(METH)acrylate monomer, and preparation method therefor and use thereof

Abstract

A (meth)acrylate monomer, and a preparation method therefor and a use thereof. The general structural formula of the (meth)acrylate monomer is as shown in (I) below, wherein n is an integer of 1-20, R1 is methyl or hydrogen, and R2 and R3 are selected from hydrogen, Br, phenyl, methyl, or (II), wherein A1 in (II) is phenyl or methyl.

Description

(Meth)acrylate monomers, their preparation methods and applications

[0001] Cross-reference of related applications

[0002] This application is based on and claims priority to Chinese Patent Application No. 2024119335388, filed on December 25, 2024, entitled "(Meth)acrylate monomers and their preparation methods and applications", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of holographic materials technology, and in particular to (meth)acrylate monomers, their preparation methods and applications. Background Technology

[0004] The various components used to make holographic recording media, such as photosensitive dyes, initiators, chain transfer agents, writing monomers, film-forming resins, and plasticizers, work together to determine the performance of the holographic recording media.

[0005] The migration rate and polymerization rate of the writing monomers jointly determine the grating formation speed. A faster migration rate than polymerization rate is required to obtain a grating with stable refractive index modulation. When the writing monomers located in the coherent bright region polymerize, the unreacted writing monomers in the coherent dark region rapidly migrate to the bright region, squeezing the film-forming resin from the bright region into the dark region. This makes the refractive index of the bright region close to that of the writing monomers, and the refractive index of the dark region close to that of the film-forming resin. Simultaneously, a refractive index difference between the writing monomers and the film-forming resin is necessary to form a refractive index-modulated volume holographic grating. A greater refractive index difference between the writing monomers and the film-forming resin allows the holographic recording medium to form a refractive index-modulated volume holographic grating more quickly. In existing refractive index-modulated phase-type volume holographic gratings prepared by photopolymers, the refractive index difference between the writing monomers and the film-forming resin is not significant enough, preventing the rapid construction of the refractive index-modulated volume holographic grating and affecting the performance of the holographic recording medium. Summary of the Invention

[0006] In view of this, this application proposes a (meth)acrylate monomer, its preparation method and application, aiming to achieve a high refractive index for the (meth)acrylate monomer, so as to improve the holographic optical performance of the photopolymer holographic recording medium containing the (meth)acrylate monomer.

[0007] The (meth)acrylate monomers proposed in the first aspect of this application have the following general structural formula:

[0008] Wherein, n is an integer from 1 to 20, R1 is methyl or hydrogen; R2 and R3 are selected from hydrogen, Br, phenyl, methyl or in A1 in the text represents either phenyl or methyl.

[0009] As can be seen from the above technical solutions, the (meth)acrylate monomers proposed in the first aspect of this application possess (meth)acrylate groups, exhibiting high refractive index and low volume shrinkage properties; they also contain multiple aromatic ring groups with high molar refractive index and low molar volume, as well as some sulfur atoms that inherently possess high refractive index, resulting in a high overall refractive index for the monomer molecule. When the monomer contains halogen and aromatic ring structures, the overall viscosity of the monomer is low due to the simultaneous presence of alkyl chains; in this application, the length of the C chain in the main chain can be adjusted by adjusting the number of n, thereby adjusting the mechanical properties, viscosity, and compatibility with other components of the entire molecule.

[0010] The preparation method of the (meth)acrylate monomers in the aforementioned examples according to the second aspect of this application includes the following steps: dissolving compound P1 and compound M1 in an organic solvent, adding a first photoinitiator, and reacting under light to obtain compound P2; completely mixing compound P2 with an acid-binding agent in an organic solvent, adding compound M2 until the reaction is complete, removing excess reactants, removing solvent, and separating to obtain the (meth)acrylate monomers;

[0011] The general structural formula of compound P1 is: R2 and R3 are selected from hydrogen, Br, phenyl, methyl, or... A1 in the text is either phenyl or methyl;

[0012] The structural formula of compound M1 is as follows: Where n is an integer from 1 to 20;

[0013] The compound M2 is R1 is either methyl or hydrogen.

[0014] The method for preparing (meth)acrylate monomers proposed in the second aspect of this application involves a two-step reaction to synthesize the desired (meth)acrylate monomers. The reaction conditions during the synthesis process are easy to control. The use of a first photoinitiator allows the reaction between compound P1 and compound M1 to be rapidly initiated and the reaction rate to be increased. In the reaction, the unsaturated bond of compound M1, which contains alkyne and hydroxyl groups, undergoes ring opening and connects to the S group in the thiol group of compound P1 to form compound P2 with saturated covalent bonds (SC bonds). The hydroxyl group in compound P2 then reacts with the halogen in compound M2 to finally generate a compound with (meth)acrylate groups. The molecular structure of the entire compound is stable.

[0015] The third aspect of this application discloses a photopolymer-type holographic recording medium containing (meth)acrylate monomers, including a writing monomer, wherein the writing monomer includes the (meth)acrylate monomer and a polymerizable monomer.

[0016] The photopolymer holographic recording medium containing (meth)acrylate monomers proposed in the third aspect of this application, by adding (meth)acrylate monomers and polymerizable monomers, the two components can cooperate to form a writing monomer component with a high refractive index, thereby enabling the writing monomer and the film-forming resin to have a greater refractive index difference, providing the necessary material basis for the formation of phase-type volume holographic gratings with refractive index modulation in the photopolymer holographic recording medium.

[0017] A holographic optical element is provided in the fourth aspect of this application, wherein the raw material of the holographic optical element includes the photopolymer type holographic recording medium of the foregoing examples.

[0018] The holographic optical element proposed in the fourth aspect of this application has excellent holographic performance, high diffraction efficiency, high sensitivity, and low required exposure amount.

[0019] An optical device is provided in the fifth aspect of this application, including the holographic optical element as described above.

[0020] The optical devices proposed in the fifth aspect of this application, such as head-up display devices, augmented reality devices, virtual reality devices, and photopolymer holographic storage optical discs, have excellent holographic performance.

[0021] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the embodiments of this application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 is a graph showing the holographic exposure characteristics of photopolymer holographic recording media 2-1, 2-2, and 2-3 in Example 2;

[0024] Figure 2 shows the holographic exposure characteristic curves on a scale. Detailed Implementation

[0025] 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. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application.

[0026] Photopolymer materials used for holographic recording utilize light to polymerize writing monomers, which then combine with film-forming resin to form a phase-type holographic grating with refractive index modulation to achieve holographic recording. In the coherent bright region, monomer polymerization is consumed, reducing its concentration, while in the coherent dark region, monomers hardly react. This difference in monomer concentration between the bright and dark regions causes monomers in the dark region to migrate towards the bright region. Simultaneously, the film-forming resin in the bright region is squeezed into the dark region. Ultimately, the refractive index of the bright region approaches the refractive index of the polymer, and the refractive index of the dark region approaches the refractive index of the film-forming resin, thus forming a phase-type volume holographic grating with refractive index modulation.

[0027] This application provides a (meth)acrylate monomer as a component of the writing monomer, which, when combined with an isocyanate-alcohol with a lower refractive index as a film-forming resin, forms a volume holographic grating with a greater refractive index difference, thereby improving the holographic performance of the photopolymer holographic recording medium.

[0028] Where there is no conflict, the following embodiments and features can be combined with each other.

[0029] The (meth)acrylate monomers of this application are described below.

[0030] According to the present application, a (meth)acrylate monomer has the following general structural formula:

[0031] Where n is an integer from 1 to 20, R1 is methyl or hydrogen; R2 and R3 are selected from hydrogen, Br, phenyl, methyl or in A1 in the text represents either phenyl or methyl.

[0032] As can be seen from the above, the (meth)acrylate monomers proposed in this application possess (meth)acrylate groups, exhibiting high refractive index and low volume shrinkage. They also contain multiple aromatic ring groups with high molar refractive index and low molar volume, as well as some sulfur atoms with inherently high refractive index, resulting in a high overall refractive index for the monomer molecule. When the monomer contains halogen and aromatic ring structures, the viscosity is low due to the presence of alkyl chains. In this application, the length of the C chain in the main chain can be adjusted by changing the number of 'n', thereby adjusting the mechanical properties, viscosity, and compatibility with other components of the entire molecule. Good compatibility with other components allows the acrylate groups to quickly connect surrounding small molecules, enhancing holographic performance when used in photopolymer-type holographic recording media.

[0033] In some examples, (meth)acrylate monomers are selected from monomers having the following structural formula:

[0034] Where R1 is methyl or hydrogen, and n is an integer from 1 to 10.

[0035] Therefore, the (meth)acrylate monomers in the above examples all possess advantages such as high refractive index, small molecular size, multiple short branches, good compatibility with other components, and easy migration. The structures of the (meth)acrylate monomers in the above examples are merely exemplary and not exhaustive; any compound belonging to the aforementioned general formula G of this application should be within the scope of protection of this application.

[0036] In some examples, the refractive index of the (meth)acrylate monomers is 1.60–1.65, and the kinematic viscosity is 20–100 mm. 2 / s.

[0037] The preparation method of the (meth)acrylate monomers of this application is described below.

[0038] The preparation methods of (meth)acrylate monomers in the foregoing examples proposed in this application include the following steps:

[0039] Step S1: Dissolve compound P1 and compound M1 in an organic solvent, add the first photoinitiator, and react under light to obtain compound P2.

[0040] The general structural formula of compound P1 in step S1 is: R2 and R3 are selected from hydrogen, Br, phenyl, methyl, or... A1 in the text is either phenyl or methyl;

[0041] The structural formula of compound M1 is Where n is an integer from 1 to 20.

[0042] In some specific examples, compound P1 is selected from compounds having the following structural formula. The following compounds are merely examples and not an exhaustive list. All compounds that conform to the general structural formula of compound P1 should be included within the scope of protection of this application:

[0043] Understandably, in step S1, the first photoinitiator is rapidly activated under light irradiation, enabling compounds P1 and M1 to reach the desired reaction conditions. The alkyne in compound M1 undergoes ring opening and combines with the thiol-S- group in compound P1. The general structural formula of compound P2 generated in step S1 is as follows:

[0044] Where n is an integer from 1 to 20, and R2 and R3 are selected from hydrogen, Br, phenyl, methyl, or A1 in the text represents either phenyl or methyl.

[0045] In some examples, the first photoinitiator is selected from at least one of (2,4,6-trimethylbenzoyl chloride)diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonate, 2-methyl-1-[4-methylthiophenyl]-2-morpholino-1-propanone, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether, methyl o-benzoylbenzoate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-1-(4-(2-hydroxy-2-methylpropionylphenyl)benzyl)-2-methyl-1-propanone, bis(2,6-difluoro-3-pyrrolephenyldicaprotitanium), and ethyl 4-dimethylaminobenzoate.

[0046] Among these examples of first photoinitiators, (2,4,6-trimethylbenzoyl chloride) diphenylphosphine oxide (also known as photoinitiator TPO) has an absorption wavelength of 350 nm to 400 nm. After being irradiated with light, it can generate two free radicals, benzoyl and phosphoryl, both of which can initiate polymerization. It has a fast photocuring speed, low volatility, non-yellowing coating, low polymerization effect, and no residue, and can be used in transparent layer structures.

[0047] Ethyl 2,4,6-trimethylbenzoylphosphonate (also known as photoinitiator TPO-L) has an absorption wavelength of 270 nm to 370 nm.

[0048] 2-Methyl-1-[4-methylthiophenyl]-2-morpholino-1-propanone (also known as photoinitiator 907) has an absorption wavelength of 231 nm to 307 nm and exhibits extremely high absorption.

[0049] 1-Hydroxy-cyclohexyl-phenyl ketone (also known as photoinitiator 184) has absorption wavelengths of 246 nm and 278 nm. It exhibits good resistance to yellowing.

[0050] 2-Hydroxy-2-methyl-1-phenyl-1-propanone (also known as photoinitiator 1173) has an absorption wavelength of 244 nm. It is a liquid product, which is easy to blend and can be compounded with other photoinitiators. It is highly efficient, has low yellowing, and has a certain degree of volatility at high temperatures.

[0051] Benzoin dimethyl ether (also known as photoinitiator BDK) has an absorption wavelength of 205 nm to 253 nm. It is a highly efficient and stable photoinitiator with stronger absorption performance compared to 1173 and 184, thus more effectively promoting the cross-linking reaction of double bonds.

[0052] Methyl phthalobenzoate (also known as photoinitiator OMBB) has an absorption wavelength of 253 nm.

[0053] The absorption wavelength of bis(2,6-difluoro-3-pyrrolephenyl)titanium ...

[0054] Phenylated bis(2,4,6-trimethylbenzoyl)phosphine oxide (also known as photoinitiator 819) has excellent ultraviolet absorption characteristics, with absorption wavelengths in the range of 295 nm and 370 nm. It can absorb long-wave ultraviolet light near these wavelengths, and a very low addition amount can provide excellent curing effect and anti-yellowing properties.

[0055] 2-Hydroxy-1-(4-(2-hydroxy-2-methylpropionylphenyl)benzyl)-2-methyl-1-propanone (also known as photoinitiator 127) has an absorption wavelength of 259 nm, low oxygen sensitivity, good surface curing effect, low volatility, and low odor of its own odor and photolysis products.

[0056] Ethyl 4-dimethylaminobenzoate (also known as photoinitiator EDB) has an absorption wavelength of 228 nm to 308 nm.

[0057] The first photoinitiator mentioned above can be used alone or in combination of multiple types.

[0058] In some examples, compounds P1, M1, and the first photoinitiator are added in a molar ratio of 1:(0.2–0.5):(0.01–0.03) and dissolved in an organic solvent. Within this ratio range, the reaction proceeds reasonably, and the reaction of compounds P1 and M1 is relatively complete with minimal residue. For example, the molar ratios of compounds P1, M1, and the first photoinitiator are 1:0.2:0.01, 1:0.3:0.02, 1:0.4:0.03, 1:0.5:0.03, etc.

[0059] In some examples, the light intensity was 5–300 mW / cm². 2 The wavelength of the light irradiation is 200–405 nm, the reaction time under irradiation is 1–3 h, and the first photoinitiator is an ultraviolet photoinitiator. By selecting a first photoinitiator that matches the wavelength of the light irradiation, step S1 can be rapidly induced under light irradiation; controlling the irradiation time to 1–3 h ensures that the reaction is complete while keeping the overall reaction time within a reasonable range. For example, the light intensity is 5 mW / cm². 2 10mW / cm 2 15mW / cm 2 20mW / cm 2 25mW / cm 2 30mW / cm 2 35mW / cm 2 45mW / cm 2 55mW / cm 2 65mW / cm 2 75mW / cm 2 85mW / cm 2 95mW / cm 2 100mW / cm 2 200mW / cm 2 300mW / cm 2 For example, the wavelength of the illumination is 200nm, 215nm, 253nm, 278nm, 308nm, 345nm, 365nm, 400nm, 405nm, etc.; for example, the illumination time is 1h, 2h, 3h, etc. More specifically, the illumination time is 1.5h to 2.5h, for example, 1.5h, 2.0h, and 2.5h.

[0060] In some examples, the solvent used in step S1 is selected from one or more of ethanol, petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, or dimethyl sulfoxide. More specifically, tetrahydrofuran, ethyl acetate, N,N-dimethylformamide, and dimethyl sulfoxide are selected. These solvents have good compatibility with compound P1, compound M1, and the first photoinitiator; they also facilitate the control of the concentrations of the two compounds, making the reaction system more homogeneous; after the reaction is complete, these solvents have good volatility, thus facilitating the removal of the solvents to obtain the desired reacted substance, which is convenient for further processing.

[0061] Step S2: Mix compound P2 and the acid-binding agent completely in an organic solvent, and add compound M2 until the reaction is complete. Remove excess reactants and solvent, and separate to obtain (meth)acrylate monomers.

[0062] The compound M2 used in step S2 is Where R1 is methyl or hydrogen, R1 is methyl methacryloyl chloride when it is methyl, and methacryloyl chloride when it is hydrogen.

[0063] In some examples, the molar ratio of compound P2, the acid-binding agent, and compound M2 is 1:(1-2):(1-2). The use of an acid-binding agent effectively neutralizes protons in the reaction system, reduces the influence of acid on the reaction, and fixes hydrogen ions in the solution, protecting other substances from the acidic environment, thus facilitating further reaction between compound P2 and compound M2. For example, specific examples show molar ratios of compound P2, the acid-binding agent, and compound M2 of 1:1:1, 1:2:1, 1:1.5:1, 1:1.5:1.5, and 1:2:2. In more specific examples, the molar ratio of compound P2, compound M2, and the acid-binding agent can be chosen to be between 1:(1-1.5):(1-1.5).

[0064] In a specific example, the acid-binding agent is selected from at least one of triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, tetrabutylammonium bromide, potassium carbonate, ammonium carbonate, and sodium carbonate. The raw materials are readily available and easy to separate from the final (meth)acrylate monomers.

[0065] In some examples, the reaction temperature of compound P2, the acid-binding agent, and compound M2 is controlled at 0°C, for example, using an ice bath. This helps control the reaction rate, prevents overheating which could lead to an increase in byproducts or decomposition of the target substance, thereby improving the yield and selectivity of the main reaction and reducing the volatilization of volatile substances and the degradation of unstable substances. It also facilitates the subsequent separation and purification of the target product.

[0066] In some examples, excess compound M2 in the reactants is removed by adding dilute hydrochloric acid.

[0067] In some examples, the mixture after the reaction in step S2 is washed sequentially with saturated NaCl solution, saturated NaHCO3 solution and deionized water, the organic phase is dried with anhydrous sodium sulfate, excess solvent is removed by rotary evaporation, and then separated by column chromatography to obtain the (meth)acrylate monomers of this application.

[0068] In some examples, the organic solvent is selected from one or more of ethanol, petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide, as long as it facilitates the reaction of compound P2 and compound M2 and has good compatibility with compound P2, the acid-binding agent, and compound M2. For example, in step S2, more specifically, the following organic solvents can be selected: dichloromethane, chloroform, and ethyl acetate.

[0069] As can be seen from the above, the method for preparing (meth)acrylate monomers proposed in this application can synthesize the desired (meth)acrylate monomers through a two-step reaction. The reaction conditions during the synthesis process are easy to control. The use of a first photoinitiator can rapidly initiate the reaction between compound P1 and compound M1 and increase the reaction rate. In the reaction, the unsaturated bond of compound M1, which contains alkyne and hydroxyl group, opens and is linked to the S in the mercapto group of compound P1 to form a saturated covalent bond. Meanwhile, the hydroxyl group in compound P2 reacts with the halogen in compound M2 to finally generate a compound with (meth)acrylate group. The molecular structure of the entire compound is stable.

[0070] Therefore, the preparation method of (meth)acrylate monomers with the general structural formula G includes the following two reaction steps:

[0071] The first step involves ring-opening of the carbon-carbon triple bond in compound M1, which combines with two molecular equivalents of a thiol group to form a -SC- saturated bond, as shown below:

[0072] The second step involves the reaction of the carbonyl group of methacryloyl chloride / acryloyl chloride with the hydroxyl group in compound P2 to generate a monomeric compound G containing methacrylate / acrylate, as shown below:

[0073] In some examples, compound P1 is selected from compounds having the following structural formula:

[0074] In other words, after compounds P1 and M1 with these structural formulas are synthesized, (meth)acrylate monomers with the aforementioned structural formulas can be synthesized accordingly. During the synthesis process, the structural formula is... In compound M1, the carbon-carbon triple bond will open, while the H in -SH in compound P1 will transfer, thus forming the polymerization of the two monomers.

[0075] The following describes a photopolymer-type holographic recording medium containing (meth)acrylate monomers.

[0076] The photopolymer holographic recording medium containing (meth)acrylate monomers from the foregoing examples, as proposed in this application, includes a writing monomer, which comprises (meth)acrylate monomers and polymerizable monomers.

[0077] The photopolymer holographic recording medium containing (meth)acrylate monomers proposed in this application, by adding (meth)acrylate monomers and polymerizable monomers, the two components can cooperate to form a writing monomer component with a high refractive index, thereby enabling the writing monomer and the film-forming resin to have a greater refractive index difference, providing the necessary material basis for the formation of phase-type volume holographic gratings with refractive index modulation in the photopolymer holographic recording medium.

[0078] In some examples of this application, the writing monomer accounts for 30% to 60% of the total weight of the photopolymer-type holographic recording medium. This ensures that the writing monomer has a sufficient concentration to achieve the concentration difference between bright and dark areas after the reaction under illumination. The photopolymer-type holographic recording medium also includes a film-forming resin, a photoinitiator, a chain transfer agent, a catalyst, and additives. The film-forming resin includes compounds with multiple isocyanate reactive functional groups and polyisocyanate compounds. When the film-forming resin and the writing monomer are combined, a volume holographic grating with refractive index modulation and refractive index difference can be formed.

[0079] In some embodiments of the application, the photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight:

[0080] First component: 20 to 50 parts of a compound having multiple isocyanate reactive functional groups. For example, it can be 20 parts, 30 parts, 40 parts, 50 parts, etc.

[0081] Second component: 10 to 40 parts of polyisocyanate compound. For example, it can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, etc.

[0082] The third component consists of 3 to 30 parts of (meth)acrylate monomers. For example, the amounts can be 3, 4, 5, 10, 15, 20, 25, or 30 parts.

[0083] Fourth component: 0.1 to 47 parts of polymerizable monomers. For example, it can be 0.1 parts, 0.3 parts, 1 part, 2 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 40 parts, 47 parts, etc.

[0084] Fifth component: 0.1 to 4 parts of photosensitizing initiator. For example, it can be 0.1, 0.2, 0.3, 0.5, 1, 1.5, 2.0, 2.5, 3.0, 3.5, or 4 parts.

[0085] Component 6: Chain transfer agent, 0.1 to 3 parts. For example, it can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3 parts, etc.

[0086] Component 7: Catalyst 0.1 to 3 parts. For example, it can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3 parts, etc.

[0087] Component 8: Additives 0.1 to 7 parts. For example, it can be 0.1 parts, 0.2 parts, 0.3 parts, 0.5 parts, 1 part, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4 parts, 5 parts, 6 parts, 6.5 parts, 7 parts, etc.

[0088] As can be seen from the above, the photopolymer holographic recording medium containing (meth)acrylate monomers proposed in this application can achieve full synergistic effect of each component by reasonably controlling the amount of each component added. This prevents the holographic performance of the final photopolymer holographic recording medium from deteriorating due to too much or too little of a certain component, thus ensuring that the overall holographic performance of the final photopolymer holographic recording medium is better.

[0089] For example, by controlling the compound having multiple isocyanate reactive functional groups to 20 to 50 parts and the polyisocyanate group compound to 10 to 40 parts, the first and second components together form a film-forming resin with a low refractive index, thereby providing support for the other components. In some specific examples, the compound having multiple isocyanate reactive functional groups is further controlled to 25 to 35 parts, and the polyisocyanate group compound is further controlled to 15 to 25 parts.

[0090] By controlling the (meth)acrylate monomers to 3-30 parts and the polymerizable monomers to 0.1-47 parts, and the third and fourth components being the writing monomers, and considering that the intermolecular bonding refractive index will be higher after polymerization, the interaction of the above four components can achieve a high refractive index component and a low refractive index component with a large refractive index difference in the photopolymer holographic recording medium, forming a high refractive index difference between the film-forming resin and the writing monomer. Thus, under the action of light, the monomers in the bright area (such as the third and fourth components) polymerize and are consumed, resulting in a decrease in concentration, while the monomers in the dark area hardly react. The difference in monomer concentration between the bright and dark areas causes the high concentration of monomers in the dark area to begin migrating to the bright area, while the components of the film-forming resin in the bright area (such as the first and second components) are squeezed into the dark area, making the refractive index of the bright area close to the refractive index of the third and fourth components, while the refractive index of the dark area close to the refractive index of the first and second components, forming a phase-type volume holographic grating with refractive index modulation. In some specific examples, the (meth)acrylate monomers are further controlled at 3 to 15 parts; the polymerizable monomers are further controlled at 25 to 40 parts.

[0091] For example, controlling the photoinitiator composition to 0.1 to 4 parts allows for the absorption of a suitable number of photons during exposure and controls the polymerization reaction at a certain rate, enabling the grating to form quickly and achieve high diffraction efficiency. Furthermore, it ensures that the final holographic recording medium has the required light transmittance and that the grating has a certain diffraction efficiency. In some specific examples, the photoinitiator composition is 0.3 to 3 parts.

[0092] For example, controlling the chain transfer agent to 0.1 to 3 parts allows the polymer chain length to be kept within a reasonable range and effectively prevents excessive polymerization, ensuring that the final holographic recording medium has the required optical properties and diffraction efficiency. In some specific examples, the chain transfer agent is further controlled to 0.5 to 2 parts.

[0093] For example, controlling the catalyst content to 0.1 to 3 parts can effectively increase the reaction rate of related components and the consumption rate of related components after exposure, thereby rapidly forming a concentration difference of monomers in the bright and dark areas and realizing a phase-type volume holographic grating with refractive index modulation. In some specific examples, the catalyst content is further controlled to 0.5 to 2 parts.

[0094] For example, controlling the additive to 0.1 to 7 parts, using the additive as a leveling agent, can effectively improve the uniformity of the mixture, enhance its flowability, and reasonably control costs. In some specific examples, the additive is further controlled to 0.6 to 6 parts.

[0095] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 25 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 21 parts of a polyisocyanate group compound; Component 3 – 31 parts of (meth)acrylate monomers; Component 4 – 19 parts of polymerizable monomers; Component 5 – 2 parts of a photoinitiator; Component 6 – 2 parts of a chain transfer agent; Component 7 – 0.7 parts of a catalyst; and Component 8 – 1.3 parts of an additive.

[0096] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 20 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 37 parts of a polyisocyanate group compound; Component 3 – 3 parts of (meth)acrylate monomers; Component 4 – 23 parts of polymerizable monomers; Component 5 – 4 parts of a photoinitiator; Component 6 – 3 parts of a chain transfer agent; Component 7 – 3 parts of a catalyst; and Component 8 – 7 parts of additives.

[0097] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 51 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 10 parts of a polyisocyanate group compound; Component 3 – 12 parts of (meth)acrylate monomers; Component 4 – 18 parts of polymerizable monomers; Component 5 – 1 part of a photoinitiator; Component 6 – 1 part of a chain transfer agent; Component 7 – 2 parts of a catalyst; and Component 8 – 5 parts of additives.

[0098] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 32 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 10 parts of a polyisocyanate group compound; Component 3 – 3 parts of (meth)acrylate monomers; Component 4 – 48 parts of polymerizable monomers; Component 5 – 4 parts of a photoinitiator combination; Component 6 – 1 part of a chain transfer agent; Component 7 – 1 part of a catalyst; and Component 8 – 1 part of an additive.

[0099] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 38 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 10 parts of a polyisocyanate group compound; Component 3 – 30 parts of (meth)acrylate monomers; Component 4 – 10.6 parts of polymerizable monomers; Component 5 – 4 parts of a photoinitiator; Component 6 – 0.1 parts of a chain transfer agent; Component 7 – 0.3 parts of a catalyst; and Component 8 – 7 parts of additives.

[0100] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 33 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 16 parts of a polyisocyanate group compound; Component 3 – 31 parts of (meth)acrylate monomers; Component 4 – 10 parts of polymerizable monomers; Component 5 – 4 parts of a photoinitiator combination; Component 6 – 3 parts of a chain transfer agent; Component 7 – 0.5 parts of a catalyst; and Component 8 – 2.5 parts of additives.

[0101] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 25 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 35 parts of a polyisocyanate group compound; Component 3 – 22 parts of (meth)acrylate monomers; Component 4 – 8 parts of polymerizable monomers; Component 5 – 0.2 parts of a photoinitiator combination; Component 6 – 0.8 parts of a chain transfer agent; Component 7 – 2 parts of a catalyst; and Component 8 – 7 parts of additives.

[0102] In some optional examples, a photopolymer-type holographic recording medium containing (meth)acrylate monomers comprises the following components in parts by weight: Component 1 – 35 parts of a compound having multiple isocyanate reactive functional groups; Component 2 – 15 parts of a polyisocyanate group compound; Component 3 – 21 parts of (meth)acrylate monomers; Component 4 – 28.6 parts of polymerizable monomers; Component 5 – 0.1 parts of a photoinitiator; Component 6 – 0.1 parts of a chain transfer agent; Component 7 – 0.1 parts of a catalyst; and Component 8 – 0.1 parts of an additive.

[0103] In some examples of this application, compounds having multiple isocyanate reactive functional groups are hydroxyl and mercapto groups. Hydroxyl groups are polar groups, and alcoholic hydroxyl groups are easily oxidized, exhibiting high reactivity; mercapto groups also have high reactivity. For example, in specific examples, compounds having multiple isocyanate reactive functional groups are low-refractive-index compounds containing two or more hydroxyl and mercapto functional groups.

[0104] More specifically, compounds having multiple isocyanate reactive functional groups are selected from 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1,6-hexanediol, 2,5-hexanediol, 1,4-cyclohexanediol, 1,8-octanediol, 1,7-heptanediol, 1,3-butanediol, 1,5-pentanediol, 1,4-cyclohexanediol, 1,3-cyclopentanediol, tetraethylene glycol, trimethylolpropane, trimethylolpropane, etc. At least one of the following: propane, glycerol, triethanolamine, polyester polyol with a molecular weight of 100 to 2000, polycarbonate polyol, polyether polyol, 2,3-dithio(2-mercapto)-1-propanethiol, 1,2-octanedithiol, 2,5-dimethylmercapto-1,4-dithiane, 1,2-butanedithiol, 1,3-butanedithiol, 3,7-dithia-1,9-nonanedithiol, and 2,3-butanedithiol. These substances also have low refractive indices. For example, 2-ethyl-1,3-hexanediol has a refractive index of 1.451; 1,6-hexanediol has a refractive index of 1.457; 2,5-hexanediol has a refractive index of 1.443; 1,4-cyclohexanediol has a refractive index of 1.427; tetraethylene glycol has a refractive index of 1.46 (20°C); 1,2,4-butanetriol has a refractive index of 1.47; trimethylolethane has a refractive index of 1.5; glycerol has a refractive index of 1.474 (20°C); and triethanolamine has a refractive index of 1.482–1.485 (20°C).

[0105] In some examples of this application, the polyisocyanate-based compounds are compounds with low refractive index and two or more isocyanate groups.

[0106] In a specific example, the polyisocyanate group compound is selected from 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. These compounds also have low refractive indices: hexamethylene diisocyanate has a refractive index of 1.453; trimethylhexamethylene diisocyanate has a refractive index of 1.462; (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tri(hexamethylene)isocyanate has a refractive index of 1.473; butane-1,4-diisocyanate has a refractive index of 1.453; isophorone diisocyanate has a refractive index of 1.484; and dicyclohexylmethane diisocyanate has a refractive index of 1.496 (25°C).

[0107] In some examples of this application, 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.

[0108] In a specific example, the alkenylnaphthalene compound is selected from at least one of 1-vinylnaphthalene and 2-vinylnaphthalene.

[0109] In a specific example, the alkenyl anthracene compound is selected from at least one of 2-vinylanthracene and 9-vinylanthracene.

[0110] In a specific example, the alkenylbenzene compound is selected from at least one of styrene, 2-chlorostyrene, 2-bromostyrene, 3-chlorostyrene, 3-bromostyrene, 4-chlorostyrene, 4-bromostyrene, p-(chloromethyl)styrene, and p-(bromomethyl)styrene.

[0111] In specific examples, methacrylic acid compounds include at least one of methacrylic acid and its derivatives.

[0112] In specific examples, the acrylate compound is selected from at least one of 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.

[0113] In specific examples, the methacrylate compounds are selected from at least one of 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-di(2-thionaphthyl)2-butyl methacrylate, pentabromobenzyl methacrylate, 2-naphthyl methacrylate, bisphenol A dimethacrylate, and tetrabromobisphenol A dimethacrylate.

[0114] In some examples of this application, the photoinitiator combination includes a photosensitizer and a second photoinitiator. The photosensitizer, when combined with the second photoinitiator, forms a visible light initiation system adaptable to lasers of different wavelengths. 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 second photoinitiator. This allows the second photoinitiator to be activated under light radiation in a wider wavelength range, generating free radicals with initiation functions. These photoinitiated free radicals can initiate monomer polymerization to construct holographic gratings, improve the photosensitivity of photopolymer-based holographic recording media, and broaden the range of selectable light sources.

[0115] Therefore, it is understandable that in other examples, when this application uses a second photoinitiator with an appropriate wavelength, a photosensitizer may not be added.

[0116] When the photoinitiator combination contains both a photosensitizer and a second photoinitiator, the mass ratio of the photosensitizer to the second photoinitiator is further (0.001–1):(0.1–3). By controlling the mass ratio of the photosensitizer to the second photoinitiator within the above range, the concentration of the photosensitizer can be effectively controlled, ensuring that the number of absorbed photons during holographic exposure is controlled within a suitable range, the polymerization reaction rate is controlled within a reasonable range, and the grating formation rate is controlled within a certain range, thus guaranteeing the transmittance of the photopolymer holographic recording medium and obtaining excellent diffraction efficiency. In a more specific example, the mass of the photosensitizer is 1 / 10 to 1 / 3 of the mass of the second photoinitiator, such as 1 / 10, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, 1 / 4, or 1 / 3.

[0117] In this application, different broadband responses can be achieved by adjusting the type of photosensitizer. For example, the photosensitizer is a dye with high electron transfer efficiency under light irradiation.

[0118] In a specific example, the photosensitizer is selected from at least one of cyanine dyes, fluorescein dyes, coumarin ketone dyes, nitrogen-containing aromatic heterocyclic compounds, aromatic amine compounds, and benzylidene cycloalkane ketone compounds.

[0119] More specifically, the photosensitizers are selected from methylene blue (maximum absorption wavelength 666 nm), thionine (absorption wavelength 602.5 nm), basic yellow (absorption wavelength 412 nm), pinacyanin chloride, rhodamine 6G (absorption wavelength 400 nm–700 nm), gallium cyanide, ethyl violet (absorption wavelength 596 nm), Victoria Blue R (maximum absorption wavelength 615 nm), celestite blue (absorption wavelength 630–640 nm), methylene blue (maximum absorption wavelength 662 nm), basic orange, and darozyme (maximum absorption wavelength 502 nm). One or more of the following: pyrrole red Y (with strong absorption wavelengths of 235nm, 267nm, 336nm, and 515nm), basic red 29, quinaldinium red (maximum absorption wavelength of 528nm), crystal violet (absorption wavelength of 588nm–592nm), ethyl violet (maximum absorption wavelength of 596nm), brilliant green (maximum absorption wavelength of 630nm), azurite A (maximum absorption wavelength of 633nm), crystal violet cyanine (maximum absorption wavelength of 579nm), malachite green cyanine, and eosin (absorption wavelength of 510nm–518nm).

[0120] In a specific example, the second photoinitiator is selected from at least one of aromatic ketone compounds, benzoin and its derivatives, benzoyl ketal, acylphosphine oxide, ammonium arylboronate, chromium salts, aryl diazonium salts, onium salts, and organometallic compounds. Other second photoinitiators with similar functions may also be selected, and this application does not impose any limitations on them.

[0121] More specifically, the second photoinitiator is selected from benzophenone (absorption wavelengths 210 nm, 255 nm), alkylbenzophenone (290 nm–360 nm), 4,4'-bis(dimethylamino)benzophenone, anthrone (299 nm–366 nm), halogenated benzophenone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide (absorption wavelengths 350 nm–400 nm), diacylphosphine oxide, phenyl dihydroxyacetate, camphorquinone (absorption wavelength 40 nm), etc. The photoinitiator comprises one or more of the following: 0nm–500nm, α-aminoalkylphenyl ketone (absorption wavelength 380nm–430nm), α,α-dialkoxyacetophenone, α-hydroxyalkylphenyl ketone (absorption wavelength 320nm–380nm), tetrabutylammonium triphenylhexylborate, tetrabutylammonium tri-(3-fluorophenyl)hexylborate, tetrabutylammonium tri-(3-chloro-4-methylphenyl)hexylborate, ferrocene-based compounds, iodonium salts, thiodonium salts, and hexaaryldiimidazole. When these second photoinitiators are irradiated with light within the corresponding wavelength range, they can be rapidly activated and generate active free radicals, thereby initiating polymerization reactions between the components of the photopolymer-type holographic recording medium, achieving the monomer concentration difference between the bright and dark areas. Alternatively, when the photosensitizer in combination absorbs light within the corresponding wavelength range, it transfers heat to the second photoinitiator, thereby activating the photoinitiator.

[0122] In some examples of this application, the chain transfer agent is a thiol compound.

[0123] In specific examples, the chain transfer agent includes one or more of the following: dodecyl mercaptoethanol, mercaptoethanol, hexamethylene mercaptoethanol, phenylethyl mercaptoethanol, 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, and 4-methyl-4H-1,2,4-triazole-3-thiol.

[0124] In some examples of this application, the catalyst is a tertiary amine catalyst or an organometallic catalyst.

[0125] In a specific example, the catalyst is selected from at least one of the following: 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. The catalyst is not limited to the types listed above; any catalyst capable of catalyzing the polymerization reaction of the aforementioned components under light irradiation is acceptable. Those skilled in the art should understand that these all fall within the scope of protection of this application.

[0126] In some examples of this application, the additives include one or more of defoamers, leveling agents, plasticizers, and dehydrating agents.

[0127] In a specific example, the defoamer is a silicone defoamer and / or a silicone-free polymeric defoamer, and the defoamer accounts for less than or equal to 3% of the weight of the photopolymeric holographic recording medium. The defoamer can reduce the surface tension of the liquid and remove foam, thereby improving the flowability of the mixture of components.

[0128] More specifically, one can choose, for example, 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, or DC65 and AFE-7820 manufactured by Dow Corning Corporation, or any mixture of these defoamers in any proportion. The BYK series of defoamers have excellent defoaming performance, good compatibility with other components, and good dispersibility; among them, 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.

[0129] In a specific example, the leveling agent is a silicone surface additive, and the percentage of the leveling agent by weight of the photopolymer holographic recording medium is less than or equal to 3%. Examples include BYK-302, BYK-306, BYK-307, BYK-327, BYK-329, BYK-333, BYK-356, BYK-358, BYK-378, BYK-3455, BYK-3566, or any mixture of these surface additives manufactured by BYK. The BYK series of leveling agents exhibits excellent leveling properties.

[0130] In a specific example, 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% of the weight of the photopolymer-type holographic recording medium. The plasticizer increases the plasticity of the polymer by intercalating between polymer molecular chains, weakening the intermolecular stress, increasing the mobility of molecular chains, and reducing crystallinity.

[0131] In specific examples, the dehydrating agents are selected from methylbenzenesulfonyl 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., etc.

[0132] In some examples, the dehydrating agent constitutes less than or equal to 3% of the weight of the photopolymer holographic recording medium. The dehydrating agent removes excess water during the reaction, allowing for better mixing of the components and preventing stratification.

[0133] The application of the aforementioned photopolymer holographic recording medium described below.

[0134] The holographic optical element proposed in this application is made of photopolymer-type holographic recording media as described in the foregoing examples. This holographic optical element includes, but is not limited to, volume holographic gratings.

[0135] As can be seen from the above, 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, namely high diffraction efficiency, high sensitivity, and small required exposure amount.

[0136] The optical device proposed in this application includes holographic optical elements 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 with very fast data transfer speeds.

[0137] 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 holographic performance, clear image, and can store a large amount of data.

[0138] The following describes the (meth)acrylate monomers, the preparation method of the (meth)acrylate monomers, and the photopolymer holographic recording medium containing (meth)acrylate monomers in this application with reference to specific embodiments.

[0139] Example 1

[0140] In this embodiment, the general structural formula of the (meth)acrylate monomer is G:

[0141] The preparation method of (meth)acrylate monomers with structural formula G includes the following steps:

[0142] Step S1: Compound P1 and compound M1 are dissolved in the organic solvent ethyl acetate at a molar ratio of 1:0.5 (i.e., 2:1), and the first photoinitiator ethyl 2,4,6-trimethylbenzoylphosphonate is added. The solution is then exposed to a light intensity of 30 mW / cm². 2 The light wavelength was 365 nm, and the reaction was carried out under light irradiation for 1.5 h to obtain compound P2. The reaction equation is as follows:

[0143] Step S2: Compound P2 and the acid-binding agent triethylamine were completely mixed in the organic solvent ethyl acetate, and compound M2 methacryloyl chloride / acryloyl chloride was added until the reaction was complete. Dilute hydrochloric acid was added to remove excess compound M2. 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 final product was obtained by column chromatography to obtain the (meth)acrylate monomer G1 of this application. The reaction equation is as follows:

[0144] So, with the reaction conditions roughly the same and M1 unchanged (e.g., n is always 1), by changing P1 containing different R2 and R3 groups in step S1 and / or changing M2 containing different R1 in step S2, different structures of (meth)acrylate monomers G in this application can be prepared. The reactants corresponding to the different structures of G in this application are shown in Table 1 below.

[0145] Table 1. Reactants and refractive indices corresponding to different structural formulas of G.

[0146] The organic solvent, first photoinitiator, and acid-binding agent in this embodiment are for illustrative purposes only and should not be construed as limiting the scope of this application. The organic solvent may be one or more of ethanol, petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, or dimethyl sulfoxide. The first photoinitiator may be at least one of (2,4,6-trimethylbenzoyl chloride)diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonate, 2-methyl-1-[4-methylthiophenyl]-2-morpholino-1-propanone, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether, methyl o-benzoylbenzoate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-1-(4-(2-hydroxy-2-methylpropionylphenyl)benzyl)-2-methyl-1-propanone, bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), and ethyl 4-dimethylaminobenzoate. The acid-binding agent includes at least one of triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, tetrabutylammonium bromide, potassium carbonate, ammonium carbonate, and sodium carbonate. Those skilled in the art should understand that these should all be within the scope of protection of this application.

[0147] Example 2

[0148] Photopolymer holographic recording media 2-1 to 2-13 containing (meth)acrylate monomers from Examples 1-1 to 1-13 are used: The specific components of photopolymer holographic recording media 2-1 to 2-13 are shown in Table 2 below.

[0149] Table 2 shows the components of each photopolymer-type holographic recording medium containing (meth)acrylate monomers from each embodiment.

[0150] In this embodiment, the selection of each component may also be other components listed above. These embodiments should not be construed as limiting the scope of protection of this application.

[0151] Comparative Example

[0152] The composition is roughly the same as that of the photopolymer holographic recording medium 2-1 in Example 2. The difference is that the (meth)acrylate monomer G1-a of the photopolymer holographic recording medium 2-1 is removed, so that the number of (meth)acrylate monomers becomes 0 parts, and the polymerizable monomer 2-vinylnaphthalene is increased to 50 parts, so as to obtain a common photopolymer holographic recording medium.

[0153] Test case

[0154] Holographic Performance Testing: The performance of the photopolymer holographic recording media 2-1 to 2-13 containing (meth)acrylate monomers from Examples 2 and the conventional photopolymer holographic recording media of the comparative example were tested. The results are shown in Table 3. During the test, different wavelengths of laser light were selected for exposure of each holographic recording medium in Example 2, depending on the photosensitive system, with an exposure intensity of 3 mW / cm². 2 .

[0155] Using the photopolymer holographic recording medium 2-1 containing (meth)acrylate monomers, the photopolymer holographic recording medium 2-2 containing (meth)acrylate monomers, and the photopolymer holographic recording medium 2-3 containing (meth)acrylate monomers from Example 2, corresponding holographic performance diagrams were plotted, resulting in Figure 1.

[0156] Specifically, for the three holographic recording media 2-1, 2-2, and 2-3, solid-state lasers with wavelengths of 633nm, 457nm, and 532nm were used as light sources, respectively. After passing through a beam expander, beam splitter, and half-wave plate, two beams of the same intensity and diameter of 8mm were obtained. The two beams were intersected within the prepared holographic recording media for exposure, with a light intensity of 3mW / cm². 2 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 photosensitivity (S) of the photopolymer holographic recording medium are calculated by formulas (1) to (3).

[0157] 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.

[0158] As shown in Figure 1, the final measured diffraction efficiency of the photopolymer holographic recording medium of this application is greater than 95%, and the exposure dose is less than 20 mJ / cm. 2 Sensitivity greater than 100cm 2 / mJ.

[0159] As shown in Figure 2, a conventional photopolymer holographic recording medium for comparison was exposed at a wavelength of 633 nm and an exposure intensity of 3 mW / cm². 2 The diffraction efficiency of the ordinary photopolymer holographic recording medium in the comparative example was found to be less than 50%, requiring an exposure dose greater than 100 mJ / cm². 2 Its sensitivity is low, less than 10cm. 2 / mJ.

[0160] The holographic performance tests of the photopolymer holographic recording media 2-1 to 2-13 in Example 2 and the ordinary photopolymer holographic recording media of the comparative example are shown in Table 3 below.

[0161] Table 3. Holographic performance test table of each photopolymer holographic recording medium in Example 2 and Comparative Examples.

[0162] Solubility test of (meth)acrylate monomers with different n values ​​in photopolymer holographic recording media: By testing the haze of photopolymer holographic recording media containing different amounts of high-refractive-index (meth)acrylate monomers, and defining complete miscibility when the haze is less than 1%, the solubility of monomers in photopolymers with different n values ​​is evaluated.

[0163] So, when the value of n in the methacrylate monomer is 1, 5, 10, 15, and 20, the solubility of the (meth)acrylate monomers in the photopolymer holographic recording media 2-1 to 2-13 containing (meth)acrylate monomers in Example 2 is tested, and the test results are shown in Table 4.

[0164] As shown in Table 4, the solubility of the (meth)acrylate monomers in the photopolymer varies with different n values. Furthermore, for the same structure, the solubility of the (meth)acrylate monomers is greater when the n value is higher. In this application, the solubility of the (meth)acrylate monomers in the photopolymer is generally higher than 20% when n is 1. Therefore, the high solubility of the (meth)acrylate monomers in the photopolymer allows for the addition of a larger amount without precipitation. This ensures that the amount of (meth)acrylate monomers added can reach a certain level, which is beneficial for increasing the refractive index of the writing monomer, thereby further enhancing the refractive index difference between the writing monomer and the film-forming resin, ultimately improving the holographic performance of the photopolymer-type holographic recording medium containing (meth)acrylate monomers.

[0165] Table 4. Solubility of different monomers in photopolymer-based holographic recording media

[0166] In summary, referring to Figures 1 and 2 and Table 3, the diffraction efficiency and sensitivity of the photopolymer holographic recording medium of this application embodiment are significantly higher than those of the comparative example, and the required exposure amount is much smaller. Referring to Table 4, the (meth)acrylate monomers of this application embodiment can be added in considerable amounts to the photopolymer holographic recording medium without precipitation, exhibiting good solubility.

[0167] 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. A (meth)acrylate monomer, wherein, Its general structural formula is as follows: wherein n is an integer from 1 to 20, R1is methyl or hydrogen; R2, R3are selected from hydrogen, Br, phenyl, methyl or wherein A1 in the text represents either phenyl or methyl.

2. The (meth)acrylate monomer according to claim 1, wherein The (meth)acrylate monomers are selected from monomers having the following structural formulas: Where R1 is methyl or hydrogen, and n is an integer from 1 to 10.

3. A process for producing the (meth)acrylate monomer as claimed in claim 1 or 2, wherein, Includes the following steps: Compound P1 and compound M1 were dissolved in an organic solvent, a first photoinitiator was added, and the mixture was reacted under light to obtain compound P2. Compound P2 was completely mixed with an acid-binding agent in an organic solvent, and compound M2 was added until the reaction was complete. Excess reactants and solvent were removed, and the (meth)acrylate monomers were separated. The structural general formula of the compound P1 is: R2, R3are selected from hydrogen, Br, phenyl, methyl or A1 in the text is either phenyl or methyl; The structural formula of the compound M1 is Where n is an integer from 1 to 20; The compound M2 is R1 is either methyl or hydrogen.

4. The method for preparing (meth)acrylate monomers as described in claim 3, wherein, The molar ratio of compound P1, compound M1, and the first photoinitiator is 1:(0.2-0.5):(0.01-0.03); The light intensity is 5–300 mW / cm². 2 The wavelength of the light is 200-405 nm, the reaction time under the light is 1-3 h, and the first photoinitiator is an ultraviolet photoinitiator.

5. The method for preparing a (meth)acrylate monomer according to claim 3, wherein, The molar ratio of compound P2, the acid-binding agent, and compound M2 is 1:(1-2):(1-2); The reaction temperature of compound P2, the acid-binding agent, and compound M2 is controlled at 0°C.

6. The method for preparing a (meth)acrylate monomer according to claim 3, wherein The removal of excess reactants includes adding dilute hydrochloric acid to remove excess reactants.

7. The method of preparing a (meth)acrylate monomer according to claim 3, wherein The solvent removal process includes: sequentially washing with saturated NaCl solution, saturated NaHCO3 solution and deionized water; drying the organic phase with anhydrous sodium sulfate; and then removing excess solvent by rotary evaporation.

8. The method of preparing a (meth)acrylate monomer according to claim 3, wherein, The organic solvents include ethanol, petroleum ether, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, or dimethyl sulfoxide.

9. The method for preparing (meth)acrylate monomers as described in claim 3, wherein, The compound P1 is selected from the group consisting of compounds having the following structural formula:

10. The method for preparing (meth)acrylate monomers according to claim 3, wherein, The first photoinitiator is selected from at least one of (2,4,6-trimethylbenzoyl chloride) diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonate, 2-methyl-1-[4-methylthiophenyl]-2-morpholino-1-propanone, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether, methyl o-benzoylbenzoate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-1-(4-(2-hydroxy-2-methylpropionylphenyl)benzyl)-2-methyl-1-propanone, bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), and ethyl 4-dimethylaminobenzoate. The acid-binding agent is selected from at least one of triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, tetrabutylammonium bromide, potassium carbonate, ammonium carbonate, and sodium carbonate.

11. A photopolymer type holographic recording medium containing the (meth)acrylate monomer according to claim 1 or 2, wherein, It includes writing monomers, which include the (meth)acrylate monomers and polymerizable monomers.

12. The photopolymer-type holographic recording medium as described in claim 11, wherein, The writing monomer accounts for 30% to 60% of the total weight of the photopolymer holographic recording medium. The photopolymer-type holographic recording medium further includes a film-forming resin, a photoinitiator, a chain transfer agent, a catalyst, and additives. The film-forming resin includes compounds having multiple isocyanate reactive functional groups and polyisocyanate-based compounds.

13. The photopolymer type holographic recording medium according to claim 12, wherein, The components include the following parts by weight: First component: 20 to 50 parts of a compound having multiple isocyanate reactive functional groups; Second component: 10 to 40 parts of polyisocyanate group compound; Third component: (meth)acrylate monomers, 3 to 30 parts; Fourth component: 0.1 to 47 parts of polymerizable monomer; Fifth component: 0.1 to 4 parts of photosensitizing initiator; Component 6: Chain transfer agent 0.1 to 3 parts; Component 7: Catalyst 0.1 to 3 parts; Component 8: 0.1 to 7 parts of additives.

14. The photopolymer type holographic recording medium according to claim 12, wherein, The components include the following parts by weight: First component: 25 to 35 parts of a compound having multiple isocyanate reactive functional groups; Second component: 15 to 25 parts of polyisocyanate group compound; Third component: 3 to 15 parts of (meth)acrylate monomers; Fourth component: 25 to 40 parts of polymerizable monomer; Fifth component: 0.3 to 3 parts of photosensitizing initiator; Component 6: Chain transfer agent 0.5 to 2 parts; Component 7: 0.5 to 2 parts of catalyst; Component 8: 0.6 to 6 parts of additives.

15. The photopolymer type holographic recording medium according to any one of claims 12 to 14, wherein In the compound having multiple isocyanate reactive functional groups, the isocyanate reactive functional groups are hydroxyl and mercapto groups; and / or, The compound having multiple isocyanate reactive functional groups is selected from 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1,6-hexanediol, 2,5-hexanediol, 1,4-cyclohexanediol, 1,8-octanediol, 1,7-heptanediol, 1,3-butanediol, 1,5-pentanediol, 1,4-cyclohexanediol, 1,3-cyclopentanediol, tetraethylene glycol, trimethylolethane, trimethylolpropane, and glycerol. At least one of the following: oil, triethanolamine, polyester polyols with a molecular weight of 100-2000, polycarbonate polyols, polyether polyols, 2,3-dithio(2-mercapto)-1-propanethiol, 1,2-octanedithiol, 2,5-dimethylmercapto-1,4-dithiane, 1,2-butanedithiol, 1,3-butanedithiol, 3,7-dithia-1,9-nonanedithiol, and 2,3-butanedithiol; and / or, The polyisocyanate compound is a low-refractive-index compound containing two or more isocyanate groups; and / or, The polymerizable monomer is selected from at least one of alkenylnaphthalene compounds, alkenylanthracene compounds, alkenylbenzene compounds, acrylic acid 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 photoinitiator combination comprises a photosensitizer and a second photoinitiator; the mass ratio of the photosensitizer to the second photoinitiator is (0.001–1):(0.1–3); the absorption wavelength range of the photosensitizer selected in the photoinitiator combination is different from that of the absorption wavelength range of the second photoinitiator; and / or, The chain transfer agent is a thiol compound; and / or, The catalyst is a tertiary amine catalyst or an organometallic catalyst; and / or, The additive is selected from one or more of defoamers, leveling agents, plasticizers, and dehydrating agents.

16. The photopolymer type holographic recording medium according to claim 15, wherein, The mass ratio of the photosensitizer to the second photoinitiator is (1 / 10 to 1 / 3):

1.

17. The photopolymer type holographic recording medium according to claim 15, wherein, The photosensitizer is selected from 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 second 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.

18. The photopolymer type holographic recording medium according to claim 15, wherein, The defoamer is a silicone defoamer and / or a silicone-free polymeric defoamer, wherein the defoamer constitutes less than or equal to 3 parts by weight of the photopolymeric holographic recording medium; or, The leveling agent is an organosilicon surface additive, and the leveling agent accounts for less than or equal to 3 parts by weight of the photopolymer-type holographic recording medium; 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 parts by weight of the photopolymer-type holographic recording medium; or, The dehydrating agent accounts for less than or equal to 3 parts by weight of the photopolymer holographic recording medium.

19. A holographic optical element, wherein, The raw material of the holographic optical element includes the photopolymer type holographic recording medium as described in any one of claims 11 to 18.

20. An optical device, wherein, Includes the holographic optical element as described in claim 19.

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