A photopolymer composition for holographic recording and a grating

Abstract

This application discloses a photopolymer composition and a grating for holographic recording, belonging to the field of optical materials technology. The photopolymer composition for holographic recording includes the following components: a polymerizable active monomer, a film-forming component, a dye compound, an initiator, a plasticizer, and surface additives; the polymerizable active monomer includes cycloallylic sulfide monomers and thiol monomers. Holographic diffraction gratings prepared based on the photopolymer composition of this application, especially reflective holographic diffraction gratings, not only possess high diffraction efficiency, refractive index modulation, exposure sensitivity, and transmittance, but also exhibit improved dimensional shrinkage. Furthermore, the photopolymer material has a wide angular selectivity and is less affected by environmental humidity and oxygen inhibition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical materials, and more particularly to a photopolymer composition for holographic recording and a grating. BACKGROUND

[0002] Photosensitive / photopolymer materials use the refractive index change of the material produced by the irreversible photopolymerization reaction for holographic recording. In a typical processing method, when a photopolymer composition is irradiated by a visible light laser to form a component, the monomers in the photopolymer composition for holographic recording are formed (cured) into polymers by a polymerization reaction. As a result, structural features capable of forming interference patterns can be produced in the component formed by the photopolymer composition. At the same time, by modulating the refractive index, a phase hologram with high diffraction efficiency can be formed. Photosensitive / photopolymer materials have the characteristics of high sensitivity, high resolution, high signal-to-noise ratio, low cost, simple processing technology, etc., and are one of the most promising recording materials in the field of volume holographic devices.

[0003] The photosensitive / photopolymer system as a holographic recording material generally contains dyes, photoinitiators, one or more monomers, film formers, plasticizers, etc. The refractive index modulation of the photopolymer comes from two main factors: (1) the increase in density; (2) the separation of the mass contrast substance (polymerized monomers and film-forming matrix). The increase in density is determined by mass transport and polymerization reaction. For a typical photopolymer, only a certain proportion of monomers in the formulation diffuses and polymerizes in the desired spatial distribution, thereby contributing to the refractive index modulation (Δn). This limitation in Δn can be alleviated by increasing the concentration of active monomers, but the saturation solubility of active monomers in the matrix solvent often limits the amount of active monomers that can be dissolved. Especially in the case of a matrix solvent that dissolves multiple components, the amount of active monomers dissolved is even lower, resulting in a generally low concentration of active monomers, which in turn leads to a low refractive index of the photopolymer and a low refractive index modulation. Moreover, most of the current photosensitive / photopolymer holographic recording materials have the problems of not high enough diffraction efficiency and not large enough angle selectivity. In addition, under normal circumstances, these recording materials need to be heat treated after recording the hologram. The expansion and contraction of the photopolymer film during the treatment process can cause deformation of the hologram fringes, and even damage the hologram. SUMMARY

[0004] 1. Technical problems to be solved

[0005] In view of the problems in the prior art, the present application aims to provide a photopolymer composition for holographic recording, a holographic diffraction grating prepared by the photopolymer composition, and in particular a reflective holographic diffraction grating, which not only has high diffraction efficiency, refractive index modulation, exposure sensitivity and light transmittance, but also has improved dimensional shrinkage. At the same time, the photopolymer material has a wide angle selectivity and is less affected by environmental humidity and oxygen inhibition.

[0006] 2. Technical solution

[0007] To solve the above problems, the present application adopts the following technical solution.

[0008] A photopolymer composition for holographic recording comprises the following components:

[0009] polymerization-active monomers, film-forming components, dye compounds, initiators, plasticizers, and surface aids;

[0010] The polymerization-active monomers comprise a cycloallyl sulfide monomer and a thiol monomer.

[0011] Further, the cycloallyl sulfide monomer has the following general formula (I) or general formula (II):

[0012]

[0013] (I)

[0014]

[0015] (II)

[0016] wherein R1 represents a hydrogen atom, an alkane group, an aromatic hydrocarbon group, an ether bond-containing group, a thioether-containing group, or a cycloalkane-containing group; R2 and R3 each independently represent a hydrogen atom, an alkyl acyl group, a double-bond-containing alkyl acyl group, an aryl acyl group, an ether bond-containing alkyl or aryl acyl group, a cycloalkane-containing alkyl or aryl acyl group, or a benzene ring-containing acyl group.

[0017] Further, the cycloallyl sulfide monomer has a refractive index of 1.53 or higher.

[0018] Further, the thiol monomer is a multifunctional thiol monomer having at least three functional groups.

[0019] Further, the molar ratio of the multifunctional thiol monomer to the cycloallyl sulfide monomer is 0.25-1:1.

[0020] Further, the multifunctional thiol monomer has the following general formula (III) or general formula (IV):

[0021]

[0022] (III)

[0023]

[0024] (IV)

[0025] wherein R4, R5 each independently represents an alkylene group, an arylene group, a phenylene alkylene group or a cycloalkane-containing alkylene group.

[0026] Further, the R4, R5 group contains a long chain alkyl group or 1-2 phenyl ring structures.

[0027] Further, the content of the film-forming component is 10-40% based on the total weight of the composition.

[0028] The content of the cycloallyl sulfide monomer is 15-40%.

[0029] The content of the thiol monomer is 2-15%.

[0030] The content of the film-forming component is 10-40%.

[0031] The content of the dye compound is 0.1-2%.

[0032] The content of the initiator is 0.5-5%.

[0033] The content of the plasticizer is 10-40%.

[0034] The content of the surface aid is 5-15%.

[0035] A holographic diffraction grating comprising a polymer film having a grating structure, which is obtained by curing the above composition.

[0036] A holographic optical waveguide display element comprising the above holographic diffraction grating.

[0037] 3. Beneficial effects

[0038] Compared with the prior art, the present application has the following advantages:

[0039] (I) The holographic grating prepared from the photopolymer composition of the present application, especially the reflective holographic diffraction grating, not only has high diffraction efficiency, refractive index modulation, exposure sensitivity and light transmittance, but also has improved dimensional shrinkage. At the same time, the photopolymer material has a wide angle selectivity and is less affected by environmental humidity and oxygen inhibition.

[0040] (II) The photopolymer composition and grating manufacturing process of the present application are simple, the raw materials are cheap and easy to obtain, and it is easy to mass-produce industrially.

[0041] (III) The grating prepared by the present application has excellent light waveguide imaging effect. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Recording-reading optical path diagram for the photopolymer composition of the present application;

[0043] Figure 2 Diffractive efficiency and Bragg angle diagram for the reflective holographic diffraction grating of Example 2 of the present application. DETAILED DESCRIPTION

[0044] A photopolymer composition for holographic recording, comprising the following components:

[0045] Polymerization-active monomers, film-forming components, dye compounds, initiators, plasticizers, and surface aids; the polymerization-active monomers include cycloallyl sulfide monomers and thiol monomers.

[0046] In the above composition, the cycloallyl sulfide monomers and the thiol monomers are polymerized, the thiol-alkene reaction adopts a step-growth radical mechanism for polymerization, and the gel time delay of the crosslinked network enables the conversion of functional groups to reach a higher level, while introducing a stable S-C structure in the monomer main chain, effectively increasing the refractive index of the monomers, further increasing the refractive index difference between the monomers and the film-forming components, thereby obtaining a photopolymer material with a high refractive index modulation degree and a wider angle selectivity. At the same time, the radical ring-opening polymerization reaction of cycloallyl sulfide and polythiol conforms to the characteristics of click chemistry reaction, has no by-products, and the polymerized monomers do not undergo a large polymerization-induced shrinkage, and the crosslinking polymerization reaction has a lower shrinkage rate, so that the photopolymer film has higher dimensional stability and storage stability. The combination of these components and the percentage ranges of the components described below are determined through a large number of experiments, and the components and percentage ranges enable the photopolymer composition material of the present application to have the above-mentioned stability, low shrinkage, wider angle selectivity, and higher diffraction efficiency and refractive index modulation.

[0047] Cycloallyl sulfide monomer

[0048] In some specific embodiments, the cycloallyl sulfide monomers suitable for the present application have a seven-membered ring or an eight-membered ring structure of the following general formula (I) or general formula (II):

[0049]

[0050] (I)

[0051]

[0052] (II)

[0053] wherein R1represents a hydrogen atom, an alkane group, an aromatic hydrocarbon group, an ether bond-containing group, a thioether bond-containing group, or a cycloalkane group; R2and R3each independently represent a hydrogen atom, an alkyl acyl group, a double bond-containing alkyl acyl group, an aryl acyl group, an ether bond-containing alkyl or aryl acyl group, a cycloalkane group-containing alkyl or aryl acyl group, or a benzene ring-containing acyl group. In some specific embodiments, the R2, R3groups can be acyl groups containing 1 or 2 benzene ring structures. Further, from the perspective of inhibiting the dimensional shrinkage after film formation and balancing the processability, in preferred embodiments, each R2and R3group, when present, is an alkyl acyl group containing 1 benzene ring structure.

[0054] In addition, the structure of the cycloalkenyl sulfide monomer in the present application is not particularly limited, and the acyl group is preferably in the form of an aliphatic acyl group or an acyl group containing a benzene ring structure. In addition, in some other specific embodiments, the hydrocarbon acyl structure in the R2, R3groups can be connected with an ether group on the hydrocarbon chain. Suitable ether groups can be thioether groups or oxygen ether groups. The sulfur or oxygen atoms in the thioether groups or oxygen ether groups can increase the refractive index of the monomer, and the thioether groups or oxygen ether groups can increase the polarity of the monomer, thereby increasing the solubility of the cycloalkenyl sulfide monomer in polar solvents and improving the diffraction efficiency of the holographic diffraction grating.

[0055] Preferably, the cycloalkenyl sulfide monomers having a seven-membered ring or an eight-membered ring structure suitable for use in the present application can have the following general formula (I-1), (I-2) and (II-1), (II-2) structures:

[0056]

[0057] (I-1)

[0058]

[0059] (I-2)

[0060]

[0061] (II-1)

[0062]

[0063] (II-2)

[0064] wherein R6, R7, R8, R9 represent a hydrogen atom, an alkane group, an alkyl group containing an epoxy group, an aromatic hydrocarbon group, an ether bond-containing group, a thioether bond-containing alkyl group, or a cycloalkane group. R8and R9do not appear at the same time, when R8is the above group, R9is a hydrogen atom, and when R9is the above group, R8is a hydrogen atom.

[0065] In some possible embodiments, the cycloallyl sulfide monomer having a seven-membered ring or an eight-membered ring structure suitable for the present application can be selected from the group consisting of alkyl-containing cycloallyl sulfides such as 6-methylene-l,4-dithiacycloheptane-2-methanol acetate, 7-methylene-l,5-dithiacyclooctane-3-acetate, 7-methylene-l,5-dithiacyclooctane-3-propionate, and the like; benzene ring-containing cycloallyl sulfides such as 6-methylene-l,4-dithiacycloheptane-2-methanol benzoate, 7-methylene-l,5-dithiacyclooctane-3-benzoate, and the like.

[0066] It should be noted that the cycloallyl sulfide monomer of the present application can be one monomer or a mixture of two or more monomers. In addition, from the viewpoint of increasing the refractive index modulation, the cycloallyl sulfide monomer suitable for the present application has a refractive index of 1.53 or more, preferably a refractive index of 1.58 or more.

[0067] Thiol monomer

[0068] From the viewpoint of improving the shrinkage and dimensional stability of the photopolymer, the thiol monomer suitable for the present application is preferably a multifunctional thiol monomer having at least three functional groups.

[0069] In some specific embodiments, the multifunctional thiol monomer suitable for the present application can have a structure represented by the following general formula (III) or general formula (IV):

[0070]

[0071] (III)

[0072]

[0073] (IV)

[0074] wherein R4and R5each independently represent an alkylene group, an arylene group, a phenylene group, or a cycloalkane-containing alkylene group. In some possible embodiments, the R4and R5groups can contain a long-chain alkyl group or 1-2 benzene ring structures. Further, from the viewpoint of suppressing the dimensional shrinkage after film formation, the R4and R5groups are preferably an alkyl group containing 1-3 carbon atoms or a benzene ring structure.

[0075] It should be noted that the multifunctional thiol monomer of the present application can be one monomer or a mixture of two or more monomers. In addition, the multifunctional thiol monomer has a refractive index of 1.52 or more.

[0076] In further embodiments, the multifunctional thiol monomer suitable for the present application has a structure represented by the following general formula (III-1) or (IV-1):

[0077]

[0078] (III-1)

[0079]

[0080] (IV-1)

[0081] Specifically, for the above-mentioned cycloallyl sulfide monomer and polyfunctional thiol monomer applicable to the present application, a photopolymer can be prepared by free radical ring-opening polymerization, and in typical embodiments, ring-opening polymerization reaction of 7-methylene-1,5-dithiacyclooctane-3-acetate with pentaerythritol tetra(3-mercaptopropionate) can be used:

[0082]

[0083] The specific reaction mechanism is shown below:

[0084]

[0085] wherein R represents a ring-opening monomer, the C=C bond of the cycloallyl sulfide monomer is broken after the addition of a free radical, forming a new C=C bond and a mercapto radical, which can migrate and further react with the cycloallyl sulfide to form a polymer.

[0086] Film forming component

[0087] The film-forming component used in the present application can be selected from a polymer or resin material having a certain adhesion with a molecular weight of 1000 or more. Preferably, these materials have a low refractive index, and in some specific embodiments, the refractive index of these materials is 1.480 or less, preferably 1.475 or less, and further preferably 1.470 or less.

[0088] From the perspective of inhibiting the dimensional shrinkage of the final grating product, improving the diffraction efficiency, and the refractive index modulation, the preferred film-forming component of the present application is selected from at least one of cellulose acetate butyrate, polyvinylpyrrolidone, and polyvinyl acetate.

[0089] In addition, for the present application, the higher the refractive index of the above-mentioned polymerization-active monomer and the greater the difference in refractive index with the film-forming component, the more advantageous it is to improve the diffraction efficiency and the refractive index modulation of the final holographic recording material. Therefore, in the present application, the difference in refractive index between the cycloallyl sulfide monomer and the film-forming component is 0.078 or more, and further preferably 0.080 or more, and the difference in refractive index between the thiol monomer and the film-forming component is 0.040 or more, and further preferably 0.045 or more.

[0090] Initiation system

[0091] In the present application, for the system for initiating polymerization of the system under irradiation, a dye compound and an initiator are included. After the dye compound is excited by irradiation, the initiator can react with the excited state of the dye to generate a radical and cause the polymerization / crosslinking reaction of the polymerization active monomer in the system.

[0092] In the present application, the dye compound is a photosensitive dye compound. Specifically, it can be selected from those having excitation activity at least in the vicinity of 532 nm light wavelength. In some specific embodiments of the present application, the dye compound can have excitation activity in the vicinity of optional other light wavelengths in addition to the excitation activity in the vicinity of 532 nm light wavelength, in which case, preferably, the dye compound has a maximum absorption peak in the vicinity of 532 nm light wavelength.

[0093] The dye compound can be selected from one or more of erythrosin B, eosin Y, erythrosin B, basic red 2, and 2,5-bis{[4-(diethylamino)-2-methylphenyl]methylene}cyclopentanone.

[0094] The initiator suitable for the present application can be selected from one or more of diphenyliodonium hexafluorophosphate, ethyl 4-dimethylaminobenzoate, N-phenylglycine, 2-(4-chlorophenyl)-4,5-diphenylimidazole.

[0095] Plasticizer

[0096] In the present application, a plasticizer is used to increase the flexibility of the photopolymer composition and to alleviate the degree of dimensional shrinkage after film formation and curing.

[0097] In some specific embodiments, the plasticizer suitable for the present application is a polymer material having good compatibility / dissolution properties, low volatility, and high boiling point. Typically, these polymer materials can be polyhydric alcohols or glycidyl ethers of polyhydric alcohols. In the preferred embodiments of the present application, from the viewpoint of suppressing dimensional shrinkage, the polyhydric alcohol can be polyethylene glycol, polypropylene glycol, or the like; the glycidyl ether of polyhydric alcohol can be polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether. In addition, the above plasticizer can be further stabilized by adding, for example, an acid anhydride, a polyisocyanate, or the like.

[0098] Some plasticizers that can be additionally used can include small molecule plasticizers such as butylene glycol phthalate, N-vinylpyrrolidone, or the like.

[0099] For the plasticizer of the present application, one or a combination of two or more can be used.

[0100] Surface aid

[0101] The surface assistant suitable for the present application can be selected from acrylic and silicone leveling agents, which can significantly improve the surface tension of the composition, so as to have good leveling and increase the wetting of the substrate.

[0102] Other ingredients

[0103] In the present application, other ingredients commonly used in the art can be used according to the actual production needs as long as they do not affect the technical effects of the present application.

[0104] Composition composition

[0105] For the composition of the photopolymer composition provided in the present application, in some preferred embodiments, the content can be, based on the total weight of the composition:

[0106] The content of the cycloallyl sulfide monomer can be 15-40%, preferably 18-30%. When the content is lower than 15%, the shrinkage of the grating is high, and the grating is prone to deformation. When the content is higher than 40%, the diffraction efficiency of the grating is low, the refractive index modulation is low, and the imaging quality is poor.

[0107] The content of the multifunctional thiol monomer is 2-15%.

[0108] The content of the dye compound can be 0.1-2%, preferably 0.4-1%. When the content is lower than 0.1%, the photosensitivity is insufficient, resulting in low efficiency. When the content is higher than 2%, it can cause the film processing property of the photopolymer composition to decrease, affecting the diffraction efficiency of the grating obtained finally.

[0109] The content of the film-forming component can be 10-40%, preferably 15-30%. When the content is lower than 10%, it is not conducive to film formation. When the content is higher than 40%, it can cause the refractive index modulation to decrease.

[0110] The content of the initiator can be 0.5-5%, preferably 1.5-2.5%.

[0111] The content of the plasticizer can be 10-40%, preferably 15-35%.

[0112] The content of the surface assistant is 5-15%.

[0113] In addition, the content of other components other than the above components is not particularly limited, and can be used according to the usual amount range in the art, provided that it does not affect the technical effects of the present application.

[0114] In some embodiments, the present application also provides a holographic diffraction grating based on the above-described photopolymer composition, comprising a polymer film having a grating structure, the polymer film being obtained by curing the components of the composition.

[0115] Specifically, the grating comprises a carrier layer and a polymer film layer, and the carrier substrate used can preferably be a layer of a material or a composite of materials that is transparent in the visible spectrum.

[0116] The thickness of the carrier substrate used in the present application can be 1.5 mm or less, preferably, it can be 20 μm to 1 mm, and further preferably, it can be 100 μm to 900 μm.

[0117] In some embodiments of the present application, the grating can be a laminate of a film formed from the photopolymer composition and a carrier, i.e., the film is formed on the carrier, or the film is sandwiched between two carriers. Thus, the film formed from the photopolymer in the present application has a grating structure by exposure, bleaching, etc., and it can exist on the carrier or be sandwiched between two carriers as a holographic recording medium. In other cases, the grating can additionally comprise a cover layer and / or other functional layer, each of which is at least partially connected to the film, optionally.

[0118] In the present application, the method for preparing the grating from the photopolymer composition and the carrier, etc. can comprise the following steps:

[0119] (i) a mixing step of mixing the components of the photopolymer composition to obtain a mixture;

[0120] (ii) a step of forming a grating structure, in which the mixture is formed into a film and a grating structure is formed on at least a part of the film.

[0121] In the step of forming the grating, the step of exposing the film to coherent light having a wavelength of about 532 nm is included.

[0122] Specifically, the mixing step is to mix the components of the composition in the appropriate container in the appropriate proportions, and if necessary, mechanical stirring or the like can be used to mix uniformly. There is no particular limitation on the temperature for mixing, and in general, mixing can be performed at room temperature or under heating.

[0123] In some embodiments of the present application, especially, a uniform mixture is formed by using a suitable heating method without using a solvent. The heating temperature can be determined according to the activity of each component in the photopolymer composition and the desired viscosity of the system. In some cases, the mixing temperature needs to be increased to obtain a lower viscosity, but this needs to avoid excessive polymerization in the unnecessary processing window to avoid causing difficulties in subsequent processing.

[0124] In some preferred embodiments of the present application, the temperature used in the mixing step is above 60°C, more preferably above 70°C, and below 115°C, preferably below 110°C. The obtained molten or liquid mixture can be used immediately or stored for a short time at the processing temperature before use.

[0125] In the step of forming a grating structure, the polymer film having a grating structure obtained by the exposure process has a thickness of 15 μm to 50 μm, preferably a thickness of 20 μm to 40 μm.

[0126] In the present application, the above-mentioned photopolymer film having a grating structure can be processed into a hologram by a suitable exposure operation for various optical applications.

[0127] In some preferred embodiments of the present application, for the exposure process of the photopolymer film, two coherent lights can be used. There is no particular limitation on the source of the coherent light with a wavelength of about 532 nm, and in some embodiments of the present application, one green laser light can be split into two coherent lights with the same or different light intensities by an optical element, and the obtained photopolymer film is exposed to the two coherent lights at the same time.

[0128] By using the coherent light for exposure, spaced bright and dark regions can be presented in the photopolymer film (two coherent lights produce alternating bright and dark stripes in the photopolymer film). The monomers in the bright regions are polymerized under the action of the initiator, and the monomer concentration is reduced; the concentration difference between the bright and dark regions causes the monomers to phase separate, and the monomers in the dark regions migrate to the bright regions, forming a refractive index difference Δn (refractive index modulation) between the bright and dark regions. For the exposure intensity, in some embodiments of the present application, it can be 5 to 30 mJ / cm 2 The exposure sensitivity of the present application can reach 5 mJ / cm 2 , and has a high exposure efficiency.

[0129] In some embodiments of the present application, two coherent lights can be used for exposure operation from one side of the polymer film at the same time (transmission grating); in other embodiments, two coherent lights are used for exposure operation from both sides of the polymer film, respectively (reflection grating).

[0130] After exposure, a refractive index distribution in the form of a sinusoidal function is formed in the photopolymer film, i.e. a diffraction grating is obtained. The difference between the peaks of the sinusoidal wave is Δn (refractive index modulation).

[0131] From the perspective of improving the angular selectivity of the grating, in the preferred embodiments of the present application, the polymer film is exposed by two coherent lights from both sides of the polymer film to form a reflective grating.

[0132] For example, Figure 1 In the above-mentioned exposure light path, a typical exposure light path (recording light path) of the present application is shown. The visible laser is split into two lasers with the same or different intensities after splitting, and both lasers are reflected by the mirror and converge on the photopolymer film to produce interference fringes.

[0133] After exposure, a holographic diffraction grating is formed in the photopolymer film, and the final reflective holographic diffraction grating containing the photopolymer film can be obtained after irradiation by natural light (without the complex post-processing of other grating element preparation in the art).

[0134] The holographic grating element of the present application can be used in a holographic optical waveguide display device, and is particularly suitable for an augmented reality (AR) head-mounted device, such as an AR display glasses device, etc.

[0135] In order to further illustrate the present application, the photopolymer composition and grating provided by the present application are described in detail below in combination with examples.

[0136] Example 1:

[0137] A photopolymer composition for holographic recording is prepared according to the following steps:

[0138] 1) In a dark room or red light environment, the components in Table 1 below are mixed in proportion to form a mixture, and heated to 100°C and stirred uniformly;

[0139] 2) Maintain 100°C, and coat the mixed solution obtained in step 1) on a glass substrate under red light, then cover another piece of substrate on the surface, and obtain a solid photopolymer dry plate after cooling to room temperature;

[0140] 3) The photopolymer dry plate is exposed to 532nm laser interference in a two-beam light path (as shown in Figure 1 ), to form a holographic grating; high laser intensity and short exposure time mode is used, and the exposure energy density is 20mJ / cm 2 ;

[0141] 4) The holographic grating can be completely fixed and bleached after being irradiated by natural light for about 30min.

[0142] The above-mentioned exposure light path is shown in Figure 1The holographic recording was performed with a 532 nm laser. The green laser emitted by the laser was split into two beams by a beam splitter, and then converged on both sides of the photopolymer recording material to perform reflective exposure after adjusting the angle by a mirror.

[0143] The components of the composition and their contents are shown in Table 1 below:

[0144] Table 1

[0145] Composition Content 2,5-bis{[4-(diethylamino)-2-methylphenyl]methylene}cyclopentanone 0.2% 2-(4-chlorophenyl)-4,5-diphenylimidazole 0.8% 7-methylene-1,5-dithiacyclooctane-3-acetate (n = 1.597) 28% Tetra(3-mercapto butyric acid) pentaerythritol ester (n = 1.523) 14% Cellulose acetate butyrate (n = 1.475) 28% Polyethylene glycol 29% Polyether modified dimethicone 5%

[0146] The diffraction efficiency of the reflective holographic grating obtained in this Example 1 is greater than 75%, and the refractive index modulation is 0.03.

[0147] Example 2

[0148] The method for preparing the holographic grating is the same as that in Example 1. In Example 2, the exposure energy density is changed based on Example 1, and the exposure energy density is 8 mJ / cm 2 The components of the composition and their contents are shown in Table 2 below:

[0149] Table 2

[0150] Composition Content Erythrosin B 0.2% N-phenylglycine 0.8% Irgacure 784 1% 7-methylene-1,5-dithiacyclooctane-3-benzoate (n = 1.607) 33% Tetra(3-mercapto butyric acid) pentaerythritol ester (n = 1.523) 11% Cellulose acetate butyrate (n = 1.475) 22% N-vinylpyrrolidone 26% Polyether modified acrylate functional dimethicone 6%

[0151] The diffraction efficiency of the reflective holographic grating obtained in this Example 2 is greater than 90% (as shown in FIG. 2), the angle selectivity is ±12°, the exposure is sensitive, and the refractive index modulation can reach 0.04. Figure 2

[0152] Example 3

[0153] The components of the composition and their contents are shown in Table 3 below:

[0154] Table 3

[0155] Composition Content Eosin Y 0.2% 4-dimethylaminobenzoic acid ethyl ester 0.8% Diphenyliodonium hexafluorophosphate 1% 7-methylene-1,5-dithiacyclooctane-3-phenylacetate (n = 1.605) 39% Tetra(3-mercaptopropionic acid) pentaerythritol ester (n = 1.553) 13% Cellulose acetate butyrate (n = 1.475) 13% Glutaric anhydride 7% Polyethylene glycol 20% Polyether modified acrylate functional dimethicone 6%

[0156] The diffraction efficiency of the reflective holographic grating obtained in this Example 3 is greater than 90%, and the refractive index modulation is greater than 0.03.

[0157] It should be noted that although the technical solutions of the present application are introduced with specific examples, those skilled in the art can understand that the present disclosure should not be limited thereto.

[0158] ​Having described above several embodiments of the disclosure, any modifications and variations that fall within the scope of the described embodiments are also intended to be within the scope of the disclosure. As will be apparent to those skilled in the art, some modifications and variations to the embodiments described above can be practiced while staying within the scope and spirit of the described embodiments. The foregoing description of the described embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the described embodiments to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. It is intended that the disclosed embodiments be limited only by the claims.

Claims

1. A photopolymer composition for holographic recording, characterized in that, comprises the following components: a polymerizable monomer, a film-forming component, a dye compound, an initiator, a plasticizer, and a surface aid; the polymerizable monomer comprises a cycloallyl sulfide monomer and a thiol monomer; the cycloallyl sulfide monomer has the following general formula (I) or general formula (II): wherein R1 represents a hydrogen atom, an alkane group, an aromatic hydrocarbon group, an ether bond-containing group, a thioether-containing group, or a cycloalkane-containing group; R2 and R3 each independently represent a hydrogen atom, an alkyl acyl group, a double bond-containing alkyl acyl group, an aryl acyl group, an ether bond-containing alkyl or aryl acyl group, a cycloalkane-containing alkyl or aryl acyl group, or a benzene ring-containing acyl group; the thiol monomer is a multifunctional thiol monomer having at least 3 functional groups.

2. A photopolymer composition for holographic recording according to claim 1, characterized in that, The cycloallyl sulfide monomer has a refractive index of 1.53 or more.

3. A photopolymer composition for holographic recording according to claim 1, wherein The molar ratio of the multifunctional thiol monomer to the cycloallyl sulfide monomer is 0.25-1:

1.

4. A photopolymer composition for holographic recording according to claim 1, wherein The multifunctional thiol monomer has the following general formula (III) or general formula (IV): wherein R4 and R5 each independently represent an alkylene group, an arylene group, a benzene alkylene group, or a cycloalkane-containing alkylene group.

5. A photopolymer composition for holographic recording according to claim 4, wherein The R4 and R5 groups contain a long-chain alkyl group or 1-2 benzene ring structures.

6. A photopolymer composition for holographic recording according to claim 1, wherein The total weight of the composition is: The content of the cycloallyl sulfide monomer is 15-40%; The content of the thiol monomer is 2-15%; The content of the film-forming component is 10-40%; The content of the dye compound is 0.1-2%; The content of the initiator is 0.5-5%; The content of the plasticizer is 10-40%; The content of the surface aid is 5-15%.

7. A holographic diffraction grating, characterized by A polymer film having a grating structure, which is obtained by curing the composition according to any one of claims 1-6.

8. A holographic optical waveguide display element, characterized by A holographic diffraction grating according to claim 7.

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