Holographic polymer dispersed liquid crystal material, grating device and preparation method thereof

Abstract

The invention provides a holographic polymer dispersed liquid crystal material, a grating device and a preparation method thereof, in a holographic polymer dispersed liquid crystal material system, uniformly dispersed zirconium dioxide nano-particles are introduced into a writing monomer according to a specific proportion, and the zirconium dioxide nano-particles are used as a nano reinforced phase to be stably combined with a photopolymer matrix; the composition and proportion of the writing monomers are synergistically optimized, and the multiple beneficial effects of improving the thermo-oxidative aging resistance of the grating device, enhancing the grating structure stability and improving the diffraction efficiency are synchronously achieved through material compounding and structure strengthening. Specifically, in the preparation process, a PGME dispersion liquid of zirconium dioxide nanoparticles and a writing monomer are preferentially and uniformly mixed, and a PGME solvent is removed by virtue of a rotary evaporation technology, so that highly uniform and stable pre-dispersion of the nanoparticles in a writing monomer matrix is realized; the problems of agglomeration and sedimentation possibly caused by compatibility difference in the subsequent integral mixing and polymerization process of the nano-particles are prevented.

Description

Technical Field

[0001] This invention relates to the field of holographic projection display, and more specifically, to a holographic polymer-dispersed liquid crystal material, a grating device, and a method for preparing the same. Background Technology

[0002] Holographic display technology is a novel display method that records and reproduces the three-dimensional optical information of objects based on the principles of interference and diffraction. It can not only restore the three-dimensional shape of objects but also reproduce their colors, textures, and even dynamic changes, thus revolutionizing the visual experience. The key to this technology lies in the preparation of holograms—recording the light field information of objects through laser interference and reproducing a three-dimensional image that can be observed from multiple angles using diffraction. Based on this, holographic polymer-dispersed liquid crystal gratings have been developed, combining holographic recording materials with polymer-dispersed liquid crystal systems to form a composite structure with periodic arrangement. This structure boasts advantages such as high efficiency, electrically controllable switching, and ease of processing, thus showing broad application potential in cutting-edge fields such as holographic storage, display, tunable filtering, laser modulation, and augmented reality. However, with the rapid development of holographic technology, holographic grating devices often face challenges in terms of aging resistance in applications with high reliability requirements, such as outdoor displays, automotive optics, and industrial inspection. Especially in high-temperature environments, the diffraction efficiency of the grating significantly decreases, while haze increases sharply, seriously affecting the long-term stability and reliability of the device.

[0003] Currently, the fabrication of holographic polymer-dispersed liquid crystal gratings mainly relies on the photopolymerization and phase separation process of a blend of monomers, liquid crystals, and photoinitiators under coherent laser irradiation. In the bright region of the interference fringes, monomers polymerize to form a polymer-rich phase, while liquid crystal molecules migrate to the dark region, ultimately forming a grating structure with periodically modulated refractive index. However, shrinkage of the polymer network is unavoidable in this process. This shrinkage leads to micro-deformation of the grating's physical structure, a decrease in the uniformity of the periodic distribution, and consequently affects the stability of its optical performance. Under thermo-oxidative aging conditions, this shrinkage effect is more pronounced, and the compatibility and interfacial stability between the polymer and the liquid crystal further deteriorate, causing liquid crystal molecule redistribution and degradation of the phase separation structure, ultimately resulting in decreased diffraction efficiency and increased haze. Existing technologies often mitigate shrinkage by optimizing the monomer structure, adjusting the ratio, or introducing plasticizers. However, these methods often improve aging performance while also reducing the refractive index modulation or response speed of the grating, making it difficult to achieve a good balance between optical performance and durability.

[0004] Therefore, there is a need to develop a holographic polymer-dispersed liquid crystal material and its grating device that can significantly improve the aging resistance, especially the heat and oxygen stability, while maintaining the regularity of the grating structure and excellent optical performance. Summary of the Invention

[0005] The present invention aims to overcome at least one of the defects of the prior art and provides a holographic polymer dispersed liquid crystal material, a grating device and a method for preparing the same, thereby improving the thermo-oxidative aging stability of the holographic polymer dispersed liquid crystal material and thus improving the overall performance and service life of the holographic polymer dispersed liquid crystal material and the grating device prepared therefrom.

[0006] The technical solution adopted by this invention firstly provides a holographic polymer-dispersed liquid crystal material, characterized in that, by mass percentage, it comprises: Photoinitiator: 0.5-2 parts Co-initiator: 2-5 parts Writing units: 35-50 copies LCD: 25-35 units Solvent: 5-10 parts Zirconia nanoparticles: 5-10 parts; The zirconium dioxide nanoparticles are uniformly dispersed in the writing monomer, and the ratio of the writing monomer to the zirconium dioxide nanoparticles is greater than 1.5:1 and less than 5:1; the particle size of the zirconium dioxide nanoparticles is 5-40 nm.

[0007] In this technical solution, in the holographic polymer-dispersed liquid crystal material system, uniformly dispersed zirconium dioxide nanoparticles are introduced into the writing monomer. The high refractive index, excellent thermal stability and high hardness of the zirconium dioxide nanoparticles are utilized to make them a nano-reinforcing phase that is stably combined with the photopolymer matrix. The composition and ratio of the writing monomer are also optimized in a synergistic manner. Through material composite and structural reinforcement, multiple beneficial effects are achieved, including improving the heat and oxygen aging resistance of the grating device, enhancing the structural stability of the grating, and improving the diffraction efficiency. Specifically, by uniformly dispersing zirconium dioxide nanoparticles in the writing monomer, the uniform dispersion of the nanoparticles in the polymerization precursor effectively provides physical support and anchoring during the subsequent photopolymerization process to form a periodic grating structure. This suppresses microstructural deformation and dimensional instability caused by polymer network shrinkage, thereby significantly enhancing the mechanical strength and shape retention of the fabricated grating device and improving its structural durability under thermo-oxidative aging conditions. Simultaneously, introducing thermally stable nanoparticles into the polymer network slows down the process of polymer chain relaxation and liquid crystal phase distribution deterioration at high temperatures, effectively curbing the diffraction efficiency decay and haze increase problems caused by aging. Furthermore, the high refractive index of zirconium dioxide directly increases the refractive index contrast between the polymer phase and the liquid crystal phase, thus improving the refractive index modulation of the holographic polymer-dispersed liquid crystal material system and enhancing the diffraction efficiency of the grating device. Simultaneously, during the formation of the holographic grating, the zirconium dioxide nanoparticles promote the orderly arrangement of liquid crystal droplets, further improving the diffraction efficiency of the grating device. Furthermore, by limiting the mass ratio between the writing monomer and zirconium dioxide nanoparticles to greater than 1.5:1 and less than 5:1, the material system is designed to ensure that there is sufficient writing monomer to fully wet, coat, and stably disperse the nanoparticles, preventing nanoparticle aggregation, while also ensuring the introduction of a relatively high concentration of nano-reinforcing phase. This results in a more significant enhancement effect on the polymer network in terms of structural strength and optical performance. In addition to greatly improving the dimensional stability and resistance to thermo-oxidative aging of the grating structure, the material system's refractive index modulation is further enhanced by improving the equivalent refractive index of the polymer phase and increasing the diffraction efficiency of the grating device. Furthermore, by using PGME (propylene glycol methyl ether) as a dispersant to provide 5-40 nm zirconium dioxide nanoparticles to the material system, the excellent dispersing effect of PGME avoids the aggregation of the zirconium dioxide nanoparticles when they are introduced into the system, ensuring the uniformity of the dispersion of the zirconium dioxide nanoparticles in the writing monomer. At the same time, controlling the size of the zirconium dioxide nanoparticles to 5-40 nm not only avoids the scattering of incident light caused by particle aggregation or excessive size, ensuring the excellent optical transparency of the material, but also allows the high refractive index characteristics of the zirconium dioxide nanoparticles to contribute more efficiently and uniformly to the refractive index modulation of the holographic grating. This enhances the aging resistance of the material and further improves the diffraction efficiency of the grating.

[0008] Furthermore, the writing unit includes: First monomer: 15-20 parts, Second monomer: 15-20 parts, Third monomer: 5-10 parts; The first monomer is selected from one or more of the following: cyclohexyl methacrylate, methyl laurate, isodecyl methacrylate, isooctyl acrylate, butyl acrylate, methyl acrylate, benzyl methacrylate, 2-phenoxyethyl methacrylate, dicyclopentyl methacrylate, and isobornyl methacrylate. The second monomer is selected from one or more of 4-(ethoxy)bisphenol A dimethacrylate, triethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, and ethylene glycol dimethacrylate; The third monomer is selected from one or two of pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, and hyperbranched acrylate.

[0009] In this technical solution, three writing monomers with different functionalities are used in synergistic cooperation to construct a stable polymer network suitable for composite zirconium dioxide nanoparticles during photopolymerization. Furthermore, the first monomer is a monofunctional monomer and the second monomer is a difunctional monomer, which provides the basic polymer network framework for the system, determines the basic strength and shape retention of the grating structure, and provides a basis for the uniform dispersion of subsequent nanoparticles and other components by utilizing its low viscosity characteristics and good compatibility. The third monomer is a multifunctional monomer, which is used to form high-functionality crosslinking points, thereby forming dense anchoring points in the network. The synergistic combination of multiple writing monomers not only provides the grating device with good diffraction efficiency and low haze, but also synergistically enhances the overall rigidity and structural integrity of the polymer matrix. This effectively resists deformation caused by polymerization shrinkage and thermal stress, stabilizes the microstructure of the periodic grating, and directly improves the device's thermal and oxygen aging resistance and long-term reliability. At the same time, the combination of writing monomers with multiple chain segments and viscosities provides conditions for the uniform incorporation and dispersion of zirconium dioxide nanomonomers. The constructed stable polymer network also provides a solid and uniform attachment framework for the uniformly dispersed zirconium dioxide nanoparticles, enabling the zirconium dioxide nanoparticles to stably achieve their enhancement and refractive indexing effects.

[0010] Furthermore, the photoinitiator is selected from one or more of the following: Bengal rose red, diiodofluorescein, methylene blue, TPO, rhodamine 6G, 3,3'-carbonylbis(7-diethylaminocoumarin), and initiator 184.

[0011] Furthermore, the co-initiator is selected from one or more of benzoyl peroxide and N-phenylglycine.

[0012] Furthermore, the liquid crystal is selected from one or more of BL038, GXP-6003, BL087, and TL213.

[0013] Furthermore, the solvent is selected from one or more of N-vinylpyrrolidone, chloroform, tetrahydrofuran, and toluene.

[0014] Another objective of this invention is to provide a holographic polymer-dispersed liquid crystal grating device resistant to heat and oxygen aging, which is prepared from the holographic polymer-dispersed liquid crystal material provided in the above technical solutions.

[0015] Another object of the present invention is to provide a method for fabricating a heat- and oxygen-resistant holographic polymer-dispersed liquid crystal grating device, comprising the following steps: S1. Weigh the holographic polymer-dispersed liquid crystal material according to the proportion, wherein the zirconium dioxide nanoparticles are provided by the zirconium dioxide PGME dispersion; mix the zirconium dioxide PGME dispersion and the writing monomer according to the proportion and form a writing monomer uniformly doped with zirconium dioxide nanoparticles by rotary evaporation. S2. The writing monomer uniformly doped with zirconium dioxide nanoparticles is mixed with other materials in the holographic polymer-dispersed liquid crystal material to obtain a uniform holographic polymer-dispersed liquid crystal material system. S3. The mixed holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell, left to stand in a dark room, and then exposed by interference under the interference light field of a dual-beam light source to obtain a heat-resistant and oxygen-aging-resistant holographic polymer-dispersed liquid crystal grating device. In S1, the writing monomer is a first monomer, and / or a second monomer, and / or a third monomer.

[0016] In this technical solution, during the fabrication of the grating device, by preferentially mixing the PGME dispersion of zirconium dioxide nanoparticles with the writing monomer and removing the solvent by rotary evaporation, the adverse effects of introducing the solvent PGME into the system are avoided. This achieves highly uniform and stable pre-dispersion of nanoparticles in the writing monomer matrix and prevents agglomeration and sedimentation problems that may occur in the subsequent overall mixing and polymerization process due to compatibility differences. Specifically, by prioritizing the construction of a uniform nanocomposite precursor with compatible writing monomers, the zirconium dioxide nanoparticles are ensured to be fully and stably embedded in the polymer network framework at the scale of individual particles. This allows the high thermal stability and high refractive index characteristics of the nanoparticles to function efficiently and consistently throughout the grating. On the one hand, this significantly enhances the mechanical stability of the polymer matrix, effectively suppressing network shrinkage and structural deformation during photopolymerization and subsequent thermal aging, thereby greatly improving the shape retention capability and long-term resistance to thermal and oxygen aging of the grating device. On the other hand, the introduction of uniformly distributed zirconium dioxide nanoparticles into the polymer system directly increases the equivalent refractive index of the polymer phase, thereby stably and significantly increasing the refractive index modulation between it and the liquid crystal phase. While optimizing the feasibility of the process, this ensures that the fabricated grating device has both higher diffraction efficiency and higher stability and reliability.

[0017] Preferably, the zirconium dioxide nanoparticles are uniformly dispersed in the first monomer. This fully utilizes the physical properties of the monofunctional monomer itself, such as low viscosity and good flowability. This not only makes it easier for the nanoparticles to be uniformly dispersed in the monomer, but also effectively maintains the dispersion state during the subsequent critical rotary evaporation process to remove the solvent PGME. This avoids problems such as uneven solvent evaporation, local aggregation or sedimentation of nanoparticles caused by excessively high system viscosity, thereby ensuring that the zirconium dioxide nanoparticles are incorporated and exist in the first monomer in a highly uniform and stable state. At the same time, it also directly improves the operability and efficiency of uniform doping of zirconium dioxide nanoparticles, making the preparation process of the nanocomposite monomer easier to control and more repeatable, further improving the convenience of the preparation process.

[0018] Furthermore, in step S1, when forming the writing monomer with uniformly doped zirconium dioxide nanoparticles using a rotary evaporator, the evaporation temperature is 40-60°C. By maintaining mild yet efficient rotary evaporation conditions, the solvent evaporates at an appropriate rate, ensuring that the zirconium dioxide nanoparticles maintain a stable and uniform dispersion in the monomer during solvent removal. This avoids the solvent residue from affecting the uniformity of subsequent polymerization due to excessively low temperatures, and effectively prevents premature thermal polymerization or decomposition of the writing monomer due to excessively high temperatures. This improves the structural integrity of the final grating device and the uniformity of nanoparticle dispersion, ultimately synergistically enhancing the grating device's resistance to thermal oxygen aging and diffraction efficiency.

[0019] Furthermore, the thickness of the liquid crystal cell is 5-10 μm; the settling time of the liquid crystal cell in the dark chamber is 1-2 hours; the interference exposure time is 1-5 minutes; the included angle of the dual-beam light source is 35-60°; and the irradiation power of the dual-beam light source is 4-6 mW / cm². 2 .

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A holographic polymer-dispersed liquid crystal material is provided. By introducing uniformly dispersed zirconium dioxide nanoparticles into the writing monomer, the high refractive index, excellent thermal stability and high hardness of the zirconium dioxide nanoparticles are utilized to stabilize them as a nano-reinforcing phase with the photopolymer matrix. The composition and ratio of the writing monomer are synergistically optimized. Through material composite and structural reinforcement, multiple beneficial effects are achieved, including improving the heat and oxygen aging resistance of grating devices, enhancing the structural stability of gratings and improving diffraction efficiency. Specifically, by uniformly dispersing zirconium dioxide nanoparticles in the writing monomer, the uniform dispersion of the nanoparticles in the polymerization precursor effectively provides physical support and anchoring during the subsequent photopolymerization process to form a periodic grating structure. This suppresses microstructural deformation and dimensional instability caused by polymer network shrinkage, thereby significantly enhancing the mechanical strength and shape retention of the fabricated grating device and improving its structural durability under thermo-oxidative aging conditions. Simultaneously, introducing thermally stable nanoparticles into the polymer network slows down the process of polymer chain relaxation and liquid crystal phase distribution deterioration at high temperatures, effectively curbing the diffraction efficiency decay and haze increase caused by aging. Furthermore, the high refractive index of zirconium dioxide directly increases the refractive index contrast between the polymer phase and the liquid crystal phase, thus improving the refractive index modulation of the holographic polymer-dispersed liquid crystal material system and enhancing the diffraction efficiency of the grating device. Additionally, during the formation of the holographic grating, zirconium dioxide nanoparticles promote the orderly arrangement of liquid crystal droplets, further improving the diffraction efficiency of the grating device.

[0021] 2. In the holographic polymer-dispersed liquid crystal material system, a stable polymer network suitable for composite zirconium dioxide nanoparticles was constructed during photopolymerization by using three writing monomers with different functionalities in synergistic cooperation. Specifically, the first monomer is a monofunctional monomer, and the second monomer is a difunctional monomer, which provides the basic polymer network framework for the system, determines the basic strength and shape retention of the grating structure, and provides a basis for the uniform dispersion of subsequent nanoparticles and other components by utilizing its good compatibility. The third monomer is a multifunctional monomer, which is used to form high-functionality crosslinking points, thereby forming dense anchoring points in the network. The synergistic combination of various writing monomers provides excellent diffraction efficiency and low haze for the grating device, while simultaneously enhancing the overall rigidity and structural integrity of the polymer matrix. This effectively resists deformation caused by polymerization shrinkage and thermal stress, stabilizing the microstructure of the periodic grating and directly improving the device's thermal and oxygen aging stability and long-term reliability. Furthermore, the combination of writing monomers with various chain segments and viscosities provides conditions for the uniform incorporation and dispersion of zirconium dioxide nanomonomers. The robust polymer network further synergistically constructed by these monomers provides a solid and uniform attachment framework for the uniformly dispersed zirconium dioxide nanoparticles, enabling the zirconium dioxide nanoparticles to stably achieve their enhancement and refractive indexing effects.

[0022] 3. A method for fabricating a heat- and oxygen-resistant holographic polymer-dispersed liquid crystal grating device is provided. By preferentially and uniformly mixing a PGME dispersion of zirconium dioxide nanoparticles with a writing monomer and removing the solvent using rotary evaporation, the adverse effects of introducing the solvent PGME into the system are avoided. This achieves highly uniform and stable pre-dispersion of nanoparticles in the writing monomer matrix, preventing agglomeration and sedimentation problems that may occur due to compatibility differences during subsequent overall mixing and polymerization. At the same time, uniformly distributed zirconium dioxide nanoparticles are introduced into the polymer system in a simple and effective way, directly increasing the equivalent refractive index of the polymer phase, thereby stably and significantly increasing the refractive index modulation between it and the liquid crystal phase. While optimizing the feasibility of the process, this method ensures that the fabricated grating device has both higher diffraction efficiency and higher stability and reliability. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] The present invention will now be further illustrated with specific examples. The following embodiments are only for explaining the present invention and do not constitute a limitation thereof. The test samples and test procedures used in the following embodiments include the following (if the specific experimental conditions are not specified in the embodiments, they are usually performed according to conventional conditions or the conditions recommended by the reagent company; the reagents, consumables, etc. used in the following embodiments can be obtained commercially unless otherwise specified).

[0026] Example 1 This embodiment provides a holographic polymer-dispersed liquid crystal material, a heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating device, and a method for preparing the same, specifically including the following steps: (1) Weigh the raw materials from the brown sample bottle according to the following proportions: 0.5 parts of 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts of N-phenylglycine, 15 parts of 2-phenoxyethyl methacrylate, 20 parts of 4-(ethoxy)bisphenol A dimethacrylate, 10 parts of trimethylolpropane triacrylate, 12 parts of N-vinylpyrrolidine, 5 parts of zirconium dioxide PGME dispersion, 25 parts of BL038; (2) Prepare a heat-resistant, oxidation-resistant holographic polymer-dispersed liquid crystal grating device according to the following steps: S1. Add 15 parts of 2-phenoxyethyl methacrylate to 5 parts of zirconium dioxide PGME dispersion, and mix by rotary evaporation at 60℃ for 30 min to form a writing monomer uniformly doped with zirconium dioxide nanoparticles. S2. The writing monomer uniformly doped with zirconium dioxide nanoparticles and the remaining raw materials are placed in an ultrasonic instrument and ultrasonically mixed for 30 minutes to obtain a homogeneous holographic polymer-dispersed liquid crystal material system. The shrinkage rate of the homogeneous holographic polymer-dispersed liquid crystal material system is tested by the volume-density method. S3. Under vacuum conditions, the homogenized holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell with a thickness of 5 μm. After pouring, the liquid crystal cell is moved together to a dark room and left to stand for 1 hour. Then, it is moved to an irradiation chamber with an angle of 60° and an irradiation power of 5 mW / cm². 2 A holographic polymer-dispersed liquid crystal grating device resistant to heat and oxygen aging was obtained by interferoexposure in the interference light field of a dual-beam light source for 5 minutes.

[0027] (3) Performance testing of heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating devices: Thermo-oxidative aging test: The prepared heat-resistant and oxidation-resistant holographic polymer-dispersed liquid crystal grating device sample was placed in an oven and baked at 80°C for 200 hours. Before and after the thermo-oxidative aging test, the diffraction efficiency of the holographic grating device sample was tested using a grating diffraction efficiency tester. The haze of the holographic grating device sample was tested using a haze meter at 23±2℃ in accordance with GB 2410-2008 "Test Methods for Transmittance and Haze of Transparent Plastics".

[0028] Example 2 This embodiment provides a holographic polymer-dispersed liquid crystal material, a heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating device, and a method for preparing the same, specifically including the following steps: (1) Weigh the raw materials from the brown sample bottle according to the following proportions: 20 parts isobornyl methacrylate, 1.5 parts photoinitiator 184, 5 parts benzoyl peroxide, 15 parts ethylene glycol dimethacrylate, 13 parts pentaerythritol tetraacrylate, 10 parts zirconium dioxide PGME dispersion, 10 parts chloroform, and 30 parts GXP-6003. (2) Prepare a heat-resistant, oxidation-resistant holographic polymer-dispersed liquid crystal grating device according to the following steps: S1. Add 20 parts of isoborneol methacrylate to 10 parts of PGME dispersion of zirconium dioxide, and mix by rotary evaporation at 60℃ for 30 min to form a writing monomer uniformly doped with zirconium dioxide nanoparticles. S2. The writing monomer uniformly doped with zirconium dioxide nanoparticles and the remaining raw materials are placed in an ultrasonic instrument and ultrasonically mixed for 30 minutes to obtain a homogeneous holographic polymer-dispersed liquid crystal material system. The shrinkage rate of the homogeneous holographic polymer-dispersed liquid crystal material system is tested by the volume-density method. S3. Under vacuum conditions, the homogenized holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell with a thickness of 5 μm. After pouring, the liquid crystal cell is moved together to a dark room and left to stand for 1 hour. Then, it is moved to an irradiation chamber with an angle of 60° and an irradiation power of 5 mW / cm². 2 A holographic polymer-dispersed liquid crystal grating device resistant to heat and oxygen aging was obtained by interferoexposure in the interference light field of a dual-beam light source for 5 minutes.

[0029] (3) Performance testing of heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating devices: Thermo-oxidative aging test: The prepared heat-resistant and oxidation-resistant holographic polymer-dispersed liquid crystal grating device sample was placed in an oven and baked at 80°C for 200 hours. Before and after the thermo-oxidative aging test, the diffraction efficiency of the holographic grating device sample was tested using a grating diffraction efficiency tester. The haze of the holographic grating device sample was tested using a haze meter at 23±2℃ in accordance with GB 2410-2008 "Test Methods for Transmittance and Haze of Transparent Plastics".

[0030] Example 3 This embodiment provides a holographic polymer-dispersed liquid crystal material, a heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating device, and a method for preparing the same, specifically including the following steps: (1) Weigh the raw materials from the brown sample bottle according to the following proportions: 17 parts benzyl methacrylate, 7 parts zirconium dioxide PGME dispersion, 1 part TPO, 4 parts N-phenylglycine, 18 parts 1,3-butanediol dimethacrylate, 15 parts pentaerythritol tetraacrylate, 15 parts toluene, 35 parts TL213; (2) Prepare a heat-resistant, oxidation-resistant holographic polymer-dispersed liquid crystal grating device according to the following steps: S1. Add 17 parts benzyl methacrylate to 7 parts zirconium dioxide PGME dispersion, and mix by rotary evaporation at 60℃ for 30 min to form a writing monomer uniformly doped with zirconium dioxide nanoparticles; S2. The writing monomer uniformly doped with zirconium dioxide nanoparticles and the remaining raw materials are placed in an ultrasonic instrument and ultrasonically mixed for 30 minutes to obtain a homogeneous holographic polymer-dispersed liquid crystal material system. The shrinkage rate of the homogeneous holographic polymer-dispersed liquid crystal material system is tested by the volume-density method. S3. Under vacuum conditions, the homogenized holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell with a thickness of 5 μm. After pouring, the liquid crystal cell is moved together to a dark room and left to stand for 1 hour. Then, it is moved to an irradiation chamber with an angle of 60° and an irradiation power of 5 mW / cm². 2 A holographic polymer-dispersed liquid crystal grating device resistant to heat and oxygen aging was obtained by interferoexposure in the interference light field of a dual-beam light source for 5 minutes.

[0031] (3) Performance testing of heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating devices: Thermo-oxidative aging test: The prepared heat-resistant and oxidation-resistant holographic polymer-dispersed liquid crystal grating device sample was placed in an oven and baked at 80°C for 200 hours. Before and after the thermo-oxidative aging test, the diffraction efficiency of the holographic grating device sample was tested using a grating diffraction efficiency tester. The haze of the holographic grating device sample was tested using a haze meter at 23±2℃ in accordance with GB 2410-2008 "Test Methods for Transmittance and Haze of Transparent Plastics".

[0032] Comparative Example 1 This comparative example provides a holographic polymer-dispersed liquid crystal material, a holographic polymer-dispersed liquid crystal grating device, and a method for preparing the same, specifically including the following steps: (1) Weigh the raw materials from the brown sample bottle according to the following proportions: 15 parts 2-phenoxyethyl methacrylate, 3 parts zirconium dioxide PGME dispersion, 0.5 parts 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts N-phenylglycine, 20 parts 4-(ethoxy)bisphenol A dimethacrylate, 10 parts trimethylolpropane triacrylate, 12 parts N-vinylpyrrolidone, 25 parts BL038; (2) Prepare a holographic polymer-dispersed liquid crystal grating device according to the following steps: S1. Add 15 parts of 2-phenoxyethyl methacrylate to 3 parts of zirconium dioxide PGME dispersion, and mix by rotary evaporation at 60℃ for 30 min to form a writing monomer uniformly doped with zirconium dioxide nanoparticles; S2. The writing monomer uniformly doped with zirconium dioxide nanoparticles and the remaining raw materials are placed in an ultrasonic instrument and ultrasonically mixed for 30 minutes to obtain a homogeneous holographic polymer-dispersed liquid crystal material system. The shrinkage rate of the homogeneous holographic polymer-dispersed liquid crystal material system is tested by the volume-density method. S3. Under vacuum conditions, the homogenized holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell with a thickness of 5 μm. After pouring, the liquid crystal cell is moved together to a dark room and left to stand for 1 hour. Then, it is moved to an irradiation chamber with an angle of 60° and an irradiation power of 5 mW / cm². 2 A holographic polymer-dispersed liquid crystal grating device was obtained by interferoscopic exposure for 5 minutes in the interference light field of a dual-beam light source.

[0033] (3) Performance testing of holographic polymer-dispersed liquid crystal grating devices: Thermo-oxidative aging test: The prepared holographic polymer-dispersed liquid crystal grating device sample was placed in an oven and baked at 80°C for 200 hours; Before and after the thermo-oxidative aging test, the diffraction efficiency of the holographic grating device sample was tested using a grating diffraction efficiency tester. The haze of the holographic grating device sample was tested using a haze meter at 23±2℃ in accordance with GB 2410-2008 "Test Methods for Transmittance and Haze of Transparent Plastics".

[0034] Comparative Example 2 This comparative example provides a holographic polymer-dispersed liquid crystal material, a holographic polymer-dispersed liquid crystal grating device, and a method for preparing the same, specifically including the following steps: (1) Weigh the raw materials from the brown sample bottle according to the following proportions: 15 parts 2-phenoxyethyl methacrylate, 12 parts zirconium dioxide PGME dispersion, 0.5 parts 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts N-phenylglycine, 20 parts 4-(ethoxy)bisphenol A dimethacrylate, 10 parts trimethylolpropane triacrylate, 12 parts N-vinylpyrrolidone, 25 parts BL038; (2) Prepare a holographic polymer-dispersed liquid crystal grating device according to the following steps: S1. Add 15 parts of 2-phenoxyethyl methacrylate to 12 parts of zirconium dioxide PGME dispersion, and mix by rotary evaporation at 60℃ for 30 min to form a writing monomer uniformly doped with zirconium dioxide nanoparticles. S2. The writing monomer uniformly doped with zirconium dioxide nanoparticles and the remaining raw materials are placed in an ultrasonic instrument and ultrasonically mixed for 30 minutes to obtain a homogeneous holographic polymer-dispersed liquid crystal material system. The shrinkage rate of the homogeneous holographic polymer-dispersed liquid crystal material system is tested by the volume-density method. S3. Under vacuum conditions, the homogenized holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell with a thickness of 5 μm. After pouring, the liquid crystal cell is moved together to a dark room and left to stand for 1 hour. Then, it is moved to an irradiation chamber with an angle of 60° and an irradiation power of 5 mW / cm². 2 A holographic polymer-dispersed liquid crystal grating device was obtained by interferoscopic exposure for 5 minutes in the interference light field of a dual-beam light source.

[0035] (3) Performance testing of holographic polymer-dispersed liquid crystal grating devices: Thermo-oxidative aging test: The prepared holographic polymer-dispersed liquid crystal grating device sample was placed in an oven and baked at 80°C for 200 hours; Before and after the thermo-oxidative aging test, the diffraction efficiency of the holographic grating device sample was tested using a grating diffraction efficiency tester. The haze of the holographic grating device sample was tested using a haze meter at 23±2℃ in accordance with GB 2410-2008 "Test Methods for Transmittance and Haze of Transparent Plastics".

[0036] Comparative Example 3 This comparative example provides a holographic polymer-dispersed liquid crystal material, a holographic polymer-dispersed liquid crystal grating device, and a method for preparing the same, specifically including the following steps: (1) Weigh the raw materials from the brown sample bottle according to the following proportions: 0.5 parts 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts N-phenylglycine, 15 parts 2-phenoxyethyl methacrylate, 20 parts 4-(ethoxy)bisphenol A dimethacrylate, 10 parts trimethylolpropane triacrylate, 12 parts N-vinylpyrrolidone, 25 parts BL038. (2) Prepare a holographic polymer-dispersed liquid crystal grating device according to the following steps: S1. Place the weighed raw materials in an ultrasonic instrument and sonicate for 30 minutes to mix them evenly to obtain a homogeneous holographic polymer-dispersed liquid crystal material system. The shrinkage rate of the homogeneous holographic polymer-dispersed liquid crystal material system is tested by the volume-density method. S2. Under vacuum conditions, the homogenized holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell with a thickness of 5 μm. After pouring, the liquid crystal cell is moved together to a dark room and left to stand for 1 hour. Then, it is moved to an irradiation chamber with an angle of 60° and an irradiation power of 5 mW / cm². 2 A holographic polymer-dispersed liquid crystal grating device was obtained by interferoscopic exposure for 5 minutes in the interference light field of a dual-beam light source.

[0037] (3) Performance testing of holographic polymer-dispersed liquid crystal grating devices: Thermo-oxidative aging test: The prepared holographic polymer-dispersed liquid crystal grating device sample was placed in an oven and baked at 80°C for 200 hours; Before and after the thermo-oxidative aging test, the diffraction efficiency of the holographic grating device sample was tested using a grating diffraction efficiency tester. The haze of the holographic grating device sample was tested using a haze meter at 23±2℃ in accordance with GB 2410-2008 "Test Methods for Transmittance and Haze of Transparent Plastics".

[0038] Comparative Example 4 This embodiment provides a holographic polymer-dispersed liquid crystal material, a heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating device, and a method for preparing the same, specifically including the following steps: (1) Weigh the raw materials from the brown sample bottle according to the following proportions: 0.5 parts of 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts of N-phenylglycine, 15 parts of trifluoroethyl acrylate, 20 parts of 4-(ethoxy)bisphenol A dimethacrylate, 10 parts of trimethylolpropane triacrylate, 12 parts of N-vinylpyrrolidine, 5 parts of zirconium dioxide PGME dispersion, 25 parts of BL038; (2) Prepare a heat-resistant, oxidation-resistant holographic polymer-dispersed liquid crystal grating device according to the following steps: S1. Add 15 parts of trifluoroethyl acrylate to 5 parts of zirconium dioxide PGME dispersion, and mix by rotary evaporation at 60℃ for 30 min to form a writing monomer doped with zirconium dioxide nanoparticles; S2. The writing monomer doped with zirconium dioxide nanoparticles and the remaining raw materials were placed in an ultrasonic instrument and ultrasonically mixed for 30 minutes to obtain a homogeneous holographic polymer-dispersed liquid crystal material system. The shrinkage rate of the homogeneous holographic polymer-dispersed liquid crystal material system was tested by the volume-density method. S3. Under vacuum conditions, the homogenized holographic polymer-dispersed liquid crystal material system is poured into a liquid crystal cell with a thickness of 5 μm. After pouring, the liquid crystal cell is moved together to a dark room and left to stand for 1 hour. Then, it is moved to an irradiation chamber with an angle of 60° and an irradiation power of 5 mW / cm². 2 A holographic polymer-dispersed liquid crystal grating device resistant to heat and oxygen aging was obtained by interferoexposure in the interference light field of a dual-beam light source for 5 minutes.

[0039] (3) Performance testing of heat- and oxidation-resistant holographic polymer-dispersed liquid crystal grating devices: Thermo-oxidative aging test: The prepared heat-resistant and oxidation-resistant holographic polymer-dispersed liquid crystal grating device sample was placed in an oven and baked at 80°C for 200 hours. Before and after the thermo-oxidative aging test, the diffraction efficiency of the holographic grating device sample was tested using a grating diffraction efficiency tester. The haze of the holographic grating device sample was tested using a haze meter at 23±2℃ in accordance with GB 2410-2008 "Test Methods for Transmittance and Haze of Transparent Plastics".

[0040] In Examples 1-3, the holographic polymer-dispersed liquid crystal material is selected and combined from the first monomer, second monomer, and third monomer provided in this technical solution. In the preparation method, the first monomer within the specified ratio range is preferentially dispersed in the PGME dispersion of zirconium dioxide nanoparticles, and the solvent is removed by rotary evaporation to form a uniform and stable nanocomposite phase. In the holographic polymer-dispersed liquid crystal materials provided in Comparative Examples 1 and 2, the ratio of the first monomer to zirconium dioxide nanoparticles in the material system is not within the preferred ratio range of this technical solution. In the holographic polymer-dispersed liquid crystal material formed in Comparative Example 3, zirconium dioxide nanoparticles consistent with this technical solution are not added. In the holographic polymer-dispersed liquid crystal material formed in Comparative Example 4, at least one of the first monomer, second monomer, and third monomer is not selected from the range provided in this technical solution.

[0041] The following table shows the results of the shrinkage rate of the holographic polymer-dispersed liquid crystal materials and the grating devices prepared therefrom in Examples 1-3 and Comparative Examples 1-4, after mixing, as well as the haze change rate and diffraction efficiency change rate after thermo-oxidative aging tests:

[0042] By comparing the examples and comparative examples, it can be found that the shrinkage rate of the obtained holographic polymer-dispersed liquid crystal material system after mixing, as well as the haze change rate and diffraction efficiency change rate after thermo-oxidative aging test, indicate that: The results of Examples 1-3 show that when the zirconium dioxide nanoparticles, the first monomer, the second monomer, and the third monomer contained in the holographic polymer-dispersed liquid crystal material are selected and combined according to the monomer range and proportion range provided in this invention, the shrinkage rate of the holographic polymer-dispersed liquid crystal material system after mixing is controlled at a low level. This suggests that the zirconium dioxide nanoparticles, as a structural reinforcing phase, effectively reduce the microstructure deformation caused by polymer network shrinkage when they enter the holographic polymer-dispersed liquid crystal material system, improve the structural stability and dimensional stability of the polymer network, and help enhance the mechanical strength and shape retention ability of the grating device prepared by it, and improve its structural durability under thermo-oxidative aging environment. Meanwhile, after thermo-oxidative aging tests, the haze change rate and diffraction efficiency change rate of the grating devices prepared in Examples 1-3 were extremely small, and the absolute value of the diffraction efficiency remained above 58%. This indicates that the holographic polymer-dispersed liquid crystal material obtained in the examples and the heat-resistant oxidation-resistant grating devices prepared therefrom not only have good diffraction efficiency and haze performance, but also show less change in device performance under long-term thermo-oxidative aging conditions, i.e., better thermal stability and more stable overall performance. This results in better overall performance and a longer service life for the prepared holographic polymer-dispersed liquid crystal grating devices, and they are also suitable for a wider range of applications. Compared to Examples 1-3, in Comparative Example 1, the amount of zirconium dioxide nanoparticles incorporated into the first monomer in the provided holographic polymer-dispersed liquid crystal material system was insufficient, resulting in a higher shrinkage rate of the mixed holographic polymer-dispersed liquid crystal material system. This limited its effect on inhibiting polymer network shrinkage. Furthermore, the diffraction efficiency of the prepared grating devices decreased significantly after thermo-oxidative aging, indicating that insufficient incorporation of zirconium dioxide nanoparticles could not effectively maintain the stability of the grating structure under thermo-oxidative conditions. In Comparative Example 2, the excessive doping of zirconium dioxide nanoparticles in the first monomer of the holographic polymer-dispersed liquid crystal material system easily leads to uneven dispersion or particle aggregation, interfering with the photopolymerization process. This affects the regularity of the grating and the effective formation of refractive index modulation, thereby reducing the diffraction efficiency of the prepared grating device, increasing its haze, and ultimately affecting the application value of the grating device. In Comparative Example 3, the holographic polymer-dispersed liquid crystal material system does not incorporate zirconium dioxide nanoparticles. Without zirconium dioxide nanoparticles as a physical structure and optical enhancement phase, the holographic polymer-dispersed liquid crystal material system not only exhibits a large shrinkage rate after mixing, but also results in poor diffraction efficiency and haze of the prepared grating device. After thermo-oxidative aging, the structure of the grating device severely degrades, leading to a sharp increase in haze and loss of diffraction ability.In Comparative Example 4, the first monomer was trifluoroethyl acrylate, which did not follow the selection range of the first monomer in this technical solution. This not only resulted in poor dispersion performance of zirconium dioxide nanoparticles in the first monomer, leading to an increase in the haze of the fabricated grating device, but also resulted in poor synergistic effect between the first monomer, the second monomer, the third monomer, and the zirconium dioxide nanoparticles, leading to excessively low diffraction efficiency of the fabricated grating device.

[0043] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. Holographic polymer dispersed liquid crystal material, characterized in that, By mass percentage, comprising: Photoinitiator: 0.5-2 parts, Co-initiator: 2-5 parts, Writing monomer: 35-50 parts, Liquid crystal: 25-35 parts, Solvent: 5-10 parts, Zirconium dioxide nanoparticles: 5-10 parts; The zirconium dioxide nanoparticles are uniformly dispersed in the writing monomer, and the ratio of the parts of the writing monomer to the zirconium dioxide nanoparticles is greater than 1.5:1 and less than 5:1; the particle size of the zirconium dioxide nanoparticles is 5-40 nm.

2. The holographic polymer dispersed liquid crystal material according to claim 1, characterized in that, The writing monomer comprises: First monomer: 15-20 parts, Second monomer: 15-20 parts, Third monomer: 5-10 parts; The first monomer is selected from one or more of cyclohexyl methacrylate, lauryl methacrylate, isodecyl methacrylate, isooctyl acrylate, butyl acrylate, methyl acrylate, benzyl methacrylate, 2-phenoxyethyl methacrylate, dicyclopentane methacrylate, and isobornyl methacrylate; The second monomer is selected from one or more of 4(ethoxy) bisphenol A dimethacrylate, triethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, and ethylene glycol dimethacrylate; The third monomer is selected from one or two of pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, and hyperbranched acrylate.

3. The holographic polymer dispersed liquid crystal material according to claim 1, wherein, The photoinitiator is selected from one or more of rose Bengal light, diiodofluorescein, methylene blue, TPO, rhodamine 6G, 3,3'-carbonyl bis(7-diethylaminocoumarin), and initiator 184.

4. The holographic polymer dispersed liquid crystal material of claim 1, wherein, The co-initiator is selected from one or more of benzoyl peroxide and N-phenyl glycine.

5. The holographic polymer dispersed liquid crystal material of claim 1, wherein, The liquid crystal is selected from one or more of BL038, GXP-6003, BL087, and TL213.

6. The holographic polymer dispersed liquid crystal material of claim 1, wherein The solvent is selected from one or more of N-vinyl pyrrolidone, chloroform, tetrahydrofuran, and toluene.

7. A holographic polymer dispersed liquid crystal grating device, characterized in that, Prepared from the holographic polymer dispersed liquid crystal material of any one of claims 1-6.

8. A method of producing a holographic polymer dispersed liquid crystal grating device, characterized by, Comprising the following steps: S1. Weighing the holographic polymer dispersed liquid crystal material according to any one of claims 1-6 in proportion, wherein the zirconium dioxide nanoparticles are provided by a PGME dispersion of zirconium dioxide; uniformly mixing the PGME dispersion of zirconium dioxide and the writing monomer in proportion, and forming a uniformly doped writing monomer with zirconium dioxide nanoparticles by a rotary evaporator; S2. Uniformly mixing the uniformly doped writing monomer with zirconium dioxide nanoparticles with other materials in the holographic polymer dispersed liquid crystal material to obtain a uniformly mixed holographic polymer dispersed liquid crystal material system; S3. Filling the uniformly mixed holographic polymer dispersed liquid crystal material system into a liquid crystal cell, standing in a dark room, and then interference exposure under the interference light field of a double-beam light source to obtain a holographic polymer dispersed liquid crystal grating device; In the S1, the writing monomer is the first monomer, and / or the second monomer, and / or the third monomer.

9. The production method according to claim 8, characterized by, In the S1, the uniform doped zirconium dioxide nanoparticles writing monomer is formed by the rotary evaporator, and the rotary evaporation temperature is 40-60℃.

10. The preparation method according to claim 8, characterized in that, In the S2, the thickness of the liquid crystal cell is 5-10 μm; the standing time of the liquid crystal cell in the dark room is 1-2 h; the time of the interference exposure is 1-5 min; the included angle of the double-beam light source is 35-60°; the irradiation power of the double-beam light source is 4-6 mW / cm 2 .

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