal polymer geometric phase lens structure prepared in Example 1;

[0050] Figure 5 The structural formulas of the right-handed agent CB-15, the left-handed agent S2011, and RM257 used in Example 1 are shown below.

[0051] Figure 6 The image shows a Jones matrix simulation of the liquid crystal molecule arrangement structure based on the optimal twist angle of 67.75° in this invention.

[0052] Figure 7 The image shown is of the liquid crystal polymer geometric phase lens sample prepared in Example 1 of this invention under a polarizing microscope.

[0053] Figure 8 The diffraction efficiency results of the liquid crystal polymer geometric phase lens samples prepared in Examples 1 to 3 of the present invention were tested twice at different positions at 20µm.

[0054] Figure 9 This is an effect diagram of the liquid crystal polymer geometric phase lens prepared in Example 1 of the present invention;

[0055] Figure 10 The image shows the diffraction effect of the liquid crystal polymer geometric phase lens prepared in Example 1 of this invention at a period of 20µm. Detailed Implementation

[0056] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0058] Example 1

[0059] This embodiment provides a method for fabricating a liquid crystal polymer geometric phase lens, see [link to documentation]. Figure 1 The specific steps are as follows:

[0060] (1) Lens Design: This embodiment introduces the Jones matrix theory to ensure the scientific validity and effectiveness of the design. The Jones matrix of the two-layer diffractive achromatic phase lens with opposite helical directions in this embodiment can be obtained by simply multiplying the Jones matrices of the two phase gratings:

[0061] (1)

[0062] T is the achromatic Jones matrix. First layer Jones matrix, The second layer of the Jones matrix.

[0063] The first liquid crystal polymer layer (left-handed layer) and the second liquid crystal polymer layer (right-handed layer) can each be decomposed into N stacked layers, each layer having For a tiny rotation, the Jones matrix of this layered grating structure can be represented as:

[0064] (2)

[0065] Where N represents the number of layers, and R is the rotation matrix. It is the optical path difference of each layer. This is the total torsion angle. Based on this theory, the simulation diffraction efficiency formula is as follows:

[0066] (3)

[0067] in, , It is the zeroth order diffraction efficiency. It is the diffraction efficiency of the positive and negative 1st order. It is a twist angle. It is the delay amount. λ is the birefringence of the liquid crystal, d is the thickness of the double layer, and λ is the center wavelength. For example... Figure 6 As shown, the simulation yielded an optimal twist angle of 67.75° for a thickness of 1466 nm.

[0068] (2) Fabrication of nanoimprint alignment layer: To achieve the specific alignment target of liquid crystal molecules, the structural parameters of the nanorods are designed, including their morphology, period, and spatial distribution. The key design feature is that the period of the nanorods exhibits a gradient decrease from the central region to the edge region. This period change strictly follows the geometric phase principle embodied by formula (5):

[0069] (5)

[0070] Where r is the radial distance from any point on the liquid crystal geometric phase lens to the optical axis, φ(r) is the phase value at position r on the liquid crystal geometric phase lens (or simply lens), λ is the designed center wavelength, and f is the focal length of the liquid crystal geometric phase lens.

[0071] like Figure 2 The diagram shown is a design diagram of the phase distribution of the 40mm aperture lens and the rotation angle distribution of the nanorods in this embodiment.

[0072] The nanoimprinted alignment layer of the designed lens consists of a nanorod array with a period of 600 nm, and the total number of nanorods in the array is precisely 66,667. 2 The required precision nanostructures were mass-produced with high fidelity using nanoimprint lithography. Characterization showed that the typical dimensions of the nanorods were approximately 400 nm in length, 100 nm in width, and 54 nm in height. This optimized micro / nano structure can precisely induce the oriented alignment of liquid crystal molecules, resulting in a sample that achieves broadband achromatic diffraction characteristics and ultra-high diffraction efficiency.

[0073] according to Figure 1 The process described above, along with the designed nanorod array, is used to prepare a nanoimprinted alignment layer on a pretreated glass substrate (transparent substrate) using nanoimprinting technology: 1) Photoresist coating: A layer of photoresist material (polymethyl methacrylate) is uniformly coated onto the substrate. 2) Template imprinting: Using a template with a specific pattern, the coated photoresist is physically imprinted, forming a micro / nano structure on the photoresist surface that is complementary to the template. 3) UV exposure: Under template imprinting, the photoresist is irradiated with UV light, causing cross-linking and curing, thereby fixing the imprinted pattern. 4) Demolding: The template is separated from the cured photoresist, leaving the desired micro / nano structure pattern on the photoresist layer. The glass substrate pretreatment steps include ultrasonic cleaning and drying to remove surface impurities and organic contaminants. SEM scans of the nanostructure of the nanoimprinted alignment layer are shown below. Figure 3 As shown.

[0074] (3) Preparation of solution:

[0075] The first solution (levorotatory layer solution) was prepared by dissolving the levorotatory agent S2011 (0.37 wt%), RM257 (24.91 wt%) and photoinitiator Irgacure819 (2.49 wt%) in PGMEA solvent (72.23 wt%). The first solution was placed at 80 °C and shaken thoroughly until it was completely dissolved and became a clear solution. The solution was then filtered once using a filter and used for later use.

[0076] A second solution (dextral layer solution) was prepared by dissolving the right-handed agent CB-15 (0.27 wt%), RM257 (29.92 wt%), and photoinitiator Irgacure 819 (2.99 wt%) in PGMEA solvent (66.82 wt%). The second solution was placed at 80°C and shaken thoroughly until completely dissolved and a clear solution was obtained. The solution was then filtered once using a filter tip for later use.

[0077] It should be noted that, according to Bragg's law of reflexion The mass concentration of the chiral agent and the pitch of the liquid crystal polymer layer satisfy the following relationship: Where λ is the central reflection wavelength, p is the pitch of the liquid crystal polymer layer, HTP is the helical twisting force of the chiral agent, and c is the mass concentration of the chiral agent in the liquid crystal polymer layer. The average refractive index is denoted as .

[0078] (4) Lens manufacturing process:

[0079] The first solution was added to the surface of the nanoimprint alignment layer, and the layer was rotated at 1800 rpm for 80 seconds, then heated on a 90°C hot stage for 300 seconds. Finally, the solution was applied at a wavelength of 365 nm and an energy of 25 J / cm². 2 The liquid crystal molecules are heated and cured under ultraviolet light for 5 minutes to arrange them in an orderly manner according to the orientation of the nanoimprint layer, thus preparing the first liquid crystal polymer layer.

[0080] The first solution was added to the surface of the first liquid crystal polymer layer, and after rotating at 1700 rpm / s for 80 seconds, an energy of 25 J / cm at a wavelength of 365 nm was applied. 2 The second liquid crystal polymer layer was prepared by heating and curing under ultraviolet light for 5 minutes. In this embodiment, the lens can be prepared by spin coating in two steps.

[0081] The purpose of high-power curing is to rapidly form a stable polymer film (the first liquid crystal polymer layer) from the liquid crystal polymer layer. The curing energy is not less than 25 J / cm². 2 This is to ensure that the liquid crystal polymer layer cures rapidly and maintains sufficient stability.

[0082] (5) Performance testing:

[0083] The lasers used in the test were red light λ=635nm, green light λ=535nm, and blue light λ=450nm. The diffraction efficiency can be calculated by formula (4) by measuring the 0th order light intensity, 1st order light intensity, 1mm incident light intensity, and reflected light intensity at the same position under left-handed circularly polarized light.

[0084] (4)

[0085] Where T inIt is the incident light intensity at 1mm, T out It is the intensity of transmitted light, I f It is a light intensity of level 0, R 反 It refers to the intensity of reflected light.

[0086] The lens sample prepared in this embodiment was tested twice at different positions at 20µm, and the results are as follows: Figure 8 As shown, the efficiency of red, green and blue light is basically 90%, among which the efficiency of red light with a wavelength of 635nm is the highest, reaching 94.57%.

[0087] By placing the lens sample prepared in this embodiment under a polarizing microscope, the orientation effect and phase period distribution can be observed, such as... Figure 7 As shown, the liquid crystal alignment effect is excellent, with superior alignment at the edges. Diffraction efficiency measurements were performed on the lens sample. Different diffraction effects were observed for left-handed and right-handed circularly polarized light. Left-handed circularly polarized light incident on the device acted as a positive lens (convex refractive lens), while right-handed circularly polarized light acted as a negative lens (concave refractive lens). In the visible light band, the first-order diffraction efficiency using left-handed circularly polarized light can reach over 90%.

[0088] See Figure 9 This is a text effect diagram of the lens sample prepared in this embodiment. The letters "HD" can form a focused real image and a divergent virtual image through the lens. See also... Figure 10 To illustrate the diffraction effect of the lens sample prepared in this embodiment, the intensity distribution of the diffraction spot further quantitatively reveals the lens's performance. The intensity of the first-order diffraction spot is much higher than that of the zero-order diffraction spot, which directly confirms that the lens has high diffraction efficiency in the target wavelength band, meaning that most of the incident light energy is effectively modulated and transferred to the designed first-order diffraction order.

[0089] Example 2

[0090] This embodiment provides a method for fabricating a liquid crystal polymer geometric phase lens. The difference between this embodiment and Embodiment 1 is that:

[0091] (4) Lens manufacturing process:

[0092] The first solution was added to the surface of the nanoimprint alignment layer, rotated at 1800 rpm / s for 80 s, and then heated on a 90.7℃ hot stage for 300 s. Finally, it was heated at a wavelength of 365 nm and an energy of 25 J / cm². 2 The liquid crystal molecules are heated and cured under ultraviolet light for 5 minutes to arrange them in an orderly manner according to the orientation of the nanoimprint layer, thus preparing the first liquid crystal polymer layer.

[0093] The first solution was added to the surface of the first liquid crystal polymer layer, and after rotating at 1800 rpm / s for 80 seconds, an energy of 25 J / cm at a wavelength of 365 nm was applied.2 The second liquid crystal polymer layer was prepared by heating and curing under ultraviolet light for 5 minutes. In this embodiment, the lens can be fabricated in two spin-coating steps. For the specific structure of the lens, please refer to [link to documentation]. Figure 4 .

[0094] (5) Performance testing:

[0095] In this embodiment, the diffraction efficiency of the lens sample was tested twice at different positions at 20µm, and the results are as follows: Figure 6 As shown, the efficiency of red, green and blue light is basically 90%, among which green light with a wavelength of 520nm has the highest efficiency of 95.84%.

[0096] Example 3

[0097] This embodiment provides a method for fabricating a liquid crystal polymer geometric phase lens. The difference between this embodiment and Embodiment 1 is that:

[0098] (3) Preparation of solution:

[0099] The first solution (levorotatory layer solution) was prepared by dissolving the levorotatory agent S2011 (0.3 wt%), RM257 (20.0 wt%) and photoinitiator Irgacure819 (20.0 wt%) in PGMEA solvent (77.7 wt%). The first solution was placed at 80 °C and shaken thoroughly until it was completely dissolved and became a clear solution. The solution was then filtered once using a filter and used for later use.

[0100] A second solution (dextral layer solution) was prepared by dissolving the right-handed agent CB-15 (0.269 wt%), RM257 (29.91 wt%), and photoinitiator Irgacure 819 (2.991 wt%) in PGMEA solvent (66.83 wt%). The second solution was placed at 80°C and shaken thoroughly until completely dissolved and a clear solution was obtained. The solution was then filtered once using a filter tip for later use.

[0101] For the structural formulas of S2011, CB-15, and RM257, please refer to [link / details]. Figure 5 .

[0102] (4) Lens manufacturing process:

[0103] The first solution was added to the surface of the nanoimprint alignment layer, rotated at 1680 rpm / s for 80 s, and then heated on a 90.7℃ hot stage for 300 s. Finally, it was heated at a wavelength of 365 nm and an energy of 25 J / cm². 2 The liquid crystal molecules are heated and cured under ultraviolet light for 5 minutes to arrange them in an orderly manner according to the orientation of the nanoimprint layer, thus preparing the first liquid crystal polymer layer.

[0104] The first solution was added to the surface of the first liquid crystal polymer layer, and after rotating at 1700 rpm / s for 80 seconds, an energy of 25 J / cm at a wavelength of 365 nm was applied. 2 The second liquid crystal polymer layer was prepared by heating and curing under ultraviolet light for 5 minutes. In this embodiment, the lens can be prepared by spin coating in two steps.

[0105] (5) Performance testing:

[0106] In this embodiment, the diffraction efficiency of the lens sample was tested twice at different positions at 20µm, and the results are as follows: Figure 6 As shown, the efficiency of red, green and blue light is basically 90%, among which green light with a wavelength of 520nm has the highest efficiency of 96.89%.

[0107] As can be seen from Examples 1 to 3, the method for preparing liquid crystal polymer geometric phase lenses of the present invention can repeatedly produce lens samples with a wide-band diffraction efficiency of over 90% under the same parameter conditions.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid crystal polymer geometric phase lens, characterized in that, It includes a transparent substrate, a nanoimprint alignment layer, a first liquid crystal polymer layer and a second liquid crystal polymer layer, which are stacked sequentially from bottom to top; The nanoimprint alignment layer is used to control the orientation of the first liquid crystal polymer layer and the second liquid crystal polymer layer; Both the first liquid crystal polymer layer and the second liquid crystal polymer layer have a cholesteric liquid crystal helical structure, and the helical direction of the first liquid crystal polymer layer is opposite to that of the second liquid crystal polymer layer.

2. The liquid crystal polymer geometric phase lens as described in claim 1, characterized in that, The nanoimprint alignment layer comprises a nanorod array with a period of 550-650 nm, wherein the nanorods in the array have a length of 390-410 nm, a width of 90-110 nm, and a height of 40-60 nm.

3. The liquid crystal polymer geometric phase lens as described in claim 2, characterized in that, Both the first liquid crystal polymer layer and the second liquid crystal polymer layer are formed by photopolymerization and curing of reactive mesocrystalline monomers; The first liquid crystal polymer layer further includes a first chiral agent, and the second liquid crystal polymer layer further includes a second chiral agent, wherein the first chiral agent and the second chiral agent have opposite chirality; The reactive mesocrystalline monomer is selected from at least one of RM257, RM82, RM105 and RM23.

4. The liquid crystal polymer geometric phase lens as described in claim 3, characterized in that, The first chiral agent is selected from one of S2011, S5011, S811 and S1011; The second chiral agent is selected from one of CB-15, R5011, R811 and R1011.

5. The liquid crystal polymer geometric phase lens as described in claim 4, characterized in that, By mass fraction: 20-32 parts of reactive mesocrystalline monomers forming the first liquid crystal polymer layer and the second liquid crystal polymer layer, and 0.05-0.5 parts of the first chiral agent and the second chiral agent.

6. A method for fabricating a liquid crystal polymer geometric phase lens, characterized in that, Includes the following steps: S1. Prepare a nanoimprint alignment layer and place the nanoimprint alignment layer on a transparent substrate; S2. A first liquid crystal polymer layer is prepared on the surface of the nanoimprint alignment layer, and then a second liquid crystal polymer layer is prepared on the surface of the first liquid crystal polymer layer to obtain the liquid crystal polymer geometric phase lens. Both the first liquid crystal polymer layer and the second liquid crystal polymer layer have a cholesteric liquid crystal helical structure, and the helical direction of the first liquid crystal polymer layer is opposite to that of the second liquid crystal polymer layer. After preparation, the overall structure is annealed to ensure the stability of the liquid crystal molecule orientation.

7. The preparation method according to claim 6, characterized in that, In S2, when preparing the first liquid crystal polymer layer, a first solution is spin-coated and cured onto the nanoimprint alignment layer; the first solution includes a first chiral agent, a reactive mesocrystalline monomer, a photoinitiator, and a solvent; When preparing the second liquid crystal polymer layer, a second solution is spin-coated and cured onto the first liquid crystal polymer layer; the second solution includes a second chiral agent, a reactive mesocrystalline monomer, a photoinitiator, and a solvent; The first chiral agent and the second chiral agent have opposite chirality.

8. The preparation method according to claim 7, characterized in that, In S2, the spin coating process is as follows: the first solution or the second solution is rotated at 1500-2000 rpm for 30-80 seconds to form a coating. The curing process is as follows: heat the spin-coated coating at 80-100℃ for 120-350 seconds and then perform UV curing for 3-8 minutes.

9. The preparation method according to claim 7, characterized in that, By weight parts: The first solution consists of: 0.05-0.5 parts of a first chiral agent, 20-32 parts of a reactive mesocrystalline monomer, 2-3 parts of a photoinitiator, and 70-80 parts of a solvent; The second solution consists of: 0.05-0.5 parts of a second chiral agent, 20-32 parts of a reactive mesocrystalline monomer, 2-3 parts of a photoinitiator, and 70-80 parts of a solvent; The first chiral agent is selected from one of S2011, S5011, S811 and S1011; The second chiral agent is selected from one of CB-15, R5011, R811, and R1011; The reactive mesocrystalline monomer is selected from at least one of RM257, RM82, RM105 and RM23; The photoinitiator is selected from at least one of irgacure819, irgacure651 and irgacure184; The solvent is selected from at least one of propylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, and propylene glycol methyl ether.

10. A liquid crystal polymer geometric phase lens according to any one of claims 1 to 5, or the application of a liquid crystal polymer geometric phase lens prepared by the preparation method according to any one of claims 6 to 9 in the preparation of a visible light band diffraction achromatic imaging devices and visible light band diffraction achromatic optical products.

Images