Matrix polymer and preparation method thereof, photopolymer composition, volume holographic grating and preparation method thereof

Abstract

The invention discloses a matrix polymer and a preparation method thereof, a photopolymer composition and a volume holographic grating and a preparation method thereof.The matrix polymer is simple in structure and rich in expandable structure, mercaptan and cyclopropane fragments serve as reaction functional groups of the matrix polymer, and due to the fact that products do not contain unsaturated fragments, the volume holographic grating is not prone to being damaged. The volume holographic grating has good optical / thermal stability, can be used for preparing the volume holographic grating, and is applied to various AR / VR display devices so as to improve the display effect. Moreover, the reaction system does not contain olefin, so that the influence between the matrix polymer and the subsequent photopolymer is further avoided, no photoresponse is ensured in the generation of the matrix polymer through the epoxypropane fragment, the compatibility of processing before exposure is facilitated, and the refractive index difference of the two polymers after exposure is ensured; and the preparation of a holographic polymer grating with a high refractive index modulation degree is facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of optical materials, and particularly relates to a matrix polymer, a preparation method thereof, a photopolymer composition, a volume holographic grating, and a preparation method thereof. Background Art

[0002] As a coupling optical element of a holographic optical waveguide, a volume holographic grating (VHG) can be used in display technologies such as virtual reality, augmented reality, mixed reality, and head-up display.

[0003] A photopolymer grating mainly consists of two parts: a matrix polymer and a photoinitiating polymer. The first part is the photoinitiating polymer, which undergoes a photopolymerization reaction under the irradiation of coherent light. The second part is the matrix polymer, which forms an interpenetrating network under the action of heat, provides the main supporting component of the holographic grating, and has a significant impact on the mechanical and optical stability of the volume holographic grating.

[0004] Currently, there are still many limitations in the matrix polymer based on organic holographic gratings, which have limited improvement on the performance of holographic gratings, thus affecting the commercial application of photopolymers. Summary of the Invention

[0005] In view of this, the present application provides a matrix polymer, a preparation method thereof, a photopolymer composition, a volume holographic grating, and a preparation method thereof.

[0006] The first aspect of the present application provides a matrix polymer, including at least one of a first polymer and a second polymer:

[0007] The structural formula of the first polymer is as follows:

[0008]

[0009] The structural formula of the second polymer is as follows:

[0010]

[0011] The second aspect of the present application provides a preparation method of a matrix polymer, including:

[0012] Adding a first monomer containing a thiol group and an epoxy group to a catalyst, and undergoing a self-polymerization reaction under the action of heat to generate a matrix polymer;

[0013] Wherein, the structural formula of the first monomer is as follows:

[0014]

[0015] The structural formula of the matrix polymer is as follows:

[0016]

[0017] A third aspect of the present application provides a method for preparing a matrix polymer, including:

[0018] Adding a second monomer containing a thiol group and a third monomer containing an epoxy group to a catalyst, and carrying out a polymerization reaction under the action of heat to generate a matrix polymer;

[0019] The structural formula of the second monomer is as follows:

[0020] The structural formula of the third monomer is as follows:

[0021] The structural formula of the matrix polymer is as follows:

[0022]

[0023] A fourth aspect of the present application provides a photopolymer composition, which includes: a photosensitizer, a basic catalyst, a photopolymerizable monomer, and a matrix polymer monomer. The matrix polymer monomer includes a first monomer, or the matrix polymer monomer includes a second monomer and a third monomer;

[0024] Wherein, the structural formula of the first monomer is as follows:

[0025]

[0026] The first monomer is used to carry out a self-polymerization reaction to generate a first polymer, and the structural formula of the first polymer is as follows:

[0027]

[0028] Wherein, the structural formula of the second monomer is as follows:

[0029] The structural formula of the third monomer is as follows:

[0030] The second monomer and the third monomer are used to carry out a polymerization reaction to generate a second polymer, and the structural formula of the second polymer is as follows:

[0031]

[0032] In some embodiments, the photopolymer composition includes the following components in weight percentages: the photosensitizer 0.4%-1.5%; the basic catalyst 1%-3%; the photopolymerizable monomer 45%-52%; the matrix polymer monomer 45%-52%.

[0033] In some embodiments, the photopolymer composition comprises components in the following weights: 0.1 g - 0.3 g of the photosensitizer; 0.4 g - 0.6 g of the basic catalyst; 9.5 g - 10.5 g of the photopolymerizable monomer; 9.5 g - 10.5 g of the matrix polymer monomer.

[0034] In some embodiments, the photopolymerizable monomer is an acrylate monomer.

[0035] The fifth aspect of the present application provides a volume holographic grating, which is obtained by curing the above-mentioned photopolymer composition.

[0036] The sixth aspect of the present application provides a method for preparing a volume holographic grating, comprising the following steps:

[0037] Provide the above-mentioned photopolymer composition;

[0038] Form a film on a substrate using the photopolymer composition;

[0039] Transfer the substrate with the formed film to an environment at 15°C - 100°C for reaction;

[0040] Expose the substrate after the reaction to obtain the volume holographic grating.

[0041] In some embodiments, the reaction time for transferring the substrate with the formed film to an environment at 15°C - 100°C for reaction is 0.1 hour - 12 hours.

[0042] As can be seen from the above technical solutions, the matrix polymer proposed in the present application has a simple structure and rich expandable structures. 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 light / thermal stability and can be used to prepare volume holographic gratings for various AR / VR display devices to improve the display effect. And since there is no olefin in the reaction system, the influence between the matrix polymer and the subsequent photopolymer is further avoided. The epoxy propane fragment ensures that no light response occurs during the formation of the matrix polymer, which is beneficial to the compatibility of the 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. Description of the Drawings

[0043] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained from these drawings without creative efforts.

[0044] Figure 1It is a schematic diagram of the reaction principle of the matrix polymer based on the cyclopropane / thiol system in this application.

[0045] Figure 2 It is a schematic diagram of the reaction principle in which the first monomer in this application undergoes a self-polymerization reaction to form a matrix polymer.

[0046] Figure 3 It is a schematic diagram of the reaction principle in which the second monomer and the third monomer in this application undergo a polymerization reaction to form a matrix polymer.

[0047] Figure 4 It is a schematic diagram of the mixture being coated on a substrate to form a thin film when preparing a volume holographic grating in this application.

[0048] Figure 5 It is a schematic diagram when the substrate with a thin film is exposed when preparing a volume holographic grating in this application.

[0049] Figure 6 It is a schematic flow diagram of the preparation method of the volume holographic grating proposed in this application. Detailed implementation manners

[0050] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the protection scope of this application.

[0051] It should also be understood that the terms used in the specification of this application are only 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.

[0052] 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 related listed items, and includes these combinations.

[0053] As a coupling optical element of a holographic optical waveguide, a volume holographic grating (VHG) can be used in display technologies such as virtual reality, augmented reality, mixed reality, and head-up display. The performance of a volume holographic grating can be measured by the refractive index modulation (△n) and the diffraction efficiency (DE). The larger these two values are, the better the light modulation performance of the holographic grating.

[0054] The photopolymer grating mainly consists of two parts: a matrix polymer and a photoinitiator polymer. The first part is the photoinitiator polymer, which undergoes a photopolymerization reaction under the irradiation of coherent light. The second part is the matrix polymer, which forms an interpenetrating network under the action of heat, providing the main supporting component of the holographic grating and having a significant impact on the mechanical and optical stability of the volume holographic grating.

[0055] Currently, there are still many limitations in the matrix polymer based on organic holographic gratings, such as slow reaction speed, incomplete reaction, and cumbersome synthesis steps. These drawbacks have limited the improvement of the performance of holographic gratings, thus affecting the commercial application of photopolymers.

[0056] In the prior art, related technicians proposed a scheme using polyols and isocyanates as reaction components and an alkali as a catalyst to produce polyurethane-based matrix polymers.

[0057] Among them, the structural formula of the polyol in this scheme is as follows:

[0058]

[0059] The structural formula of the isocyanate is as follows:

[0060]

[0061] However, this scheme uses polyols and isocyanates to produce matrix polymers. This reaction is usually slow and not conducive to large-scale production. Moreover, the polyurethane disclosed in this scheme contains unsaturated bonds and is prone to yellowing under long-term ultraviolet light irradiation, affecting the display effect. There are problems with the stability of polyurethane itself, and it can undergo hydrolysis when encountering moisture, which is not conducive to the stable operation of the grating.

[0062] In addition, related technicians also proposed a scheme using an olefin fragment substituted with an electron-withdrawing group as a reaction precursor and an alkyl mercaptan as the second component. A certain amount of alkali is added to the blended system to undergo a nucleophilic addition reaction.

[0063] Among them, the structural formula of the electron-withdrawing olefin in this scheme is as follows:

[0064]

[0065] The structural formula of the mercaptan is as follows:

[0066]

[0067] However, this scheme uses mercaptan olefins to generate polymer matrices, which overlaps with the second-order photopolymerization reaction substrates. There is an overreaction of olefins, which is not conducive to the preparation of volume holographic gratings with high refractive index modulation. And this reaction requires strict light avoidance to prevent the photopolymerization process from occurring during the matrix formation process, thus affecting the reaction and making the actual production operation difficult.

[0068] Therefore, the embodiment of the present application provides a matrix polymer having the advantages of fast reaction rate, high conversion rate, no reversible reaction of the generated polymer, good stability, etc. It can be used to prepare volume holographic gratings and applied to various AR / VR display devices to improve the display effect.

[0069] like Figure 1 As shown, the reaction principle of the matrix polymer based on the cyclopropane / thiol system of the present application is as follows:

[0070] Since the thiol fragment has a certain acidity, when a catalytic amount of base (such as organic amine) is added, the base captures the hydrogen atom to form a sulfur-containing anion with strong nucleophilicity. The propylene oxide fragment of the blend system can be attacked by the sulfur anion nucleophilically to generate a ring-opened oxygen anion product, followed by hydrogen atom transfer to generate the final thioether polymer.

[0071] In an optional embodiment, the matrix polymer provided in the embodiment of the present application includes at least one of a first polymer and a second polymer:

[0072] The structural formula of the first polymer is as follows:

[0073]

[0074] The structural formula of the second polymer is as follows:

[0075]

[0076] like Figure 2 As shown, the present application embodiment also provides a method for preparing a matrix polymer, comprising:

[0077] A first monomer containing a thiol group and an epoxy group is added to a catalyst and self-polymerized under heat to generate a matrix polymer;

[0078] Wherein, the structural formula of the first monomer is as follows:

[0079]

[0080] The structural formula of the matrix polymer is as follows:

[0081]

[0082] In an alternative embodiment, the first polymer is formed by adding a catalyst to a first monomer and subjecting it to a self-polymerization reaction under heat; wherein the first monomer is a compound containing a thiol group and an epoxy group. By using a propylene oxide segment to undergo a click reaction with the thiol, the monomer conversion rate is high, and the product has better long-term stability. At the same time, the propylene oxide segment ensures that no light response occurs during the formation of the matrix polymer, which is beneficial to the compatibility of pre-exposure processing, thereby ensuring the refractive index difference between the two polymers after exposure and contributing to the preparation of a holographic polymer grating with a high refractive index modulation.

[0083] As Figure 2 shown, the first type of monomer of the matrix polymer in the embodiment of the present application can be a first monomer having a thiol and an epoxy segment. By adding a certain amount of a basic catalyst, such as an organic amine, etc., and subjecting it to a self-polymerization reaction under heat, a matrix polymer segment is formed.

[0084] As Figure 3 shown, the embodiment of the present application also provides a method for preparing a matrix polymer, including:

[0085] Adding a second monomer containing a thiol group and a third monomer containing an epoxy group to a catalyst, and subjecting them to a polymerization reaction under heat to form a matrix polymer;

[0086] The structural formula of the second monomer is as follows:

[0087] The structural formula of the third monomer is as follows:

[0088] The structural formula of the matrix polymer is as follows:

[0089]

[0090] In an alternative embodiment, the second polymer is formed by adding a second monomer and a third monomer to a catalyst and subjecting them to a polymerization reaction under heat; wherein the second monomer is a compound containing a thiol group, and the third monomer is a compound containing an epoxy group. By using a propylene oxide segment to undergo a click reaction with the thiol, the monomer conversion rate is high, and the product has better long-term stability. At the same time, the propylene oxide segment ensures that no light response occurs during the formation of the matrix polymer, which is beneficial to the compatibility of pre-exposure processing, thereby ensuring the refractive index difference between the two polymers after exposure and contributing to the preparation of a holographic polymer grating with a high refractive index modulation.

[0091] As Figure 3 shown, the second type of monomer of the matrix polymer in the embodiment of the present application can be based on thiol / propylene oxide as two components of 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 subjecting it to a polymerization reaction under heat, a linear polymer is formed.

[0092] It should be noted that, in order to form an ordered polymer network, the monomers of this type of matrix polymer are not limited to linear ones, and matrix polymers with a spatial network structure can also be used as the matrix.

[0093] The matrix polymer proposed in the embodiment of the present application has a simple structure and a rich expandable structure. The thiol and cyclopropane fragments are the reactive functional groups of the matrix polymer. Since the product does not contain unsaturated fragments, it has good light / thermal stability and can be used to prepare volume holographic gratings and applied to various AR / VR display devices to improve the display effect. In addition, since the reaction system does not contain olefins, the influence between the matrix polymer and the subsequent photopolymer is further avoided. The propylene oxide fragment ensures that no light response occurs during the generation of the matrix polymer, which is beneficial to the compatibility of pre-exposure processing, thereby ensuring the difference in the refractive index of the two polymers after exposure, and is helpful for the preparation of holographic polymer gratings with high refractive index modulation.

[0094] The embodiment of the present application also provides a photopolymer composition, comprising: a photosensitizer, an alkaline catalyst, a photopolymerization monomer and a matrix polymer monomer. The matrix polymer monomer comprises a first monomer, or the matrix polymer monomer comprises a second monomer and a third monomer.

[0095] Wherein, the structural formula of the first monomer is as follows:

[0096]

[0097] The first monomer is used to undergo a self-polymerization reaction to generate a first polymer, and the structural formula of the first polymer is as follows:

[0098]

[0099] Wherein, the structural formula of the second monomer is as follows:

[0100] The structural formula of the third monomer is as follows:

[0101] The second monomer and the third monomer are used to undergo a polymerization reaction to generate a second polymer, and the structural formula of the second polymer is as follows:

[0102]

[0103] In some embodiments, the photopolymer composition includes the following components in weight percentage: 0.4%-1.5% photosensitizer; 1%-3% alkaline catalyst; 45%-52% photopolymerizable monomer; 45%-55% matrix polymer monomer, wherein the matrix polymer monomer is used for polymerization reaction to generate the above-mentioned matrix polymer.

[0104] In an alternative embodiment, the photopolymer composition may comprise the following components by weight percentage: photosensitizer 1%; basic catalyst 1%; photopolymerizable monomer 48%; matrix polymer monomer 50%.

[0105] In an alternative embodiment, the photopolymer composition may comprise the following components by weight percentage: photosensitizer 0.4%; basic catalyst 2.6%; photopolymerizable monomer 45%; matrix polymer monomer 52%.

[0106] In an alternative embodiment, the photopolymer composition may comprise the following components by weight percentage: photosensitizer 1.5%; basic catalyst 1.5%; photopolymerizable monomer 52%; matrix polymer monomer 45%.

[0107] In an alternative embodiment, the photopolymer composition may comprise the following components by weight percentage: photosensitizer 1%; basic catalyst 3%; photopolymerizable monomer 45%; matrix polymer monomer 51%.

[0108] In an alternative embodiment, the photopolymer composition may comprise the following components by weight percentage: photosensitizer 1%; basic catalyst 3%; photopolymerizable monomer 51%; matrix polymer monomer 45%.

[0109] In an alternative embodiment, the basic catalyst includes an organic base and an inorganic base, such as triethylamine, sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium carbonate, potassium carbonate, etc.

[0110] In an alternative embodiment, the photosensitizer may be a commonly used photosensitizer such as red light, methylene blue, malachite green, or azure I.

[0111] In an alternative embodiment, the photopolymer composition comprises the following components by weight: photosensitizer 0.1 g - 0.3 g; basic catalyst 0.4 g - 0.6 g; photopolymerizable monomer 9.5 g - 10.5 g; matrix polymer monomer 9.5 g - 10.5 g.

[0112] In an alternative embodiment, the photopolymer composition comprises the following components by weight: photosensitizer 0.1 g - 0.3 g, basic catalyst 0.4 g - 0.6 g, photopolymerizable monomer 9.5 g - 10.5 g, and matrix polymer monomer 9.5 g - 10.5 g.

[0113] In an alternative embodiment, the photopolymer composition comprises: photosensitizer 0.1 g, basic catalyst 0.5 g, photopolymerizable monomer 10 g, and matrix polymer monomer 10 g.

[0114] In an alternative embodiment, the photopolymer composition comprises: photosensitizer 0.2 g, basic catalyst 0.4 g, photopolymerizable monomer 9.5 g, and matrix polymer monomer 9.5 g.

[0115] In an alternative embodiment, the photopolymer composition comprises: 0.3 g of a photosensitizer, 0.6 g of a basic catalyst, 10.5 g of a photopolymerizable monomer, and 10.5 g of a matrix polymer monomer.

[0116] In an alternative embodiment, the photopolymerizable monomer is an acrylate monomer, such as a methacrylate or other acrylate monomer.

[0117] In an alternative embodiment, the photopolymerizable monomer may have the following general formula:

[0118]

[0119] Wherein, X may be H or a carbon chain, such as an alkane, alkene, alkyne or arene with 1-15 carbon atoms; Y may be H or a halogen; A may be H or an acetoxy group, and may also be an aryl group.

[0120] The acrylate monomer proposed in this embodiment has a simple structure and a rich expandable structure, 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, enabling the preparation of a holographic grating with a high refractive index modulation. Thus, the holographic grating prepared using this acrylate monomer has good mechanical stability, high light transmittance, and low shrinkage.

[0121] In an alternative embodiment, the structural formula of the acrylate monomer is as follows:

[0122] Or,

[0123] Or,

[0124] Or,

[0125]

[0126] In an alternative embodiment, the photopolymerizable monomer may also be an aryl urethane acrylate-based writing monomer. The structural formula of the aryl urethane acrylate-based writing monomer is as follows:

[0127] Or,

[0128]

[0129] In an alternative embodiment, the photopolymerizable monomer may also be a polyaryl methacrylate-based writing monomer (carbazole monomer).

[0130] The structural formula of the polyaryl methacrylate-based writing monomer is as follows:

[0131] Or,

[0132]

[0133] Of course, in other embodiments, the photopolymerizable monomer may also be a photoresponsive liquid crystal monomer or a photoresponsive nanoparticle.

[0134] The embodiments of the present application also provide a volume holographic grating, which is obtained by curing the above-mentioned photopolymer composition. The volume holographic grating of the embodiments of the present application can be applied to various AR / VR display devices. Among them, the photopolymer composition includes the above-mentioned matrix polymer monomer. The matrix polymer monomer ensures that no photoresponse occurs during the formation of the matrix polymer through the propylene oxide segment, which is beneficial to the compatibility of pre-exposure processing, thereby ensuring the refractive index difference between the two polymers after exposure, contributing to the preparation of a holographic polymer grating with a high refractive index modulation, and being applied to various AR / VR display devices to improve the display effect.

[0135] As Figures 4 - 6 shown, the embodiments of the present application also provide a preparation method S10 of a volume holographic grating, including the following steps:

[0136] S11, providing the above-mentioned photopolymer composition, and the photopolymer composition of the above embodiment can be placed in a reaction vessel and stirred evenly to form a mixture.

[0137] S12, forming a film on the substrate with the photopolymer composition. 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 endows the thin film with strong mechanical properties and transmittance. At the same time, the network of the thioether polymer is filled with other photoresponsive components.

[0138] S13, transferring the substrate with the formed film to an environment at 15°C - 100°C for reaction. In a specific application, the substrate with the thin film can be transferred to a constant temperature environment at 15°C - 100°C, such as an incubator;

[0139] S14, exposing the reacted substrate 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 photoresponsive components in the bright area undergo a photocatalytic polymerization reaction at this time. They can be acrylate monomers, photoresponsive liquid crystal monomers, photoresponsive nanoparticles, etc. 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, and the larger the angular bandwidth of the VHG, so the better the performance.

[0140] In an alternative embodiment, the substrate can be a glass or plastic substrate. The formation of the matrix polymer endows the film with strong mechanical properties and transmittance. At the same time, the network of the thioether polymer is filled with other light-responsive components.

[0141] In an alternative embodiment, the substrate with the 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.

[0142] In an alternative embodiment, the reaction time for transferring the film-formed substrate to an environment of 15°C - 100°C for reaction is 0.1 hour - 12 hours.

[0143] In an alternative embodiment, the substrate with the film can react in the incubator for 0.1 hour, 5 hours, 12 hours or any time within the range of 0.1 hour - 12 hours, which can be adjusted according to the actual situation.

[0144] The matrix polymer of the present invention will be further described below in conjunction with specific embodiments and test data. In the following examples and comparative examples, except for the matrix polymer, the other variables selected are exactly the same, such as photosensitizer, photopolymerizable monomer, holographic exposure process, etc.

[0145] Example 1: Preparation of a volume holographic grating based on a first polymer

[0146] The first monomer was purified by standard column chromatography. The mass of the monomer used was 10 g. 10 g of the photopolymerizable monomer methacrylate, 0.1 g of the red-light photosensitizer, and 0.5 g of triethylamine were placed in a round-bottom flask and stirred with a magnetic stirrer for 10 minutes to ensure uniform mixing. Subsequently, it was coated on a glass substrate to form a film (spin coating or blade coating 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 exposure with red light for 30 s, a holographic grating could be prepared. The refractive index modulation of the prepared holographic grating was characterized by an optical bench and was 0.02.

[0147] Example 2: Preparation of a volume holographic grating based on a second polymer

[0148] The second monomer and the third monomer were purified by standard column chromatography. The mass of the monomers used was 10 g (the molar ratio of thiol to epoxy in the second monomer and the third monomer was 1:1). 10 g of the photopolymerizable monomer methacrylate, 0.1 g of the red-light photosensitizer, and 0.5 g of triethylamine 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 spatula to form a film (spin coating / doctor blading was both 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, a holographic grating could be prepared. The refractive index modulation of the prepared holographic grating was characterized by an optical bench and was 0.04.

[0149] Comparative Example 1: Preparation of a volume holographic grating based on an existing polyurethane-based matrix polymer

[0150] Take polyol and isocyanate as reaction components. Among them, the structural formula of the polyol is as follows:

[0151]

[0152] The structural formula of the isocyanate is as follows:

[0153]

[0154] The mass of the monomers was 10 g (the molar ratio of alcohol to isocyanate was 1:1). 10 g of the photopolymerizable monomer methacrylate, 0.1 g of the red-light photosensitizer, and 0.5 g of triethylamine 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 spatula to form a film (spin coating / doctor blading was both 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, a holographic grating could be prepared. The refractive index modulation of the prepared holographic grating was characterized by an optical bench and was 0.01.

[0155] From the data analysis of Example 1-2 and Comparative Example 1, it can be seen that:

[0156] To compare the effect of the thiol-epoxy matrix polymer of the present invention, it was compared with the polyurethane-based matrix polymer under the same conditions. The refractive index modulation could reach 0.02-0.04, and the refractive index modulation of the control system was 0.01, which proved the effectiveness of the matrix polymer in the examples of this application. After the refractive index modulation increased, the angular bandwidth of the prepared holographic grating could increase, which was beneficial to improving the AR / VR display effect.

[0157] Subject to no contradiction, those skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0158] As described above, the foregoing are only specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily conceive of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application shall be subject to the scope of protection of the claims.

Claims

1. A matrix polymer, characterized in that, Comprising at least one of a first polymer and a second polymer: The structural formula of the first polymer is as follows: The structural formula of the second polymer is as follows:

2. A method for preparing a matrix polymer, characterized in that, Comprising: Adding a first monomer containing a thiol group and an epoxy group to a catalyst, and subjecting it to a self-polymerization reaction under the action of heat to form a matrix polymer; Wherein, the structural formula of the first monomer is as follows: The structural formula of the matrix polymer is as follows:

3. A method for preparing a matrix polymer, characterized in that, Comprising: Adding a second monomer containing a thiol group and a third monomer containing an epoxy group to a catalyst, and subjecting them to a polymerization reaction under the action of heat to form a matrix polymer; The structural formula of the second monomer is as follows: The structural formula of the third monomer is as follows: The structural formula of the matrix polymer is as follows:

4. A photopolymer composition, characterized in that, The photopolymer composition comprises: A photosensitizer; A basic catalyst; A photopolymerizable monomer; A matrix polymer monomer; The matrix polymer monomer comprises the first monomer, or the matrix polymer monomer comprises the second monomer and the third monomer; Wherein, the structural formula of the first monomer is as follows: The first monomer is used to undergo a self-polymerization reaction to form a first polymer, and the structural formula of the first polymer is as follows: Among them, the structural formula of the second monomer is as follows: The structural formula of the third monomer is as follows: The second monomer and the third monomer are used to undergo a polymerization reaction to form a second polymer, and the structural formula of the second polymer is as follows:

5. The photopolymer composition according to claim 4, characterized in that, The photopolymer composition comprises the following components by weight percentage: The photosensitizer 0.4% - 1.5%; The basic catalyst 1% - 3%; The photopolymerizable monomer 45% - 52%; The matrix polymer monomer 45% - 52%.

6. The photopolymerizable composition according to claim 5, characterized in that, The photopolymer composition comprises the following components by weight: The photosensitizer 0.1 g - 0.3 g; The basic catalyst 0.4 g - 0.6 g; The photopolymerizable monomer 9.5 g - 10.5 g; The matrix polymer monomer 9.5 g - 10.5 g.

7. The photopolymerizable composition according to any one of claims 4 to 6, characterized in that, The photopolymerizable monomer is an acrylate monomer.

8. A volume holographic grating, characterized in that, The volume holographic grating is obtained by curing the photopolymer composition according to any one of claims 4 - 6.

9. A method for preparing a volume holographic grating, characterized in that, Comprising the following steps: Providing the photopolymer composition according to any one of claims 4 - 7; Forming a film on a substrate using the photopolymer composition; Transferring the substrate with the formed film to an environment at 15°C - 100°C for reaction; Exposing the substrate after the reaction to obtain the volume holographic grating.

10. The preparation method according to claim 9, characterized in that, The reaction time for transferring the substrate with the formed film to an environment at 15°C - 100°C for reaction is 0.1 hour - 12 hours.

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