Optical monomer and preparation method and application thereof

Abstract

The invention discloses an optical monomer and a preparation method and application thereof, the structural general formula of the optical monomer is shown in the specification, R is a sulfur-containing group, and the sulfur-containing group is selected from one of the following groups: C2-C5 alkyl substituted by at least two sulfur, phenyl substituted by two sulfur, biphenyl substituted by two sulfur and naphthyl substituted by two sulfur. According to the optical monomer provided by the invention, thioether bonds existing in molecules greatly increase the electron cloud density and polarizability in unit volume, and the refractive index of the optical monomer is improved; a sulfur heterocyclic structure in the optical monomer can effectively improve the rigidity of the whole compound and improve the toughness of molecules; thioether bonds do not have characteristic absorption in visible light and near-infrared regions, influence on dispersion of visible light is small, transparency of the whole compound can be improved, and the Abbe number of the optical monomer is increased; the sulfydryl groups at the two ends of the molecule in the optical monomer can be used as reactive functional groups to react with other active functional groups such as isocyanate groups.

Description

Technical Field

[0001] This invention relates to the field of optical materials technology, and in particular to optical monomers, their preparation methods, and applications. Background Technology

[0002] High-performance optical devices are increasingly trending towards lightweighting, miniaturization, and integration. Among these, optical resin materials, due to their lightweight nature, good impact resistance, and ease of processing and molding, can be used to fabricate precision optical components and have a good foundation for application in head-mounted devices such as AR (Augmented Reality), VR (Virtual Reality), and MR (Mixed Reality) devices.

[0003] Increasing the refractive index of optical resin materials facilitates material thinning. However, in related technologies, lenses made from resin materials suffer from issues such as insufficient image clarity and poor image quality due to the increased refractive index coupled with a lower Abbe number; some resin lenses are also prone to scratches; and others have long curing times, impacting production efficiency. Summary of the Invention

[0004] In view of this, the present invention proposes an optical monomer, its preparation method and application, aiming to achieve an optical monomer with the required structural strength, high refractive index and suitable Abbe number.

[0005] The optical unit proposed in the first aspect of this invention has the following general structural formula: Wherein, R is a sulfur-containing group, and the sulfur-containing group is selected from one of the following groups: at least two sulfur-substituted C2~C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups.

[0006] As can be seen from the above technical solutions, the optical monomer proposed in the first aspect of the present invention, by introducing a large amount of sulfur element into the optical monomer, the thioether bonds present in the molecule greatly increase the electron cloud density and polarizability per unit volume, thereby improving the refractive index of the optical monomer; the sulfur heterocyclic structure in the optical monomer can effectively improve the rigidity of the entire compound and improve the toughness of the molecule; in addition, the thioether bonds have no characteristic absorption in the visible and near-infrared regions, and have little effect on the dispersion of visible light; the two sulfur heterocycles contained in the molecule can improve the transparency of the entire compound, which is beneficial to improving the Abbe number of the optical monomer; the thiol groups located at both ends of the molecule in the optical monomer can act as reactive functional groups, which facilitates reactions with other active functional groups such as isocyanate groups.

[0007] The second aspect of this invention provides a method for preparing an optical monomer, comprising the following steps: reacting 2-mercaptoprop-1-ol with epichlorohydrin in a ring-opening reaction to generate a first product containing hydroxyl and chlorine; reacting the first product, a first reactant, and a basic reagent in a first organic solvent in a nucleophilic substitution reaction to generate a second product, wherein the first reactant is an aliphatic dithiol or an aliphatic dithiol containing a sulfur heteroatom, a benzene dithiol, a biphenyl dithiol, or a naphthyl dithiol; dispersing the second product uniformly in a second organic solvent and reacting it in a ring-closing reaction under the action of Lawson's reagent to generate a third product containing a sulfur heterocycle; reacting the third product with a bromine source in a third organic solvent with a first catalyst in a bromine-containing reaction to generate a fourth product containing bromine; reacting the fourth product with thiourea in a fourth organic solvent at a temperature for a first reaction time, and adding an alkaline aqueous solution to continue the reaction for a second reaction time, followed by post-treatment to generate an optical monomer containing a thiol; wherein the optical monomer is the optical monomer described in the foregoing embodiments; the structural formula of the first product is: The general structural formula of the second product is: The general structural formula of the third product is: The general structural formula of the fourth product is: ; wherein, R in the second product, the third product, the fourth product and the optical monomer is a sulfur-containing group, and the sulfur-containing group is selected from one of the following groups: at least two sulfur-substituted C2~C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups.

[0008] As can be seen from the above technical solutions, the method for preparing optical monomers proposed in the second aspect of this invention reduces the generation of by-products and improves the purity and yield of the product by using a persulfation system to synthesize thiols. The raw materials required for the reaction are readily available, the conditions are simple and controllable, and it is convenient for large-scale production and industrial application. Specifically, by performing a nucleophilic substitution reaction between the first reactant and the first product, the sulfur-containing group R required for the optical monomer of this application can be rapidly introduced; by the ring-closing reaction of the second product with Lawson's reagent, the sulfur heterocyclic structure required for the optical monomer of this application can be introduced; and by the reaction of the fourth product with thiourea, the reactive functional group thiol required for the optical monomer of this application can be introduced, thereby preparing an optical monomer having the structural formula of the aforementioned embodiments of this application.

[0009] The resin proposed in the third aspect of the present invention comprises, as a raw material, the optical monomer described in the foregoing embodiments or the optical monomer prepared by the preparation method of the optical monomer described in the foregoing embodiments.

[0010] As can be seen from the above technical solutions, the resin proposed in the third aspect of the present invention can simultaneously improve the refractive index and Abbe number of the resin by adding the optical monomers of the aforementioned embodiments to the raw materials, and give the resin the required structural strength.

[0011] The optical element proposed in the fourth aspect of the present invention comprises, as a raw material, the optical monomer described in the foregoing embodiments or the optical monomer prepared by the preparation method of the optical monomer described in the foregoing embodiments.

[0012] As can be seen from the above technical solutions, the optical element proposed in the fourth aspect of the present invention can achieve thinness, lightness and good display effect; when used in head-mounted devices, it provides a high user wearing experience and can achieve comfortable wearing for a long time without dizziness.

[0013] 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 the present invention. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the synthesis reaction steps of the optical monomer proposed in Example 1 of the present invention; Figure 2 This is a schematic diagram of the synthesis reaction steps of the optical monomer proposed in Example 2 of the present invention; Figure 3 This is a schematic diagram of the synthesis reaction steps of the optical monomer proposed in Example 3 of the present invention; Figure 4 This is a schematic diagram of the synthesis reaction steps of the optical monomer proposed in Example 4 of the present invention; Figure 5 This is a schematic diagram of the synthesis reaction steps of the optical monomer proposed in Example 5 of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0017] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0018] Head-mounted devices, such as AR glasses, are placing increasingly higher demands on miniaturization and thinness. The core optical indicator of the optical materials used in these devices is primarily the refractive index, which significantly impacts the performance of the optical system, the degree of miniaturization, and user comfort. However, in pursuing higher refractive indices, it is often impossible to simultaneously achieve a good Abbe number; that is, the refractive index and Abbe number cannot be balanced. This results in poor image quality in the manufactured optical devices, potentially causing discomfort or even dizziness during wear.

[0019] Therefore, the present invention provides an optical monomer, its preparation method, and its application, aiming to solve at least one of the aforementioned technical problems.

[0020] Where there is no conflict, the various embodiments of this application and the features in the embodiments can be combined with each other.

[0021] The optical unit of the present application will now be described by way of example.

[0022] An embodiment of the present invention provides an optical unit, the general structural formula of which is shown below: Wherein, R is a sulfur-containing group, which is selected from one of the following groups: at least two sulfur-substituted C2~C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups.

[0023] It should be noted that the at least two sulfur-substituted C2-C5 alkyl groups here can be straight-chain or branched; for example, they can be -S-CH2-CH2-S-, -S-CH2-CH2-CH2-S-, -S-CH2-CH2-S-CH2-CH2-S-, -S-CH2-CHS-CH2-, -CH2-CH2-CHS-CHS-CH2-, -CH2-CHS-SS-, CH3-CH2-CHS-S-, etc.; the two sulfur-substituted phenyl groups here can be located in the meta, ortho, or para positions; the two sulfur-substituted biphenyl groups here can be located in the para position of the biphenyl group; the two sulfur-substituted naphthyl groups here can be in different positions of the naphthyl group.

[0024] The optical monomer proposed in this invention introduces a large amount of sulfur into the optical monomer, which contains a large number of thioether bonds in the molecule, such as thioether bonds in sulfur heterocycles and thioether bonds in sulfur-containing groups. The thioether bonds in the molecule greatly increase the electron cloud density and polarizability per unit volume, thereby improving the refractive index of the optical monomer.

[0025] In optical monomers, the relative slippage between the short chains of the sulfide heterocycle structure is relatively difficult and requires a lot of energy. Other chains connected to the sulfide heterocycle are also restricted by the two sulfide heterocycles, which restricts the free rotation of other chains and thus effectively improves the rigidity of the entire compound. The carbon-sulfur bonds inside the sulfide heterocycle can produce certain stretching and twisting phenomena after being subjected to force, which can absorb a certain amount of energy and thus improve the toughness of the molecule.

[0026] Furthermore, thioether bonds have no characteristic absorption in the visible and near-infrared regions, and have little effect on the dispersion of visible light. The two sulfur heterocycles contained in the molecule can improve the transparency of the entire compound, which is beneficial to improving the Abbe number of optical monomers.

[0027] The thiol groups located at both ends of the molecule in optical monomers can act as reactive functional groups, facilitating reactions with other active functional groups such as isocyanate groups, thus making them suitable as raw materials for resins or other optical components.

[0028] Therefore, the optical unit of the present application embodiment can have the required structural strength, high refractive index and suitable Abbe number.

[0029] In some embodiments, the sulfur-containing group comprises at least two sulfur-substituted C2-C5 saturated aliphatic chains, the number of carbons being limited and the chains being either straight or branched, excluding cycloalkane chains, thereby controlling the length of the sulfur-containing group within a suitable range, neither too long nor too short, and ensuring that the optical monomer has the desired refractive index.

[0030] In some further embodiments, the sulfur-containing group is selected from groups having the following structural formula: wherein , , , , , All are C2-C5 alkyl groups with at least two sulfur substitutions; among them , , All are phenyl groups with two sulfur substitutions; among them It is a biphenyl with two sulfur substitutions; among which , , , or All of them are two sulfur-substituted naphthyl groups. In these embodiments, by employing the sulfur-containing groups of the above-described structure, the number of thioether bonds in the entire optical monomer molecule is further increased, which is also beneficial to maintaining a high refractive index of the entire optical monomer molecule; for sulfur-containing groups containing phenyl, biphenyl, or naphthyl groups, since these aromatic groups can provide greater polarizability, the refractive index of the optical monomer can be further improved; the introduction of these groups can also improve the rigidity of the optical monomer.

[0031] In some embodiments of this application, the optical monomer is selected from monomers having the following structural formula: , , , or These optical monomers have a high number of thioether bonds in their molecules, resulting in a high refractive index and a suitable Abbe number. Their overall molecular chains are relatively short, which facilitates rapid cross-linking reactions with other components when applied to resins or optical components, enabling faster curing. This allows for the production of materials with high refractive index groups per unit volume, which is beneficial for improving the refractive index of the final material.

[0032] The following describes an exemplary method for preparing an optical monomer according to an embodiment of this application.

[0033] The embodiments of the present invention provide a method for preparing optical monomers of the foregoing embodiments, including the following steps: step S100, step S200, step S300, step S400 and step S500.

[0034] Step S100: 2-Mercaptoprop-1-ol is reacted with epichlorohydrin in a ring-opening reaction to generate a first product containing a hydroxyl group and chlorine. The structural formula of the first product is as follows: In step S100, commercially available 2-mercaptoprop-1-ol (CAS No. 3001-64-7) and epichlorohydrin (CAS No. 106-89-8) are used. The thiol group in 2-mercaptoprop-1-ol acts as a nucleophile, attacking the more strained three-membered epoxy ring in epichlorohydrin. This causes the three-membered epoxy ring to cleave, forming the first product with a β-hydroxy sulfide, while retaining the hydroxyl group of 2-mercaptoprop-1-ol and the chlorine in epichlorohydrin, facilitating subsequent reactions.

[0035] The reaction formula for step S100 is expressed as follows: .

[0036] In some embodiments, 2-mercaptoprop-1-ol and water are added to a container and stirred until homogeneous, and then epichlorohydrin is added dropwise to allow for a complete reaction.

[0037] In some embodiments, the molar ratio of 2-mercaptoprop-1-ol to epichlorohydrin is 1:1 to ensure complete reaction and reduce byproducts.

[0038] In a further embodiment, in step S100, 2-mercaptoprop-1-ol and epichlorohydrin are reacted at room temperature for a reaction time of 3 to 5 hours, such as 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or any range between any two of the aforementioned specific values, so that the two reactants react fully to obtain the first product.

[0039] In some embodiments, step S100 further includes the following pretreatment step: evacuating the container, filling it with nitrogen, and repeating this process three or more times to achieve a relatively stable reaction environment.

[0040] In some embodiments, step S100 further includes the following post-processing steps: the system is extracted multiple times with dichloromethane, the organic phases are combined, washed with water to pH=7, the organic phase is concentrated to solvent-free distillation, the crude product is passed through a column, and eluted with a combination of petroleum ether (PE) and ethyl acetate (EA), with a ratio of 10:1 to 2:1 (e.g., a change in the eluent phase from low polarity to high polarity), resulting in a colorless liquid. Extraction with dichloromethane allows for the extraction of a larger amount of the first product, maximizing the yield of the first product. Washing with water to pH=7 effectively removes water-soluble impurities from the organic phase, improving the purity of the first product. Concentrating the organic phase to solvent-free distillation yields a crude product, which can be easily purified by column chromatography to obtain a purer first product, thus significantly improving the purity of the first product.

[0041] Step S200: The first product, the first reactant, and the basic reagent undergo a nucleophilic substitution reaction in a first organic solvent to generate a second product. The first reactant is an aliphatic dithiol or aliphatic dithiol containing a sulfur heteroatom, a benzene dithiol, a biphenyl dithiol, or a naphthyl dithiol. In step S200, the second product is generated by reacting the first product synthesized in step S100 with a commercially available first reactant. The general structural formula of the second product is: R represents a sulfur-containing group selected from one of the following groups: at least two sulfur-substituted C2-C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups. The basic reagent provides basic conditions, while the first organic solvent ensures good dispersion of the reagents and provides a relatively stable reaction environment. The first reactant, containing a thiol structure, generates a sulfide anion under basic conditions. This sulfide anion attacks the carbon atom in the first product bonded to chlorine, breaking the C-Cl bond and forming a CS- bond, further enriching the second product with more thioether bonds. During the reaction, the skeleton of the first product containing two hydroxyl groups and the skeleton of the first reactant are introduced into the second product, providing a basis for subsequent reactions of the second product.

[0042] The reaction formula for step S200 is expressed as follows: In the reaction formula, HRH represents a substance with two thiol groups, where the H shown is the H in a thiol group (SH-) bonded to S.

[0043] In some embodiments, the molar ratio of the first product to the first reactant is 2:1. In these embodiments, since the first reactant itself has two molecules of thiol groups available for reaction, when the two molecules of thiol groups react with one molecule of the first product, a roughly symmetrical structure with R as the symmetrical region can be formed. This allows more reactive functional groups to be integrated on the entire optical monomer, providing the structural basis required for the ring-closing reaction to generate two thioheterocycles in the subsequent step S300.

[0044] In some embodiments, the first reactant is selected from ethylenedithiol (CAS No. 540-63-6), dithioethyl sulfide (CAS No. 3570-55-6), 1,2-propanedithiol (CAS No. 814-67-5), 2,3-propanedithiol (CAS No. 109-80-8), 2,3-pentanedithiol (available from Tengzhou Wutong Flavoring Co., Ltd.), ethylenedithiool (available from Shandong Tianxiang Food Ingredients Co., Ltd.), propanedithiol (available from Baishun (Beijing) Chemical Technology Co., Ltd.), 1,4-phenylenediol (CAS No. 624-39-5), 1, One of the following: 2-phenylenediamine (CAS No. 17534-15-5), 1,3-phenylenediamine (CAS No. 626-04-0), biphenyl-4,4'-dithiol (CAS No. 6954-27-4), 1,5-dimercaptonaphthalene (CAS No. 5325-88-2), 1,6-naphthalenediamine (CAS No. 856198-91-9), 2,3-naphthalenediamine (CAS No. 99643-52-4), 2,7-naphthyldithiol (CAS No. 71977-56-5), and 2,6-naphthalenedithiophenol (CAS No. 96892-95-4). These substances are all commercially available and can provide sulfur-containing groups during synthesis.

[0045] In some embodiments, the first organic solvent is selected from at least one of ethanol and methanol. This first organic solvent can dissolve the alkaline reagent and also disperse the reactants well, making the entire system more homogeneous. In other embodiments, other organic solvents with similar effects may also be selected.

[0046] In some embodiments, the alkaline reagent is at least one selected from sodium hydroxide, potassium hydroxide, sodium methoxide, and sodium ethoxide. These alkaline reagents provide the alkaline environment required for the reaction, allowing the thiol groups of the first reactant to be deprotonated to generate sulfide anions, which facilitates the smooth progress of step S200. These alkaline reagents can also be dissolved in the first organic solvent.

[0047] In some embodiments, the first reactant, the first organic solvent, and the basic reagent are added to a container and stirred until homogeneous, and then the first product is added dropwise to allow for a complete reaction.

[0048] In a further embodiment, in step S200, the first reactant and the first product react at room temperature for a reaction time of 15 to 17 hours, such as 15 hours, 15.5 hours, 16 hours, 16.5 hours, 17 hours, or any range between any two of the aforementioned specific values, so that the two reactants react fully to obtain the second product.

[0049] In some embodiments, step S200 further includes the following pretreatment step: evacuating the container, filling it with nitrogen, and repeating this process three or more times to achieve a relatively stable reaction environment.

[0050] In some embodiments, step S200 further includes the following post-processing steps: the system is extracted with dichloromethane, washed with water until neutral, the organic phase is concentrated to solvent-free distillate, and the crude product is passed through a column, for example, using a combination of petroleum ether and ethyl acetate as the eluent, with a ratio of 5:1 to 1:1 between the two eluent phases (e.g., a change in the eluent phase from low polarity to high polarity). The liquid obtained after elution is cleaned of the organic phase to obtain a white solid. Using dichloromethane extraction allows for the extraction of a larger amount of the second product, thereby maximizing the yield of the second product. Washing with water to neutral effectively removes water-soluble impurities from the organic phase, improving the purity of the second product. Concentrating the organic phase to solvent-free distillate yields a crude product, which can be easily purified by column chromatography to obtain a purer second product, thus greatly improving the purity of the second product.

[0051] Step S300: The second product is uniformly dispersed in the second organic solvent and subjected to a ring-closing reaction under the action of Lawson's reagent to generate a third product containing a sulfur heterocycle. The general structural formula of the third product is: R represents a sulfur-containing group, selected from one of the following groups: at least two sulfur-substituted C2-C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups. In step S300, the second product synthesized in step S200 is used, with the participation of commercially available Lawson's reagent (a deoxythioreagent), which activates two closely spaced hydroxyl groups in the second product, causing the hydroxyl groups to leave sequentially, and replacing one of the hydroxyl groups with a sulfur atom, ultimately forming a thiohexacyclic ring with one sulfur atom added for every two hydroxyl groups removed.

[0052] The reaction formula for step S300 is expressed as follows: .

[0053] In some embodiments, the second organic solvent is selected from at least one of toluene and xylene. The second organic solvent can provide a stable environment for the reaction of the second product and Lawson's reagent and make the concentration of the reactants appropriate, thereby controlling the reaction rate.

[0054] In some embodiments, the closed-loop reaction includes heating to a second organic solvent for reflux and reacting for 3 to 6 hours, such as values ​​of 3 hours, 4 hours, 5 hours, 6 hours, and any range between any two of the aforementioned specific values, thereby enabling the reaction to proceed at a high speed.

[0055] In some embodiments, the molar ratio of the second product, the second organic solvent, and the Lawson reagent is 0.05:3.7 to 4.0:0.1, which is beneficial for the second product and the Lawson reagent to react fully at a certain rate and reduce by-products.

[0056] In some embodiments, step S300 further includes the following pretreatment step: evacuating the container, filling it with nitrogen, and repeating this process three or more times to achieve a relatively stable reaction environment.

[0057] In some embodiments, step S300 further includes the following post-processing steps: After the reaction solution is naturally cooled to room temperature, it is cooled to 0°C~5°C using an ice-water bath. A saturated sodium bicarbonate solution is slowly added to the reaction solution until no gas is emitted. A 5% sodium hydroxide solution is added, and the mixture is stirred for 8 to 12 minutes. The mixture is then separated, the organic phase is washed with water until neutral, concentrated until no solvent is distilled off, and the crude product is passed through a column. For example, a combination of petroleum ether and ethyl acetate is used as the eluent, with a ratio of 40:1 to 5:1 (e.g., a gradient from low polarity to high polarity in the eluent phase). The liquid obtained after elution is cleaned of the organic phase to obtain a light yellow solid. Natural cooling allows the reaction system after vigorous reflux to cool down smoothly, avoiding violent contraction or boiling due to sudden cooling. Combined with an ice bath, this effectively reduces the byproducts generated during the reaction. The saturated sodium bicarbonate solution can remove unreacted Lawson's reagent or acidic phosphorus-containing and sulfur-containing byproducts formed during the reaction; sodium hydroxide can further remove acidic impurities, thereby improving the purity of the third product. Liquid-liquid separation enables rapid separation of the organic and aqueous phases. Washing with water until neutral effectively removes water-soluble impurities from the organic phase, improving the purity of the tertiary product. Concentrating the organic phase to solvent-free distillation yields a crude product, which can be easily purified by column chromatography to obtain a purer tertiary product, thus significantly improving its purity.

[0058] Step S400: The third product and the bromine source are reacted with the first catalyst in a third organic solvent to produce a bromine-containing fourth product. The general structural formula of the fourth product is: R is a sulfur-containing group, selected from one of the following groups: at least two sulfur-substituted C2-C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups. The bromine source in step S400 provides bromine, and the third product provides a methyl group of a sulfur heterocycle that can be activated. Under the action of the bromine source and the first catalyst, the methyl group adjacent to the sulfur heterocycle is activated and combines with a bromine atom to form a fourth product containing a bromomethyl group on the side chain of the sulfur heterocycle, facilitating subsequent step S500.

[0059] The reaction formula for step S400 is expressed as follows: .

[0060] In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," and "fourth" may explicitly or implicitly include one or more of the stated features.

[0061] In some embodiments, the bromine source is selected from at least one of N-bromosuccinimide (NBS) and N-bromophthalimide. In step S400, the use of the above-mentioned bromine source can provide selective bromination under mild conditions without destroying the sulfur heterocycle, thereby allowing the methyl group of the sulfur heterocycle to be brominated to a bromomethyl group.

[0062] In some embodiments, the first catalyst is selected from at least one of triphenylphosphine (Ph3P) and tributylphosphine (TBP). Using these catalysts, the bromine source can be activated in step S400 to generate a bromine source with controllable activity, such as a brominated triphenylphosphine salt, preventing the opening of the sulfur heterocycle and facilitating the substitution of hydrogen on the methyl group of the sulfur heterocycle side chain with bromine. With the above-mentioned first catalyst, the HBr generated in step S400 can also be rapidly captured by PPh3 or TBP, stabilizing the entire reaction process and reducing the generation of byproducts.

[0063] In some embodiments, the third organic solvent is selected from at least one of dichloromethane, 1,2-dichloroethane, 2-methyltetrahydrofuran, and toluene. The aforementioned third organic solvent can simultaneously and effectively dissolve the aforementioned reactants, catalyst, and products, allowing the reaction to proceed in a homogeneous phase, improving reaction efficiency, and facilitating separation and removal after the reaction is complete.

[0064] In a further embodiment, in step S400, the third product and the bromine source react at room temperature for a reaction time of 15 to 17 hours, such as 15 hours, 15.5 hours, 16 hours, 16.5 hours, 17 hours, or any range between any two of the aforementioned specific values, so that the two reactants react fully to obtain the fourth product.

[0065] In some embodiments, the molar ratio of bromine source to third product is 3 to 3.33:1; the molar ratio of bromine source to first catalyst is 6 to 6.66:1. By controlling the above molar ratios, the first catalyst can sufficiently activate the bromine source, and the methyl group of the sulfur heterocyclic side chain of the third product can form a bromomethyl group.

[0066] In some embodiments, step S400 further includes the following pretreatment step: evacuating the container, filling it with nitrogen, and repeating this process three or more times to achieve a relatively stable reaction environment.

[0067] In some embodiments, step S400 further includes the following post-processing steps: washing the reaction solution with water until neutral, concentrating the organic phase until solvent-free distillation, and passing the crude product through a column chromatography column, for example, using a combination of petroleum ether (PE) and ethyl acetate (EA) as the eluent, with a ratio of 30:1 to 5:1 (e.g., a gradient from low to high polarity in the eluent). The collected liquid after elution is used to remove the organic phase, yielding a pale yellow solid. Washing with water to neutral effectively removes water-soluble impurities from the organic phase, improving the purity of the fourth product. Concentrating the organic phase until solvent-free distillation yields the crude product, which can be easily purified by column chromatography to obtain a purer fourth product, thereby significantly improving the purity of the third product.

[0068] Step S500: The fourth product and thiourea are reacted at a temperature in a fourth organic solvent for a first reaction time, and then an alkaline aqueous solution is added to continue the reaction for a second reaction time. Post-treatment is then performed to generate an optical monomer containing a thiol; the optical monomer is any of the optical monomers described in the preceding embodiments. The thiourea in step S500 can provide sulfur, and the sulfur atom of the thiourea can replace the bromine in the fourth product, and hydrolyze under alkaline conditions to form a sulfur heterocyclic compound with a thiol terminal group, thereby providing the optical monomer of this application with reactive functionality.

[0069] The reaction formula for step S500 is expressed as follows: .

[0070] In some embodiments, the fourth organic solvent is selected from methanol or ethanol. By using these solvents, thiourea and the fourth product can be effectively dissolved, making the reaction system more homogeneous and also facilitating subsequent removal.

[0071] In some embodiments, the alkaline aqueous solution is selected from at least one of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. These alkaline aqueous solutions provide a strong alkaline environment, which is conducive to hydrolysis and further generation of thiol groups, promotes the continuous progress of the reaction, and can also neutralize the acidic byproducts produced.

[0072] In some embodiments, the temperature of the heat-preserving reaction is approximately the boiling point of the fourth organic solvent, and the first reaction time is 10 h to 14 h, for example, the first reaction time includes values ​​such as 10 h, 10.3 h, 11 h, 11.5 h, 12 h, 12.8 h, 13 h, 13.4 h, 14 h, and any range between any two of the aforementioned specific values, so that thiourea and the fourth product react fully and bromine is fully replaced by sulfur. The second reaction time is 5 h to 10 h, for example, the second reaction time includes values ​​such as 5 h, 5.2 h, 5.7 h, 6 h, 6.1 h, 6.4 h, 6.8 h, 7 h, 7.2 h, 7.4 h, 7.9 h, 8 h, 8.6 h, 9 h, 9.5 h, 10 h, and any range between any two of the aforementioned specific values, so that the reaction proceeds further and fully forms thiol groups.

[0073] In some embodiments, the molar ratio of the fourth product to thiourea is 1:2 to 2.2, thereby ensuring that the bromine in the fourth product can be sufficiently replaced by sulfur and ultimately form -SH.

[0074] In some embodiments, step S500 further includes the following pretreatment step: evacuating the container, filling it with nitrogen, and repeating this process three or more times to achieve a relatively stable reaction environment.

[0075] In some embodiments, step S500 further includes the following post-processing steps: After the reaction is complete, allow the mixture to cool naturally to room temperature. Extract multiple times with ethyl acetate, combine the organic phases, add dilute hydrochloric acid to pH=7, and wash twice with water. Concentrate the organic phase until solvent-free distillate, and pass the crude product through a column chromatography column, eluing with a combination of petroleum ether and ethyl acetate, with a ratio of 10:1 to 1:1 (e.g., a gradient from low to high polarity). Remove the organic phase from the collected liquid after elution to obtain a pale yellow solid. Ethyl acetate extraction allows for the aggregation of a larger quantity of crude optical monomers, thereby increasing the yield. Washing with water to neutral effectively removes water-soluble impurities from the organic phase, improving the purity of the optical monomers. Concentrating the organic phase until solvent-free distillate yields the crude product, which can be easily purified by column chromatography to obtain purer optical monomers, thus significantly improving their purity.

[0076] As can be seen from the above, the method for preparing the optical monomer proposed in this application reduces the generation of by-products and improves the purity and yield of the product by using a persulfation system to synthesize thiols. The raw materials required for the reaction are readily available, the conditions are simple and controllable, and it is easy to scale up production and suitable for industrial applications. Specifically, by performing a nucleophilic substitution reaction between the first reactant and the first product, the sulfur-containing group R required for the optical monomer of this application can be rapidly introduced. By performing a ring-closing reaction between the second product and Lawson's reagent, a ring-closing reaction is carried out on the polyol, which introduces sulfur atoms and constructs a cyclic structure, thereby improving the rigidity of the polymer and introducing the sulfur heterocyclic structure required for the optical monomer of this application. By reacting the fourth product with thiourea, the reactive functional group thiol required for the optical monomer of this application can be introduced, thereby preparing an optical monomer with the structural formula of the aforementioned embodiments of this application.

[0077] The resins of embodiments of this application will now be described by way of example.

[0078] An embodiment of the present invention provides a resin, the raw materials of which include: the optical monomer of the foregoing embodiment or the optical monomer prepared by the preparation method of the optical monomer of the foregoing embodiment.

[0079] As can be seen from the above, the resin proposed in the embodiments of the present invention, by adding the optical monomers of the aforementioned embodiments to the raw materials, can simultaneously improve the refractive index and Abbe number of the resin, and give the resin the required structural strength.

[0080] In some embodiments, the resin further includes a diisocyanate compound, wherein the mass ratio of the diisocyanate compound to the optical monomer is 26.9~29.5:70.5~73.1, for example, a mass ratio of 70.5:29.5, 72.6:27.4, or 73.1:26.9. One molecule of the diisocyanate compound provides two molecules of isocyanate groups, which can induce cross-linking and curing with the thiol groups in the optical monomer under suitable conditions to form a resin. The resulting resin, due to the presence of the optical monomer of this application, further maintains a high refractive index and a high Abbe number. Since the optical monomers of this application are all short-chain compounds, they can cross-link with the diisocyanate compound relatively quickly. Furthermore, the network structure formed after cross-linking has high structural strength because the optical monomers themselves contain many sulfur heterocyclic structures, and some optical monomers also contain some aromatic groups.

[0081] In some embodiments, the diisocyanate compound is selected from phenylenediamine diisocyanate, isophorone diisocyanate, and tetramethylphenylenediamine diisocyanate. Phenyleneamine diisocyanate can provide the resin with more aromatic ring structures, thereby helping to further improve the refractive index of the resin. The addition of isophorone diisocyanate can further improve the rigidity of the resin and enhance its resistance to yellowing. Tetramethylphenylenediamine diisocyanate exhibits small volume shrinkage and low internal stress during the reaction with optical monomers.

[0082] The optical elements of embodiments of this application will now be described by way of example.

[0083] An embodiment of the present invention provides an optical element, the raw material of which includes the optical monomer of the foregoing embodiment or the optical monomer prepared by the preparation method of the optical monomer of the foregoing embodiment.

[0084] As can be seen from the above, the optical element proposed in the embodiments of the present invention can achieve thinness, lightness, and good display effect; when used in head-mounted devices, it provides a high level of user comfort and allows for comfortable wear for extended periods without dizziness. For example, the optical element can be a resin lens.

[0085] Furthermore, the optical elements in the embodiments of this application can be further used in optical devices, including but not limited to head-up display (HUD), augmented reality (AR) devices, virtual reality (VR) devices, etc., and the optical devices can be lighter, have better imaging effects, and clearer images.

[0086] Unless otherwise specified, the reagents and solvents used in the embodiments of this invention can be obtained from commercially available sources.

[0087] The optical monomer and its preparation method of the present invention will be described below with reference to specific embodiments.

[0088] Example 1 The structural formula of the optical unit in this embodiment is: , denoted as G1.

[0089] refer to Figure 1 The preparation method of optical monomer G1 includes the following steps: Step 100: Synthesis of the first product – 1a.

[0090] Vacuum was drawn into a 500ml three-necked flask equipped with a magnetic stir bar, and nitrogen gas was introduced. This process was repeated at least three times. 100ml of water and 23g of 2-mercaptoprop-1-ol were added. After stirring for 5 minutes, 23g of epichlorohydrin was added dropwise. After the addition was complete, the mixture was allowed to react at room temperature for 4 hours. After the reaction was complete, the system was extracted three times with 150ml of dichloromethane. The organic phases were combined, washed with water until pH=7, and concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA=10:1 to 2:1) to obtain a colorless liquid. The yield of the first product 1a was 85%.

[0091] Step 200: Synthesis of the second product – 1b The mixture was transferred to a 500 ml three-necked flask equipped with a magnetic stir bar, evacuated, and purged with nitrogen. This process was repeated at least three times. Then, 250 ml of ethanol, 8 g of sodium hydroxide, and 9.4 g (0.1 mol) of ethylene dithiol were added. After stirring for 10 min, 36.8 g (0.2 mol) of product 1a was added dropwise. The mixture was stirred at room temperature for 16 h. After the reaction was complete, 400 ml of dichloromethane was added for extraction. The mixture was washed with water until neutral. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 5:1 to 1:1) to obtain a white solid. The yield of the second product 1b was 82%.

[0092] Step 300: Synthesis of the third product – 1c A 1000ml three-necked flask equipped with a magnetic stir bar was evacuated and filled with nitrogen gas, repeated at least three times. Anhydrous toluene (400ml, approximately 346.8g, 3.764mol) and 1b (19.5g) were added, and the mixture was stirred at room temperature for 30 minutes to disperse evenly. A toluene solution of 40.5g Lawson's reagent was added dropwise. The reaction was stopped after reflux for 4 hours. The reaction solution was allowed to cool naturally to room temperature, then cooled to 0°C using an ice-water bath. Slowly, saturated sodium bicarbonate solution was added until no gas was emitted. 50ml of 5% sodium hydroxide solution was added, and the mixture was stirred for 10 minutes. The mixture was separated, the organic phase was washed with water until neutral, and concentrated until no solvent was distilled off. The crude product was passed through a column (PE / EA = 40:1 to 5:1) to obtain a pale yellow solid. The yield of the third product 1c was 60%.

[0093] Step 400: Synthesis of the fourth product – 1d A 500 ml three-necked flask equipped with a magnetic inlet was evacuated and purged with nitrogen, repeated at least three times. Then, 200 ml of dichloromethane, 26.7 g of NBS (approximately 0.150 mol), 5.9 g of triphenylphosphine (approximately 0.0225 mol), and 18.55 g of 1c (approximately 0.048 mol) were added. The mixture was reacted at room temperature for 16 hours. After the reaction was complete, the reaction solution was washed with water until neutral. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 30:1 to 5:1) to give a pale yellow solid. The yield of the fourth product (1d) was 70%.

[0094] Step 500: Synthesis of optical monomer G1 Vacuum was drawn into a 500 ml three-necked flask equipped with a magnetic stir bar, and nitrogen gas was introduced. This process was repeated at least three times. 200 ml of ethanol, 27.1 g of 1d (approximately 0.05 mol), and 8.36 g of thiourea (approximately 0.1098 mol) were added. The mixture was heated to reflux and held at this temperature for 12 hours. An aqueous solution of sodium hydroxide (8 g sodium hydroxide, 30 ml water) was then added, and the mixture was refluxed for another 6 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The mixture was extracted twice with 210 ml of ethyl acetate. The organic phases were combined, and the solution was diluted with dilute hydrochloric acid to pH 7 and washed twice with water. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 10:1 to 1:1) to obtain a pale yellow solid. The yield of optical monomer G1 was 82%.

[0095] Example 2 The structural formula of the optical unit in this embodiment is: , denoted as G2.

[0096] refer to Figure 2 The preparation method of optical monomer G2 includes the following steps: Step 100: Synthesis of the first product—2a. The synthesis of 2a is the same as that of 1a, and will not be repeated here. The yield is 85%.

[0097] Step 200: Synthesis of the second product – 2b.

[0098] The mixture was transferred to a 500 ml three-necked flask equipped with a magnetic stir bar, evacuated, and purged with nitrogen. This process was repeated at least three times. Then, 250 ml of ethanol, 8 g of sodium hydroxide, and 15.4 g (approximately 0.1 mol) of dimercaptoethyl sulfide were added. After stirring for 10 min, 36.8 g of product 2a was added dropwise. The mixture was stirred at room temperature for 16 h. After the reaction was complete, 400 ml of dichloromethane was added for extraction. The mixture was washed with water until neutral. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 5:1 to 1:1) to obtain a white solid. The yield of the second product 2b was 80%.

[0099] Step 300: Synthesis of the third product – 2c.

[0100] A 1000ml three-necked flask equipped with a magnetic stir bar was evacuated and filled with nitrogen gas, repeated at least three times. Anhydrous toluene (400ml) and 2b (22.5g, approximately 0.0499mol) were added, and the mixture was stirred at room temperature for 30 minutes to disperse evenly. A toluene solution of 40.5g Lawson's reagent was added dropwise. The mixture was heated to reflux and reacted for 4.5 hours before the reaction was stopped. After the reaction solution cooled naturally to room temperature, it was cooled to 3°C using an ice-water bath. Slowly, saturated sodium bicarbonate solution was added to the reaction solution until no gas was emitted. 50ml of 5% sodium hydroxide solution was added, and the mixture was stirred for 10 minutes. The mixture was separated, and the organic phase was washed with water until neutral. The solution was concentrated until no solvent was distilled off. The crude product was passed through a column (PE / EA = 40:1 to 5:1) to obtain a pale yellow solid. The yield of the third product 2c was 58%.

[0101] Step 400: Synthesis of the fourth product – 2d The mixture was transferred to a 500 ml three-necked flask equipped with a magnetic stir bar, evacuated, and purged with nitrogen. This process was repeated at least three times. Then, 200 ml of dichloromethane, 26.7 g of NBS, 5.9 g of triphenylphosphine, and 22.3 g of 2c were added. The mixture was reacted at room temperature for 16 hours. After the reaction was complete, the reaction solution was washed with water until neutral. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 30:1 to 5:1) to obtain a pale yellow solid. The yield of the fourth product, 2d, was 66%.

[0102] Step 500: Synthesis of optical monomer G2 The mixture was transferred to a 500 ml three-necked flask equipped with a magnetic stir bar, evacuated, and purged with nitrogen. This process was repeated at least three times. Then, 200 ml of ethanol, 30.1 g of 2d, and 8.36 g of thiourea were added. The mixture was heated to reflux and held at this temperature for 12 hours. A sodium hydroxide aqueous solution (8 g sodium hydroxide, 30 ml water) was then added, and the mixture was refluxed for another 6 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. Extraction was performed twice with ethyl acetate (210 ml). The organic phases were combined, and the mixture was washed twice with water after adding dilute hydrochloric acid to pH 7. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 10:1 to 1:1) to obtain a pale yellow solid. The yield of optical monomer G2 was 84%.

[0103] Example 3 The structural formula of the optical unit in this embodiment is: , denoted as G3.

[0104] refer to Figure 3 The preparation method of optical monomer G3 includes the following steps: Step 100: Synthesis of the first product – 3a. The synthesis of 3a is the same as that of 1a, and will not be repeated here. The yield of the first product 3a is 80%.

[0105] Step 200: Synthesis of the second product – 3b.

[0106] The mixture was transferred to a 500ml three-necked flask equipped with a magnetic stir bar, evacuated, and purged with nitrogen. This process was repeated at least three times. Then, 250ml of ethanol, 8g of sodium hydroxide, and 14.2g of 1,4-benzenedithiol were added. After stirring for 10 minutes, 36.8g of product 3a was added dropwise. The mixture was stirred at room temperature for 16 hours. After the reaction was complete, 400ml of dichloromethane was added for extraction. The mixture was washed with water until neutral. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 5:1 to 1:1) to obtain a white solid. The yield of the second product 3b was 81%.

[0107] Step 300: Synthesis of the third product – 3c.

[0108] A 1000ml three-necked flask equipped with a magnetic stir bar was evacuated and filled with nitrogen gas, repeated at least three times. Anhydrous toluene: 400ml (approximately 3.764mol) and 3b: 21.9g (approximately 0.04999mol) were added, and the mixture was stirred at room temperature for 30 min to disperse evenly. A toluene solution of 40.5g (approximately 0.1001mol) of Lawson's reagent was added dropwise. The reaction was stopped after reflux for 4 h. The reaction solution was allowed to cool naturally to room temperature, then cooled to 5°C using an ice-water bath. Saturated sodium bicarbonate solution was slowly added to the reaction solution until no gas was emitted. 50ml of 5% sodium hydroxide solution was added, and the mixture was stirred for 10 min. The mixture was separated, the organic phase was washed with water until neutral, and concentrated until no solvent was distilled off. The crude product was passed through a column (PE / EA = 40:1 to 5:1) to obtain a pale yellow solid. The yield of the third product 3c was 62%.

[0109] Step 400: Synthesis of the fourth product – 3d The mixture was transferred to a 500 ml three-necked flask equipped with a magnetic inlet, evacuated, and purged with nitrogen. This process was repeated at least three times. Then, 200 ml of dichloromethane, 26.7 g of NBS, 5.9 g of triphenylphosphine, and 21.7 g of 2c were added. The mixture was reacted at room temperature for 16 hours. After the reaction was complete, the reaction solution was washed with water until neutral. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 30:1 to 5:1) to obtain a pale yellow solid. The yield of the fourth product, 3d, was 67%.

[0110] Step 500: Synthesis of optical monomer G3 in Example 3 The mixture was transferred to a 500 ml three-necked flask equipped with a magnetic stir bar, evacuated, and purged with nitrogen. This process was repeated at least three times. Then, 200 ml of ethanol, 29.5 g of 3d, and 8.36 g of thiourea were added. The mixture was heated to reflux and held at this temperature for 12 hours. A sodium hydroxide aqueous solution (8 g sodium hydroxide, 30 ml water) was then added, and the mixture was refluxed for another 6 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The mixture was extracted twice with 210 ml of ethyl acetate. The combined organic phases were washed twice with water after adding dilute hydrochloric acid to pH 7. The organic phase was concentrated until solvent-free distillation was achieved. The crude product was passed through a column (PE / EA = 10:1 to 1:1) to obtain a pale yellow solid. The yield of optical monomer G3 was 87%.

[0111] Example 4 The structural formula of the optical unit in this embodiment is as follows: , denoted as G4.

[0112] The preparation method of the optical monomer in this embodiment can refer to the preparation method of Example 3. The difference is that the first reactant in step S200 is biphenyl-4,4'-dithiol, and the R of the other second, third, and fourth products and the final optical monomer are successively changed to .

[0113] Example 5 The structural formula of the optical unit in this embodiment is as follows: , denoted as G5.

[0114] The preparation method of the optical monomer in this embodiment can refer to the preparation method of Example 3. The difference is that the first reactant in step S200 is 2,3-naphthalenedithiol, and the R of the other second, third, and fourth products and the final optical monomer are successively changed to .

[0115] Comparative Example 1 The preparation method is largely the same as in Example 1, except that the first reactant is 1,11-undecanedithiol, and the resulting optical monomer has 11 carbon atoms in its sulfur-containing group, represented by the chemical formula -SC. 11 H 22 The optical monomer obtained by S- is denoted as D1, and its structural formula is... .

[0116] Comparative Example 2 The preparation method is largely the same as in Example 1, except that the first reactant is 1,4-cyclohexanedithiol, and the resulting optical monomer has a sulfur-containing group containing 6 carbon atoms. The structural formula of the sulfur-containing group is shown below.

[0117] The optical monomer obtained is denoted as D2, and its structural formula is... .

[0118] Test case G1 to G5 from Examples 1 to 5 and D1 and D2 from Comparative Examples 1 to 2 were respectively prepared with dimethyl phthalate at a mass ratio of 70.5:29.5 to prepare resin raw materials. After curing for a certain period of time, 1 mm thick resin samples were obtained. Each resin sample was recorded as resin sample 1 to resin sample 7, and the time required for curing was recorded as shown in Table 1.

[0119] 1. The refractive index of resin samples 1 to 7 was tested. Resin samples 1 to 7 were dispersed in a solvent, such as tetrachloroethane, and then spin-coated onto silicon wafers. After baking, their refractive index at 589 nm was measured using an ellipsometer. The transmittance of resin samples 1 to 7 is shown in Table 1.

[0120] 2. Abbe number test. The Abbe number is calculated using the refractive index at wavelengths of 486 nm, 587.6 nm, and 656.3 nm. The calculation formula is as follows: Vd = (n D -1) / (n F -n C ) The Abbe numbers obtained from the tests of resin samples 1 to 7 are shown in Table 1.

[0121] 3. Glass transition temperature (Tg) test. A TA Instruments Japan 2910 differential scanning calorimeter was used for the test, with a heating rate of 10℃ / min. The glass transition temperatures (Tg) obtained for resin samples 1 to 7 are shown in Table 1.

[0122] Table 1 Performance Test Table for Resin Samples 1 to 7

[0123] As can be seen from the above, the resin samples 1-5 formed by the optical monomers in this application, under the same curing time, all have a refractive index greater than or equal to 1.70, an Abbe number greater than or equal to 30, and a glass transition temperature greater than 122°C. This demonstrates that the optical monomers in this application can improve the refractive index of the resin and maintain the Abbe number within a reasonable range, which is beneficial for ensuring image quality. Under the same curing time, the Tg of the optical monomers in this application is greater than 122, which gives the resin monomers better mechanical properties. When the resin monomers are made into thin lenses, they have a high refractive index and sufficient hardness and resistance to deformation.

[0124] Compared to resin sample 6 prepared in Comparative Example 1 and resin sample 7 prepared in Comparative Example 2, resin samples 1 to 5 prepared from optical monomers G1 to G5 in Examples 1 to 5 of this application have significantly higher refractive indices, indicating that the sulfur-containing groups of the optical monomers in this application are suitable to be controlled within five carbons. Compared to resin sample 7 prepared in Comparative Example 2, resin samples 3 to 5 prepared from optical monomers G3 to G5 in Examples 3 to 5 of this application have higher refractive indices and significantly improved Tg, indicating that the refractive indices and Tg of resin samples prepared using optical monomers with structures containing benzene rings, biphenyl rings, and naphthalene rings are significantly better than those of resin samples prepared using optical monomers with saturated cyclic cyclohexane. Therefore, the optical monomers in this application containing two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups have good application value in resin products, for example, they can be used to make thinner lenses while having sufficient resistance to deformation.

[0125] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention 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 the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An optical unit, characterized in that, Its general structural formula is shown below: Wherein, R is a sulfur-containing group, and the sulfur-containing group is selected from one of the following groups: at least two sulfur-substituted C2~C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups.

2. The optical unit as described in claim 1, characterized in that, The sulfur-containing group is selected from groups having the following structural formula: , , , , , , , , , , , , , or .

3. The optical unit as described in claim 2, characterized in that, The optical monomer is selected from monomers having the following structural formula: , , , or .

4. A method for preparing an optical monomer as described in any one of claims 1 to 3, characterized in that, Includes the following steps: 2-Mercaptoprop-1-ol was reacted with epichlorohydrin in a ring-opening reaction to produce a first product containing hydroxyl groups and chlorine. The first product, the first reactant, and the basic reagent are subjected to a nucleophilic substitution reaction in a first organic solvent to generate a second product. The first reactant is an aliphatic dithiol or an aliphatic dithiol containing sulfur heteroatoms, a benzene dithiol, a biphenyl dithiol, or a naphthyl dithiol. The second product is uniformly dispersed in a second organic solvent and subjected to a ring-closing reaction under the action of Lawson's reagent to generate a third product containing a sulfur heterocycle. The third product and a bromine source are reacted with a first catalyst in a third organic solvent to produce a bromine-containing fourth product. The fourth product is reacted with thiourea in a fourth organic solvent at a certain temperature for a first reaction time, and then an alkaline aqueous solution is added to continue the reaction for a second reaction time. After post-treatment, an optical monomer containing thiol is generated; the optical monomer is the optical monomer according to any one of claims 1 to 3. The structural formula of the first product is: ; The general structural formula of the second product is: ; The general structural formula of the third product is: ; The general structural formula of the fourth product is: ; Wherein, R in the second product, the third product, the fourth product and the optical monomer is a sulfur-containing group, and the sulfur-containing group is selected from one of the following groups: at least two sulfur-substituted C2~C5 alkyl groups, two sulfur-substituted phenyl groups, two sulfur-substituted biphenyl groups, and two sulfur-substituted naphthyl groups.

5. The method for preparing an optical monomer as described in claim 4, characterized in that, The molar ratio of the first product to the first reactant is 2:1; The first reactant is selected from one of ethylenedithiol, dimercaptoethyl sulfide, 1,2-propanedithiol, 2,3-propanedithiol, 2,3-pentanedithiol, ethylenedithiodithiol, propanedithiol, 1,4-benzenedithiol, 1,2-benzenedithiol, 1,3-benzenedithiol, biphenyl-4,4'-dithiol, 1,5-dimercaptonaphthalene, 1,6-naphthalenedithiol, 2,3-naphthalenedithiol, 2,7-naphthalenedithiol, and 2,6-naphthalenedithiophenol; The first organic solvent is selected from at least one of ethanol and methanol; The alkaline reagent is at least one of sodium hydroxide, potassium hydroxide, sodium methoxide, and sodium ethoxide.

6. The method for preparing an optical monomer as described in claim 4, characterized in that, The second organic solvent is selected from at least one of toluene and xylene; The closed-loop reaction includes heating to the second organic solvent, refluxing, and reacting for 3 to 6 hours. The molar ratio of the second product, the second organic solvent, and Lawson's reagent is 0.05:3.7~4.0:0.

1.

7. The method for preparing an optical monomer as described in claim 4, characterized in that, The bromine source is selected from at least one of N-bromosuccinimide and N-bromophthalimide; The first catalyst is selected from at least one of triphenylphosphine and tributylphosphine; The third organic solvent is selected from at least one of dichloromethane, 1,2-dichloroethane, 2-methyltetrahydrofuran, and toluene.

8. The method for preparing an optical monomer as described in claim 4, characterized in that, The fourth organic solvent is selected from methanol or ethanol; The alkaline aqueous solution is selected from at least one of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution; The temperature of the heat preservation reaction is approximately the boiling point of the fourth organic solvent, the first reaction time is 10h~14h, and the second reaction time is 5h~10h.

9. A resin, characterized in that, The raw materials for the resin include: optical monomers prepared by any one of claims 1 to 3 or by any one of claims 4 to 8.

10. The resin according to claim 9, characterized in that, It also includes a diisocyanate compound, wherein the mass ratio of the diisocyanate compound to the optical monomer is 26.9~29.5: 70.5~73.

1.

11. The resin according to claim 10, characterized in that, The diisocyanate compound is selected from one of phenyl diisocyanate, isophorone diisocyanate, and tetramethylphenyl diisocyanate.

12. An optical element, characterized in that, The raw materials for the optical element include optical monomers as described in any one of claims 1 to 3 or optical monomers prepared by the method described in any one of claims 4 to 8.

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