Acrylate monomer and preparation method thereof, photopolymer composition and volume holographic grating and preparation method thereof

Abstract

The invention discloses an acrylate monomer and a preparation method thereof, a photopolymer composition and a volume holographic grating and a preparation method thereof, the acrylate monomer provided by the invention is simple in structure and rich in expandable structure, so that the synthesis steps are simple and convenient, the cost is reduced, a relatively high refractive index of the monomer is realized on the basis of introduction of more sulfur atoms into the monomer, and the volume holographic grating has a good application prospect. In the subsequent photopolymerization process, the difference between the refractive index of the generated polymer and the refractive index of the common matrix is larger, so that the preparation of the holographic grating with high-refractive-index modulation degree can be realized.

Description

Technical Field

[0001] The present application relates to the technical field of optical materials, and in particular, to an acrylate monomer, a preparation method thereof, a photopolymer composition, a volume holographic grating, and a preparation method thereof. Background Art

[0002] With the development of technologies such as virtual reality, augmented reality, mixed reality, and head-up display, holographic optical elements prepared from photopolymers have attracted the attention of many researchers. Among them, a volume holographic grating (VHG) can be used as a coupling optical element for a holographic optical waveguide.

[0003] Generally, the photopolymer formulation for a volume holographic grating consists of three main components: a photoinitiating system (including a photoinitiator and / or a photosensitizer), a writing monomer (acrylate), and a matrix. Among them, the writing monomer is the component that undergoes polymerization in the photopolymer and directly affects the optical recording performance of the final hologram. However, the writing monomer currently has disadvantages such as a complex structure, many preparation steps, and high purification difficulty, which is not conducive to the commercial application of the photopolymer. Summary of the Invention

[0004] In view of this, the present application provides an acrylate monomer, a preparation method thereof, a photopolymer composition, a volume holographic grating, and a preparation method thereof.

[0005] In a first aspect of the present application, an acrylate monomer is provided, having the following general formula:

[0006]

[0007] wherein, X is H or a carbon chain;

[0008] Y is H or a halogen;

[0009] A is H, an acetoxy group, or an aryl group.

[0010] In some embodiments, the structural formula of the acrylate monomer is as follows:

[0011] Or,

[0012] Or,

[0013] Or,

[0014]

[0015] In a second aspect of the present application, a preparation method of an acrylate monomer is provided, including the following steps:

[0016] The acrylate monomer is formed by using a first compound and allyl acyl chloride or 2-butenoyl chloride;

[0017] Among them, the first compound has the following general formula:

[0018]

[0019] R is H, an alkyl group or an aromatic hydrocarbon.

[0020] In some embodiments, the preparation steps of the first compound include:

[0021] The first compound is formed by using benzenethiol and 2-chloroethanol or 2-chloro-1,3-propanediol.

[0022] In some embodiments, the benzenethiol and the 2-chloroethanol or the benzenethiol and the 2-chloro-1,3-propanediol are dissolved in a first solvent and reacted under the action of a basic catalyst to form the first compound; wherein, the molar ratio of the benzenethiol to the 2-chloroethanol or the 2-chloro-1,3-propanediol is 1:0.8 - 1:1.2, the molar amount of the first solvent is 10 times - 100 times the molar amount of the benzenethiol, and the molar amount of the basic catalyst is 0.1 times - 1 times the molar amount of the benzenethiol.

[0023] In some embodiments, the first compound and the allyl acyl chloride or the first compound and the 2-butenoyl chloride are dissolved in a second solvent so that the first compound reacts with the allyl acyl chloride to form the acrylate monomer; wherein, the molar ratio of the first compound to the allyl acyl chloride or the 2-butenoyl chloride is 1:0.8 - 1:1.2, and the molar amount of the second solvent is 10 times - 100 times that of the allyl acyl chloride or the 2-butenoyl chloride.

[0024] In some embodiments, the first solvent is chloroform or N,N-dimethylformamide; and / or, the second solvent is chloroform.

[0025] In some embodiments, the benzenethiol and the 2-chloroethanol or the benzenethiol and the 2-chloro-1,3-propanediol react for 5 hours - 7 hours at room temperature under the action of the basic catalyst, and are extracted by an extractant, then the first solvent is removed by rotary evaporation, and the first compound is obtained by recrystallization with ethanol; and / or,

[0026] After the first compound reacts with the allyl acyl chloride or the first compound reacts with the 2-butenoyl chloride at room temperature for 1-3 hours to obtain a product, column chromatography is carried out on the product with petroleum ether and ether to separate and purify to obtain the acrylate monomer, and the molar ratio of the petroleum ether to the ether is 1:0.05-0.15.

[0027] The third aspect of the present application provides a photopolymer composition, which includes: a photosensitizer and / or a photocatalyst; a basic catalyst; a matrix polymer monomer; and the above-mentioned acrylate monomer.

[0028] In some embodiments, the photopolymer composition includes the following components by weight percentage: photosensitizer and / or photocatalyst 0.4%-1.5%; basic catalyst 1%-3%; matrix polymer monomer 45%-52%; and the above-mentioned acrylate monomer 45%-52%.

[0029] The fourth aspect of the present application provides a volume holographic grating, which is obtained by curing the above-mentioned photopolymer composition.

[0030] The fifth aspect of the present application provides a method for preparing a volume holographic grating, which includes the following steps:

[0031] Provide the above-mentioned photopolymer composition;

[0032] Form a film on a substrate with the photopolymer composition;

[0033] Transfer the substrate with the formed film to an environment of 15°C-100°C for reaction;

[0034] Expose the substrate after the reaction to obtain the volume holographic grating.

[0035] In some embodiments, the reaction time for transferring the substrate with the formed film to an environment of 15°C-100°C for reaction is 0.1 hour-12 hours.

[0036] It can be seen from the above technical solutions that the acrylate monomer proposed in the present application has a simple structure and rich expandable structures, so that its synthesis steps are simple and the cost is reduced. Based on the introduction of more sulfur atoms in the monomer, a higher refractive index of the monomer is achieved. In the subsequent photopolymerization process, the generated polymer has a greater refractive index difference from common matrices (such as polyurethane). Therefore, a holographic grating with a high refractive index modulation can be prepared, and thus the holographic grating prepared with the acrylate monomer has good mechanical stability, high light transmittance and low shrinkage rate. Description of the Drawings

[0037] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained as these drawings.

[0038] Figure 1 It is a schematic diagram of the principle of the first-step reaction in the preparation methods of acrylate monomers MB-S-4Ph-1 and MB-S-4Ph-2 proposed by the present application.

[0039] Figure 2 It is a schematic diagram of the principle of the second-step reaction in the preparation method of acrylate monomer MB-S-4Ph-1 proposed by the present application.

[0040] Figure 3 It is a schematic diagram of the principle of the second-step reaction in the preparation method of acrylate monomer MB-S-4Ph-2 proposed by the present application.

[0041] Figure 4 It is a schematic diagram of the principle of the first-step reaction in the preparation methods of acrylate monomers MB-S-4Ph-3 and MB-S-4Ph-4 proposed by the present application.

[0042] Figure 5 It is a schematic diagram of the principle of the second-step reaction in the preparation method of acrylate monomer MB-S-4Ph-3 proposed by the present application.

[0043] Figure 6 It is a schematic diagram of the principle of the second-step reaction in the preparation method of acrylate monomer MB-S-4Ph-4 proposed by the present application.

[0044] Figure 7 It is a schematic diagram of the principle of the polymerization reaction of acrylate monomer MB-S-4Ph-1 under light irradiation proposed by the present application.

[0045] Figure 8 It is a schematic flow diagram of the preparation method of the volume holographic grating proposed by the present application. Detailed implementation manners

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0047] It should also be understood that the terms used in the specification of this application are merely for the purpose of describing specific embodiments and are not intended to limit this application. As used in the specification of this application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0048] It should be further understood that the term "and / or" used in the specification of this application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0049] With the development of technologies such as virtual reality, augmented reality, mixed reality, and head-up display, holographic optical elements prepared from photopolymers have attracted the attention of many researchers. Among them, volume holographic gratings (VHGs) can be used as coupling optical elements for holographic optical waveguides.

[0050] To obtain high-performance volume holographic gratings VHGs and expand the angular bandwidth of diffracted light, polymer gratings with a high refractive index modulation (Δn > 0.02) are a prerequisite. So far, only a few photopolymer material systems can meet this requirement.

[0051] Generally speaking, the photopolymer formulation for volume holographic gratings consists of three main components: a photoinitiating system (including photoinitiators and / or photosensitizers), a writing monomer (acrylate) and a matrix. When preparing polymer VHGs, the following process occurs: First, a crosslinked matrix is formed, which provides a physical support function before exposure, and the writing monomer, etc., can diffuse and migrate therein. Subsequently, under the irradiation of two coherent laser beams, the photoinitiating system causes the polymerization of the monomer, and a photopolymerization reaction occurs in the bright regions. The writing monomer will tend to migrate from the dark stripes to the bright stripes to participate in the polymerization. At the same time, the main matrix in the bright stripes will be squeezed by the migrated monomer and the formed polymer, and part of it will be forced to transfer to the dark stripes. Finally, due to the refractive index difference between the bright stripes and the dark stripes, a refractive index modulation VHG is generated.

[0052] According to the grating formation principle, increasing the refractive index difference between the (meth)acrylate monomer and the matrix is the main strategy for obtaining VHGs with a high Δn value. In the prior art, in order to increase the refractive index of the (meth)acrylate monomer, there are usually the following several schemes:

[0053] Scheme 1: A certain company has developed an arylurethane acrylate-based writing monomer for the production of holographic films, with a refractive index modulation Δn of 0.04. The structural formula of this arylurethane acrylate-based writing monomer is as follows:

[0054] Or,

[0055]

[0056] However, in the above-mentioned scheme, the structure of arylurethane acrylate monomers is complex and the synthesis is difficult. During the preparation of the amino-containing fragment, due to the monomer having three amino groups, the hydrogen bond force is strong and the purification is extremely difficult; the price of the triphenyl compound raw material is relatively high, the material production efficiency is low, and the large-scale commercialization is difficult.

[0057] Scheme 2: A research group developed a writing monomer based on polyaryl methacrylate (carbazole monomer) for the production of holographic recording media, and its refractive index modulation Δn is 0.046. The structural formula of this polyaryl methacrylate writing monomer is as follows:

[0058] Or,

[0059]

[0060] However, in the above-mentioned scheme, although the synthesis route of the monomer designed based on the carbazole fragment is further simplified, the carbazole fragment is a fused-ring structure, which makes the solubility of the monomer poor and is not conducive to uniform dispersion in the photopolymer system; in addition, due to the existence of the fused-ring structure, the aromatic ring of the carbazole group has no other functional group modifications, which limits the post-modification / space structure optimization of this monomer material. Therefore, it can only be matched with a small part of photosensitizers and polyurethane systems.

[0061] Therefore, the embodiments of the present application provide an acrylate monomer, which has a simple chemical structure and an aromatic ring that is easy to introduce other substituents, so as to have strong expandability, simplify its synthesis steps, reduce costs, and at the same time improve the refractive index of the monomer by introducing sulfur atoms. Thus, it can overcome the disadvantages of the monomers in the prior art, such as complex structure, many preparation steps, high purification difficulty, high material synthesis difficulty, high cost, etc., and has excellent properties such as high refractive index, high light transmittance, and low haze. It can be used to prepare volume holographic gratings and applied to various AR / VR display devices to improve the display effect, realize the improvement of the refractive index modulation of the volume holographic grating, and promote the commercial application of photopolymers.

[0062] The acrylate monomer provided by the embodiments of the present application has the following general formula:

[0063]

[0064] Among them, X can be H or a carbon chain, such as an alkane, alkene, alkyne or arene with 1-15 carbon atoms, etc.; Y can be H or a halogen; A can be H or an acetoxy group, and can also be an aryl group.

[0065] The acrylate monomer proposed in the embodiments of the present application has a simple structure and rich expandable structures, making its synthesis steps simple and reducing costs. Based on the introduction of more sulfur atoms in the monomer, a relatively high refractive index of the monomer is achieved. During the subsequent photopolymerization process, the generated polymer has a greater refractive index difference from common matrices (such as polyurethane). Therefore, holographic gratings with a high refractive index modulation can be prepared, so that the holographic gratings prepared with this acrylate monomer have good mechanical stability, high light transmittance, and low shrinkage rate.

[0066] In an alternative embodiment, the acrylate monomer is an MB-S-4Ph type writing monomer, which may include any one of MB-S-4Ph-1, MB-S-4Ph-2, MB-S-4Ph-3, and MB-S-4Ph-4.

[0067] As an implementation manner, the structural formula of the acrylate monomer MB-S-4Ph-1 may be:

[0068]

[0069] Among them, the refractive index n(550nm) of MB-S-4Ph-1 is 1.68, which is much greater than the refractive index of the writing monomers in the prior art, thus achieving a high refractive index modulation.

[0070] As an implementation manner, the structural formula of the acrylate monomer MB-S-4Ph-2 may be:

[0071]

[0072] Among them, the refractive index n(550nm) of MB-S-4Ph-2 is 1.65, which is much greater than the refractive index of the writing monomers in the prior art, thus achieving a high refractive index modulation.

[0073] As an implementation manner, the structural formula of the acrylate monomer MB-S-4Ph-3 may be:

[0074]

[0075] Among them, the refractive index n(550nm) of MB-S-4Ph-3 is 1.65, which is much greater than the refractive index of the writing monomers in the prior art, thus achieving a high refractive index modulation.

[0076] As an implementation manner, the structural formula of the acrylate monomer MB-S-4Ph-4 may be:

[0077]

[0078] Among them, the refractive index n(550nm) of MB-S-4Ph-4 is 1.63, which is much greater than that of the writing monomers in the prior art, thereby achieving a high refractive index modulation degree.

[0079] In an alternative embodiment, the olefin fragment of the acrylate monomer can be methacrylate, such as MB-S-4Ph-1 and MB-S-4Ph-3, and the olefin fragment of the acrylate monomer can also be acrylate, such as MB-S-4Ph-2 and MB-S-4Ph-4.

[0080] In an alternative embodiment, the olefin fragment of the acrylate monomer can be a monoolefin (such as MB-S-4Ph-1) or a polysubstituted olefin (such as MB-S-4Ph-3), which can be reasonably regulated according to matrices such as polyurethane. In specific applications, the use of polysubstituted olefins has more significant mechanical stability and better elastic tensile recovery.

[0081] As Figures 1-6 shown, the embodiment of the present application also provides a preparation method of an acrylate monomer, including the following steps:

[0082] React a first compound with allyl acyl chloride or 2-butenoyl chloride to form an acrylate monomer;

[0083] Among them, the first compound has the following general formula:

[0084]

[0085] R is H, an alkyl group or an aromatic hydrocarbon.

[0086] In some embodiments, the preparation step of the first compound includes: reacting benzenethiol with 2-chloroethanol or 2-chloro-1,3-propanediol to form the first compound.

[0087] As an implementation manner, as Figure 1 shown, benzenethiol can be reacted with 2-chloroethanol to form the first compound, and the structural formula of the formed first compound is as follows:

[0088]

[0089] As an implementation manner, as Figure 4 shown, benzenethiol can be reacted with 2-chloro-1,3-propanediol to form the first compound, and the structural formula of the formed first compound is as follows:

[0090]

[0091] In some embodiments, during the preparation of the acrylate monomer, as Figure 1 and Figure 4 shown, the first-step reaction is as follows:

[0092] Dissolve thiophenol and 2-chloroethanol or thiophenol and 2-chloro-1,3-propanediol in a first solvent, and react them under the action of a basic catalyst to form a first compound; wherein, the molar ratio of thiophenol to 2-chloroethanol or 2-chloro-1,3-propanediol is 1:0.8 - 1:1.2, the molar amount of the first solvent is 10 times - 100 times the molar amount of thiophenol, and the molar amount of the basic catalyst is 0.1 times - 1 times the molar amount of thiophenol.

[0093] In some embodiments, during the preparation of the acrylate monomer, as Figures 2-3 , Figure 5 shown in - and 6, the second-step reaction is as follows:

[0094] Dissolve the first compound and allyl chloride or the first compound and 2-butenoyl chloride in a second solvent, so that the first compound reacts with allyl chloride to form an acrylate monomer; wherein, the molar ratio of the first compound to allyl chloride or 2-butenoyl chloride is 1:0.8 - 1:1.2, and the molar amount of the second solvent is 10 times - 100 times that of allyl chloride or 2-butenoyl chloride.

[0095] The acrylate monomer can be obtained by mixing and reacting the first compound with or allyl chloride. The preparation steps are simple, reducing the difficulty of purification and the difficulty of material synthesis, thereby reducing costs. Among them, thiophenol can react with 2-chloroethanol to form the first compound, or react with 2-chloro-1,3-propanediol to form the first compound, and other halogen-substituted alcohols can also be used.

[0096] In the preparation method of the acrylate monomer proposed in the embodiments of the present application, only two-step reactions are required to synthesize MB-S-4Ph monomers. The preparation steps are simple, reducing the difficulty of purification and the difficulty of material synthesis, thereby reducing costs. Specifically, industrial-grade thiophenol can be used as the starting substrate for constructing the acrylate monomer, and thiophenol undergoes a nucleophilic substitution reaction with 2-chloroethanol or 2-chloro-1,3-propanediol under the action of a basic catalyst to form a first compound, and then the first compound undergoes a substitution reaction with allyl chloride or 2-butenoyl chloride to release hydrogen chloride and form an acrylate monomer.

[0097] In some embodiments, the molar ratio of thiophenol to 2-chloroethanol or 2-chloro-1,3-propanediol can be 1:1, 0.8:1, 1:2, etc.

[0098] In some embodiments, the molar amount of the first solvent is 10 times, 50 times, 100 times, etc. the molar amount of thiophenol.

[0099] In some embodiments, the molar amount of the basic catalyst is 0.1 times, 0.5 times, 1 times, etc. the molar amount of thiophenol.

[0100] In some embodiments, the molar ratio of the first compound to allyl acyl chloride or crotonyl chloride can be 1:1, 0.8:1, 1:2, etc.

[0101] In some embodiments, the molar amount of the second solvent is 10 times, 50 times, 100 times, etc. that of allyl acyl chloride or crotonyl chloride.

[0102] In alternative embodiments, the first solvent can be chloroform or N,N-dimethylformamide, and can also be other solvents capable of dissolving benzenethiol and 2-chloroethanol or 2-chloro-1,3-propanediol.

[0103] In alternative embodiments, the second solvent can be chloroform or other solvents capable of dissolving the first compound and allyl acyl chloride or crotonyl chloride.

[0104] In alternative embodiments, the basic catalyst includes organic bases and inorganic bases, such as triethylamine, sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium carbonate, potassium carbonate, etc.

[0105] In alternative embodiments, benzenethiol and 2-chloroethanol or 2-chloro-1,3-propanediol react for 5 to 7 hours under the action of a basic catalyst at room temperature, and are extracted with an extractant. After removing the first solvent by rotary evaporation, the first compound is obtained by recrystallization with ethanol.

[0106] In alternative embodiments, after the first compound and allyl acyl chloride or crotonyl chloride react for 1 to 3 hours at room temperature to obtain a product, the product is subjected to column chromatography with petroleum ether and ether for separation and purification to obtain an acrylate monomer, and the molar ratio of petroleum ether to ether is 1:0.05 - 0.15.

[0107] In alternative embodiments, the reaction time of benzenethiol and 2-chloroethanol or 2-chloro-1,3-propanediol under the action of a basic catalyst at room temperature can be 5 hours, 6 hours, 7 hours, etc.

[0108] In alternative embodiments, the first compound and allyl acyl chloride or crotonyl chloride react for 1 hour, 2 hours, 3 hours, etc. at room temperature.

[0109] In alternative embodiments, after the first compound and allyl acyl chloride or crotonyl chloride react at room temperature to obtain a product, the product is subjected to column chromatography with petroleum ether and ether for separation and purification to obtain an acrylate monomer, and the molar ratio of petroleum ether to ether can be 1:0.05, 1:0.1, 1:0.15, etc.

[0110] An embodiment of the present application also provides a photopolymer composition, which includes a photosensitizer and / or a photocatalyst, a basic catalyst, a matrix polymer monomer, and the above-mentioned acrylate monomer. Among them, the matrix polymer monomer is used to undergo a polymerization reaction to generate a matrix polymer.

[0111] In an alternative embodiment, the photopolymer composition may include the following components in weight percentages: photosensitizer or photocatalyst 0.4% - 1.5%; basic catalyst 1% - 3%; photopolymerizable monomer 45% - 52%; matrix polymer monomer 45% - 55%.

[0112] In an alternative embodiment, the photopolymer composition may include the following components in weight percentages: photosensitizer 1%; basic catalyst 1%; photopolymerizable monomer 48%; matrix polymer monomer 50%.

[0113] In an alternative embodiment, the photopolymer composition may include the following components in weight percentages: photosensitizer 0.4%; basic catalyst 2.6%; photopolymerizable monomer 45%; matrix polymer monomer 52%.

[0114] In an alternative embodiment, the photopolymer composition may include the following components in weight percentages: photosensitizer 1.5%; basic catalyst 1.5%; photopolymerizable monomer 52%; matrix polymer monomer 45%.

[0115] In an alternative embodiment, the photopolymer composition may include the following components in weight percentages: photosensitizer 1%; basic catalyst 3%; photopolymerizable monomer 45%; matrix polymer monomer 51%.

[0116] In an alternative embodiment, the photopolymer composition may include the following components in weight percentages: photosensitizer 1%; basic catalyst 3%; photopolymerizable monomer 51%; matrix polymer monomer 45%.

[0117] In an alternative embodiment, the photoinitiator may be a commonly used photoinitiator such as alkyl-containing diethanolamine (such as N-methyldiethanolamine, N-ethyldiethanolamine, etc.), N-phenyldiethanolamine, etc.

[0118] In an alternative embodiment, the photosensitizer may be a commonly used photosensitizer such as red light, methylene blue, malachite green, or azure I.

[0119] In an alternative embodiment, the matrix polymer monomer may be a first monomer having thiol and epoxy segments. When a certain amount of basic catalyst, such as organic amine, is added and under the action of heat, a self-polymerization reaction occurs to generate a first polymer. The structural formula of the first monomer is as follows:

[0120]

[0121] The structural formula of the first polymer is as follows:

[0122]

[0123] In an alternative embodiment, the matrix polymer monomer can also be two components based on thiol / propylene oxide as the second monomer and the third monomer respectively. By adding a certain amount of a basic catalyst, such as an organic amine, etc., and also under the action of heat, a polymerization reaction occurs to form a second polymer.

[0124] The structural formula of the second monomer is as follows:

[0125] The structural formula of the third monomer is as follows:

[0126] The structural formula of the second polymer is as follows:

[0127]

[0128] In the above embodiments, using thiol and cyclopropane fragments as the reactive functional groups of the matrix polymer, since the product does not contain unsaturated fragments, it has good photo / thermal stability and can be used to prepare volume holographic gratings, which are applied to various AR / VR display devices to improve the display effect. And since there are no olefins in the reaction system, the influence between the matrix polymer and the subsequent photopolymer is further avoided. The propylene oxide fragment ensures that no photo-response occurs during the formation of the matrix polymer, which is beneficial to the compatibility of pre-exposure processing, thus ensuring the refractive index difference between the two polymers after exposure and contributing to the preparation of holographic polymer gratings with high refractive index modulation.

[0129] In an alternative embodiment, the matrix polymer monomer can also be polyol and isocyanate. Using polyol and isocyanate as the reaction components and an alkali as the catalyst, a polyurethane-based matrix polymer is formed.

[0130] Among them, the structural formula of the polyol in this embodiment is as follows:

[0131]

[0132] The structural formula of the isocyanate is as follows:

[0133]

[0134] In an alternative embodiment, the matrix polymer monomer can also be an electron-withdrawing olefin and an alkyl thiol. Using the olefin fragment substituted with an electron-withdrawing group as the reaction precursor and the alkyl thiol as the second component, a certain amount of alkali is added to the blended system to undergo a nucleophilic addition reaction to form a polymer matrix.

[0135] Among them, the structural formula of the electron-withdrawing olefin in this embodiment is as follows:

[0136]

[0137] The structural formula of the thiol is as follows:

[0138]

[0139] The embodiment of the present application also provides a volume holographic grating, which is obtained by curing the above-mentioned photopolymer composition. The volume holographic grating of the embodiment of the present application can be applied to various AR / VR display devices to improve the display effect. Among them, the photopolymer composition includes the above-mentioned acrylate monomer. The acrylate monomer has a simple chemical structure, and an aromatic ring is easily introduced with other substituents, so it has strong expansibility, making its synthesis steps simple, reducing costs. At the same time, by introducing sulfur atoms, the refractive index of the monomer is increased. Thus, it can overcome the disadvantages of the existing monomers, such as complex structure, many preparation steps, high purification difficulty, high material synthesis difficulty, high cost, etc., and has excellent properties such as high refractive index, high light transmittance, and low haze, thereby improving the refractive index modulation degree of the volume holographic grating.

[0140] As Figure 8 shown, the embodiment of the present application also provides a preparation method S10 of a volume holographic grating, including the following steps:

[0141] S11, Provide the above-mentioned photopolymer composition. The photopolymer composition of the above embodiment can be placed in a reaction vessel and stirred evenly to form a mixture.

[0142] S12, Use the photopolymer composition to form a film on the substrate. In a specific application, a doctor blade can be used to coat the mixture on the substrate to form a thin film. At this time, the matrix polymer monomer generates a thioether polymer under the catalysis of an alkaline catalyst. The formation of the matrix makes the thin film have strong mechanical properties and transmittance. At the same time, the network of the thioether polymer is filled with other light-responsive components.

[0143] S13, Transfer the substrate with the formed film to an environment of 15°C - 100°C for reaction. In a specific application, the substrate with the thin film can be transferred to a constant temperature environment of 15°C - 100°C, such as in an incubator;

[0144] S14, Expose the substrate after the reaction to obtain a volume holographic grating. In a specific application, a volume holographic grating can be obtained after exposure using a holographic exposure device. Among them, the light-responsive component in the bright area, that is, the acrylate monomer, undergoes a photocatalytic polymerization reaction at this time. The polymerization reaction in the illuminated area and the unreacted components in the non-illuminated area form a refractive index difference. The larger the statistical refractive index difference, the better the refractive index modulation degree, and the larger the angular bandwidth of the VHG, so the better the performance.

[0145] In an alternative embodiment, the substrate can be a glass or plastic substrate. The formation of the matrix polymer endows the thin film with strong mechanical properties and transmittance. At the same time, the network of the thioether polymer is filled with other light-responsive components.

[0146] In an alternative embodiment, the substrate with the thin film can be transferred to an incubator at 15 °C, 50 °C, 100 °C, or any temperature in the range of 15 °C - 100 °C, which can be adjusted according to the actual situation.

[0147] In an alternative embodiment, the substrate with the thin film can react in the incubator for 0.1 hour, 5 hours, 12 hours, or any time in the range of 0.1 hour - 12 hours, which can be adjusted according to the actual situation.

[0148] Exemplarily, the above-mentioned acrylate monomer is blended with a photoinitiator and / or photosensitizer and a matrix polymer monomer, and a thin film is formed by coating. Then, after exposure with red light for 25 seconds - 40 seconds at room temperature, a volume holographic grating can be obtained. Among them, as Figure 7 shown, the monomer MB-S-4Ph-1 reacts with the photosensitive component (responding to the light emitted by the light source at a specific wavelength) and the matrix component (such as polyurethane) between the bright and dark fringes of the interference light, and the acrylate monomer polymerization reaction occurs under light irradiation to generate a polymer, and the reaction ends.

[0149] The acrylate monomer of the present invention will be further described below in conjunction with specific examples and test data.

[0150] Example 1

[0151] Synthesis of acrylate monomer MB-S-4Ph-1:

[0152] As Figure 1 shown, in the first-step reaction: First, thiophenol and 2-chloroethanol are mixed at room temperature (the molar ratio of the reactants is 1:1), using chloroform / N,N-dimethylformamide as the reaction solvent (the amount of chloroform / N,N-dimethylformamide is 50 times the molar amount of thiophenol to dissolve it), adding 0.1 - 1 times the amount of triethylamine as the base, reacting at room temperature for 6 hours, extracting with chloroform, rotary evaporation to remove the solvent, and recrystallizing with ethanol to obtain the aryl diol substrate.

[0153] As Figure 2 shown, in the second-step reaction: The aryl diol and allyl acyl chloride are mixed (the reaction molar ratio is 1:1), using chloroform as the solvent, and reacting at room temperature for 2 hours to obtain the product, which can be further separated and purified by column chromatography (petroleum ether: diethyl ether 1:0.1)

[0154] Preparation of holographic grating of MB-S-4Ph-1: MB-S-4Ph-1, a photosensitive system (red light photosensitive), and a matrix system were placed in a round-bottom flask and stirred for 10 minutes using a magnetic stirrer to ensure uniform mixing. Subsequently, it was coated on a glass substrate with a scraper to form a film (spin coating or scraping is acceptable). Then, the substrate with the film was transferred to an incubator at 50 °C and reacted for 5 hours. During the constant temperature period, the polymerization reaction of the matrix polymer occurred. The substrate was taken out and exposed using a standard holographic exposure device. In this example, after 30 s of red light exposure, the holographic grating could be prepared.

[0155] Example 2

[0156] Synthesis of acrylate monomer MB-S-4Ph-2:

[0157] As Figure 1 shown, the first-step reaction: First, benzenethiol and 2-chloroethanol were mixed at room temperature (reactant molar ratio 1:1), using chloroform / N,N-dimethylformamide as the reaction solvent ((chloroform / N,N-dimethylformamide was 50 times the molar amount of benzenethiol to dissolve it)), adding 0.1 - 1 times the amount of triethylamine as the base, reacting at room temperature for 6 hours, extracting with chloroform, rotary evaporating to remove the solvent, and recrystallizing with ethanol to obtain the aryl diol substrate.

[0158] As Figure 3 shown, the second-step reaction: The aryl diol and 2-butenoyl chloride were mixed (reaction molar ratio 1:1), using chloroform as the solvent, and reacting at room temperature for 2 hours to obtain the product, which could be further separated and purified by column chromatography (petroleum ether:ethyl ether 1:0.1)

[0159] Preparation of holographic grating of MB-S-4Ph-2: MB-S-4Ph-2, a photosensitive system (red light photosensitive), and a matrix system were placed in a round-bottom flask and stirred for 10 minutes using a magnetic stirrer to ensure uniform mixing. Subsequently, it was coated on a glass substrate with a scraper to form a film (spin coating or scraping is acceptable). Then, the substrate with the film was transferred to an incubator at 50 °C and reacted for 5 hours. During the constant temperature period, the polymerization reaction of the matrix polymer occurred. The substrate was taken out and exposed using a standard holographic exposure device. In this example, after 30 s of red light exposure, the holographic grating could be prepared.

[0160] Example 3

[0161] Synthesis of acrylate monomer MB-S-4Ph-3:

[0162] As Figure 4As shown, the first step of the reaction: First, mix benzenethiol with 2-chloro-1,3-propanediol at room temperature (the molar ratio of the reactants is 1:1). Use chloroform / N,N-dimethylformamide as the reaction solvent (chloroform / N,N-dimethylformamide is 50 times the molar amount of benzenethiol to dissolve it), add 0.1 - 1 equivalent of triethylamine as the base, react at room temperature for 6 hours, extract with chloroform, rotary evaporate to remove the solvent, and recrystallize with ethanol to obtain the aryl diol substrate.

[0163] As Figure 5 shown, the second step of the reaction: Mix the aryl diol with allyl acyl chloride (the reaction molar ratio is 1:1), use chloroform as the solvent, and react at room temperature for 2 hours to obtain the product, which can be further separated and purified by column chromatography (petroleum ether: diethyl ether 1:0.1)

[0164] Preparation of the holographic grating of MB-S-4Ph-3: Place MB-S-4Ph-3, the photosensitive system (red light photosensitive), and the matrix system in a round-bottom flask, stir with a magnetic stirrer for 10 minutes to ensure uniform mixing. Then coat it on a glass substrate with a spatula to form a film (either spin coating or scraping coating is acceptable). Then transfer the substrate with the film to an incubator at 50 °C and react for 5 hours. During the constant temperature period, the polymerization reaction of the matrix polymer occurs. Take out the substrate and use a standard holographic exposure device for exposure. In this example, after exposing with red light for 30 s, the holographic grating can be prepared.

[0165] Example 4

[0166] Synthesis of the acrylate monomer MB-S-4Ph-4:

[0167] As Figure 4 shown, the first step of the reaction: First, mix benzenethiol with 2-chloro-1,3-propanediol at room temperature (the molar ratio of the reactants is 1:1). Use chloroform / N,N-dimethylformamide as the reaction solvent (chloroform / N,N-dimethylformamide is 50 times the molar amount of benzenethiol to dissolve it), add 0.1 - 1 equivalent of triethylamine as the base, react at room temperature for 6 hours, extract with chloroform, rotary evaporate to remove the solvent, and recrystallize with ethanol to obtain the aryl diol substrate.

[0168] As Figure 6 shown, the second step of the reaction: Mix the aryl diol with 2-butenoyl chloride (the reaction molar ratio is 1:1), use chloroform as the solvent, and react at room temperature for 2 hours to obtain the product, which can be further separated and purified by column chromatography (petroleum ether: diethyl ether 1:0.1)

[0169] Preparation of the holographic grating of MB-S-4Ph-4: MB-S-4Ph-4, a photosensitive system (red-light photosensitive), and a matrix system are placed in a round-bottom flask and stirred for 10 minutes using a magnetic stirrer to ensure uniform mixing. Subsequently, it is coated on a glass substrate with a scraper to form a film (spin coating or blade coating is acceptable). Then, the substrate with the film is transferred to an incubator at 50 °C and reacted for 5 hours. During the constant temperature period, the polymerization reaction of the matrix polymer occurs. The substrate is taken out and exposed using a standard holographic exposure device. In this example, after 30 s of red-light exposure, the holographic grating can be prepared.

[0170] Experimental comparison data and analysis:

[0171]

[0172] As shown in the above table, the transmittance in the visible light region of Examples 1-4 is all above 88%, meeting the light transmittance requirements for AR displays. In addition, Examples 3-4 using polyene segments have more remarkable mechanical stability, better elastic tensile recovery, and can reach more than 1.5 times that of Examples 1-2 at the same level, indicating that the number of olefin functional groups is crucial in such molecules. In addition to mechanical properties, increasing the number of functionalized olefins is also beneficial to reducing the shrinkage rate. The shrinkage rate of Example 3 is 0.8%, showing good anti-shrinkage performance.

[0173] Without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0174] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. An acrylate monomer, characterized in that, The acrylate monomer has the following general formula: Wherein, X is H or a carbon chain; Y is H or a halogen; A is H, acetoxy or an aryl group.

2. The acrylate monomer according to claim 1, wherein The structural formula of the acrylate monomer is as follows: Or, Or, Alternatively, 3. A method for preparing an acrylate monomer, characterized in that, Comprising the following steps: Using a first compound and allyl acyl chloride or 2-butenoyl chloride to form the acrylate monomer; Wherein, the first compound has the following general formula: R is H, an alkyl group or an aryl group.

4. The preparation method according to claim 3, characterized in that, The preparation steps of the first compound include: Using benzenethiol and 2-chloroethanol or 2-chloro-1,3-propanediol to form the first compound.

5. The preparation method according to claim 4, characterized in that, Dissolving the benzenethiol and the 2-chloroethanol or dissolving the benzenethiol and the 2-chloro-1,3-propanediol in a first solvent, and reacting under the action of a basic catalyst to form the first compound; Wherein, the molar ratio of the benzenethiol to the 2-chloroethanol or the 2-chloro-1,3-propanediol is 1:0.8 - 1:1.2, the molar amount of the first solvent is 10 times - 100 times the molar amount of the benzenethiol, and the molar amount of the basic catalyst is 0.1 times - 1 times the molar amount of the benzenethiol.

6. The preparation method according to claim 5, characterized in that, Dissolving the first compound and the allyl acyl chloride or dissolving the first compound and the 2-butenoyl chloride in a second solvent, so that the first compound reacts with the allyl acyl chloride to form the acrylate monomer; Wherein, the molar ratio of the first compound to the allyl acyl chloride or the 2-butenoyl chloride is 1:0.8 - 1:1.2, and the molar amount of the second solvent is 10 times - 100 times that of the allyl acyl chloride or the 2-butenoyl chloride.

7. The preparation method according to claim 6, characterized in that, The first solvent is chloroform or N,N-dimethylformamide; and / or, The second solvent is chloroform.

8. The preparation method according to claim 4, characterized in that, The benzenethiol and the 2-chloroethanol or the benzenethiol and the 2-chloro-1,3-propanediol react at room temperature for 5 hours - 7 hours under the action of a basic catalyst, and are extracted with an extractant, then the first solvent is removed by rotary evaporation, and the first compound is obtained by recrystallization with ethanol; and / or, The first compound and the allyl acyl chloride or the first compound and the 2-butenoyl chloride react at room temperature for 1 - 3 hours to obtain a product, and then the product is subjected to column chromatography with petroleum ether and ether for separation and purification to obtain the acrylate monomer, and the molar ratio of the petroleum ether to the ether is 1:0.05 - 0.

15.

9. A photopolymer composition, characterized in that, The photopolymer composition comprises: A photosensitizer and / or a photocatalyst; A basic catalyst; A matrix polymer monomer; The acrylate monomer as described in claims 1 - 2.

10. The photopolymerizable composition according to claim 9, characterized in that, The photopolymer composition comprises the following components in weight percentages: A photosensitizer and / or a photocatalyst 0.4% - 1.5%; A basic catalyst 1% - 3%; A matrix polymer monomer 45% - 52%; The acrylate monomer as described in claims 1 - 2 45% - 52%.

11. A volume holographic grating, characterized in that, The volume holographic grating is obtained by curing the photopolymer composition according to any one of claims 9 - 10.

12. A method for preparing a volume holographic grating, characterized in that, Comprising the following steps: Providing the photopolymer composition as described in claim 10 or 11; Using the photopolymer composition to form a film on a substrate; Transfer the substrate after film formation to an environment of 15°C - 100°C for reaction; Expose the substrate after reaction to obtain the volume holographic grating.

13. The preparation method according to claim 12, characterized in that, The reaction time for transferring the substrate after film formation to an environment of 15°C - 100°C for reaction is 0.1 hour - 12 hours.

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