Optical monomer, holographic recording medium, method of manufacture and related devices

Abstract

The application discloses an optical monomer, a holographic recording medium, a preparation method and related devices, wherein a chemical structure general formula of the optical monomer is wherein R1 represents hydrogen or a methyl group, n is a positive integer and n=2-10, the optical monomer provided by the application has multifunctionality, a high refractive index and low viscosity, and the preparation method is simple, further, the optical monomer with the above structure is introduced into a photopolymer type holographic recording medium, thereby obtaining a holographic recording medium with high sensitivity and high diffraction efficiency, and the application also provides a preparation method of the holographic recording medium, a volume holographic grating containing the holographic recording medium, a holographic optical element and an optical device.

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] Therefore, improving the performance of photopolymers generally requires the base resin to have a lower refractive index and the writing monomer to have a higher refractive index in order to increase the refractive index difference between the two.

[0004] It should be noted that during holographic exposure, the diffraction efficiency of the grating often gradually decreases after reaching its maximum value. This is because shorter polymer chains tend to diffuse from the coherent bright region to the coherent dark region. Therefore, related technologies usually suppress the migration of shorter polymer chains by adding multifunctional monomers. However, multifunctional monomers with high refractive indices have limited selectivity, and they generally have a high degree of molecular conjugation, often containing large π-conjugated systems such as fused rings. As a result, these monomers are mostly solids or highly viscous liquids at room temperature. During holographic exposure, the high viscosity significantly hinders the diffusion and migration of monomer molecules, thereby reducing the refractive index difference between the writing monomer and the film-forming resin, leading to a decline in material performance. Summary of the Invention

[0005] This application aims to provide an optical monomer, a holographic recording medium, a preparation method, and related devices. The optical monomer has both high refractive index and low viscosity, so as to improve the problem in related technologies where the monomer's diffusion and migration are hindered due to excessive viscosity, resulting in a small difference in refractive index between the writing monomer and the film-forming resin, and a decline in material performance.

[0006] In a first aspect, this application provides an optical unit with the following general structural formula: , Where R1 represents hydrogen or methyl, and n is a positive integer and n=2~10.

[0007] As can be seen from the above technical solution, the optical monomer provided in the first aspect of this application simultaneously introduces a six-membered nitrogen-containing aromatic heterocyclic structure and a thiocarbonyl group. The nitrogen atom has high electronegativity, many lone pairs of electrons, and high electronic polarizability. Furthermore, the six-membered heterocycle is rigid and tightly packed intermolecularly, resulting in a high density of polarized groups per unit volume. Compared to chain-like aliphatic amines and ordinary benzene rings, it has a higher density of polarized groups, which can significantly improve the monomer's refractive index. The three sulfur groups formed by the C=S double bond and two CS single bonds in the thiocarbonyl group work together to enhance polarizability, resulting in a very significant increase in refractive index. Its refractive index is greater than 1.6 and less than 1.75, which can effectively match common photosensitive resin systems, reduce light scattering loss during holographic recording, and improve diffraction efficiency. At the same time, the higher refractive index helps to enhance the optical anisotropy of the material, optimizing the resolution and storage capacity of the hologram. Furthermore, the optical monomer provided in this application has multiple acrylate functional groups, providing abundant crosslinking sites for the polymerization reaction, which can significantly increase the crosslinking density of the polymer, thereby fixing short-chain oligomers and inhibiting the migration and diffusion of shorter polymer chains. Secondly, compared with the large conjugated structure of fused rings, the optical monomer provided in this application has a smaller degree of conjugation, so its viscosity is lower (viscosity <100 cP). Therefore, it is easy to diffuse and migrate during holographic exposure, which can ensure the stability of the refractive index difference between the optical monomer (i.e., the recording monomer) and the film-forming resin.

[0008] Secondly, this application provides a method for preparing the aforementioned optical monomer, comprising: Dissolve cyanuric chloride in the first solvent, add sodium trithiocarbonate and react for a period of time, then add compound M1 to react and obtain compound P1. The compound P1 and the acid-binding agent were dissolved in a second solvent, and compound M2 was added to react and obtain the optical monomer. Wherein, the general structural formula of compound M1 is X represents a bromine atom or a chlorine atom, n is a positive integer, and n=2~10, and the compound M2 is acryloyl chloride or methacryloyl chloride.

[0009] 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 and has a high yield, which is convenient for large-scale production.

[0010] 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) The aforementioned optical monomers; Component d) Polymerizable monomers; Component e) Photosensitive initiation system; Component f) Chain transfer agent; Component g) Optional catalyst; Component h) Optional additives.

[0011] As can be seen from the above technical solution, this application provides a photopolymer-type holographic recording medium containing the aforementioned optical monomer. By introducing an optical monomer with a six-membered nitrogen-containing aromatic heterocyclic structure and a thiocarbonyl group into the photopolymer-type holographic recording medium, the optical monomer, due to its low viscosity and high refractive index, easily diffuses and migrates during holographic exposure, significantly increasing the refractive index difference between the optical monomer (i.e., the recording monomer) and the film-forming resin. This results in a photopolymer-type holographic recording medium with excellent properties such as high sensitivity and high diffraction efficiency. Specifically, the photopolymer-type holographic recording medium has a diffraction efficiency greater than 95%, a sensitivity greater than 100 cm / mJ, and an exposure dose less than 20 mJ / cm. 2 The shrinkage rate is less than 0.3%.

[0012] 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 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.

[0013] 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.

[0014] Fifthly, this application provides a volume holographic recording grating, the raw material of which includes the photopolymer type holographic recording medium as described above.

[0015] Sixthly, this application provides a holographic optical element, the raw material of which includes the aforementioned photopolymer-type holographic recording medium.

[0016] In a seventh aspect, this application provides an optical device including the holographic optical element as described above.

[0017] As can be seen from the above technical solutions, this application also provides a related device made using the aforementioned photopolymer holographic recording medium, based on the fact that the photopolymer holographic recording medium has a sensitivity greater than 100 cm / mJ and an exposure dose less than 20 mJ / cm. 2 It also has excellent properties such as a recording grating diffraction efficiency greater than 95%.

[0018] 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. Based on an exposure energy below 20 mJ / cm... 2 This demonstrates that only a small amount of light energy is needed to complete the curing and photopolymerization of the photopolymer holographic recording medium, thus avoiding overheating and deformation of the material caused by high-energy exposure. Based on a diffraction efficiency greater than 95%, it indicates that almost all incident light energy is diffracted to the target direction by the grating, thereby reducing light energy loss and resulting in a clearer image. Therefore, target devices (such as volume holographic recording gratings, optical elements, and optical devices) fabricated using photopolymer holographic recording media possess optical properties such as high recording speed and clear imaging. Attached Figure Description

[0019] Figure 1 The chemical reaction formula for preparing optical monomers according to embodiments of this application is shown. Figure 2 The chemical reaction formula for preparing optical monomer 1 in Example 1 of this application is shown; Figure 3 The chemical reaction formula for preparing optical monomer 2 in Example 2 of this application is shown; Figure 4 The chemical reaction formula for preparing optical monomer 3 in Example 3 of this application is shown; Figure 5 This application illustrates the photopolymer-type holographic recording medium 4 in Embodiment 4. Exposure characteristic curves of photopolymer holographic recording media 4-3; Figure 6 The exposure characteristic curves of the photopolymer holographic recording media in Comparative Examples 1 to 3 of this application are shown. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] It should be noted that the terms "photopolymer holographic recording medium" and "holographic recording medium" are equivalent in this application, "volume holographic grating" is equivalent to "phase-type volume holographic grating", "holographic grating" and "recording grating", and "substrate resin" is equivalent to "film-forming resin".

[0026] It should be understood that photopolymer-based holographic recording media materials used for holographic recording achieve holographic recording by using light to polymerize writing monomers, which then form a refractive index-modulated phase-type holographic grating with the film-forming resin. Specifically, when the writing monomers in the coherent bright region are consumed and their concentration decreases, the unreacted writing monomers in the coherent dark region rapidly migrate to the coherent bright region, squeezing the film-forming resin in the bright region into the coherent dark region. Ultimately, the refractive index of the coherent bright region approaches the refractive index of the writing monomers, and the refractive index of the coherent dark region approaches the refractive index of the film-forming resin, thus forming a refractive index-modulated phase-type volume holographic grating.

[0027] It should be noted that photopolymer-based holographic recording media with superior performance typically require the film-forming resin to have a lower refractive index and the writing monomer to have a higher refractive index in order to increase the difference in refractive index between the two.

[0028] However, in existing technologies, high-refractive-index monomers generally possess a high degree of molecular conjugation, often containing large π-conjugated systems such as fused rings. This results in these monomers being mostly solids or highly viscous liquids at room temperature. During holographic exposure, this high viscosity significantly hinders the diffusion and migration of monomer molecules, thereby reducing the refractive index modulation difference between the exposed and unexposed areas. This severely affects the diffraction efficiency of photopolymer-based holographic recording media, leading to a decline in material performance. For example, it reduces the grating's ability to control incident light, causes excessive light energy loss, and results in low diffraction efficiency of optical devices and unclear imaging, failing to meet the growing demands of users.

[0029] Based on this, this application provides an optical monomer as a component of a writing monomer, the general chemical formula of which is shown below: , where R1 represents hydrogen or methyl, and n is a positive integer and n=2~10.

[0030] As can be seen from the general structural formula of the optical monomer, it simultaneously introduces a six-membered nitrogen-containing aromatic heterocyclic structure and a thiocarbonyl group. The nitrogen atom has high electronegativity, numerous lone pairs of electrons, and high electronic polarizability. Furthermore, the six-membered heterocycle is rigid and tightly packed intermolecularly, resulting in a high density of polarized groups per unit volume. Compared to chain-like aliphatic amines and ordinary benzene rings, it exhibits a higher density of polarized groups, significantly improving the monomer's refractive index. The C=S double bond and the three sulfur groups formed by the two CS single bonds in the thiocarbonyl group further enhance the polarizability, resulting in a very significant increase in refractive index. Its refractive index is greater than 1.6 and less than 1.75, effectively matching common photosensitive resin systems, reducing light scattering loss during holographic recording, and improving diffraction efficiency. Simultaneously, the higher refractive index helps enhance the optical anisotropy of the material, optimizing the resolution and storage capacity of the hologram. Furthermore, the optical monomer provided in this application has multiple acrylate functional groups, providing abundant crosslinking sites for the polymerization reaction, which can significantly increase the crosslinking density of the polymer, thereby fixing short-chain oligomers and inhibiting the migration and diffusion of shorter polymer chains. Secondly, compared with the large conjugated structure of fused rings, the optical monomer provided in this application has a smaller degree of conjugation, so its viscosity is lower (viscosity <100 cP). Therefore, it is easy to diffuse and migrate during holographic exposure, which can ensure the stability of the refractive index difference between the optical monomer (i.e., the recording monomer) and the film-forming resin.

[0031] For example, the value of n can be 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0032] For example, an optical monomer can be a compound having the following chemical structural formula: , or Etc. It should be noted that the above optical components are merely illustrative examples, and the optical components provided in this application are not limited to these.

[0033] Furthermore, such as Figure 1 As shown, this application also provides a method for preparing the above-mentioned optical monomer, including the following steps S1 and S2: Step S1: Dissolve cyanuric chloride in the first solvent, add sodium trithiocarbonate, and react for a period of time. Then, add compound M1 to react and obtain compound P1. The general structural formula of compound M1 is: X represents a bromine or chlorine atom, and n is a positive integer, with n=2~10.

[0034] It is understandable that in step S1, cyanuric chloride reacts with sodium trithiocarbonate to first generate trithiocarbonate, which then undergoes a substitution reaction with compound M1 to yield compound P1. The general structural formula of compound P1 is... , where n is a positive integer and n = 2 to 10.

[0035] In some examples, step S1 is carried out in an ice bath (0°C) and an inert environment. The inert environment is, for example, protected by an inert gas, including but not limited to nitrogen and argon. It should be understood that reacting in an inert gas atmosphere can maintain the stability of the reaction system, thereby avoiding the destruction of sensitive reaction substrates or intermediates, and thus improving the reaction yield. Therefore, those skilled in the art can provide inert protection for the reaction according to actual needs, and this application does not limit it.

[0036] For example, step S1 is performed in an ice bath (0°C) under nitrogen protection.

[0037] In some examples, the molar ratio of cyanuric chloride, sodium trithiocarbonate, and compound M1 is 1:(3–3.2):(3–3.2). Typical, but not limiting, the molar ratio of cyanuric chloride, sodium trithiocarbonate, and compound M1 can be, for example, 1:3:3, 1:3.1:3.1, 1:3.2:3.2, 1:3.1:3.2, 1:3.2:3.1, 1:3:3.2, 1:3:3.1, 1:3.1:3, or 1:3.2:3, etc.

[0038] For example, under ice bath (0°C) and nitrogen protection, 1 equivalent of cyanuric chloride was dissolved in an anhydrous solvent, and 3 equivalents of sodium trithiocarbonate were added dropwise. After the addition was complete, the reaction was stirred for about 10-60 minutes, and then the reaction system was slowly restored to room temperature and stirred for another 10-60 minutes. Subsequently, the temperature was slowly increased to 50-100°C and stirred for another 10-60 minutes. The reaction system was then slowly cooled to 0-4°C, and 3 equivalents of compound M1 were added dropwise, while stirring was continued for 30-60 minutes. After the reaction was completed, excess solvent was removed by rotary evaporation, and compound P1 was obtained by column chromatography.

[0039] It should be noted that in some examples, the trithiocarbonate produced by the reaction of cyanuric chloride and sodium trithiocarbonate can be separated and purified before reacting with compound M1. This application does not impose any limitations.

[0040] The first solvent includes, but is not limited to, one or more of acetone, tetrahydrofuran, chloroform, dichloroethane, DMF (N,N-dimethylformamide), acetonitrile, or toluene.

[0041] Step S2: Dissolve compound P1 and an acid-binding agent in a second solvent, and add compound M2 to react and obtain an optical monomer. Compound M2 is acryloyl chloride or methacryloyl chloride.

[0042] The second solvent includes, but is 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, and 1,4-dioxane. It should be noted that the above solvents are merely illustrative, and the solvents that can be used in this application are not limited to these.

[0043] It is understandable that in step S2, compound P1 is activated by an acid-binding agent to generate a more reactive alkoxy group, thereby enhancing nucleophilicity and further promoting the substitution reaction between compound P1 and compound M2 to obtain an optical monomer.

[0044] In some specific examples, the reaction is typically carried out at 0°C (i.e., in an ice bath), and a reaction time of 0.5 h to 3 h usually yields better results. For example, compound M2 is added dropwise to a mixed solution of compound P1 and an acid-binding agent at 0°C to avoid local overheating or excessive concentration that could trigger side reactions. The acid-binding agent includes, but is not limited to, triethylamine, pyridine, N,N Diisopropylethylamine, 4 One or more of the following: dimethylaminopyridine, tetrabutylammonium bromide, sodium acetate, sodium hydroxide, potassium hydroxide, calcium oxide, potassium tert-butoxide, potassium carbonate, ammonium carbonate, and sodium carbonate.

[0045] It should be further understood that, because compound M2 (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 the second intermediate B 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 used in excess. Specifically, in some examples, the molar ratio of compound P1, acid-binding agent, and compound M2 is 1:(6-9):(4-6).

[0046] Typical, but not limiting, molar ratios of compound P1, acid-binding agent, and compound M2 can be, for example, 1:6:4, 1:6:6, 1:9:4, 1:9:6, 1:7:5, 1:8:4, 1:5:5, or 1:9:5.

[0047] In some specific examples, the reaction is more effective when the reaction solvent in step S2 is any one of dichloromethane, trichloromethane, and ethyl acetate.

[0048] For example, 1 equivalent of compound P1 and 6-9 equivalents of triethylamine were dissolved in dichloromethane under ice bath conditions. After stirring for 10 min, 4-6 equivalents of acryloyl chloride or methacryloyl chloride were added dropwise to the mixed solution of compound P1 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 target optical monomer was then obtained by column chromatography.

[0049] In this embodiment, the method for preparing the optical monomer provided in this application is simple and has a high yield, making it easy to scale up production.

[0050] This application also provides a photopolymer holographic recording medium, including a writing monomer, which includes an optical monomer and a polymerizable monomer.

[0051] 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.

[0052] 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) The aforementioned optical monomer, Component d) Polymerizable monomers, Component e) Photosensitive initiation system, Component f) Chain transfer agent, Component g) Optional catalyst, Component h) Optional additives, Among them, compounds with multiple isocyanate reactive functional groups and polyisocyanate group compounds form film-forming resins.

[0053] In this embodiment, an optical monomer with a high refractive index is used as a component of the writing monomer, thereby allowing for a greater refractive index difference between the writing monomer and the film-forming resin. This results in a photopolymer-type holographic recording material possessing 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 an exposure dose less than 20 mJ / cm. 2 .

[0054] 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%.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] In some embodiments, the optical monomer accounts for 0.1 wt% to 30 wt% of the total photopolymer holographic recording medium.

[0066] 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.

[0067] 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.

[0068] 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 ranging from 1.50 to 1.55 and having two or more hydroxyl functional groups.

[0069] For example, compounds having multiple isocyanate reactive functional groups include compounds with a refractive index of 1.50, 1.51, 1.52, 1.53, 1.54, 1.55 or any value between any two of these values, and compounds having two or more hydroxyl functional groups.

[0070] Optionally, the polyisocyanate-based compound includes compounds with a refractive index ranging from 1.50 to 1.55 and having two or more isocyanate groups.

[0071] For example, polyisocyanate compounds include compounds with a refractive index of 1.50, 1.51, 1.52, 1.53, 1.54, 1.55 or any value between any two of these values, and which have two or more isocyanate groups.

[0072] In this embodiment, a compound with multiple isocyanate reactive functional groups and a refractive index between 1.50 and 1.55 and having two or more hydroxyl functional groups forms a low-refractive-index film-forming resin with a polyisocyanate compound having a refractive index between 1.50 and 1.55 and having two or more isocyanate groups. 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 and avoid the increase in background noise caused by the high refractive index of the substrate itself.

[0073] 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.

[0074] Furthermore, in some examples, compounds having multiple isocyanate reactive functional groups may be, for example, 1,2-ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, neopentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1 4-Cyclohexanediol, glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, 1,2,4-butanetriol, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tripentaerythritol, bis(trimethylolpropane), polyethylene glycol with a molecular weight of 200–2000, polypropylene glycol with a molecular weight of 200–2000, polytetramethylene ether glycol with a molecular weight of 200–2000, polytetrahydrofuran with a molecular weight of 200–2000, 1,4-butenylene glycol, 1,4-butynediol, 1,2-decanediol, 1,2-dodecadiol, 2-methyl-1,3-propanediol, 1,7-heptanediol, 1,9-nonanediol, 2,2-diethyl-1, 3-Propanediol, 1,4-Dimethylolcyclohexane, 1,2,3-Hexanetriol, 1,2,4-Hepanetriol, 1,3,5-Pentanetriol, Poly(oxypropylene)triol, Poly(ε-caprolactone)diol, Poly(ε-caprolactone)triol, Poly(propylene carbonate)diol, Poly(butadiene)diol, Hydrogenated poly(butadiene)diol, Poly(ethylene adipate)diol, Poly(butylene adipate)diol, Poly(1,4-butanediol adipate)diol, Poly(glycerol sebacate)diol, Trimethylolpropane ethoxylate (TMP-EO), Trimethylolpropane propoxylate, Pentaerythritol ethoxylate, Glyceryl ethoxylate, Glyceryl propoxylate, Ethylene Diaminetetra(propoxylated), diethylenetriaminepenta(propoxylated), partially hydrolyzed polyvinyl alcohol, poly(1,2-butanediol), poly(1,3-propanediol), poly(1,4-butanediol), poly(1,6-hexanediol), poly(neopentyl glycol), poly(3-methyl-1,5-pentanediol), poly(1,4-cyclohexanediol), tris(2-hydroxyethyl)isocyanurate, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, 2,2,3-trimethyl-1,3-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 1,3-butanediol, or 2-methyl-2,4-pentanediol, but not limited thereto.

[0075] For example, trimethylolpropane ethoxylates are typically trifunctional polyether polyols obtained by reacting trimethylolpropane (TMP) with ethylene oxide (EO). Trimethylolpropane ethoxylates with different EO addition numbers have different molecular weights, viscosities, etc. For instance, TMP... 3EO (also known as polyether TMP) 3) Trimethylolpropane ethoxylate, obtained by adding 3 mol of ethylene oxide (EO) to trimethylolpropane, has a total EO addition number of 3 and contains 3 free terminal hydroxyl groups, with a molecular weight of 266.

[0076] 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, or dicyclohexylmethane diisocyanate.

[0077] 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, or trans-N-3-yntynebutenylcarbazole.

[0078] Among them, alkenylbenzene compounds include, but are not limited to, styrene, 2-chlorostyrene, 2-bromostyrene, 3-chlorostyrene, 3-bromostyrene, 4-chlorostyrene, 4-bromostyrene, p-(chloromethyl)styrene, or p-(bromomethyl)styrene.

[0079] 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, or tetrabromobisphenol A dimethacrylate, etc.

[0080] 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, or 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, etc.

[0081] In specific examples, vinylanthracene compounds may be selected from 2-vinylanthracene, 9-vinylanthracene, etc.

[0082] In specific examples, vinylnaphthalene compounds can be selected from 1-vinylnaphthalene, 2-vinylnaphthalene, etc.

[0083] 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.

[0084] 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.

[0085] 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, 0.005:0.2, 0.01:0.3, 0.02:0.5, 0.05:1.0, 0.1:0.5, 0.2:1.0, 0.3:1.2, 0.5:1.5, 1:0.1, 0.6:2.0, 0.8:2.0, 0.9:2.5, 1.0:2.0, 0.01:0.5, 0.1:1.0, 0.3:1.5, 0.5:2.0, or 1.0:3.0, etc. 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.

[0086] 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.

[0087] 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, pyrylium I, azurite A, crystal violet cyanocyanate, malachite green cyanocyanate, etc.

[0088] Photoinitiators are initiators that can be activated by photochemical radiation and initiate polymerization reactions of corresponding polymerizable groups. They include, but are not limited to, aromatic ketones, benzoin and its derivatives, benzoyl ketals, acylphosphine oxides, ammonium arylboronate, chromium salts, aryl diazonium salts, onium salts, or organometallic compounds.

[0089] 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, or hexaaryldiimidazole.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] In some embodiments, the catalyst is selected from at least one of tertiary amine catalysts and organometallic catalysts, such as 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, but is not limited thereto.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] This application also provides a method for preparing a photopolymer-based holographic recording medium, the method comprising steps S301 and S302, as detailed below: Step S301: Weigh components a), b), c), d), e), f), g), and h) into a container and stir until dissolved to form a mixture solution.

[0104] Step S302: 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.

[0105] 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.

[0106] Furthermore, this application provides a volume holographic recording grating, which is fabricated from the aforementioned photopolymer-type holographic recording medium through holographic exposure.

[0107] 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.

[0108] Specifically, in some examples, the photopolymer holographic recording medium proposed in this application has a sensitivity greater than 100 cm / mJ, a recording grating diffraction efficiency greater than 95%, and an exposure amount less than 20 mJ / cm. 2 It has excellent properties.

[0109] Furthermore, in some examples, the photopolymer holographic recording medium provided in this application also has a shrinkage rate of less than 0.3%, which can ensure accurate grating period precision, avoid optical distortion, and reduce the quality of imaging.

[0110] It is understood that the volume holographic recording grating made from this photopolymer holographic recording medium also possesses the advantages of the aforementioned photopolymer holographic recording medium. In other words, the volume holographic recording grating proposed in this application has high sensitivity, greater than 100 cm / mJ, and a recording grating diffraction efficiency greater than 95%, a shrinkage rate less than 0.3%, and an exposure amount less than 20 mJ / cm. 2 Advantages.

[0111] It should also be understood that a sensitivity greater than 100 cm / mJ indicates that 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. 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 resulting in a clearer image. Exposure energy is required to be below 20 mJ / cm. 2 This demonstrates that only a small amount of light energy is needed to complete the curing and photopolymerization process of the photopolymer holographic recording medium, avoiding overheating and deformation of the material caused by high-energy exposure. Furthermore, the photopolymer holographic recording medium provided in this application significantly increases the refractive index difference between the writing monomer and the film-forming resin by using a high-refractive-index optical monomer as one of the components of the writing monomer and matching it with a low-refractive-index film-forming resin. This further enhances the refractive index modulation of the photopolymer holographic recording medium, thereby strengthening the diffraction capability of the grating and contributing to a wider field of view.

[0112] Furthermore, this application also provides a holographic optical element, which includes the aforementioned volume holographic recording grating. This holographic optical element includes, but is not limited to, an optical waveguide.

[0113] It is understood that the holographic optical element proposed in this application, since the volume holographic recording grating contains 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.

[0114] Furthermore, 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-type holographic storage optical discs, wherein the photopolymer-type holographic storage optical disc can be erasable and rewritable and records in real time, making it suitable for storing large amounts of data and providing very fast data transfer speeds. Therefore, the optical device exhibits excellent optical performance, provides a clear image, and can store large amounts of data.

[0115] For example, AR devices include, but are not limited to, AR glasses.

[0116] 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.

[0117] Example 1 like Figure 2 As shown, optical monomer 1 is prepared.

[0118] Under ice bath (0℃) and nitrogen protection, cyanuric chloride (10 mmol) was dissolved in acetone (30 mL), and sodium trithiocarbonate (30 mmol) was added dropwise. After about 10-60 min of addition, the reaction system was brought back to room temperature and stirred for another 10-60 min. Then, the temperature was raised to 50-100℃ and stirred for another 10-60 min. After cooling the reaction system to 0-4℃, compound M1-1 (30 mmol) was added dropwise and stirred for another 30-60 min. After the reaction was completed, excess solvent was removed by rotary evaporation, and compound P1-1 was obtained by column chromatography.

[0119] Under ice bath conditions, compound P1-1 (10 mmol) and triethylamine (60 mmol) were dissolved in dichloromethane (20 mL). After stirring for 10 min, acryloyl chloride (40 mmol) was added dropwise to the mixed solution of compound P1-1 and triethylamine at 0 °C. After the reaction was complete, dilute hydrochloric acid was added to remove excess acryloyl chloride. The mixture was 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 1 of this application was obtained by column chromatography with a yield of 96.4%.

[0120] The characterization data are as follows: 1H NMR (600 MHz, CDCl3) δ 6.13 – 6.06 (m, 3H), 5.87 (dd, J = 13.5, 0.8Hz, 6H), 4.40 (t, J = 7.1 Hz, 6H), 3.53 (t, J = 7.1 Hz, 6H). 13 C NMR (151 MHz, CDCl3) δ 208.84, 176.94, 166.65, 131.68, 128.23,64.29, 34.39. Example 2 like Figure 3 As shown, optical monomer 2 is prepared.

[0121] Under ice bath (0℃) and nitrogen protection, cyanuric chloride (10 mmol) was dissolved in tetrahydrofuran (30 mL), and sodium trithiocarbonate (32 mmol) was added dropwise. After about 10-60 min of addition, the reaction system was brought back to room temperature and stirred for another 10-60 min. Then, the temperature was raised to 50-100℃ and stirring was continued for about 10-60 min. After cooling the reaction system to 0-4℃, compound M1-2 (32 mmol) was added dropwise and stirring was continued for 30-60 min. After the reaction was completed, excess solvent was removed by rotary evaporation, and compound P1-2 was obtained by column chromatography.

[0122] Under ice bath conditions, compound P1-2 (10 mmol) and pyridine (90 mmol) were dissolved in chloroform (20 mL). After stirring for 10 min, methacryloyl chloride (40 mmol) was added dropwise to the mixed solution of compound P1-2 and pyridine at 0 °C. After the reaction was complete, dilute hydrochloric acid was added to remove excess methacryloyl chloride. The mixture was 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 2 of this application was obtained by column chromatography with a yield of 95.9%.

[0123] The characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 5.96 (m, 3H), 5.61 (m, 3H), 4.12 – 4.08 (m,6H), 3.15 (t, J = 7.1 Hz, 6H), 1.94 (s, 9H), 1.75 (m, 12H), 1.56 – 1.49 (m,6H). 13C NMR (151 MHz, CDCl3) δ 209.00, 176.94, 167.23, 136.62, 125.04, 65.99, 34.57, 28.29, 28.06, 25.22, 18.27. Example 3 like Figure 4 As shown, optical monomer 3 was prepared.

[0124] Under ice bath (0℃) and nitrogen protection, cyanuric chloride (10 mmol) was dissolved in toluene (30 mL), and sodium trithiocarbonate (31 mmol) was added dropwise. After about 10-60 min of addition, the reaction system was brought back to room temperature and stirred for another 10-60 min. Then, the temperature was raised to 50-100℃ and stirring was continued for about 10-60 min. After cooling the reaction system to 0-4℃, compound M1-3 (32 mmol) was added dropwise and stirring was continued for 30-60 min. After the reaction was completed, excess solvent was removed by rotary evaporation, and compound P1-3 was obtained by column chromatography.

[0125] Compound P1-3 (10 mmol) and N,N were reacted under ice bath conditions. Diisopropylethylamine (80 mmol) was dissolved in dichloromethane (20 mL), stirred for 10 min, and then acryloyl chloride (50 mmol) was added dropwise to compound P1-3 and N,N at 0 °C. 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 the excess solvent was removed by rotary evaporation. The optical monomer 3 of this application was obtained by column chromatography with a yield of 98.7%.

[0126] The characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 6.13 – 6.06 (m, 3H), 5.89 – 5.83 (m, 6H), 3.82 (t, J = 7.1 Hz, 6H), 3.13 (t, J = 7.1 Hz, 6H), 1.69 (dp, J = 27.0, 7.2Hz, 12H), 1.42 – 1.28 (m, 18H), 1.28 – 1.22 (m, 18H). 13C NMR (151 MHz, CDCl3) δ 202.01, 172.69, 166.40, 131.49, 128.33,65.10, 32.52, 29.77, 29.51, 29.47, 29.36, 29.31, 28.74, 26.13. Example 4 Photopolymer-type holographic recording media 4-1 to 4-3 were prepared using the optical monomers described in Examples 1-3. 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 and contents of the photopolymer-type holographic recording media 4-1 to 4-3 are shown in Tables 1 to 3.

[0127] Table 1

[0128] Table 2

[0129] Table 3

[0130] Comparative Example 1 Compared with the photopolymer-type holographic recording medium 4 in Example 4 The components of 1 are roughly the same, except that optical monomer 1 is not added in the comparative example, but 25 wt% of 2-naphthalene methacrylate is added to obtain a common photopolymer type holographic recording medium 1.

[0131] Comparative Example 2 Compared with the photopolymer-type holographic recording medium 4 in Example 4 The components of 2 are roughly the same, except that the optical monomer 2 is not added in the comparative example, but 48 wt% of 2-vinylnaphthalene is added to obtain a common photopolymer type holographic recording medium 2.

[0132] Comparative Example 3 Compared with the photopolymer-type holographic recording medium 4 in Example 4 The components of 3 are roughly the same, except that optical monomer 3 is not added in the comparative example, but 42 wt% of p-bromophenyl methacrylate is added to obtain a common photopolymer type holographic recording medium 3.

[0133] Test case (1) Test the refractive index and viscosity of the optical monomers synthesized in Examples 1 to 3.

[0134] The refractive index of the optical components in Examples 1-3 was tested using an Abbe refractometer at a temperature of 20°C. The test method was in accordance with the national standard GB / T 6488-2022. The test results are shown in Table 4 below.

[0135] The viscosity of the optical monomers in Examples 1-3 was tested using a viscometer at a temperature of 25°C. The test method was carried out according to the rotation method in GB / T 10247 2008. The test results are shown in Table 4 below.

[0136] (2) The performance of the photopolymer holographic recording media 4-1 to 4-3 containing optical monomers in Example 4 and the ordinary photopolymer holographic recording media of the comparative example were tested, and the results are shown in Table 5.

[0137] During testing, the various holographic recording media in Example 4 can be exposed to lasers of different wavelengths depending on the photosensitive system, with an exposure intensity of 3 mW / cm². 2 .

[0138] 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) of the photopolymer holographic recording medium is calculated by formula (1), and the photosensitivity (S) of the photopolymer holographic recording medium is calculated by formula (2).

[0139]

[0140] In the formula, η is the diffraction efficiency, and I d For diffracted light, I t denoted as transmitted light, S as photosensitivity, E as exposure energy, and ΔE as the exposure energy required to achieve maximum diffraction efficiency.

[0141] Table 4. Refractive index and viscosity of optical monomers in Examples 1-3

[0142] Table 5. Holographic performance parameters of the holographic recording media in Example 4 and the comparative example.

[0143] Please refer to Tables 4 and 5. Table 4 shows the refractive index and viscosity data of the optical monomers prepared in Examples 1-3 of this application, and Table 5 shows the holographic performance parameters of the photopolymer holographic recording medium measured when optical monomers 1 to 3 are applied to the photopolymer holographic recording medium.

[0144] As shown in Table 4, the refractive indices of optical monomers 1 to 3 provided in this application embodiment are between 1.66 and 1.70. The high refractive indices of these optical monomers, when applied to photopolymer holographic recording media, can 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 generate a stronger grating structure and increase the grating storage density. Simultaneously, the viscosities of optical monomers 1 to 3 are between 21 cP and 35 cP. Lower viscosity optical monomers facilitate migration and diffusion during holographic exposure, resulting in a holographic recording medium with uniform texture and excellent performance.

[0145] Please see Figure 5 , Figure 6 According to Table 5, the photopolymer holographic recording media 4-1 to 4-3 provided in this application, due to containing the aforementioned optical monomers 1 to 3, have an exposure amount of 5.10 mJ / cm. 2 ~ 8.96mJ / cm 2 The diffraction efficiency was 95.51% ~ 96.40%, and the sensitivity was 109.27 cm / mJ ~ 191.63 cm / mJ, while the exposure of the ordinary photopolymer holographic recording media 1 to 3 prepared in Comparative Examples 1 to 3 was 53.37 mJ / cm. 2 ~ 84.25 mJ / cm 2 The diffraction efficiency is 36.78% ~ 68.23%, and the sensitivity is 7.84 cm / mJ ~ 15.48 cm / mJ. That is, the exposure of the photopolymer holographic recording medium provided in this application is much less than that of the ordinary holographic recording medium prepared in the comparative example. Moreover, the diffraction efficiency and sensitivity of the photopolymer holographic recording medium provided in this application are much higher than those of the ordinary holographic recording medium prepared in the comparative example. This means that the holographic recording medium provided in this application has high light energy utilization, significantly improved brightness and clarity of holographic display, faster data transmission speed, and the material is not prone to overheating and deformation due to high-energy exposure.

[0146] Specifically, such as Figure 5 and Figure 6 As shown, comparing the photopolymer holographic recording medium 4-1 containing the optical monomer 1 of this application with the ordinary photopolymer holographic recording medium 1 of Comparative Example 1, comparing the photopolymer holographic recording medium 4-2 containing the optical monomer 2 of this application with the ordinary photopolymer holographic recording medium 2 of Comparative Example 2, and comparing the photopolymer holographic recording medium 4-3 containing the optical monomer 3 of this application with the ordinary photopolymer holographic recording medium 3 of Comparative Example 3, it can be seen that the photopolymer holographic recording medium containing the optical monomer of this application has a higher diffraction efficiency and requires a lower exposure.

[0147] 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 chemical structural formula is shown below: ， Where R1 represents hydrogen or methyl, and n is a positive integer and n=2~10.

2. The optical unit according to claim 1, characterized in that, The optical monomer comprises at least the following compounds with the following chemical structural formulas: , or .

3. A method for preparing an optical monomer as described in claim 1, characterized in that, The steps include the following: Cyanuric chloride was dissolved in the first solvent and sodium trithiocarbonate was added and reacted for a period of time. Then, compound M1 was added and reacted to obtain compound P1. The compound P1 and the acid-binding agent were dissolved in a second solvent, and compound M2 was added to react and obtain the optical monomer. The general chemical structural formula of compound M1 is as follows: X represents a bromine or chlorine atom, n is a positive integer, and n = 2~10. The general chemical structural formula of the compound P1 is: The compound M2 is acryloyl chloride or methacryloyl chloride.

4. The preparation method according to claim 3, characterized in that, The first solvent is selected from one or more of acetone, tetrahydrofuran, chloroform, dichloroethane, N,N-dimethylformamide, acetonitrile, or toluene; And / or, 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 methanol, ethanol, petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, benzene, toluene, N,N-dimethylformamide, dimethyl sulfoxide, dimethoxyethane, and 1,4-dioxane.

5. The preparation method according to claim 3 or 4, characterized in that, The molar ratio of the cyanuric chloride, the sodium trithiocarbonate, and the compound M1 is 1:(3-3.2):(3-3.2). And / or, the molar ratio of the compound P1, the acid-binding agent and the compound M2 is 1:(6-9):(4-6).

6. 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) The optical monomer as described in claim 1; Component d) Polymerizable monomers; Component e) Photosensitive initiation system; Component f) Chain transfer agent; Component g) Optional catalyst; Component h) Optional additives.

7. The photopolymer-type holographic recording medium according to claim 6, 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%.

8. The photopolymer-type holographic recording medium according to claim 6, 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.

9. The photopolymer-type holographic recording medium according to claim 6, characterized in that, The isocyanate reactive functional group is hydroxyl; and the compound having multiple isocyanate reactive functional groups includes compounds with a refractive index ranging from 1.50 to 1.55 and having two or more hydroxyl functional groups. And / or, the polyisocyanate-based compound includes compounds with a refractive index ranging from 1.50 to 1.55 and having two or more isocyanate groups; 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 selected from at least one of tertiary amine catalysts and organometallic catalysts; And / or, the additives include at least one of defoamers, leveling agents, plasticizers, and dehydrating agents.

10. The photopolymer-type holographic recording medium according to claim 9, characterized in that, The compounds having multiple isocyanate reactive functional groups include 1,2-ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, neopentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol. Alcohols, glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, 1,2,4-butanetriol, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tripentaerythritol, bis(trimethylolpropane), polyethylene glycol with a molecular weight of 200–2000, polypropylene glycol with a molecular weight of 200–2000, polytetramethylene ether glycol with a molecular weight of 200–2000, polytetrahydrofuran with a molecular weight of 200–2000, 1,4-butenylene glycol, 1,4-butynediol, 1,2-decanediol, 1,2-dodecadiol, 2-methyl-1,3-propanediol, 1,7-heptanediol, 1,9-nonanediol, 2,2-diethyl- 1,3-Propane glycol, 1,4-Dimethylolcyclohexane, 1,2,3-Hexanetriol, 1,2,4-Hepanetriol, 1,3,5-Pentanetriol, Poly(oxypropylene)triol, Poly(ε-caprolactone)diol, Poly(ε-caprolactone)triol, Poly(propylene carbonate)diol, Poly(butadiene)diol, Hydrogenated poly(butadiene)diol, Poly(ethylene adipate)diol, Poly(butylene adipate)diol, Poly(1,4-butanediol adipate)diol, Poly(glycerol sebate)diol, Trimethylolpropane ethoxylate, Trimethylolpropane propoxylate, Pentaerythritol ethoxylate, Glyceryl ethoxylate, Glyceryl propoxylate, Ethylene glycol At least one of the following: amine tetra(propoxylate), diethylenetriaminepenta(propoxylate), partially hydrolyzed polyvinyl alcohol, poly(1,2-butanediol), poly(1,3-propanediol), poly(1,4-butanediol), poly(1,6-hexanediol), poly(neopentyl glycol), poly(3-methyl-1,5-pentanediol), poly(1,4-cyclohexanediol), tris(2-hydroxyethyl)isocyanurate, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, 2,2,3-trimethyl-1,3-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 1,3-butanediol, or 2-methyl-2,4-pentanediol; 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.

11. The photopolymer-type holographic recording medium according to claim 9, 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 is selected from at least one of aromatic ketone compounds, benzoin and its derivatives, benzoyl ketal, acylphosphine oxide, ammonium arylboronate, chromium salt, aryl diazonium salt, onium salt and organometallic compounds; The mass ratio of the photosensitizer to the photoinitiator is (0.001~1): (0.1~3).

12. The photopolymer-type holographic recording medium according to claim 9, 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, triethyl orthoformate, CUWR-WB20 dehydrating agent, ALT-201 dehydrating agent, or PCCI dehydrating agent, wherein the dehydrating agent accounts for less than or equal to 3 wt% of the photopolymer holographic recording medium.

13. A method for preparing a photopolymer-type holographic recording medium as described in any one of claims 6-12, 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 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.

14. The preparation method according to claim 13, 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.

15. A volume holographic recording grating, characterized in that, The volumetric holographic recording grating is fabricated by holographic exposure of the photopolymer holographic recording medium as described in any one of claims 6-12.

16. A holographic optical element, characterized in that, The holographic optical element includes the volume holographic recording grating as described in claim 15.

17. An optical device, characterized in that, Includes the holographic optical element as described in claim 16.

Images