UV photocuring glue, preparation method and application thereof, and preparation method of liquid crystal micro-nano optical element

Abstract

The invention belongs to the technical field of optical elements, and particularly relates to UV photocuring glue, a preparation method and application thereof and a preparation method of a liquid crystal micro-nano optical element. The UV photocuring glue provided by the invention comprises a resin component and a photoinitiator, the resin component is prepared from bisphenol A type epoxy acrylate, triethoxylated trimethylolpropane triacrylic acid and nonaethoxylated trimethylolpropane triacrylic acid. The UV photocuring glue provided by the invention is low in curing shrinkage rate, can realize that the PV value of transmission wavefront of multiple batches of samples does not exceed 1 / 3 lambda, and can avoid internal defects, such as micropores and cracks, caused by stress concentration in the laminating and curing process of optical elements. And meanwhile, the reduction of the strength of the base material caused by shrinkage stress can be effectively improved, the interface problem of the composite material is improved, the problem of uneven surface type uniformity can be well solved when the composite material is used for a glass laminating protection process of a production line, and the yield is high.

Description

Technical Field

[0001] This invention belongs to the field of optical element technology, specifically relating to a UV-curable adhesive, its preparation method and application, and a method for preparing liquid crystal micro / nano optical elements. Background Technology

[0002] As core foundational materials in advanced manufacturing, information technology, aerospace, and other high-end fields, optical materials directly determine the precision and reliability of downstream optical components and terminal equipment. In recent years, with the rapid iteration of technologies such as 5G communication, artificial intelligence, virtual reality, and high-resolution imaging, the market has placed unprecedentedly stringent demands on the lightweight, miniaturization, high transmittance, and surface precision of optical components. This demand directly impacts the field of optical materials, driving the research and innovation of high-functionality, high-performance optical materials to become the core driving force for industry development. In the fabrication processes of advanced optical components, optical resins, with their advantages of convenient molding, controllable cost, and high degree of freedom in optical design, are gradually replacing some traditional inorganic optical materials, becoming the core processing material for key components such as micro / nano optical elements and optical bonding assemblies. Low curing shrinkage rate, as one of the core performance indicators of optical resins, directly restricts the fabrication quality and application effects of optical components.

[0003] UV curing technology, with its advantages of fast curing speed, low energy consumption, and environmental friendliness, has been widely used in the molding and processing of optical resins. However, during the curing process, the chemical reaction between monomers and crosslinking agents leads to a tight arrangement of molecular chains, inevitably causing volume shrinkage. This curing shrinkage often becomes a key factor in causing performance defects in optical components. Specifically, in the bonding and curing process of optical components, the internal stress generated during shrinkage easily forms stress concentration areas within the material, inducing microscopic defects such as micropores, cracks, and silver streaks. These defects not only severely reduce the optical properties of the resin, such as transmittance and refractive index uniformity, leading to problems like light scattering and light attenuation, but also damage the integrity of the material structure, shortening the lifespan of the optical components. For high-precision optical systems, even micron-level shrinkage deformation or microscopic defects can cause optical path deviation, affecting the imaging accuracy and stability of the optical components and resulting in substandard product performance.

[0004] In addition to the direct defects mentioned above, the stress generated by curing shrinkage also has a significant negative impact on the mechanical properties and interfacial bonding quality of optical components. On the one hand, shrinkage stress leads to residual internal stress within the resin matrix, causing a significant decrease in the tensile strength, flexural strength, and other mechanical properties of the material. This is especially true for thin-walled or micro / nano-structured optical components, which are highly susceptible to breakage or deformation during subsequent processing. On the other hand, in the fabrication of optical composite materials, a mismatch in shrinkage rates between the resin and the substrate (such as glass, quartz, polymer films, etc.) can cause problems such as interfacial delamination and layering, damaging the interfacial bonding of the composite material and leading to overall material performance degradation. This problem is particularly prominent in the fabrication of liquid crystal polymer micro / nano optical components—liquid crystal polymers have a unique molecular arrangement structure, requiring extremely high dimensional stability during the molding process. Shrinkage deformation during UV resin bonding or encapsulation directly leads to deviations in the surface accuracy of liquid crystal polymer components, damaging their optical control functions and severely restricting the application expansion of liquid crystal polymers in the field of micro / nano optics.

[0005] Currently, existing UV resin products on the market generally suffer from high curing shrinkage rates. For example, the NOA series cannot meet the requirement that the transmission wavefront PV value of multiple batches of liquid crystal polymer micro-nano optical components should not exceed 1 / 3λ, resulting in uneven surface uniformity in the glass bonding and protection process of the production line, which cannot meet the requirements for the preparation of high-precision optical components. Summary of the Invention

[0006] The purpose of this invention is to provide a UV-curable adhesive, its preparation method, and its application, as well as a method for preparing liquid crystal micro / nano optical elements. The UV-curable adhesive provided by this invention has a low curing shrinkage rate, enabling multiple batches of samples to achieve a transmission wavefront PV value of no more than 1 / 3λ. This not only avoids internal defects such as micropores and cracks caused by stress concentration during the bonding and curing process of optical elements, but also effectively improves the reduction in the strength of the matrix material due to shrinkage stress and improves the interface problems of composite materials. When used in the glass bonding protection process of a production line, it can effectively solve the problem of uneven surface uniformity, resulting in a high yield.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a UV-curable adhesive, comprising a resin component and a photoinitiator; the resin component comprises bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate, wherein the mass ratio of the bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate is (30~70):(10~30):(20~40); the photoinitiator accounts for 0.3~0.6% of the mass of the resin component.

[0008] Preferably, the mass ratio of bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate is 50:20:30.

[0009] Preferably, the photoinitiator includes photoinitiator 907 and photoinitiator 1173; the mass percentage of photoinitiator 907 in the resin component is 0.15~0.3%; the mass percentage of photoinitiator 1173 in the resin component is 0.15~0.3%.

[0010] Preferably, the mass percentage of the photoinitiator 907 to the mass percentage of the resin component is 0.25%; the mass percentage of the photoinitiator 1173 to the mass percentage of the resin component is 0.25%.

[0011] This invention provides a method for preparing the UV-curable adhesive described in the above technical solution, comprising the following steps: The resin components and photoinitiator were stirred and mixed sequentially and then allowed to stand for degassing to obtain the UV-curable adhesive.

[0012] Preferably, the stirring speed is 1500~2500 rpm and the time is 3~8 min.

[0013] This invention provides the application of the UV-curable adhesive described in the above technical solution or the UV-curable adhesive prepared by the preparation method described in the above technical solution in the fabrication of optical components.

[0014] This invention provides a method for fabricating liquid crystal micro / nano optical elements, comprising the following steps: The surface of the first optical substrate is coated with a photo-inducing alignment agent solution, and then subjected to heat treatment and exposure in sequence to obtain the exposed optical substrate; The exposed surface of the optical substrate after exposure is coated with a liquid crystal solution, and then subjected to a first ultraviolet curing to obtain a liquid crystal polymer material film layer. The surface of the liquid crystal polymer material film is coated with adhesive, then covered with a second optical substrate, and finally subjected to a second ultraviolet curing to obtain a liquid crystal micro-nano optical element; the adhesive is the UV-curable adhesive described in the above technical solution or the UV-curable adhesive prepared by the preparation method described in the above technical solution.

[0015] Preferably, the photo-inducing alignment agent solution is an organic solution of SD1, and the content of SD1 in the photo-inducing alignment agent solution is 15~25wt%; the heat treatment temperature is 90~105℃, and the time is 2~5min; the exposure is performed under a polarized blue LED light source, and the power density of the polarized blue LED light source is 3~5mW / cm². 2The exposure time is 10-20 minutes.

[0016] Preferably, the liquid crystal solution comprises liquid crystal monomer M1, photoinitiator 651, and organic solvent, and the content of liquid crystal monomer M1 in the liquid crystal solution is 30-40 wt%; the first and second ultraviolet curing are carried out under ultraviolet lamp irradiation conditions, and the power density of the ultraviolet lamp is 3-8 mW / cm². 2 The first UV curing time is 2-5 minutes; the second UV curing time is 1-2 minutes.

[0017] This invention provides a UV-curable adhesive, comprising a resin component and a photoinitiator. The resin component includes bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate, wherein the mass ratio of the bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate is (30~70):(10~30):(20~40). The photoinitiator accounts for 0.3~0.6% of the mass of the resin component. The UV-curable adhesive provided by this invention uses a compound of bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate as the resin component, and optimizes the mass ratio of the three raw materials. This effectively reduces the volume shrinkage rate during the adhesive curing process, and avoids internal defects such as micropores and cracks caused by stress concentration during the bonding and curing process of optical components. Simultaneously, it can effectively improve the decrease in matrix material strength caused by shrinkage stress, improve the interface problem of composite materials, and effectively solve the problem of uneven surface uniformity in the glass bonding protection process of the production line, resulting in a high yield. The results of the examples show that the UV-curable adhesive provided by this invention has a volume shrinkage rate of only 2.1% in the resin material before and after curing, based on the expansion and curing method. This well meets the surface design requirements of liquid crystal polymer micro / nano production lines. Only 10% of the 1064nm half-wave batch samples have a transmission wavefront range greater than 1 / 3λ, and the yield meeting the standard is ≥90%, greatly improving the preparation yield of highly complex liquid crystal polymer homogenized DOEs.

[0018] Furthermore, in this invention, the photoinitiator includes photoinitiator 907 and photoinitiator 1173; the mass percentage of photoinitiator 907 in the resin component is 0.15~0.3%; the mass percentage of photoinitiator 1173 in the resin component is 0.15~0.3%. By selecting photoinitiator 907 and photoinitiator 1173 to be compounded with the above-mentioned resin component, this invention achieves synergy between the resin component and photocuring, which is more conducive to reducing the volume shrinkage rate during the adhesive curing process. This results in superior surface appearance, strong uniformity, and high yield of micro / nano optical element fabrication after bonding, achieved through homogenization of the liquid crystal polymer.

[0019] This invention provides a method for fabricating liquid crystal micro / nano optical elements. The adhesive used for bonding during the fabrication process is either the UV-curable adhesive described in the above-described technical solution or a UV-curable adhesive prepared by the method described in the above-described technical solution. This invention uses a UV-curable adhesive with low curing shrinkage. After bonding, optical testing is performed using a Zygo transmission wavefront testing instrument. This results in multiple batches of ≥10 pieces having a transmission wavefront PV value not exceeding 1 / 3λ. This not only avoids internal defects such as micropores and cracks caused by stress concentration during the bonding and curing process of the optical elements, but also effectively improves the reduction in matrix material strength caused by shrinkage stress and improves the interface problem of composite materials. This is of great significance for solving the surface shape problem of liquid crystal polymer micro / nano optical elements. Attached Figure Description

[0020] Figure 1 This is a structural exploded view of the liquid crystal micro / nano optical element prepared in Example 2 of the present invention; Figure 2 Test data for the liquid crystal micro / nano optical element prepared in Example 2 of this invention, ranging from 0 to 1 / 10λ. Figure 3 The test data for the liquid crystal micro / nano optical element prepared in Example 2 of this invention are 1 / 10λ to 1 / 3λ. Figure 4 The test data are for liquid crystal micro / nano optical elements prepared in Example 2 of this invention at a rate of 1 / 3λ or higher. In the figure: 1-Second optical substrate, 2-Adhesive, 3-Liquid crystal polymer material film (LCP), 4-Optical alignment layer (SD1), 5-First optical substrate. Detailed Implementation

[0021] This invention provides a UV-curable adhesive, comprising a resin component and a photoinitiator; the resin component comprises bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate, wherein the mass ratio of the bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate is (30~70):(10~30):(20~40); the photoinitiator accounts for 0.3~0.6% of the mass of the resin component.

[0022] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0023] In this invention, the bisphenol A epoxy acrylate was purchased from Anage Chemicals, industrial grade. The triethoxylated trimethylolpropane triacrylate was purchased from DSM GmbH, Germany, analytical grade. The nonaethoxylated trimethylolpropane triacrylate was purchased from DSM GmbH, Germany, analytical grade. The preferred mass ratio of the bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonaethoxylated trimethylolpropane triacrylate is 50:20:30.

[0024] In this invention, the photoinitiator preferably includes photoinitiator 907 and photoinitiator 1173. The mass percentage of photoinitiator 907 relative to the mass of the resin component is preferably 0.15-0.3%, and in some embodiments it can be 0.25%. The mass percentage of photoinitiator 1173 relative to the mass of the resin component is preferably 0.15-0.3%, and in some embodiments it can be 0.25%.

[0025] In a specific embodiment of the present invention, the UV-curable adhesive preferably comprises bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, nonethoxylated trimethylolpropane triacrylate, photoinitiator 907, and photoinitiator 1173; the mass ratio of the bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, nonethoxylated trimethylolpropane triacrylate, photoinitiator 907, and photoinitiator 1173 is preferably (30~70):(10~30):(20~40):(0.15~0.3):(0.15~0.3), and in the embodiment it can be 50:20:30:0.25:0.25.

[0026] This invention provides a method for preparing the UV-curable adhesive described in the above technical solution, comprising the following steps: The resin component and photoinitiator are sequentially stirred, mixed, and allowed to stand for degassing to obtain the UV-curable adhesive. In this invention, the stirring and mixing can be done using magnetic stirring. The stirring speed is preferably 1500~2500 rpm, and in the example, it can be 2000 rpm. The stirring and mixing time is preferably 3~8 minutes, and in the example, it can be 5 minutes.

[0027] In this invention, the UV-curable adhesive is stored in a nitrogen cabinet at a constant temperature of 25°C to protect it from light.

[0028] This invention provides the application of the UV-curable adhesive described in the above-described technical solution or the UV-curable adhesive prepared by the preparation method described in the above-described technical solution in the fabrication of optical elements. In this invention, the optical element can be a liquid crystal micro / nano optical element, also known as a liquid crystal polymer homogenization diffraction optical element (DOE) or a liquid crystal polymer micro / nano element.

[0029] In this invention, the UV-curable adhesive is preferably applied in the bonding process during the fabrication of the liquid crystal micro / nano optical element.

[0030] This invention provides a method for fabricating liquid crystal micro / nano optical elements, comprising the following steps: The surface of the first optical substrate is coated with a photo-inducing alignment agent solution, and then subjected to heat treatment and exposure in sequence to obtain the exposed optical substrate; The exposed surface of the optical substrate after exposure is coated with a liquid crystal solution, and then subjected to a first ultraviolet curing to obtain a liquid crystal polymer material film layer. The surface of the liquid crystal polymer material film is coated with adhesive, then covered with a second optical substrate, and finally subjected to a second ultraviolet curing to obtain a liquid crystal micro-nano optical element; the adhesive is the UV-curable adhesive described in the above technical solution or the UV-curable adhesive prepared by the preparation method described in the above technical solution.

[0031] This invention involves coating the surface of a first optical substrate with a photo-inducing alignment agent solution, followed by sequential heat treatment and exposure to obtain an exposed optical substrate. In this invention, the first optical substrate can be a fused silica substrate or 7980 glass. Preferably, the first optical substrate undergoes pretreatment, which preferably includes sequential washing, drying, and ultraviolet irradiation. The washing reagents are preferably acetone, ethanol, and water, respectively. The ethanol can be anhydrous ethanol. The water can be ultrapure water. The washing time for each reagent wash is preferably 3-5 minutes. The washing is preferably performed under ultrasonic conditions. The drying is preferably oven drying, and the drying temperature is preferably 50-60°C. The wavelength of the ultraviolet irradiation is preferably 254 nm, the power is preferably 10-15 mV, and the time is preferably 3-5 minutes.

[0032] In this invention, the photo-inducing alignment agent solution is preferably an organic solution of SD1. The organic solvent in the photo-inducing alignment agent solution is preferably N,N-dimethylformamide (DMF). The content of SD1 in the photo-inducing alignment agent solution is 15-25 wt%, and in the examples, it can be 20 wt%. The coating is preferably spin-coating, and the spin-coating is preferably performed using a spin coater. Preferably, the first optical substrate is placed on the spin coater stage of the spin coater, and vacuum adsorption is performed using negative pressure, where the negative pressure can be 1 unit. The spin-coating speed is preferably 2500-3000 rpm, and the time is preferably 25-30 s. The heat treatment is preferably performed on a hot stage. The heat treatment temperature is preferably 90-105℃, and in the examples, it can be 100℃; the time is preferably 2-5 min, and in the examples, it can be 3 min. The exposure is preferably performed under a polarized blue LED light source. The power density of the polarized blue LED light source is preferably 3-5 mW / cm². 2 In the example, it can be 4mW / cm 2 The exposure time is preferably 10-20 minutes, and in this embodiment, it can be 15 minutes. The exposure is performed in a laser direct writing device. Before exposure, the optical phase program is preferably imported into the software of the laser direct writing device. After exposure, the exposed optical substrate is stored in a nitrogen cabinet at room temperature.

[0033] After obtaining the exposed optical substrate, the present invention coats the exposed surface of the exposed optical substrate with a liquid crystal solution, and then performs a first ultraviolet curing to obtain a liquid crystal polymer material film layer. In the present invention, the liquid crystal solution includes liquid crystal monomer M1, photoinitiator 651, and organic solvent. The organic solvent can be ethyl acetate. The content of liquid crystal monomer M1 in the liquid crystal solution is preferably 30-40 wt%, and in the example it can be 35 wt%. The mass ratio of the liquid crystal monomer M1 to the photoinitiator 651 can be 100:3. The liquid crystal solution is preferably dispersed by ultrasonication. The coating is preferably spin-coating, and the spin-coating is preferably performed using a spin coater. The present invention preferably places the exposed optical substrate on the spin coater table of the spin coater and uses negative pressure vacuum adsorption, and the negative pressure can be 1 negative pressure. The spin-coating speed is preferably 2500-3000 rpm, and the time is preferably 25-30 s. The first ultraviolet curing is performed under ultraviolet lamp conditions, and the power density of the ultraviolet lamp is preferably 3-8 mW / cm². 2 In the example, it can be 5mW / cm 2 The preferred UV curing time is 2-5 minutes, and in this example it can be 3 minutes.

[0034] After obtaining the liquid crystal polymer material film, the present invention coats the surface of the liquid crystal polymer material film with adhesive, then covers it with a second optical substrate, and finally performs a second ultraviolet curing to obtain a liquid crystal micro / nano optical element; the adhesive is the UV-curable adhesive described in the above technical solution or the UV-curable adhesive prepared by the preparation method described in the above technical solution. In the present invention, the coating can be drop-coating. The second optical substrate can be a fused silica substrate. Before performing the second ultraviolet curing, the present invention preferably further includes using a pressurized method to remove air bubbles between the adhesive and the second optical substrate. The second ultraviolet curing is performed under ultraviolet lamp irradiation conditions, and the power density of the ultraviolet lamp is preferably 3~8 mW / cm². 2 In the example, it can be 5mW / cm 2 The second UV curing time is preferably 1-2 minutes, and in the example, it can be 1 minute.

[0035] A schematic diagram showing the structural breakdown of the liquid crystal micro / nano optical element prepared by this invention is shown below. Figure 1 As shown, the liquid crystal micro / nano optical element sandwich structure provided by the present invention includes, from bottom to top, a first optical substrate, a light alignment layer, a liquid crystal polymer material film layer, an adhesive, and a second optical substrate stacked together.

[0036] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 This embodiment provides a UV-curable adhesive, specifically prepared by mixing bisphenol A type epoxy acrylate, triethoxylated trimethylolpropane triacrylate, nonethoxylated trimethylolpropane triacrylate, photoinitiator 907, and photoinitiator 1173 in a mass ratio of 50:20:30:0.25:0.25. The mixture is stirred at 2000 rpm for 5 minutes using a magnetic stirrer, and then allowed to stand to remove bubbles, yielding the UV-curable adhesive. It is then stored in a nitrogen chamber at 25°C in the dark for later use. Based on the dilatation method, the volume shrinkage rate of the UV-curable adhesive before and after curing is only 2.1%.

[0038] The dilatometer method involves placing the sample in the center of a glass slide, surrounding the uncured UV adhesive with a non-reactive solvent, connecting a capillary tube at the top, and introducing a UV light source at the bottom to cure the sample in real time. Based on the change in material volume, the dilatometer reading changes accordingly, thus indirectly indicating the volume change.

[0039] Example 2 This embodiment provides a method for fabricating liquid crystal micro / nano optical elements. The structural disassembled diagram of the liquid crystal micro / nano optical element provided in this embodiment is shown below. Figure 1 As shown.

[0040] A fused silica substrate measuring 25.4 × 3 mm was immersed in acetone, placed in an ultrasonic cleaner and vibrated for 5 minutes, then removed and placed in anhydrous ethanol and sonicated for 5 minutes. After that, it was placed in ultrapure water and sonicated for 5 minutes. Then it was dried in a 60°C oven and irradiated with ultraviolet light at a power of 10 mW and a wavelength of 254 nm for 5 minutes.

[0041] The treated fused silica substrate was placed on a spin coater. Using a negative pressure vacuum adsorption, 20wt% photo-inducing alignment agent SD1-DMF solution was drawn with a syringe and 0.1mL was added to the substrate. After spin coating at 3000rpm for 30s, the substrate was placed on a 100℃ hot stage for 3min and then stored in a nitrogen cabinet at room temperature.

[0042] The substrate coated with photoinducible agent was placed in a power density of 4 mW / cm². 2 Expose for 15 minutes in a laser direct writing device under a polarized blue LED light source. The optical phase program has been imported into the software of the laser direct writing device. After the direct writing is completed, store it in a nitrogen cabinet at room temperature.

[0043] Liquid crystal monomer M1 and photoinitiator 651 were mixed with ethyl acetate at a mass ratio of 100:3 and ultrasonically stirred to obtain a liquid crystal solution with 35 wt% liquid crystal monomer M1, which was then stored in a constant temperature oven at 50°C. The exposed film was placed on a spin coater, and 0.1 mL was added dropwise onto the exposed substrate using a negative pressure vacuum adsorption method. After spin coating at 3000 rpm for 30 s, the film was then coated at 5 mW / cm². 2 Curing under ultraviolet light for 3 minutes yields a DOE film layer prepared from liquid crystal polymer material.

[0044] The cured liquid crystal polymer was placed on a phase retardation measurement platform for testing, and relevant test data were collected. After dropping 0.5 mL of the UV-curable adhesive provided in Example 1 onto the center of the liquid crystal polymer, a cleaned fused silica substrate was placed on top. Pressure was applied to remove air bubbles from the interlayer, and the pressure was maintained at 5 mW / cm². 2 Curing under ultraviolet light for 1 minute yields a liquid crystal micro / nano optical element sample, namely a liquid crystal polymer homogenized DOE optical element.

[0045] The liquid crystal micro-nano optical element samples were placed on the zygo surface shape testing platform for liquid crystal micro-nano optical elements, and the surface shape effect of the liquid crystal micro-nano optical elements was tested. The PV values ​​of each sample are shown in Table 1 below.

[0046] Table 1. Statistical data of PV values ​​for each sample in Example 1

[0047] Figure 2 , Figure 3 and Figure 4 The figures show experimental data for various wavefront ranges of the liquid crystal polymer micro / nano devices prepared in Example 2. Figure 2 The test data for the liquid crystal polymer micro / nano element prepared in Example 2 of this invention are 0~1 / 10λ. Figure 3 The test data for the liquid crystal polymer micro / nano devices prepared in Example 2 of this invention are 1 / 10λ to 1 / 3λ. Figure 4 The test data for the liquid crystal polymer micro / nano element prepared in Example 2 of this invention are greater than 1 / 3λ. (From Table 1...) Figure 2 , Figure 3 and Figure 4 It can be seen that the UV-curable adhesive provided in Example 1 can well meet the surface design requirements of liquid crystal polymer micro-nano production lines. Only 10% of the 1064nm half-wave batch samples prepared have a surface transmission wavefront range of more than 1 / 3λ, and the yield rate that meets the standard is ≥90%, which greatly improves the preparation yield of liquid crystal polymer homogenized DOE with high process complexity.

[0048] Comparative Example 1 This embodiment provides a UV-curable adhesive, specifically prepared by mixing bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, nonethoxylated trimethylolpropane triacrylate, photoinitiator 907, and photoinitiator 1173 in a mass ratio of 90:5:5:0.25:0.25. The mixture is stirred at 2000 rpm for 5 minutes using a magnetic stirrer, and then allowed to stand to remove bubbles, yielding the UV-curable adhesive. It is then stored in a nitrogen chamber at 25°C in the dark for later use. The volume shrinkage rate of the UV adhesive before and after curing, measured using a dilatometer, is 5.7%.

[0049] Comparative Example 2 The method is basically the same as that provided in Example 2, except that the adhesive prepared in Comparative Example 1 is used for bonding the fused silica substrate. Subsequently, the liquid crystal micro / nano optical element sample prepared in Comparative Example 2 is placed on the Zygo surface model testing platform for liquid crystal micro / nano optical elements, and the surface model effect of the liquid crystal micro / nano optical element is tested. The PV values ​​of each sample are shown in Table 2 below.

[0050] Table 2. Statistical data on PV values ​​of each sample in Comparative Example 2

[0051] As shown in Table 2, changing the mass ratio of bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate in the adhesive cannot meet the surface design requirements of the liquid crystal polymer micro / nano production line. The proportion of the 1064nm half-wave batch samples with a transmission wavefront range of more than 1 / 3λ is as high as 90%, while only 10% meet the standard. The surface yield of the liquid crystal polymer homogenized DOE preparation is greatly limited.

[0052] Comparative Example 3 The method is basically the same as that provided in Example 2, except that NOA61 adhesive is used for bonding the fused silica substrate. Subsequently, the liquid crystal micro / nano optical element sample prepared in Comparative Example 3 was placed on the Zygo surface model testing platform for liquid crystal micro / nano optical elements, and the surface model effect of the liquid crystal micro / nano optical element was tested. The PV values ​​of each sample are shown in Table 3 below.

[0053] Table 3. Statistical data of PV values ​​for each sample in Comparative Example 3

[0054] As shown in Table 3, the commonly used UV curing adhesive NOA61 cannot meet the surface design requirements of liquid crystal polymer micro-nano production lines. Among the 1064nm half-wave batch samples prepared, the proportion of surface transmission wavefront range above 1 / 3λ is as high as 95%, and only 5% meet the standard. The surface yield of liquid crystal polymer homogenized DOE preparation is greatly limited.

[0055] Comparative Example 4 The adhesive was prepared according to Example 1 disclosed in Chinese Patent CN119552581A: Ethylene oxide-2-acrylate, acrylic acid, hydroquinone, photoinitiator 651, and 1,5-pentanediol diacrylate were prepared in a mass ratio of 100:100:2:4:50. The mixture was stirred at 1500 rpm for 5 minutes with an electric stirrer and allowed to stand to remove bubbles, resulting in the glue.

[0056] Using the adhesive prepared in Comparative Example 4, liquid crystal micro / nano optical element samples were prepared according to the method in Example 2. Subsequently, the liquid crystal micro / nano optical element samples prepared in Comparative Example 4 were placed on the Zygo surface model testing platform for liquid crystal micro / nano optical elements, and the surface model effect of the liquid crystal micro / nano optical elements was tested. The PV values ​​of each sample are shown in Table 4 below.

[0057] Table 4. Statistical data of PV values ​​for each sample in Comparative Example 4

[0058] As shown in Table 4, compared with the adhesive disclosed in the prior art CN119552581A, the UV curable adhesive provided by the present invention, through optimization of the formula and introduction of component materials with low volume shrinkage, achieves the advantages of excellent surface shape, strong uniformity, and high yield of liquid crystal polymer homogenized DOE products after bonding, and high yield of micro-nano optical element fabrication.

[0059] As can be seen from the above embodiments, compared with the liquid crystal polymer homogenized DOE products prepared by existing photocurable adhesive bonding technology, which have problems such as poor surface shape, low uniformity, and low yield in surface shape testing (the main indicator is the PV value transmitted across the wavefront), the UV-curable adhesive provided by the present invention can improve the product competitiveness and production yield of micro-nano optical components. The UV-curable adhesive provided by the present invention introduces component materials with low volume shrinkage rate to achieve the advantages of excellent surface shape, strong uniformity, and high yield of micro-nano optical component fabrication after bonding.

[0060] The liquid crystal micro / nano optical element product provided by this invention has a sandwich structure, with a first optical substrate and a second optical substrate (e.g., Corning 7980 glass) as the upper and lower layers. A layer of photo-alignment agent SD1 is deposited on the surface of the first optical substrate. A pre-set optical phase is programmed using laser direct writing, which effectively induces the orientation of the photo-alignment agent under polarized blue light, thus achieving patterning. The patterned sample is placed on a spin coater, and a prepared liquid crystal monomer solution is spin-coated onto it, followed by curing in a UV lamp chamber. After film formation, the optical retardation is measured. Then, the UV-curable adhesive provided by this invention is used for dispensing, and the second optical substrate is bonded. After bonding, optical testing is performed using a Zygo transmission wavefront testing instrument, achieving a transmission wavefront PV value of no more than 1 / 3λ for multiple batches of ≥10 pieces of samples. The UV-curable adhesive provided by this invention can meet the requirement that the transmission wavefront PV value of liquid crystal polymer micro-nano optical element samples in the bonding process can be kept stable at no more than 1 / 3λ for multiple batches of liquid crystal polymer micro-nano optical elements. It can effectively solve the technical problem of uneven surface uniformity in the bonding and protection process of liquid crystal micro-nano optical elements in the production line.

[0061] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A UV-curable adhesive, characterized in that, The product includes a resin component and a photoinitiator; the resin component comprises bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate, wherein the mass ratio of the bisphenol A epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate is (30~70):(10~30):(20~40); the photoinitiator accounts for 0.3~0.6% of the mass of the resin component.

2. The UV-curable adhesive according to claim 1, characterized in that, The mass ratio of the bisphenol A type epoxy acrylate, triethoxylated trimethylolpropane triacrylate, and nonethoxylated trimethylolpropane triacrylate is 50:20:

30.

3. The UV-curable adhesive according to claim 1 or 2, characterized in that, The photoinitiator includes photoinitiator 907 and photoinitiator 1173; the mass percentage of photoinitiator 907 in the resin component is 0.15~0.3%; the mass percentage of photoinitiator 1173 in the resin component is 0.15~0.3%.

4. The UV-curable adhesive according to claim 3, characterized in that, The photoinitiator 907 accounts for 0.25% of the mass of the resin component; the photoinitiator 1173 accounts for 0.25% of the mass of the resin component.

5. A method for preparing the UV-curable adhesive according to any one of claims 1 to 4, characterized in that, Includes the following steps: The resin components and photoinitiator were stirred and mixed sequentially and then allowed to stand for degassing to obtain the UV-curable adhesive.

6. The preparation method according to claim 5, characterized in that, The stirring speed is 1500~2500 rpm, and the time is 3~8 min.

7. The application of the UV-curable adhesive according to any one of claims 1 to 4 or the UV-curable adhesive prepared by the preparation method according to claim 5 or 6 in the fabrication of optical components.

8. A method for fabricating a liquid crystal micro / nano optical element, characterized in that, Includes the following steps: The surface of the first optical substrate is coated with a photo-inducing alignment agent solution, and then subjected to heat treatment and exposure in sequence to obtain the exposed optical substrate; The exposed surface of the optical substrate after exposure is coated with a liquid crystal solution, and then subjected to a first ultraviolet curing to obtain a liquid crystal polymer material film layer. The surface of the liquid crystal polymer material film is coated with adhesive, then covered with a second optical substrate, and finally subjected to a second ultraviolet curing to obtain a liquid crystal micro-nano optical element; the adhesive is the UV-curable adhesive according to any one of claims 1 to 4 or the UV-curable adhesive prepared by the preparation method according to claim 5 or 6.

9. The preparation method according to claim 8, characterized in that, The photo-inducing alignment agent solution is an organic solution of SD1, and the content of SD1 in the photo-inducing alignment agent solution is 15~25wt%; the heat treatment temperature is 90~105℃, and the time is 2~5min; the exposure is performed under a polarized blue LED light source, and the power density of the polarized blue LED light source is 3~5mW / cm². 2 The exposure time is 10-20 minutes.

10. The preparation method according to claim 8, characterized in that, The liquid crystal solution comprises liquid crystal monomer M1, photoinitiator 651, and organic solvent, wherein the content of liquid crystal monomer M1 in the liquid crystal solution is 30-40 wt%; the first and second ultraviolet curing are carried out under ultraviolet lamp irradiation conditions, wherein the power density of the ultraviolet lamp is 3-8 mW / cm². 2 ; The first UV curing time is 2-5 minutes; the second UV curing time is 1-2 minutes.

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