Optical monomer, holographic recording medium, preparation method and related device

Abstract

The invention discloses an optical monomer, a holographic recording medium, a preparation method and a related device, the structural general formula of the optical monomer is as shown in G1 and G2, the monomer is high in refractive index, the preparation method is simple, further, the optical monomer with the structure is introduced into the photopolymer type holographic recording medium, and the photopolymer type holographic recording medium is prepared. The invention further provides a preparation method of the holographic recording medium, a volume holographic grating containing the holographic recording medium, a holographic optical element containing the holographic recording medium and an optical device containing the holographic recording medium.

Description

Technical Field

[0001] This application relates to the field of holographic materials technology, and in particular to an optical monomer, a holographic recording medium, a preparation method, and related apparatus. Background Technology

[0002] Photopolymers used to fabricate holographic recording media typically include components such as photosensitive dyes, initiators, chain transfer agents, writing monomers, film-forming resins, and plasticizers. Photopolymers utilize light to polymerize the writing monomers, which then combine with the film-forming resin to form a refractive index-modulated phase-type holographic grating, thus achieving holographic recording. Specifically, when the writing monomers located in the coherent bright region are consumed and their concentration decreases, unreacted writing monomers located in the coherent dark region rapidly migrate to the coherent bright region, squeezing the film-forming resin from the bright region into the dark region. Ultimately, this results in the refractive index of the coherent bright region approaching that of the writing monomers, and the refractive index of the coherent dark region approaching that of the film-forming resin, thereby forming a refractive index-modulated phase-type volume holographic grating.

[0003] However, existing photopolymers typically exhibit significant volume shrinkage after exposure, causing the recording grating to shift and resulting in a discrepancy between the resulting recording grating and the theoretical design. Although adding dendritic monomers can effectively reduce the volume shrinkage of photopolymers, there are currently few available dendritic monomers, and their refractive index is usually below 1.65. Consequently, the refractive index modulation of the resulting recording grating is low (Δn < 0.07), further reducing the recording grating's ability to control incident light, resulting in excessive light energy loss, low diffraction efficiency of optical devices, and unclear imaging. Summary of the Invention

[0004] This application aims to provide an optical monomer, a holographic recording medium, a preparation method, and related apparatus. The optical monomer has a high refractive index to solve the problem of volume shrinkage of the photopolymer holographic recording medium after exposure, which causes the recording grating to shift, thereby improving the holographic performance of the holographic recording grating.

[0005] In a first aspect, this application provides an optical unit, the general structural formula of which is shown in any of the following: ; ; Where R1 represents R2 represents , , R3 represents H, C1-C4 alkyl, R4 represents hydrogen or methyl, R5 represents C1-C4 alkyl, n=1~10, and n is a positive integer.

[0006] As can be seen from the above technical solution, the optical monomer provided in the first aspect of this application is a dendritic monomer with multiple aromatic thioacetals. The high electronic polarizability and molecular packing effect of sulfur atoms have a significant impact on the refractive index of the monomer. Moreover, based on the presence of multiple benzene rings, the conjugation effect superimposed on the polarization of sulfur, giving the monomer a high refractive index, which is greater than 1.70 and less than 1.75.

[0007] Secondly, this application provides a method for preparing the aforementioned optical monomer, comprising: Compound M1 and an acid reagent were dissolved in an organic solvent. After performing the first treatment operation, compound M2 was added to react and compound P1 was obtained. The compound P1 was reduced to obtain compound P2; Compound M3 and an acid reagent were dissolved in an organic solvent. After performing the first treatment operation, compound P2 was added to react and compound P3 was obtained. The first processing operation includes at least a heating operation and a stirring operation, and the compound M1 is selected from compounds with the following structural formulas: , The structural formula of compound M2 is shown below: , The structural formula of compound P1 is shown below: , , The structural formula of compound P2 is shown below: , , The general structural formula of compound M3 is shown below. , The general structural formula of compound P3 is shown below: , And R3 represents H, C1-C4 alkyl, R5 represents C1-C4 alkyl.

[0008] As can be seen from the above technical solutions, the preparation method of the optical monomer provided in the second aspect of this application is simple in synthesis, has a short route, requires inexpensive and readily available raw materials, and is easy to scale up for production.

[0009] Thirdly, this application provides a photopolymer-type holographic recording medium, the raw material of which comprises the following components a) Component h); Component a) A compound having multiple isocyanate reactive functional groups; Component b) Polyisocyanate group compounds; Component c) Optical monomers; Component d) Polymerizable monomers; Component e) Photosensitive initiation system; Component f) Chain transfer agent; Component g) optionally a catalyst; Component h) Optional additives; The optical monomer is at least one of the aforementioned optical monomers G1 or G2.

[0010] As can be seen from the above technical solution, this application provides a photopolymer-type holographic recording medium containing the aforementioned optical monomers. By introducing high-refractive-index, dendritic optical monomers into the photopolymer-type holographic recording medium, not only can the volume shrinkage of the photopolymer-type holographic recording medium during exposure be effectively reduced, but also, due to the high refractive index of the monomers, the refractive index difference between the recording monomers and the film-forming resin can be effectively increased, thereby obtaining a photopolymer-type holographic recording medium with excellent properties such as high sensitivity and high diffraction efficiency. Specifically, the diffraction efficiency of the photopolymer-type holographic recording medium is greater than 95%, the sensitivity is greater than 100 cm / mJ, and the shrinkage rate is less than 0.3%.

[0011] Fourthly, this application provides a method for preparing the aforementioned photopolymer-type holographic recording medium, comprising: Weigh the compound having multiple isocyanate reactive functional groups, the polyisocyanate group compound, the optical monomer, the polymerizable monomer, the photoinitiator system, the chain transfer agent, the catalyst and the additive into a container, and stir thoroughly until dissolved to form a mixed solution; The mixture solution is filtered using a filter membrane to obtain a first solution; The first solution is coated onto a substrate and dried to obtain the photopolymer holographic recording medium.

[0012] As can be seen from the above technical solutions, the preparation method of the photopolymer-based holographic recording medium provided in this application is simple to operate and low in cost. It can ensure the uniform dispersion of each component, improve the light transmittance and refractive index modulation of the holographic recording medium, thereby enhancing the resolution and diffraction efficiency of the hologram. In addition, the filtration step can effectively remove impurities, reduce light scattering, and improve the storage stability and imaging quality of the holographic medium.

[0013] Fifthly, this application provides a volume holographic recording grating, the raw material of which includes the photopolymer type holographic recording medium as described above.

[0014] Sixthly, this application provides a holographic optical element, the raw material of which includes the aforementioned photopolymer-type holographic recording medium.

[0015] In a seventh aspect, this application provides an optical device including the holographic optical element as described above.

[0016] As can be seen from the above technical solutions, this application also provides related devices (such as volume holographic recording gratings, holographic optical elements and optical devices) made using the above-mentioned photopolymer holographic recording medium, based on the excellent properties of the photopolymer holographic recording medium, such as sensitivity greater than 100 cm / mJ, shrinkage rate less than 0.3% and recording grating diffraction efficiency greater than 95%.

[0017] Furthermore, based on a sensitivity greater than 100 cm / mJ, only extremely low exposure energy is required to form a stable grating, which can shorten exposure time, reduce laser power requirements, increase recording speed, and reduce energy consumption efficiency, making it suitable for dynamic recording and low-power devices. With a shrinkage rate of less than 0.3%, the optical uniformity of the photopolymer holographic recording medium can be maintained, optical distortion reduced, and grating structure ensured stability, thereby extending the lifetime of holographic storage. With a diffraction efficiency greater than 95%, it means that almost all incident light energy is diffracted to the target direction by the grating, thus reducing light energy loss and resulting in a clearer image. Therefore, target devices (such as volume holographic recording gratings, holographic optical elements, and optical devices) fabricated using photopolymer holographic recording media have optical properties such as fast recording speed and clear imaging. Attached Figure Description

[0018] Figure 1 The exposure characteristic curves of photopolymer holographic recording media 6-1, 6-2, 6-4 and 6-5 in Embodiment 6 of this application are shown. Figure 2 The exposure characteristic curves of the photopolymer holographic recording media of Comparative Example 1 and Comparative Example 2 of this application are shown. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0021] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0023] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] In recent years, photopolymer-based holographic recording media have been considered the most promising holographic recording materials due to their high sensitivity, high diffraction efficiency, and simple manufacturing process. It should be understood that photopolymer-based holographic recording media utilize light to polymerize writing monomers, which then combine with a film-forming resin to form a refractive index-modulated phase-type holographic grating to achieve holographic recording. Specifically, when the writing monomers in the coherent bright region are consumed and their concentration decreases, unreacted writing monomers in the coherent dark region rapidly migrate to the coherent bright region, squeezing the film-forming resin from the bright region into the dark region. Ultimately, this results in the refractive index of the bright region approaching that of the writing monomers, and the refractive index of the dark region approaching that of the film-forming resin, thus forming a refractive index-modulated phase-type volume holographic grating. Therefore, photopolymer-based holographic recording media with superior performance typically require a lower refractive index for the film-forming resin and a higher refractive index for the writing monomers to increase the refractive index difference between them.

[0025] However, existing photopolymer holographic recording media exhibit significant volume shrinkage after exposure, causing the holographic recording grating to shift. This results in the grating obtained after exposure not matching the theoretical design, affecting the clarity of image reproduction.

[0026] Currently, the common approach to reduce the volume shrinkage of photopolymers is to add dendritic monomers. However, there are not many dendritic monomers available, and their refractive index is usually below 1.60. This results in a small difference in refractive index between the writing monomer and the film-forming resin (usually 0.1~0.2). Consequently, the refractive index modulation of the holographic recording grating is low (Δn<0.07), which further reduces the grating's ability to control incident light, leads to excessive light energy loss, and causes low diffraction efficiency and unclear imaging of optical devices.

[0027] Based on this, this application provides an optical monomer as a component of a writing monomer, the general structural formula of which is shown in any of the following: , , Where R1 represents R2 represents , or R3 represents H, C1-C4 alkyl, R4 represents hydrogen or methyl, R5 represents C1-C4 alkyl, n=1~10, and n is a positive integer.

[0028] It is understood that the optical monomer provided in this application is a dendritic monomer with aromatic thioal as the central starting point and the molecular chain extending into three-dimensional space. Due to the large steric hindrance of the branching unit and the high space occupancy rate, a dense network can be formed without significantly reducing the intermolecular distance during the polymerization process, thereby suppressing the magnitude of volume shrinkage during the polymerization process.

[0029] It is also understandable that the optical monomer, due to its aromatic thioacetal structure, has a significant impact on its refractive index due to the high electronic polarizability and molecular packing effect of sulfur atoms. Simultaneously, the conjugation effect of multiple benzene rings, combined with the polarization effect of sulfur, further increases the refractive index of the monomer, resulting in an extremely high refractive index for the entire monomer molecule, greater than 1.70 and less than 1.75. This effectively matches common photosensitive resin systems, reducing light scattering loss during holographic recording and improving diffraction efficiency. Furthermore, the higher refractive index helps enhance the optical anisotropy of the material, optimizing the resolution and storage capacity of the hologram.

[0030] In some specific examples, the optical monomer can be a compound having the following structural formula: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , .

[0031] In some embodiments, the optical monomer can also be a compound having the following general structural formula: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , where n = 1 to 10, and n is a positive integer.

[0032] In this embodiment, the optical monomer is dendritic, which can significantly reduce the volume shrinkage of the photopolymer holographic recording medium during the polymerization process, so that the related devices made from the photopolymer holographic recording medium can maintain optical uniformity and reduce optical distortion.

[0033] This application also provides a method for preparing the above-mentioned optical monomer, including: Step S1: Dissolve compound M1 and an acid reagent in an organic solvent, perform the first treatment operation, then add compound M2 to react and obtain compound P1. The first treatment operation includes at least heating and stirring. Compound M1 is selected from compounds with the following structural formula: or The compound, and the structural formula of compound M2 is as follows: Therefore, the structural formula of the compound P1 obtained after the reaction is: or .

[0034] It is understandable that in step S1, the thiol (i.e., compound M1), after being pre-activated by the acid reagent, exhibits stronger nucleophilicity and further undergoes a thioacetalization reaction with the aldehyde (i.e., compound M2) to generate a thioacetal (i.e., compound P1). This step typically requires controlling the addition rate of the aldehyde (i.e., compound M2) to avoid direct contact between the aldehyde (i.e., compound M2) and the high-concentration acid reagent, which could trigger a self-condensation side reaction and reduce the formation of byproducts. Therefore, compound M2 needs to be slowly added dropwise to the reaction system. Specifically, compound M2 can also be dissolved in an organic solvent and then slowly added dropwise to the reaction system.

[0035] The first processing operation includes at least a heating operation and a stirring operation. The heating operation and the stirring operation can be performed simultaneously or separately. For example, the heating operation can be performed while stirring, or the stirring operation can be performed for a period of time before the heating operation is performed. This application does not limit the specific operation.

[0036] In some embodiments, the thioacetalization reaction is performed at 20°C-80°C for 0.5-36 hours with optimal results. This is understandable because, on the one hand, excessively high reaction temperatures may trigger oxidation side reactions of the thiol (i.e., compound M1), leading to decreased reaction selectivity; conversely, excessively low temperatures result in low molecular collision frequencies, significantly reduced reaction rates, and prolonged reaction times. On the other hand, the reaction temperature is also related to the selection of the reaction substrate and solvent, such as the stability of the reaction substrate (e.g., compound M1), the boiling point of the solvent, or the stability of the reaction product (e.g., compound P1).

[0037] In some specific examples, the molar ratio of compound M1, acid reagent, and compound M2 is (4–4.8):(2–4):1. Typical, but not limiting, the molar ratio of compound M1, acid reagent, and compound M2 can be, for example, 4:2:1, 4:4:1, 4.8:2:1, 4.8:4:1, 4.2:3:1, 4.5:3:1, 4.8:3:1, etc.

[0038] Acid reagents include, but are not limited to, one or more of the following: p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, camphorsulfonic acid, naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, sulfosalicylic acid, citric acid, acetic acid, formic acid, phosphoric acid, anhydrous hydrogen peroxide, tetrafluoroboric acid, trifluoroacetic acid, pentafluoroacetic acid, heptafluoropropionic acid, and phosphoric acid.

[0039] It should be understood that in the thioacetal reaction, the acid reagent has the functions of activating thiols (i.e., compound M1) and aldehydes (i.e., compound M2), promoting the reaction process, and inhibiting the occurrence of side reactions (such as thiols oxidation reaction and aldehyde self-condensation reaction).

[0040] In addition, organic solvents include, but are not limited to, one or more of methanol, ethanol, petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, benzene, toluene, N,N-dimethylformamide, dimethyl sulfoxide, dimethoxyethane, 1,4-dioxane, n-hexane, cyclohexane, and chloroform.

[0041] In some embodiments, step S1 uses one or more of dichloromethane, trichloromethane, and ethyl acetate as the reaction solvent, which results in better reaction performance.

[0042] It is understood that the organic solvent should ensure the dissolution of the reaction substrates (i.e., compounds M1 and M2) to allow them to fully dissolve in the reaction system, forming a homogeneous reaction system, thereby promoting molecular collisions between compounds M1 and M2 to generate new compounds. It should be noted that the solvents described above are merely illustrative, and the solvents that can be used in this application are not limited to these.

[0043] For example, 4 equivalents of compound M1 and 2-4 equivalents of p-toluenesulfonic acid were dissolved in dichloromethane. The reaction system was heated to 20-80°C. 1 equivalent of compound M2 was dissolved in dichloromethane and slowly added dropwise to the above reaction system. The reaction was continued with stirring for 0.5-36 h. After the reaction was completed, sufficient triethylamine was added to quench the reaction, and the organic phase was extracted three times. The organic phase was dried with anhydrous sodium sulfate, excess solvent was removed by rotary evaporation, and compound P1 was obtained by column chromatography.

[0044] It is also understood that in step S1, the order of adding thiol (i.e., compound M1) and aldehyde (i.e., compound M2) can be changed. In other words, the aldehyde (i.e., compound M2) and acid reagent can be dissolved in an organic solvent first, and then the thiol (i.e., compound M1) can be added. With the other conditions unchanged, compound P1 can also be obtained. This application does not impose any restrictions on this.

[0045] Step S2: Compound P1 is reduced to obtain compound P2, wherein the structural formula of compound P2 is as follows: or .

[0046] It is understandable that step S2 reduces the carboxylic acid group of compound P1 to an aldehyde group to obtain compound P2, which provides the material basis for further thioacetalization of compound P2 in the next step S3.

[0047] In some embodiments, compound P1 is first acylated to obtain an acylated product, and then the acylated product is reduced to obtain compound P2, which can further improve the yield of compound P2. This is because the reducing activity of the acylated product (e.g., acyl chloride) is much higher than that of carboxylic acid. It can be selectively reduced to aldehyde under mild conditions (e.g., using reducing agents such as LiAlH(OtBu)3 or DIBAL-H, reacting at -78~0℃). This not only protects the thioacetal structure from being destroyed, but also avoids excessive reduction.

[0048] In some implementations, step S2 includes the following steps: Step S201: Dissolve compound P1 in the first solvent, add thionyl chloride, and perform the first treatment operation to obtain intermediate I.

[0049] Step S202: Under hydrogen atmosphere, intermediate I, Pd / BaSO4 catalyst and quinoline-S inhibitor are dissolved in xylene and reacted to obtain compound P2.

[0050] In some implementations, step S201 typically involves adding a catalytic amount of DMF to activate the chlorinating agent, thereby accelerating the reaction process of converting carboxylic acid groups into acyl chloride groups and significantly improving the generation efficiency of acyl chlorides.

[0051] It should be noted that the organic solvent includes the first solvent, which should be selected as a solvent that does not react with the chlorinating reagent and does not destroy the thioacetal structure. Specifically, the first solvent includes, but is not limited to, one or more of dichloromethane, petroleum ether, n-hexane, cyclohexane, benzene, toluene, and chloroform.

[0052] It should also be noted that the acylation reaction of carboxylic acids usually produces irritating and corrosive toxic gases such as sulfur dioxide and hydrogen chloride. Both sulfur dioxide and hydrogen chloride are air pollutants, and direct emission of these gases will pollute the air. Therefore, a gas absorption device is required in the experiment to absorb sulfur dioxide and hydrogen chloride gases. For example, a dilute NaOH solution that is connected to the gas flow is required.

[0053] Furthermore, since acyl chloride is an exothermic reaction, thionyl chloride needs to be added slowly to avoid a rapid increase in system temperature, which would reduce reaction efficiency. Excessive temperature can also exacerbate the hydrolysis of the thioacetal structure, further reducing yield. In addition, rapid addition can lead to excessively high concentrations of sulfur dioxide and hydrogen chloride gas in localized areas, generating numerous bubbles and posing risks of material spillage and safety hazards.

[0054] In some embodiments, the volume ratio of the first solvent to the mass of compound P2 is 5, in mL / g, which results in a better reduction effect.

[0055] In some embodiments, the volume ratio of xylene solvent to the mass of intermediate I is 5, in mL / g, which results in a better reduction effect.

[0056] In some embodiments, the mass of the Pd / BaSO4 catalyst is 10 wt% to 20 wt% of the mass of intermediate I, resulting in better reduction performance.

[0057] In some embodiments, the mass of the quinoline-S inhibitor is 1 wt% to 2 wt% of the Pd / BaSO4 catalyst, resulting in better reduction performance.

[0058] For example, in a dry round-bottom flask, one equivalent of compound P1 is dissolved in toluene and a reflux condenser is installed. The upper end of the condenser is connected to a gas absorption device (dilute NaOH solution to absorb sulfur dioxide and hydrogen chloride tail gas). In a fume hood, 8-12 equivalents of thionyl chloride are slowly added dropwise through a constant-pressure dropping funnel. After the addition is complete, a few drops of DMF are added to the reaction system, and the mixture is heated to 60-70°C and refluxed for 1-2 hours until no more gas is emitted. After the reaction is complete, excess thionyl chloride and toluene solvent are evaporated using a rotary evaporator in a fume hood to obtain a colorless or pale yellow crude product (i.e., intermediate I).

[0059] Add the above crude product (i.e., intermediate I), Pd / BaSO4 catalyst (the mass of Pd / BaSO4 catalyst used is 10 wt%~20 wt% of the crude product), quinoline-S inhibitor (the mass of quinoline-S inhibitor used is 1 wt%~2 wt% of the Pd / BaSO4 catalyst), and xylene (the volume ratio of xylene solvent used to the crude product is 5, in mL / g) to a hydrogenation flask. Evacuate the system, then replace the air with hydrogen, repeating this process 2-3 times, maintaining the reaction system at an appropriate hydrogen pressure (usually atmospheric pressure or slightly above atmospheric pressure), and stir at 90-120°C. The reaction endpoint is determined by monitoring the amount of hydrogen absorbed. Stop the reaction when the theoretical amount of hydrogen has been absorbed. After the reaction solution cooled, the reaction solution was filtered and the catalyst was recovered. The filtrate was first washed with water to remove HCl, then washed with dilute acid to remove quinoline, and finally washed with saturated NaHCO3 solution and water. The organic phase obtained after extraction was dried with anhydrous MgSO4 or Na2SO4, and the xylene solvent was removed by vacuum distillation. The compound P2 was obtained by column chromatography.

[0060] Step S3: Dissolve compound M3 and acid reagent in an organic solvent, perform the first treatment operation, add compound P2 to react, and obtain compound P3.

[0061] The general structural formula of compound M3 is shown below. , The general structural formula of compound P3 is shown below: , And R3 represents H, C1-C4 alkyl, R5 represents C1-C4 alkyl.

[0062] It is understood that step S3 and step S1 have the same reaction type and reaction principle, only the reaction substrates (i.e., compound M3 and compound P2) are different. For relevant details, please refer to step S1 above, and it will not be repeated here.

[0063] In some embodiments, the molar ratio of compound M3, acid reagent, and compound P2 is (8–9.6):(4–8):1. Typical, but not limiting, the molar ratio of compound M1, acid reagent, and compound M2 may be, for example, 8:4:1, 8:8:1, 8:4.5:1, 9.6:4:1, 9.6:8:1, 9.6:4.5:1, 8.5:4:1, 8.5:8:1, 8.5:4.5:1, etc.

[0064] In this embodiment, the preparation method of the aforementioned optical monomer provided by this application has the advantages of simple synthesis method, short route, and cheap and readily available raw materials.

[0065] The general formula for the prepared structure is G1, and R2 represents... In addition to steps S1 to S3, the optical unit also includes the following steps: Step S401: Dissolve compound P3 and an acid-binding agent in an organic solvent, and add compound M4 to react, yielding optical monomer G1. Compound M4 is acryloyl chloride or methacryloyl chloride.

[0066] Steps S1 to S3 are as described above and will not be repeated here. It can be understood that in step S401, compound P3 is activated by the acid-binding agent to generate a more reactive alkoxy group, thereby enhancing nucleophilicity and further promoting the substitution reaction between compound P3 and compound M4, ultimately yielding the optical monomer G1. In some specific examples, the reaction is usually controlled at 0°C (i.e., in an ice bath), and compound M4 is added dropwise to the mixed solution of compound P3 and the acid-binding agent at 0°C to avoid local overheating or excessive concentration leading to side reactions. A reaction time of 0.5 h to 3 h typically yields optimal reaction results.

[0067] Among them, acid-binding agents include, but are not limited to, triethylamine, pyridine, N,N Diisopropylethylamine, 4 One or more of dimethylaminopyridine, tetrabutylammonium bromide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium acetate, sodium hydroxide, potassium hydroxide, calcium oxide, and potassium tert-butoxide.

[0068] It should be further understood that, because compound M4 (i.e., acryloyl chloride or methacryloyl chloride) is a highly reactive acylating agent, it is prone to side reactions, leading to a reduction in the amount actually participating in the target reaction. Therefore, it is usually necessary to use an excess to compensate for the consumption by side reactions and ensure that sufficient acryloyl chloride reacts with the substrate. In addition, since the acid-binding agent needs to provide basic conditions to promote the deprotonation of compound P3 and neutralize the hydrochloric acid generated in the reaction to prevent the decomposition of the substrate or product, the acid-binding agent is also usually required to be used in excess. Specifically, in some examples, the molar ratio of compound P3, the acid-binding agent, and compound M4 is 1:(2-4):(1-3). Typical, but not limiting, the molar ratio of compound P3, the acid-binding agent, and compound M4 can be, for example, 1:2:1, 1:2:2, 1:2:3, 1:3:1, 1:3:2, 1:3:3, 1:4:1, 1:4:2, 1:4:3, 1:3.5:2.5, etc.

[0069] In some specific examples, the reaction is more effective when the reaction solvent in step S401 is any one of dichloromethane, trichloromethane, and ethyl acetate.

[0070] For example, 1 equivalent of compound P3 and 2-4 equivalents of triethylamine were dissolved in dichloromethane under ice bath conditions. After stirring for 10 min, 1-3 equivalents of acryloyl chloride or methacryloyl chloride were added dropwise to the mixed solution of compound P3 and triethylamine at 0 °C. After the reaction was complete, dilute hydrochloric acid was added dropwise to remove excess acryloyl chloride or methacryloyl chloride. The mixture was then washed successively with saturated NaCl solution, saturated NaHCO3 solution, and deionized water. The organic phase was dried over anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. The optical monomer G1 was obtained by column chromatography.

[0071] It can be understood that the general structural formula of the optical unit G1 obtained through step S401 is, for example: or And R3 represents H, C1-C4 alkyl, R5 represents C1-C4 alkyl.

[0072] The general formula for the prepared structure is G1, and R2 represents... or In addition to steps S1 to S3, the optical unit also includes the following steps: Step S402: Dissolve compound P3 in a second solvent, perform a second treatment operation, add a deprotonating agent, and after a period of time, add compound M5 to obtain optical monomer G1. The second treatment operation includes at least a cooling operation and a stirring operation, and compound M5 is 3-bromo-1-propene or 3-bromo-1-propyne.

[0073] Steps S1 to S3 are as described above and will not be repeated here. It can be understood that the deprotonating agent deprotonates the hydroxyl group in compound P3, forming a more reactive oxonium intermediate II. Oxonium intermediate II further attacks the carbon atom directly bonded to the halogen atom in the brominated hydrocarbon (i.e., compound M5), and the bromide ion leaves as a leaving group, thus yielding R2. or The optical monomer G1. It can also be understood that step S402 converts compound P3 into the more reactive oxygen anion intermediate II, thereby making the reaction substrate (i.e., compound P3) more active and accelerating the reaction efficiency.

[0074] The second processing operation includes at least a cooling operation and a stirring operation. The cooling operation and the stirring operation can be performed simultaneously or separately. For example, the cooling operation can be performed while stirring, or the stirring operation can be performed for a period of time before the cooling operation is performed. This application does not limit the operation.

[0075] It should be noted that deprotonating agents include, but are not limited to, one or more of organometallic bases, metal amino compounds, metal alkoxides and metal hydrides, inorganic bases and organic bases.

[0076] Organometallic bases include, but are not limited to, alkyllithium reagents, aryllithium reagents, and aminolithium reagents. Typically, when using organometallic bases and metal amino compounds, the reaction must be carried out under anhydrous and oxygen-free conditions, and they are usually added dropwise to the reaction system at -78°C. Further, alkyllithium reagents include at least n-butyllithium and tert-butyllithium, aryllithium reagents include at least phenyllithium, and aminolithium reagents include at least diisopropylaminolithium and hexamethyldisilaminolithium. Metal amino compounds include, but are not limited to, sodium amino, potassium amino, and bis(trimethylsilyl)aminosodium. Metal alkoxides include, but are not limited to, sodium methoxide, sodium ethoxide, potassium tert-butoxide, and sodium tert-butoxide; metal hydrides include, but are not limited to, sodium hydride and potassium hydride; inorganic bases include, but are not limited to, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, and potassium phosphate; and organic bases include, but are not limited to, triethylamine, 1,5-diazabicyclo[4.3.0]non-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, and tetramethylsilyltrifluoromethanesulfonate.

[0077] It should be further understood that when using deprotonating agents to deprotonate, it is necessary to determine whether the reaction needs to be carried out in an inert environment based on factors such as the different types of deprotonating agents and the properties of the reaction substrate. For example, inert gas protection can be used, including but not limited to nitrogen and argon. In other words, those skilled in the art can provide inert protection for the reaction according to actual needs, and this application does not limit it.

[0078] It should be noted that deprotonation reactions typically need to be carried out at low temperatures (-80℃ to 0℃). The choice of reaction temperature depends on the selection of the deprotonating agent, the stability and activity of the reaction substrate, and the melting point of the reaction solvent. After the deprotonation reaction is completed, the temperature can be raised according to actual needs (e.g., the activity of the reaction substrate, the reaction rate, etc.). Specifically, when organometallic bases and metal amino compounds (e.g., n-butyllithium) are used as deprotonating agents, the deprotonation reaction usually needs to be carried out at -30 to -80℃ in an inert environment to obtain better reaction results, suppress the generation of side reactions, and improve the regioselectivity of the reaction. When metal alkoxides and metal hydrides (e.g., sodium hydride, sodium methoxide, etc.) are used as deprotonating agents, the deprotonation reaction is usually carried out at 0℃ (i.e., in an ice bath), and the reaction time is usually 0.5 h to 10 h. It can be understood that the reaction time is related to the amount of deprotonating agent and the activity of the reaction substrate, etc., which are not limited in this application.

[0079] It should also be noted that the deprotonating agent should be added to the reaction system in batches and slowly to avoid a violent reaction that could cause injury to the sprayed material and personnel. Furthermore, protonated solvents such as methanol, ethanol, isopropanol, acetic acid, and water should be avoided in the deprotonation reaction. Therefore, it can also be understood that the aforementioned organic solvents include a second solvent, which at least does not include protonated solvents. The second solvent can be, for example, one or more of petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, benzene, toluene, N,N-dimethylformamide, dimethyl sulfoxide, dimethoxyethane, and 1,4-dioxane.

[0080] In some specific examples, the molar ratio of compound P3, the deprotonating agent, and compound M5 is 1:(1-2):(1-2).

[0081] Typical, but not limiting, molar ratios of compound P3, the deprotonating agent, and compound M5 can be, for example, 1:1:1, 1:1.2:1, 1:1.5:1, 1:2:1, 1:1:1.2, 1:1:1.5, 1:1:2, 1:2:2, 1:1.2:1.2, 1:1.5:1.3, 1:1.3:1.5, and 1:1.5:1.5, etc.

[0082] For example, under ice bath conditions, 1 equivalent of compound P3 was dissolved in tetrahydrofuran, and 1-2 equivalents of deprotonating agent were slowly added. After stirring for 0.5-10 h, 1-2 equivalents of 3-bromo-1-propene or 3-bromo-1-propyne were added dropwise to the reaction system. After the addition was completed, stirring was continued for 0.5-10 h. After the reaction was completed, dilute hydrochloric acid was slowly added dropwise to quench the reaction, excess solvent was removed by rotary evaporation, and the optical monomer G1 was obtained by column chromatography.

[0083] It can be understood that the general structural formula of the optical unit G1 obtained through step S402 is, for example: , , or And R3 represents H, C1-C4 alkyl, R5 represents C1-C4 alkyl.

[0084] In addition to steps S1 to S3, the preparation of an optical monomer with the general structural formula G2 also includes the following steps: Step S5: Dissolve compound P3 in a second solvent, perform the second treatment operation, add a deprotonating agent, and after a period of time, add compound M6 to obtain compound P4.

[0085] The general structural formula of compound M6 is as follows: The general structural formula of compound P4 is: , n is a positive integer, and n = 0 to 10.

[0086] The contents of steps S1 to S3 are as described above and will not be repeated here. It can be understood that the reaction principle of step S5 is similar to that of step S3, both of which involve converting compound P3 into oxonium intermediate II and then carrying out a substitution reaction. The main difference lies in the different reaction substrates (i.e., using compound M5 or compound M6). Therefore, the relevant contents can be referred to step S3 and will not be repeated here.

[0087] In some specific examples, the molar ratio of compound P3, the deprotonating agent, and compound M6 is 1:(1-2):(1-2). Typical, but not limiting, the molar ratio of compound P3, the deprotonating agent, and compound M6 can be, for example, 1:1:1, 1:1.2:1, 1:1.5:1, 1:2:1, 1:1:1.2, 1:1:1.5, 1:1:2, 1:2:2, 1:1.2:1.2, 1:1.5:1.3, 1:1.3:1.5, and 1:1.5:1.5, etc.

[0088] For example, one equivalent of compound P3 was dissolved in tetrahydrofuran, and one to two equivalents of sodium hydride were slowly added at 0°C. After stirring for 0.5 to 10 h, one to two equivalents of compound M6 were added dropwise to the reaction system. After the addition was complete, the reaction was continued for another 0.5 to 10 h. After the reaction was complete, dilute hydrochloric acid was slowly added dropwise to quench the reaction, excess solvent was removed by rotary evaporation, and compound P4 was obtained by column chromatography.

[0089] Specifically, the general formula for the prepared structure is G2, and R2 represents... The optical unit, in addition to steps S1 to S3 and step S5, also includes the following steps: Step S601: Dissolve compound P4 and an acid-binding agent in an organic solvent, and add compound M4 to react, to obtain optical monomer G2.

[0090] Steps S1 to S3 and S5 are described above and will not be repeated here. It should be noted that the reaction principle and conditions of step S601 are the same as those of step S401, only the reaction substrate is different (i.e., compound P3 or compound P4). The relevant content can be found in step S401 and will not be repeated here.

[0091] In some specific examples, the molar ratio of compound P4, the acid-binding agent, and compound M4 is 1:(2-4):(1-3). Typical, but not limiting, the molar ratio of compound P4, the acid-binding agent, and compound M4 can be, for example, 1:2:1, 1:2:2, 1:2:3, 1:3:1, 1:3:2, 1:3:3, 1:4:1, 1:4:2, 1:4:3, 1:3.5:2.5, etc.

[0092] It can be understood that the general structural formula of the optical unit G2 obtained through step S601 is, for example: or And R3 represents H, C1-C4 alkyl, R5 represents C1-C4 alkyl.

[0093] Specifically, the general formula for the prepared structure is G2, and R2 represents... or The optical unit, in addition to steps S1 to S3 and step S5, also includes the following steps: Step S602: Dissolve compound P4 in a second solvent, perform the second treatment operation, add a deprotonating agent, and after a period of time, add compound M5 to obtain optical monomer G2.

[0094] Steps S1 to S3 and S5 are described above and will not be repeated here. It should be noted that the reaction principle and conditions of step S602 are the same as those of step S402, only the reaction substrate is different (i.e., compound P3 or compound P4). The relevant content can be found in step S402 and will not be repeated here.

[0095] In some specific examples, the molar ratio of compound P4, the deprotonating agent, and compound M5 is 1:(1-2):(1-2).

[0096] Typical, but not limiting, molar ratios of compound P4, the deprotonating agent, and compound M5 can be, for example, 1:1:1, 1:1.2:1, 1:1.5:1, 1:2:1, 1:1:1.2, 1:1:1.5, 1:1:2, 1:2:2, 1:1.2:1.2, 1:1.5:1.3, 1:1.3:1.5, and 1:1.5:1.5, etc.

[0097] It can be understood that the general structural formula of the optical unit G2 obtained through step S602 is, for example: , , or And R3 represents H, C1-C4 alkyl, R5 represents C1-C4 alkyl.

[0098] This application also provides a photopolymer holographic recording medium, including a writing monomer, which includes the aforementioned optical monomer and polymerizable monomer.

[0099] It should be understood that the refractive index of the optical element is positively correlated with the refractive index of the writing element; that is, when the refractive index of the optical element is high, the refractive index of the resulting writing element is also high.

[0100] Furthermore, in some embodiments, the raw material of the photopolymer-type holographic recording medium includes the following components a) Component h): Component a) A compound having multiple isocyanate reactive functional groups. Component b) Polyisocyanate group compounds, Component c) at least one of the aforementioned optical monomers G1 or G2, Component d) Polymerizable monomers, Component e) Photosensitive initiation system, Component f) Chain transfer agent, Component g) optionally a catalyst, Component h) Optional additives, Among them, compounds with multiple isocyanate reactive functional groups and polyisocyanate group compounds form film-forming resins.

[0101] In this embodiment, an optical monomer with a high refractive index is used as a component of the writing monomer, thereby allowing the writing monomer and the film-forming resin to have a greater refractive index difference, thus forming a photopolymer-type holographic recording material with excellent properties such as high sensitivity and high diffraction efficiency. Specifically, in some examples, the photopolymer-type holographic recording medium has a sensitivity greater than 100 cm / mJ, a recording grating diffraction efficiency greater than 95%, and a shrinkage rate less than 0.3%.

[0102] More specifically, in some examples, the composition and content of photopolymer-type holographic recording media are as follows: Component a) 10 wt% to 50 wt% of compounds having multiple isocyanate reactive functional groups. Component b) Polyisocyanate group compound 10 wt%~50 wt%. Component c) Optical monomers 1 wt%~30 wt%. Component d) Polymerizable monomers 10 wt%~40 wt%. Component e) Photoinitiator system 0.1 wt%~3 wt%. Component f) Chain transfer agent 0.1 wt%~3 wt%. Component (g) Catalyst 0.1 wt%~5 wt%. Component h) Additives 0.1 wt%~10 wt%.

[0103] Specifically, the content of component a) can be, for example, 10 wt%, 20 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, and 50 wt%, etc.; the content of component b) can be, for example, 10 wt%, 20 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, and 50 wt%, etc.; the content of component c) can be, for example, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt%, etc.; the content of component d) can be, for example, 10 wt%, 20 wt%, 30 wt%, 35 wt%, and 40 wt%, etc.; the content of component e) can be, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, and 3 wt%, etc.; and the content of component f) can be, for example, 0.1 wt%, 0.5 wt%, 1 ... The content of component g) can be, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, and 5 wt%, and the content of component h) can be, for example, 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%, etc.

[0104] More specifically, in some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 10 wt% of a compound having multiple isocyanate reactive functional groups, component b) 30 wt% of a polyisocyanate-based compound, component c) 30 wt% of an optical monomer, component d) 20 wt% of a polymerizable monomer, component e) 1 wt% of a photoinitiator system, component f) 1 wt% of a chain transfer agent, component g) 1 wt% of a catalyst, and component h) 7 wt% of an additive.

[0105] In some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 25 wt% of a compound having multiple isocyanate reactive functional groups, component b) 32 wt% of a polyisocyanate-based compound, component c) 3 wt% of an optical monomer, component d) 24 wt% of a polymerizable monomer, component e) 3 wt% of a photoinitiator system, component f) 3 wt% of a chain transfer agent, component g) 3 wt% of a catalyst, and component h) 7 wt% of an additive.

[0106] In some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 50 wt% of a compound having multiple isocyanate reactive functional groups, component b) 15 wt% of a polyisocyanate-based compound, component c) 2 wt% of an optical monomer, component d) 23 wt% of a polymerizable monomer, component e) 1 wt% of a photoinitiator system, component f) 1 wt% of a chain transfer agent, component g) 2 wt% of a catalyst, and component h) 6 wt% of an additive.

[0107] In some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 24 wt% of a compound having multiple isocyanate reactive functional groups, component b) 15 wt% of a polyisocyanate-based compound, component c) 1 wt% of an optical monomer, component d) 40 wt% of a polymerizable monomer, component e) 3 wt% of a photoinitiator system, component f) 3 wt% of a chain transfer agent, component g) 5 wt% of a catalyst, and component h) 9 wt% of an additive.

[0108] In some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 10 wt% of a compound having multiple isocyanate reactive functional groups, component b) 50 wt% of a polyisocyanate-based compound, component c) 20 wt% of an optical monomer, component d) 10 wt% of a polymerizable monomer, component e) 2.9 wt% of a photoinitiator system, component f) 0.1 wt% of a chain transfer agent, component g) 2 wt% of a catalyst, and component h) 5 wt% of an additive.

[0109] In some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 33 wt% of a compound having multiple isocyanate reactive functional groups, component b) 21.9 wt% of a polyisocyanate-based compound, component c) 20 wt% of an optical monomer, component d) 11 wt% of a polymerizable monomer, component e) 2 wt% of a photoinitiator system, component f) 2 wt% of a chain transfer agent, component g) 0.1 wt% of a catalyst, and component h) 10 wt% of an additive.

[0110] In some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 25 wt% of a compound having multiple isocyanate reactive functional groups, component b) 30 wt% of a polyisocyanate-based compound, component c) 10 wt% of an optical monomer, component d) 25 wt% of a polymerizable monomer, component e) 0.2 wt% of a photoinitiator system, component f) 0.8 wt% of a chain transfer agent, component g) 3 wt% of a catalyst, and component h) 6 wt% of an additive.

[0111] In some optional examples, the photopolymer-type holographic recording medium containing optical monomers comprises the following components in the following amounts: component a) 35 wt% of a compound having multiple isocyanate reactive functional groups, component b) 15 wt% of a polyisocyanate-based compound, component c) 21 wt% of an optical monomer, component d) 28.6 wt% of a polymerizable monomer, component e) 0.1 wt% of a photoinitiator system, component f) 0.1 wt% of a chain transfer agent, component g) 0.1 wt% of a catalyst, and component h) 0.1 wt% of an additive.

[0112] In this embodiment, by rationally controlling the composition ratio of the photopolymer holographic recording medium, the various components can work together fully, and the holographic performance of the final photopolymer holographic recording medium will not deteriorate due to an excess or deficiency of a certain component. This ensures that the final photopolymer holographic recording medium has better overall holographic performance, thereby achieving high resolution, high diffraction efficiency and long-term stability.

[0113] In some embodiments, the optical monomer accounts for 0.1 wt% to 30 wt% of the total photopolymer holographic recording medium.

[0114] Typically, but not limitingly, the content of optical monomers in the entire photopolymer holographic recording medium can be 0.1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or any range of two values.

[0115] In this embodiment, the content of optical monomers ranges from 0.1 to 30 wt% to ensure that sufficient active monomers are provided to participate in photopolymerization so that the resulting writing monomers have a sufficient concentration to achieve the concentration difference between the bright and dark areas after the reaction under light.

[0116] In some embodiments, the isocyanate reactive functional group is a hydroxyl group. Compounds having multiple isocyanate reactive functional groups include compounds with a refractive index less than or equal to a first refractive index threshold and having two or more hydroxyl functional groups, wherein the first refractive index threshold is any value between 1.5 and 1.55. Optionally, polyisocyanate-based compounds include compounds with a refractive index less than or equal to a second refractive index threshold and having two or more isocyanate groups, wherein the second refractive index threshold is any value between 1.5 and 1.55.

[0117] Typically, but not restrictively, the first refractive index threshold can be 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, or any value between any two values, and the second refractive index threshold can be 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, or any value between any two values.

[0118] In this embodiment, a compound with multiple isocyanate reactive functional groups having a refractive index less than or equal to 1.5 to 1.55 forms a low-refractive-index film-forming resin with a polyisocyanate group compound having a refractive index less than or equal to 1.5 to 1.55. The low-refractive-index film-forming resin and the high-refractive-index writing monomer (i.e., including the aforementioned optical monomer) form a significant refractive index difference (Δn≥0.1), which can enhance the diffraction efficiency of the holographic grating, while avoiding the increase in background noise caused by the high refractive index of the substrate itself.

[0119] In some embodiments, the isocyanate reactive functional group is a hydroxyl group, and the molar ratio of hydroxyl group to isocyanate functional group is 1:1. That is, in the film-forming resin that forms a photopolymer type holographic recording medium, the molar ratio of hydroxyl group in the compound having multiple isocyanate reactive functional groups to isocyanate functional group in the polyisocyanate group compound is 1:1.

[0120] Furthermore, in some examples, the compound having multiple isocyanate reactive functional groups may be one or more of tetraethylene glycol, trimethylolethane, glycerol, triethanolamine, polyester polyols with a molecular weight of 200 to 2000, polycarbonate polyols, and polyether polyols, but is not limited thereto.

[0121] Polyisocyanate compounds include, but are not limited to, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tri(hexamethylene)isocyanate, butane-1,4-diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0122] In some examples, the polymerizable monomer is selected from at least one of alkenylnaphthalene compounds, alkenylanthracene compounds, alkenylbenzene compounds, acrylic compounds, methacrylic acid compounds, acrylate compounds, methacrylate compounds, N-vinylpyrrole, N-vinylcarbazole, N-vinylimidazol, N-vinylindole, N-vinylpyrrolidone, and trans-N-3-yntynebutenylcarbazole.

[0123] In specific examples, alkenylbenzene compounds include, but are not limited to, benzene. Ethylene, 2-chlorostyrene, 2-bromostyrene, 3-chlorostyrene, 3-bromostyrene, 4-chlorostyrene, 4-bromostyrene, p-(chloromethyl)styrene, p-(bromomethyl)styrene.

[0124] For example, methacrylic acid compounds can be methacrylic acid and its derivatives. For instance, methacrylate compounds can be selected from 2-phenoxyethyl methacrylate, benzyl methacrylate, p-bromophenyl methacrylate, p-chlorophenyl methacrylate, 2,4,6-trichlorophenyl methacrylate, pentabromophenyl methacrylate, pentachlorophenyl methacrylate, phenoxyethyl methacrylate, phenoxyethoxyethyl methacrylate, 1,4-bis(2-thionaphthyl)2-butyl methacrylate, pentabromobenzyl methacrylate, 2-naphthyl methacrylate, bisphenol A dimethacrylate, tetrabromobisphenol A dimethacrylate, etc.

[0125] In specific examples, acrylate compounds include, but are not limited to, pentabromophenyl acrylate, pentachlorophenyl acrylate, phenoxyethyl acrylate, pentabromobenzyl acrylate, 2-naphthyl acrylate, 1,4-di(2-thionaphthyl)2-butyl acrylate, phenoxyethoxyethyl acrylate, bisphenol A diacrylate, tetrabromobisphenol A diacrylate, 2-phenoxyethyl acrylate, benzyl acrylate, p-chlorophenyl acrylate, 2,4,6-trichlorophenyl acrylate, p-bromophenyl acrylate, 2,4,6-tribromophenyl acrylate, propane-2,2-diylbis[(2,6-dibromo-4,1-phenylene)oxy(2-{[3,3,3-tris(4-chlorophenyl)propionyl]oxy}propane-3,1-diyl)oxyethane-2,1-diyl]diacrylate.

[0126] In specific examples, vinylanthracene compounds may be selected from 2-vinylanthracene, 9-vinylanthracene, etc.

[0127] In specific examples, vinylnaphthalene compounds can be selected from 1-vinylnaphthalene, 2-vinylnaphthalene, etc.

[0128] In some implementations, the photoinitiation system is composed of a photosensitizer and a photoinitiator, which work synergistically to construct a broadband visible light initiation system. The photosensitizer selectively absorbs laser energy at specific wavelengths (e.g., 532 nm or 633 nm) and activates the photoinitiator through an energy transfer mechanism, thereby significantly expanding the system's photosensitive wavelength range. Therefore, different broadband responses can be achieved by controlling the type of photosensitizer. Under irradiation with light within a specific wavelength range, the photosensitizer in the photoinitiation system is activated accordingly, absorbs light energy, and transfers the light energy to the photoinitiator. This allows the photoinitiator to be activated under light radiation of more frequencies. The activated photoinitiator efficiently generates active free radicals, rapidly initiating monomer polymerization reactions, thus enabling the construction of a holographic grating structure. This improves the photosensitivity of the photopolymer-based holographic recording medium and enhances compatibility with lasers of different wavelengths, providing a more flexible light source selection scheme for holographic storage.

[0129] It is understandable that when a photoinitiator with a suitable wavelength is selected in the raw materials of a photopolymer holographic recording medium, a photosensitizer may not be added. For example, when the photoinitiator is diacetic titanium (Irgacure 784), a photosensitizer may not be added. This highly reactive orange solid photoinitiator can initiate the polymerization reaction of unsaturated resins under visible or ultraviolet light.

[0130] In some examples, the mass ratio of photosensitizer to photoinitiator is (0.001~1):(0.1~3). Typical, but not limiting, the mass ratio of photosensitizer to photoinitiator can be 0.001~0.1, 0.001~3, 1:0.1, 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, or 1:3, etc.

[0131] By adjusting the ratio of photosensitizer and photoinitiator within the above range, the energy transfer efficiency of the photosensitizer and the free radical yield of the photoinitiator can be balanced, avoiding energy waste caused by excessive photosensitizer or side reactions caused by excessive initiator. This allows for efficient initiation of the polymerization reaction while controlling the reaction rate within a reasonable range, thus controlling the grating formation speed within a certain range and ensuring the light transmittance of the photopolymer holographic recording medium, thereby achieving excellent diffraction efficiency.

[0132] Among them, photosensitizers are dyes that have high electron transfer efficiency under light irradiation, including but not limited to cyanine dyes, fluorescein dyes, coumarin ketone dyes, nitrogen-containing aromatic heterocyclic compounds, aromatic amine compounds, and benzylidene cycloalkanes ketone compounds.

[0133] For example, the photosensitizer may be one or more of the following: neomethylene blue, thionine, basic yellow, pinacyanin chloride, rhodamine 6G, gallium cyanide, ethyl violet, Victoria blue R, azurite blue, methylene blue, basic orange 21, darone red, pyrrole red Y, basic red 29, quinaldinium red, crystal violet, brilliant green, pyrimethium I, azurite A, crystal violet cyanocyanate, malachite green cyanocyanate, etc.

[0134] Photoinitiators are initiators that can be activated by photochemical radiation and initiate polymerization reactions of corresponding polymerizable groups, including but not limited to aromatic ketones, benzoin and its derivatives, benzoyl ketals, acylphosphine oxides, ammonium arylboronate, chromium salts, aryl diazonium salts, onium salts, and organometallic compounds.

[0135] Specifically, the photoinitiator can be one or more of the following: benzophenone, alkylbenzophenone, 4,4'-bis(dimethylamino)benzophenone, anthrone and halogenated benzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, diacylphosphine oxide, phenyl dihydroxyacetate, camphorquinone, α-aminoalkylphenyl ketone, α,α-dialkoxyacetophenone, α-hydroxyalkylphenyl ketone, tetrabutylammonium triphenylhexylborate, tetrabutylammonium tri-(3-fluorophenyl)hexylborate, tetrabutylammonium tri-(3-chloro-4-methylphenyl)hexylborate, ferrocene compounds, iodonium salts, thiodonium salts, hexaaryldiimidazole, etc.

[0136] As a chain transfer agent, the chain transfer agent can control the polymer chain length within a certain reasonable range and effectively prevent excessive polymerization, ensuring that the final holographic recording medium has the required optical properties and diffraction efficiency.

[0137] In some embodiments, the chain transfer agent may be a thiol compound, such as one or more of dodecyl mercaptoethanol, mercaptoethanol, hexamethylene mercaptoethanol, phenylethyl mercaptoethanol, 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, 4-methyl-4H-1,2,4-triazole-3-thiol, but not limited thereto.

[0138] It is understandable that the molecular weight of the polymerized optical monomers and polymerizable monomers can be controlled by the photoinitiator system, the amount of chain transfer agent used, and the reaction conditions, and the amount used can be appropriately adjusted according to their types.

[0139] As a catalyst, the catalyst can effectively increase the reaction rate of the relevant components and the consumption rate of the relevant components after exposure, thereby quickly forming the concentration difference of monomers in the bright and dark areas and realizing the phase-type volume holographic grating with refractive index modulation.

[0140] In some embodiments, the catalyst can be a tertiary amine catalyst or an organometallic catalyst, such as triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropanediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts, and bismuth carboxylate catalysts, but not limited thereto.

[0141] For example, additives can be selected from at least one of defoamers, leveling agents, plasticizers, and dehydrating agents. For instance, as defoamers, defoamers include silicone defoamers and silicone-free polymeric defoamers. Defoamers are mainly used to eliminate or suppress bubbles generated during material preparation and photocuring to ensure high resolution, high diffraction efficiency, and structural uniformity of the hologram.

[0142] Specifically, the defoamer can be selected from BYK-011, BYK-012, BYK-014, BYK-023, BYK-051N, BYK-085, BYK-1610, BYK-1707, BYK-1740, and BYK-1760 manufactured by BYK Corporation, DC65 and AFE-7820 manufactured by Dow Corning, or any mixture of these defoamers in any proportion, but is not limited thereto. Among them, the BYK series defoamers have excellent defoaming performance, good compatibility with other components, and good dispersibility. BYK-011, BYK-012, BYK-014, and BYK-051N are silicone-free polymeric defoamers. DC65 is a water-based ink that dries quickly, provides good printing results, and is not easily peeled off. AFE-7820 has highly efficient defoaming performance. The defoamer content in the photopolymer holographic recording medium is less than or equal to 3 wt%. Typically, but not limitingly, the defoamer content in the photopolymer holographic recording medium can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc.

[0143] In a specific example, the leveling agent is an organosilicon surface additive, and the leveling agent accounts for less than or equal to 3 wt% of the photopolymer holographic recording medium. Typically, but not limitingly, the leveling agent content in the photopolymer holographic recording medium can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc.

[0144] The leveling agent may be selected from BYK series leveling agents with excellent leveling properties manufactured by BYK Corporation, such as BYK-302, BYK-306, BYK-307, BYK-327, BYK-329, BYK-333, BYK-356, BYK-358, BYK-378, BYK-3455, BYK-3566, or any proportion of these surface additives, but is not limited thereto.

[0145] As a plasticizer, the plasticizer increases the plasticity of the polymer by intercalating between polymer molecular chains, weakening intermolecular stress, increasing molecular chain mobility, and reducing crystallinity. In specific examples, the plasticizer may be selected from one or more of toluene, xylene, dimethylformamide, dimethylacetamide, glycerol, and phthalates, but is not limited to these. The plasticizer content in the photopolymer holographic recording medium is less than or equal to 3 wt%. Typically, but not limitingly, the plasticizer content in the photopolymer holographic recording medium may be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc.

[0146] It is understandable that residual moisture in photopolymer-based holographic recording media may cause hydrolysis and failure of the photoinitiator system (such as the photoinitiator), reducing photosensitivity. Simultaneously, moisture can react with isocyanate groups (-NCO) involved in film-forming resin, generating urea bonds and releasing CO2, leading to bubbles or microstructural defects. Therefore, adding a dehydrating agent to maintain system dryness ensures the efficiency of the photopolymerization reaction, thereby improving the uniformity of the holographic grating and the storage life of the medium.

[0147] As dehydrating agents, dehydrating agents include, but are not limited to, p-toluenesulfonyl isocyanate, triethyl orthoformate, CUWR-WB20 dehydrating agent from Guangzhou Yourun Synthetic Materials Co., Ltd., ALT-201 dehydrating agent from Anxiang Elite Chemical Co., Ltd., and PCCI dehydrating agent from Shanghai Luer Chemical Trading Co., Ltd.

[0148] In some embodiments, the content of the dehydrating agent in the photopolymer holographic recording medium is less than or equal to 3 wt%. Typically, but not limitingly, the content of the dehydrating agent in the photopolymer holographic recording medium can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc.

[0149] This application also provides a method for preparing a photopolymer-based holographic recording medium, the method comprising: Step 1: Weigh components a), b), c), d), e), f), g), and h) into a container and stir thoroughly until dissolved to form a mixture solution.

[0150] Step 2: Filter the mixture solution using a filter membrane to obtain a first solution, coat the first solution onto a substrate, and dry it to obtain the photopolymer holographic recording medium.

[0151] For example, drying is carried out in a dark room with a humidity of 10% to 85% and a temperature of 20°C to 50°C.

[0152] Furthermore, this application provides a volume holographic recording grating, the raw material of which includes the photopolymer type holographic recording medium described in any of the above embodiments.

[0153] It is understandable that volume holographic recording gratings are fabricated by exposing photopolymer holographic recording media using the principle of light interference. Therefore, the holographic optical properties of the photopolymer holographic recording media determine the quality of the volume holographic recording grating.

[0154] For example, the photopolymer holographic recording medium proposed in this application possesses excellent properties such as a sensitivity greater than 100 cm / mJ, a recording grating diffraction efficiency greater than 95%, and a shrinkage rate less than 0.3%. Therefore, the volume holographic recording grating made from it also possesses the advantages of the photopolymer holographic recording medium of this application. Specifically, a sensitivity greater than 100 cm / mJ means that only extremely low exposure energy is required to form a stable grating, which can shorten the exposure time, reduce laser power requirements, increase recording speed, and reduce energy consumption efficiency, making it suitable for dynamic recording and low-power devices. A diffraction efficiency greater than 95% means that almost all incident light energy is diffracted to the target direction by the grating, thereby reducing light energy loss and making the image clearer. A shrinkage rate less than 0.3% ensures the optical uniformity of the photopolymer holographic recording medium, reduces optical distortion, ensures the stability of the grating structure, and thus extends the lifetime of holographic storage. Meanwhile, based on the fact that the optical monomer provided in this application has a high refractive index, the refractive index difference between it and the photopolymer holographic recording medium formed by the low refractive index film-forming resin is large, which further improves the refractive index modulation of the photopolymer holographic recording medium, thereby enhancing the diffraction capability of the grating and helping to form a wider field of view.

[0155] As can be seen from the above, the volume holographic recording grating proposed in this application has high sensitivity, greater than 100 cm / mJ, and the diffraction efficiency of the recording grating is greater than 95%, and the shrinkage rate is less than 0.3%.

[0156] This application also provides a holographic optical element, the raw material of which includes the aforementioned photopolymer-type holographic recording medium. This holographic optical element includes, but is not limited to, optical waveguides and holographic lenses.

[0157] It is understood that the holographic optical element proposed in this application, since it includes the aforementioned photopolymer holographic recording medium, also has the advantages of the photopolymer holographic recording medium of this application, and thus has optical performance such as fast recording speed and clear imaging.

[0158] This application also provides an optical device, including the holographic optical element as described above. This optical device includes, but is not limited to, head-up displays (HUDs), augmented reality (AR) devices, virtual reality (VR) devices, and photopolymer holographic storage optical discs. Photopolymer holographic storage optical discs can be erasable and rewritable, and can record in real time, making them suitable for storing large amounts of data and providing very fast data transfer speeds.

[0159] As can be seen from the above, the optical device proposed in this application, since it includes the aforementioned holographic optical element, also has the advantages of the holographic optical element in this application. The optical device has excellent optical performance, clear image, and can store a large amount of data.

[0160] The optical monomer, the preparation method of the optical monomer, and the photopolymer holographic recording medium containing the optical monomer are described below with reference to specific embodiments.

[0161] Example 1 Synthesis of optical monomer G1-1

[0162] Compound M1-1 (40 mmol) and p-toluenesulfonic acid (30 mmol) were dissolved in ethyl acetate (20 mL) and the mixture was heated to 40 °C. Compound M2 (10 mmol) was dissolved in ethyl acetate (10 mL) and slowly added dropwise to the mixed solution of compound M1-1 and p-toluenesulfonic acid. The reaction was stirred for 0.5–36 h. After the reaction was completed, sufficient triethylamine was added to quench the reaction, and the organic phase was extracted three times. The organic phase was dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. Compound P1-1 was obtained by column chromatography.

[0163]

[0164] In a dry round-bottom flask, compound P1-1 (10 mmol) was dissolved in toluene and a reflux condenser was installed. The upper end of the condenser was connected to a gas absorption device (dilute NaOH solution to absorb sulfur dioxide and hydrogen chloride tail gas). In a fume hood, thionyl chloride (80 mmol) was slowly added dropwise through a constant-pressure dropping funnel. After the addition was complete, a few drops of DMF were added to the reaction system, and the mixture was heated to 110°C and refluxed for 1-2 hours until no more gas was emitted. After the reaction was complete, excess thionyl chloride and toluene solvent were evaporated using a rotary evaporator in a fume hood to obtain the crude product.

[0165] Add the above crude product, Pd / BaSO4 catalyst (10 wt% of the crude product mass), quinoline-S inhibitor (1 wt% of the Pd / BaSO4 catalyst mass), and xylene solvent (volume to crude product mass ratio of xylene solvent is 5 mL / g) to a hydrogenation flask. Then, evacuate the system and replace the air with hydrogen, repeating this process 2-3 times. Maintain the reaction system at an appropriate hydrogen pressure (usually atmospheric or slightly above atmospheric pressure) and stir at 90-120°C. The reaction endpoint is determined by monitoring the amount of hydrogen absorbed. Stop the reaction when the theoretical amount of hydrogen has been absorbed. After the reaction solution cooled, the reaction solution was filtered and the catalyst was recovered. The filtrate was first washed with water to remove HCl, then washed with dilute acid to remove quinoline, and finally washed with saturated NaHCO3 solution and water. The organic phase obtained after extraction was dried with anhydrous MgSO4 or Na2SO4, and the xylene solvent was removed by vacuum distillation. The compound P2-1 was obtained by column chromatography.

[0166]

[0167] Compound M3-1 (80 mmol) and acetic acid (80 mmol) were dissolved in dichloromethane (50 mL) and heated to 40 °C. Compound P2-1 (10 mmol) was dissolved in dichloromethane (10 mL) and slowly added dropwise to the mixed solution of compound M3-1 and acetic acid. The reaction was stirred for 0.5–36 h. After the reaction was completed, sufficient triethylamine was added to quench the reaction, and the organic phase was extracted three times. The organic phase was dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. Compound P3-1 was obtained by column chromatography.

[0168]

[0169] Compound P3-1 (10 mmol) and... N,N Diisopropylethylamine (40 mmol) was dissolved in dichloromethane (20 mL), stirred for 10 min, and then acryloyl chloride (30 mmol) was added dropwise to compound P3-1 at 0 °C. N,N The reaction was carried out in a mixed solution of diisopropylethylamine. After the reaction was completed, dilute hydrochloric acid was added dropwise to remove excess acryloyl chloride. The mixture was then washed successively with saturated NaCl solution, saturated NaHCO3 solution, and deionized water. The organic phase was dried over anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. The optical monomer G1-1 of this application was obtained by column chromatography.

[0170] The characterization data are as follows: 1 H NMR (600 MHz, CDCl3)δ7.47–7.37 (m, 16H), 7.34–7.24 (m, 40H), 7.17(tt, J = 1.5, 0.8 Hz, 1H), 7.09 (d, J = 1.5 Hz, 2H), 6.15–6.06 (m, 1H), 5.88–5.79 (m, 2H), 5.73 (s, 4H), 5.55 (s, 2H). 13 C NMR (151 MHz, CDCl3)δ167.04, 137.75, 137.11, 136.44, 136.37,132.23, 129.06, 129.03, 128.51, 128.10, 127.60, 127.16, 126.46, 113.97,93.68, 83.97. Example 2 Synthesis of optical monomer G1-2

[0171] Compound M3-2 (80 mmol) and acetic acid (80 mmol) were dissolved in dichloromethane (50 mL) and heated to 40 °C. Compound P2-1 (10 mmol) was dissolved in dichloromethane (10 mL) and slowly added dropwise to the mixed solution of compound M3-2 and acetic acid. The reaction was stirred for 0.5–36 h. After the reaction was completed, sufficient triethylamine was added to quench the reaction, and the organic phase was extracted three times. The organic phase was dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. Compound P3-2 was obtained by column chromatography.

[0172]

[0173] Under ice bath conditions, compound P3-2 (10 mmol) was dissolved in tetrahydrofuran (20 mL), and sodium hydride (12 mmol) was slowly added. After stirring for 0.5–10 h, 3-bromo-1-propene (15 mmol) was added dropwise. After the addition was complete, stirring was continued for another 0.5–10 h. After the reaction was complete, dilute hydrochloric acid was slowly added dropwise to quench the reaction. Excess solvent was removed by rotary evaporation, and the optical monomer G1-2 of this application was obtained by column chromatography.

[0174] The characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 7.36 – 7.31 (m, 17H), 7.28 (s, 16H), 7.26 –7.19 (m, 16H), 6.87 (d, J = 1.5 Hz, 2H), 6.03 (tt, J = 13.7, 6.2 Hz, 1H), 5.68 (s, 4H), 5.53 (s, 2H), 5.33 (dt, J = 13.4, 1.0 Hz, 2H), 4.50 (dt, J =6.2, 1.0 Hz, 2H), 2.49 (s, 24H). 13 C NMR (151 MHz, CDCl3) δ 155.38, 137.11, 136.44, 136.39, 134.81,128.91, 127.29, 126.76, 126.60, 118.52, 117.84, 101.37, 83.97, 69.08, 15.88. Example 3 Synthesis of optical monomer G1-3, the structural formula of G1-3 is as follows:

[0175] Compound M1-2 (80 mmol) and trifluoroacetic acid (80 mmol) were dissolved in acetonitrile (80 mL) and the mixture was heated to 60 °C. Compound M2 (20 mmol) was dissolved in ethyl acetate (20 mL) and slowly added dropwise to the mixed solution of compound M1-2 and trifluoroacetic acid. The reaction was stirred for 0.5–36 h. After the reaction was completed, sufficient triethylamine was added to quench the reaction, and the organic phase was extracted three times. The organic phase was dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. Compound P1-2 was obtained by column chromatography.

[0176]

[0177] In a dry round-bottom flask, compound P1-2 (20 mmol) was dissolved in chloroform (20 ml), and a reflux condenser was installed. The upper end of the condenser was connected to a gas absorption device (dilute NaOH solution to absorb sulfur dioxide and hydrogen chloride tail gas). In a fume hood, thionyl chloride (200 mmol) was slowly added dropwise through a constant-pressure dropping funnel. After the addition was complete, a few drops of DMF were added to the reaction system, and the mixture was heated to 65 °C and refluxed for 1-2 hours until no more gas was emitted. After the reaction was complete, excess thionyl chloride and chloroform solvent were evaporated using a rotary evaporator in a fume hood to obtain the crude product.

[0178] Add the above crude product, Pd / BaSO4 catalyst (10 wt% of the crude product mass), quinoline-S inhibitor (1 wt% of the Pd / BaSO4 catalyst mass), and xylene solvent (volume to crude product mass ratio of xylene solvent is 5 mL / g) to a hydrogenation flask. Then, evacuate the system and replace the air with hydrogen, repeating this process 2-3 times. Maintain the reaction system at an appropriate hydrogen pressure (usually atmospheric or slightly above atmospheric pressure) and stir at 90-120°C. The reaction endpoint is determined by monitoring the amount of hydrogen absorbed. Stop the reaction when the theoretical amount of hydrogen has been absorbed. After the reaction solution cooled, the reaction solution was filtered and the catalyst was recovered. The filtrate was first washed with water to remove HCl, then washed with dilute acid to remove quinoline, and finally washed with saturated NaHCO3 solution and water. The organic phase obtained after extraction was dried with anhydrous MgSO4 or Na2SO4, and the xylene solvent was removed by vacuum distillation. The compound P2-2 was obtained by column chromatography.

[0179]

[0180] Compound M3-3 (80 mmol) and tetrafluoroboric acid (60 mmol) were dissolved in chloroform (80 mL) and heated to 40 °C. Compound P2-2 (10 mmol) was dissolved in chloroform (10 mL) and slowly added dropwise to the mixed solution of compound M3-3 and tetrafluoroboric acid. The reaction was stirred for 0.5–36 h. After the reaction was completed, sufficient triethylamine was added to quench the reaction, and the organic phase was extracted three times. The organic phase was dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. Compound P3-3 was obtained by column chromatography.

[0181]

[0182] At -78°C, compound P3-3 (10 mmol) was dissolved in tetrahydrofuran, and n-butyllithium (15 mmol) was slowly added. After stirring for 0.5 h to 10 h, 3-bromo-1-propyne (12 mmol) was added dropwise to the reaction system. After the addition was completed, stirring was continued for 0.5 to 10 h. After the reaction was completed, saturated ammonium chloride aqueous solution was slowly added dropwise to quench the reaction, and the organic phase was extracted three times. The organic phase was dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. The optical monomer G1-3 of this application was obtained by column chromatography.

[0183] The characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 7.43 – 7.33 (m, 8H), 7.33 – 7.15 (m, 40H), 7.11 – 7.07 (m, 1H), 6.89 (d, J = 1.5 Hz, 2H), 5.59 (d, J = 0.9 Hz, 4H), 5.53(s, 2H), 4.79 (d, J = 2.9 Hz, 2H), 3.56 (t, J = 3.0 Hz, 1H), 2.29 (s, 24H). 13 C NMR (151 MHz, CDCl3) δ 156.14, 140.51, 137.78, 136.37, 135.28,129.71, 129.27, 129.11, 129.06, 128.29, 126.74, 126.50, 125.85, 119.39,93.68, 56.98, 19.48. Example 4 Synthesis of optical monomer G2-1

[0184] Under ice bath conditions, compound P3-2 (10 mmol) was dissolved in dichloromethane (10 mL), and potassium tert-butoxide (10 mmol) was slowly added. After stirring for 0.5–10 h, compound M6-1 (15 mmol) was added dropwise to the reaction system. After the addition was complete, the reaction was continued for another 0.5–10 h. After the reaction was complete, dilute hydrochloric acid was slowly added dropwise to quench the reaction. The organic phase was extracted three times, dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. Compound P4-1 was obtained by column chromatography.

[0185]

[0186] Compound P4-1 (10 mmol) and... N,N Diisopropylethylamine (20 mmol) was dissolved in dichloromethane (20 mL), stirred for 10 min, and then methacryloyl chloride (30 mmol) was added dropwise to compound P4-1 at 0 °C. N,N The reaction was carried out in a mixed solution of diisopropylethylamine. After the reaction was completed, dilute hydrochloric acid was added dropwise to remove excess methacryloyl chloride. The mixture was then washed successively with saturated NaCl solution, saturated NaHCO3 solution, and deionized water. The organic phase was dried over anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. The optical monomer G2-1 of this application was obtained by column chromatography.

[0187] The characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 7.40 – 7.30 (m, 16H), 7.28 (s, 16H), 7.25 –7.16 (m, 16H), 7.11 – 7.06 (m, 1H), 6.86 (d, J = 1.4 Hz, 2H), 5.97 (dq, J =2.0, 1.0 Hz, 1H), 5.68 (s, 4H), 5.62 (dq, J = 2.0, 1.0 Hz, 1H), 5.53 (s, 2H), 4.11 (t, J = 7.1 Hz, 2H), 4.04 (t, J = 7.1 Hz, 2H), 2.49 (s, 24H), 1.93 (t, J= 1.0 Hz, 3H), 1.75 (p, J = 7.1 Hz, 2H), 1.69 (p, J = 7.1 Hz, 2H), 1.49 –1.39 (m, 2H), 1.35 (dq, J = 7.6, 6.5 Hz, 2H), 1.29 – 1.17 (m, 8H). 13 C NMR (151 MHz, CDCl3) δ 167.88, 155.40, 137.11, 136.44, 134.81,129.06, 126.76, 126.60, 124.90, 117.84, 101.37, 83.97, 68.81, 64.81, 30.32,30.19, 29.64, 29.09, 27.08, 18.75, 15.88. Example 5 Synthesis of optical monomer G2-2

[0188] Under ice bath conditions, compound P3-3 (10 mmol) was dissolved in toluene (10 mL), and sodium methoxide (10 mmol) was slowly added. After stirring for 0.5–10 h, compound M6-2 (13 mmol) was added dropwise to the reaction system. After the addition was complete, the reaction was continued for another 0.5–10 h. After the reaction was complete, dilute hydrochloric acid was slowly added dropwise to quench the reaction. The organic phase was extracted three times, dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. Compound P4-2 was obtained by column chromatography.

[0189]

[0190] Under ice bath conditions, compound P4-2 (10 mmol) was dissolved in tetrahydrofuran (10 mL), and potassium hydride (12 mmol) was slowly added. After stirring for 0.5–10 h, 3-bromo-1-propene (15 mmol) was added dropwise. After the addition was complete, stirring was continued for another 0.5–10 h. After the reaction was complete, dilute hydrochloric acid was slowly added dropwise to quench the reaction. The organic phase was extracted three times, dried with anhydrous sodium sulfate, and excess solvent was removed by rotary evaporation. The optical monomer G2-2 of this application was obtained by column chromatography.

[0191] The characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 7.41 – 7.33 (m, 8H), 7.33 – 7.17 (m, 40H), 7.07 (q, J = 1.2 Hz, 1H), 6.85 (d, J = 1.5 Hz, 2H), 5.84 (tt, J = 13.4, 6.1Hz, 1H), 5.59 (d, J = 0.9 Hz, 4H), 5.54 (s, 2H), 5.20 (dt, J = 13.5, 1.0 Hz, 2H), 4.15 (t, J = 7.1 Hz, 2H), 3.93 (dt, J = 6.2, 1.0 Hz, 2H), 3.72 (t, J =7.1 Hz, 2H), 2.29 (s, 24H). 13C NMR (151 MHz, CDCl3) δ 154.25, 140.51, 137.78, 136.37, 135.28,129.71, 128.91, 128.84, 128.03, 126.89, 126.76, 125.18, 117.84, 117.48,86.05, 71.98, 70.20, 69.04, 19.48. Example 6 Photopolymer-type holographic recording media 6-1 to 6-5 were prepared using the optical monomers described in Examples 1 to 5. The preparation method involved mixing all components thoroughly, filtering the mixture using a filter membrane, coating the resulting filtrate onto a substrate, and drying it in a darkroom with a humidity of 10%–85% and a temperature of 20°C–50°C to obtain the photopolymer-type holographic recording media (hereinafter referred to as holographic recording media). The specific components of photopolymer-type holographic recording media 6-1 to 6-5 are shown in Tables 1 to 5.

[0192] Table 1

[0193] Table 2

[0194] Table 3

[0195] Table 4

[0196] Table 5

[0197] Comparative Example 1 Compared with the photopolymer-type holographic recording medium 6 in Example 6 The components of 1 are roughly the same, except that the optical monomer G1-1 is not added in the comparative example, but 48 wt% of p-(chloromethyl)styrene is added to obtain a common photopolymer type holographic recording medium 1.

[0198] Comparative Example 2 Compared with the photopolymer-type holographic recording medium 6 in Example 6 The components of the second example are roughly the same, except that the optical monomer G1-2 is not added in the comparative example; instead, 52 wt% of [unspecified ingredient] is added. N -Vinylpyrrolidone, thus obtaining a common photopolymer type holographic recording medium2.

[0199] Comparative Example 3 Compared with the photopolymer-type holographic recording medium 6 in Example 6 The components of 4 are roughly the same, except that the optical monomer G2-1 is not added in the comparative example, but 30 wt% of pentabromophenyl methacrylate is added, thus obtaining a common photopolymer type holographic recording medium 3.

[0200] Comparative Example 4 Compared with the photopolymer-type holographic recording medium 6 in Example 6 The components of 5 are roughly the same, except that the optical monomer G2-2 is not added in the comparative example, but 24.3 wt% of 2-naphthalene acrylate is added, thus obtaining a common photopolymer type holographic recording medium 4.

[0201] Test case (1) The refractive index of the optical monomers synthesized in Examples 1 to 5 was tested, and the results are shown in Table 6.

[0202] (2) The performance of the photopolymer holographic recording media 6-1 to 6-5 containing optical monomers in Example 6 and the ordinary photopolymer holographic recording media of Comparative Examples 1 to 4 were tested, and the results are shown in Table 7.

[0203] During testing, the various holographic recording media in Example 6 can be exposed to lasers of different wavelengths depending on the photosensitive system, with an exposure intensity of 3 mW / cm². 2 .

[0204] The detection light source uses a 785nm wavelength solid-state laser that does not react with the recording medium. The detection light is incident on the exposure area from the Bragg angle. The transmitted light and diffracted light are monitored in real time by a photodetector. The single grating diffraction efficiency (η) and the photosensitivity (S) of the photopolymer holographic recording medium are calculated by formulas (1) to (3).

[0205]

[0206] In the formula, η is the diffraction efficiency, η max For the highest diffraction efficiency, I d For diffracted light, I t S represents transmitted light, S represents photosensitivity, E represents exposure energy, and ΔE represents the exposure energy required to achieve maximum diffraction efficiency.

[0207] Table 6 Refractive indices of the monomers synthesized in Examples 1-5

[0208] Table 7. Holographic performance parameters of the holographic recording media of Example 6 and the comparative example.

[0209] The optical monomer provided in this application has a high refractive index, greater than 1.70 and less than 1.75. Please refer to Table 6. As shown in Table 6, the refractive indices of the optical monomers prepared in Examples 1 to 5 of this application are between 1.71 and 1.75. Therefore, the optical monomer provided in this application, as a component of the writing monomer, is expected to further enhance the refractive index difference between the writing monomer and the film-forming resin, thereby improving the refractive index modulation of the holographic recording medium to produce a stronger grating structure and increase the grating storage density.

[0210] Specifically, photopolymer-type holographic recording media 6-1 to 6-5 were prepared using the optical monomers from Examples 1 to 5, referring to the component tables in Tables 1 to 5. As shown in Table 7, the diffraction efficiency of the holographic recording media containing the optical monomers of this application prepared in Example 6 is greater than 95%, which is much greater than the diffraction efficiency of the ordinary photopolymer-type holographic recording media prepared in Comparative Examples 1 to 4. That is, the diffraction efficiency of the holographic recording media provided by this application is greater than 95%. High diffraction efficiency means high light energy utilization and low light energy loss. In other words, almost all the incident light energy is diffracted to the target direction by the grating, which greatly improves the brightness and clarity of the holographic display. In addition, the holographic recording media provided by this application also has a sensitivity greater than 100 cm / mJ and an exposure amount less than 20 mJ / cm. 2 The advantages include higher sensitivity, larger interference pattern area that can be recorded per unit energy (millijoules), shorter hologram writing time, faster data transmission speed, and lower exposure, which means that only a small amount of light energy is needed to complete curing and photopolymerization, avoiding overheating and deformation of materials caused by high-energy exposure.

[0211] Furthermore, referring to Table 7, the shrinkage rate of the photopolymer holographic recording medium made from the optical monomer provided in this application is much lower than that of ordinary photopolymer holographic recording media (such as Comparative Examples 1 to 4). Therefore, the optical monomer provided in this application has the advantage of reducing the volume shrinkage of the photopolymer holographic recording medium, maintaining the optical uniformity of the photopolymer holographic recording medium, reducing optical distortion, ensuring the stability of the grating structure, and thus extending the lifespan of holographic storage. Referring to Tables 1 and 7 and Comparative Example 1, the total amount of writing monomers in the photopolymer holographic recording medium 6-1 reaches 48 wt%, of which 8 wt% is the dendritic optical monomer G1-1 of this application. As a result, the shrinkage rate of the photopolymer holographic recording medium 6-1 is only 0.70%. In contrast, the comparative example does not contain dendritic monomers (i.e., the optical monomers provided in this application), and the shrinkage rate of the ordinary photopolymer holographic recording medium obtained is as high as 2.2%. Referring to the photopolymer holographic recording media 6-3 and 6-5, it can be seen that the higher the total amount of writing monomers and the higher the content of polymerizable monomers, the greater the volume shrinkage rate of the photopolymer holographic recording medium.

[0212] See Figure 1 and Figure 2 The photopolymer holographic recording medium containing the optical monomers of this application has a concentration of 4.92 mJ / cm². 2 Up to 9.41 mJ / cm 2 At a lower exposure level, a superior diffraction efficiency of greater than 95% is achieved, while the ordinary holographic recording media prepared in Comparative Examples 1 and 2 require higher exposure levels (148.3 mJ / cm², respectively). 2 and 68.5 mJ / cm 2 Only by using these methods can diffraction efficiencies of 38.47% and 27.33% be achieved, resulting in low light energy utilization and high energy loss.

[0213] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical unit, characterized in that, Its general structural formula is shown in any of the following examples: 、 ； Where R1 represents R2 represents , or R3 represents H, C1-C4 alkyl, R4 represents hydrogen or methyl, R5 represents C1-C4 alkyl, n=1~10, and n is a positive integer.

2. The optical unit according to claim 1, characterized in that, The optical monomer is a compound with the following structural formula: ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； Where n = 1 to 10, and n is a positive integer.

3. A method for preparing an optical monomer as described in claim 1, characterized in that, include: Compound M1 and an acid reagent were dissolved in an organic solvent. After performing the first treatment operation, compound M2 was added to react and compound P1 was obtained. The compound P1 was reduced to obtain compound P2; Compound M3 and an acid reagent were dissolved in an organic solvent. After performing the first treatment operation, compound P2 was added to react and compound P3 was obtained. The first processing operation includes at least a heating operation and a stirring operation, and the compound M1 is selected from compounds with the following structural formulas: , The structural formula of compound M2 is shown below: The structural formula of compound P1 is shown below: , ; The structural formula of compound P2 is shown below: , ; The general structural formula of compound M3 is shown below. , The general structural formula of compound P3 is shown below: , And R3 represents H, C1-C4 alkyl, R5 represents C1-C4 alkyl.

4. The method for preparing an optical monomer according to claim 3, characterized in that, The reduction of compound P1 to obtain compound P2 includes the following steps: The compound P1 was dissolved in a first solvent, thionyl chloride was added, and a first treatment operation was performed to obtain intermediate I; The intermediate I, Pd / BaSO4 catalyst, and quinoline-S inhibitor were dissolved in xylene and reacted in a hydrogen atmosphere to obtain compound P2.

5. The method for preparing an optical monomer according to claim 4, characterized in that, The first solvent is selected from one or more of dichloromethane, petroleum ether, n-hexane, cyclohexane, benzene, toluene, and chloroform; And / or, the ratio of the volume of the first solvent to the mass of the compound P1 is 5, in mL / g. And / or, the volume ratio of the xylene solvent to the mass of intermediate I is 5, in mL / g. And / or, the mass of the Pd / BaSO4 catalyst is 10 wt% to 20 wt% of the mass of intermediate I. And / or, the mass of the quinoline-S inhibitor is 1 wt% to 2 wt% of the Pd / BaSO4 catalyst.

6. The method for preparing an optical monomer according to claim 3, characterized in that, The general structural formula of the optical unit is G1, where R2 represents... The process includes the following steps: The compound P3 and an acid-binding agent are dissolved in an organic solvent, and compound M4 is added to react and obtain the optical monomer G1; wherein, compound M4 is acryloyl chloride or methacryloyl chloride; Alternatively, the general structural formula of the optical unit is G1, and R2 represents... or The process includes the following steps: The compound P3 is dissolved in a second solvent, and after performing a second treatment operation, a deprotonating agent is added. After a period of time, compound M5 is added to obtain the optical monomer G1. The second treatment operation includes at least a cooling operation and a stirring operation. The compound M5 is 3-bromo-1-propene or 3-bromo-1-propyne.

7. The method for preparing an optical monomer according to claim 3, characterized in that, When the general structural formula of the optical unit is G2, the following steps are also included: The compound P3 was dissolved in a second solvent, and after performing a second treatment operation, a deprotonating agent was added. After a period of time, compound M6 was added to obtain compound P4. The second processing operation includes at least a cooling operation and a stirring operation, and the general structural formula of the compound M6 is: The general structural formula of the compound P4 is: , n is a positive integer, and n = 0 to 10.

8. The method for preparing an optical monomer according to claim 7, characterized in that, The general structural formula of the optical unit is G2, and R2 represents... The process also includes the following steps: The compound P4 and an acid-binding agent are dissolved in an organic solvent, and compound M4 is added to react, yielding the optical monomer G2; wherein, compound M4 is acryloyl chloride or methacryloyl chloride; Alternatively, the general structural formula of the optical unit is G2, and R2 represents... or The process includes the following steps: The compound P4 is dissolved in a second solvent, and after performing a second treatment operation, a deprotonating agent is added. After a period of time, compound M5 is added to obtain the optical monomer G2. The second treatment operation includes at least a cooling operation and a stirring operation. The compound M5 is 3-bromo-1-propene or 3-bromo-1-propyne.

9. The preparation method according to claim 3, characterized in that, The organic solvent is selected from one or more of methanol, ethanol, petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, benzene, toluene, N,N-dimethylformamide, dimethyl sulfoxide, dimethoxyethane, 1,4-dioxane, n-hexane, cyclohexane, and chloroform. And / or, the acid reagent is selected from one or more of p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, camphorsulfonic acid, naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, sulfosalicylic acid, citric acid, acetic acid, formic acid, phosphoric acid, anhydrous hydrogen peroxide, tetrafluoroboric acid, trifluoroacetic acid, pentafluoroacetic acid, heptafluoropropionic acid, and phosphoric acid; And / or, the molar ratio of compound M1, the acid reagent, and compound M2 is (4-4.8):(2-4):1; And / or, the molar ratio of the compound M3, the acid reagent, and the compound P2 is (8-9.6):(4-8):

1.

10. The preparation method according to claim 6 or 8, characterized in that, The acid-binding agent is selected from triethylamine, pyridine, N,N Diisopropylethylamine, 4 One or more of dimethylaminopyridine, tetrabutylammonium bromide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium acetate, sodium hydroxide, potassium hydroxide, calcium oxide, and potassium tert-butoxide; And / or, the second solvent is selected from one or more of petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, benzene, toluene, N,N-dimethylformamide, dimethyl sulfoxide, dimethoxyethane, and 1,4-dioxane; And / or, the deprotonating agent is selected from one or more of n-butyllithium, tert-butyllithium, phenyllithium, sodium hydride, potassium hydride, sodium amino, potassium amino, sodium bis(trimethylsilyl)amino, diisopropylaminolithium, potassium hydroxide, sodium hydroxide, sodium methoxide, sodium tert-butoxide, potassium tert-butoxide, triethylamine, 1,5-diazabicyclo[4.3.0]non-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, tetramethylsilyltrifluoromethanesulfonate, potassium phosphate, potassium carbonate, sodium carbonate, and sodium bicarbonate.

11. A photopolymer-based holographic recording medium, characterized in that, Its raw materials include the following components a) Component h); Component a) A compound having multiple isocyanate reactive functional groups; Component b) Polyisocyanate group compounds; Component c) Optical monomers; Component d) Polymerizable monomers; Component e) Photosensitive initiation system; Component f) Chain transfer agent; Component g) optionally a catalyst; Component h) Optional additives; Wherein, the optical unit is at least one of the optical units G1 or G2 as described in claim 1.

12. The photopolymer-type holographic recording medium according to claim 11, characterized in that, The composition and content of the photopolymer-type holographic recording medium are as follows: Component a) 10 wt% to 50 wt% of compounds having multiple isocyanate reactive functional groups; Component b) Polyisocyanate group compounds 10 wt%~50 wt%; Component c) Optical monomers 1 wt%~30 wt%; Component d) Polymerizable monomers 10 wt%~40 wt%; Component e) Photoinitiator system 0.1 wt%~3 wt%; Component f) Chain transfer agent 0.1 wt%~3 wt%; Component (g): Catalyst 0.1 wt%~5 wt%; Component h) Additives 0.1 wt%~10 wt%.

13. The photopolymer-type holographic recording medium according to claim 11, characterized in that, The optical monomer accounts for 0.1 wt% to 30 wt% of the total content of the photopolymer holographic recording medium. And / or, the isocyanate reactive functional group is a hydroxyl group, and the molar ratio of the hydroxyl group in component a) the compound having a plurality of isocyanate reactive functional groups to the isocyanate functional group in component b) the polyisocyanate group compound is 1:

1.

14. The photopolymer-type holographic recording medium according to claim 11, characterized in that, The isocyanate reactive functional group is a hydroxyl group; the compound having multiple isocyanate reactive functional groups includes compounds with a refractive index less than or equal to a first refractive index threshold and having two or more hydroxyl functional groups, wherein the first refractive index threshold is any value between 1.5 and 1.

55. And / or, the polyisocyanate-based compound includes compounds with a refractive index less than or equal to a second refractive index threshold and having two or more isocyanate groups; the second refractive index threshold is any value between 1.5 and 1.55; And / or, the polymerizable monomer is selected from at least one of alkenylnaphthalene compounds, alkenylanthracene compounds, alkenylbenzene compounds, acrylic compounds, methacrylic acid compounds, acrylate compounds, methacrylate compounds, N-vinylpyrrole, N-vinylcarbazole, N-vinylimidazol, N-vinylindole, N-vinylpyrrolidone, and trans-N-3-yntynebutenylcarbazole; And / or, the photoinitiating system includes a photosensitizer and a photoinitiator; And / or, the chain transfer agent is a thiol compound; And / or, the catalyst is a tertiary amine catalyst and an organometallic catalyst; And / or, the additives include at least one of defoamers, leveling agents, plasticizers, and dehydrating agents.

15. The photopolymer-type holographic recording medium according to claim 14, characterized in that, The compound having multiple isocyanate reactive functional groups includes at least one of tetraethylene glycol, trimethylolethane, glycerol, triethanolamine, polyester polyol with a molecular weight of 200 to 2000, polycarbonate polyol, and polyether polyol. And / or, the polyisocyanate group compound includes at least one of hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tri(hexamethylene)isocyanate, butane-1,4-diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate; And / or, the chain transfer agent comprises at least one of dodecyl mercaptan, mercaptoethanol, hexamethylene mercaptan, phenylethyl mercaptan, 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, and 4-methyl-4H-1,2,4-triazole-3-thiol; And / or, the catalyst comprises at least one of the following: triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylaminoethoxy)ethanol, trimethylhydroxyethylpropanediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts, and bismuth carboxylate catalysts.

16. The photopolymer-type holographic recording medium according to claim 15, characterized in that, The photosensitizer includes at least one of cyanine dyes, fluorescein dyes, coumarin ketone dyes, nitrogen-containing aromatic heterocyclic compounds, aromatic amine compounds, and benzylidene cycloalkane ketone compounds; The photoinitiator includes aromatic ketone compounds, benzoin and its derivatives, benzoyl ketal, acylphosphine oxide, ammonium arylboronate, chromium salt, aryl diazonium salt, onium salt, organometallic compound, or at least one of these compounds; The mass ratio of the photosensitizer to the photoinitiator is (0.001~1): (0.1~3).

17. The photopolymer-type holographic recording medium according to claim 15, characterized in that, The defoamer is a silicone defoamer and / or a silicone-free polymeric defoamer, and the content of the defoamer in the photopolymeric holographic recording medium is less than or equal to 3 wt%. And / or, the leveling agent is an organosilicon surface additive, and the leveling agent accounts for less than or equal to 3 wt% of the photopolymer-type holographic recording medium; And / or, the plasticizer is selected from at least one of toluene, xylene, dimethylformamide, dimethylacetamide, glycerol, and phthalates, and the plasticizer accounts for less than or equal to 3 wt% of the photopolymer-type holographic recording medium; And / or, the dehydrating agent includes at least one of p-toluenesulfonyl isocyanate and triethyl orthoformate, and the dehydrating agent accounts for less than or equal to 3 wt% of the photopolymer holographic recording medium.

18. A method for preparing a photopolymer-type holographic recording medium as described in any one of claims 11-17, characterized in that, Weigh the compound having multiple isocyanate reactive functional groups, the polyisocyanate group compound, the optical monomer, the polymerizable monomer, the photoinitiator system, the chain transfer agent, the catalyst and the additive into a container, and stir thoroughly until dissolved to form a mixed solution; The mixture solution is filtered using a filter membrane to obtain a first solution; The first solution is coated onto a substrate and dried to obtain the photopolymer holographic recording medium.

19. The preparation method according to claim 18, characterized in that, The drying process is carried out in a dark room with a humidity of 10% to 85% and a temperature of 20°C to 50°C.

20. A volume holographic recording grating, characterized in that, Its raw materials include the photopolymer type holographic recording medium as described in any one of claims 11-17.

21. A holographic optical element, characterized in that, Its raw materials include the photopolymer type holographic recording medium as described in any one of claims 11-17.

22. An optical device, characterized in that, Includes the holographic optical element as described in claim 21.

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