Holographic recording medium and preparation method thereof, grating, optical waveguide and equipment

Abstract

The invention relates to the technical field of holographic materials, and provides a holographic recording medium and a preparation method thereof, a grating, an optical waveguide and equipment, the holographic recording medium comprises a polymerizable monomer and a nanoparticle, the refractive index of the nanoparticle is lower than that of the polymerizable monomer, and the refractive index of the nanoparticle is lower than that of the polymerizable monomer under exposure. The polymerizable monomer in the coherent dark area is migrated to the coherent bright area to participate in the polymerization reaction, and meanwhile, the nanoparticles in the coherent bright area are migrated to the coherent dark area. According to the embodiment of the invention, the refractive index difference between the coherent bright region and the coherent dark region is increased, so that the grating can obtain higher diffraction efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of holographic materials, and in particular to a holographic recording medium and a preparation method, grating, optical waveguide, and equipment thereof. Background Art

[0002] AR (Augmented Reality) glasses based on holographic waveguide systems have the advantages of being light, portable, highly transparent, and having realistic and natural virtual images. The core optical element of the holographic waveguide system is a pair of reflective volume holographic gratings, which are usually prepared using photopolymers. The diffraction efficiency of the volume holographic grating is affected by the refractive index difference between the coherent bright area and the coherent dark area. A large refractive index difference between the coherent bright area and the coherent dark area can improve the diffraction efficiency of the volume holographic grating. However, the refractive index difference between the coherent bright area and the coherent dark area needs to be improved. Summary of the invention

[0003] The present application provides a holographic recording medium and a preparation method thereof, a grating, an optical waveguide, and a device, aiming to increase the refractive index difference between the coherent bright area and the coherent dark area of ​​a photopolymer holographic recording medium.

[0004] To achieve the above-mentioned purpose, the present application provides a photopolymer holographic recording medium, comprising a polymerizable monomer and nanoparticles, wherein the refractive index of the nanoparticles is lower than the refractive index of the polymerizable monomer, and under exposure, the polymerizable monomer in the coherent dark area migrates to the coherent bright area to participate in the polymerization reaction, and at the same time, the nanoparticles in the coherent bright area migrate to the coherent dark area.

[0005] In addition, to achieve the above-mentioned purpose, the present application also provides a method for preparing a photopolymer holographic recording medium, comprising the following steps:

[0006] Weigh each component of the photopolymer holographic recording medium into a container, and stir thoroughly until all components are dissolved;

[0007] Filter the mixture using a membrane filter;

[0008] The mixture is coated on a substrate and cured to obtain the photopolymer holographic recording medium.

[0009] In addition, to achieve the above-mentioned purpose, the present application also provides a volume holographic grating, and the photopolymer holographic recording medium used by the volume holographic grating includes the photopolymer holographic recording medium as described above.

[0010] In addition, to achieve the above-mentioned purpose, the present application also provides a volume holographic optical waveguide, wherein the volume holographic optical waveguide includes the volume holographic grating as described above.

[0011] In addition, to achieve the above-mentioned purpose, the present application also provides a holographic device, which includes the volume holographic optical waveguide as described above.

[0012] The present application discloses a holographic recording medium and a preparation method thereof, a grating, an optical waveguide and an apparatus. The photopolymer holographic recording medium comprises a polymerizable monomer and nanoparticles. The refractive index of the nanoparticles is lower than that of the polymerizable monomer. Under exposure, the polymerizable monomer in the coherent dark area migrates to the coherent bright area to participate in the polymerization reaction, and the nanoparticles in the coherent bright area migrate to the coherent dark area. Finally, the refractive index of the coherent bright area is close to that of the polymerizable monomer, that is, the refractive index is high, and the refractive index of the coherent dark area is close to that of the nanoparticles, that is, the refractive index is low, thereby increasing the refractive index difference between the coherent bright area and the coherent dark area, which is beneficial for the grating to obtain a higher diffraction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 is a schematic flow chart of the steps of a method for preparing a photopolymer holographic recording medium provided in an embodiment of the present application;

[0015] Figure 2 is a schematic diagram of the holographic performance of the photopolymer holographic recording medium of Examples 1, 3, 5, and 7 of the present application;

[0016] Figure 3 is a schematic diagram of the holographic performance of a common photopolymer holographic recording medium of an experimental example;

[0017] Figure 4 It is a schematic diagram of UV-visible transmittance curves corresponding to the photopolymer holographic recording medium of Example 3 of the present application and the common photopolymer holographic recording medium of the test example. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0020] It should be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0021] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0022] The embodiments of the present application provide a holographic recording medium and a preparation method thereof, a grating, an optical waveguide, and a device for increasing the refractive index difference between the coherent bright area and the coherent dark area of ​​a photopolymer holographic recording medium.

[0023] In the absence of conflict, the following embodiments and features of the embodiments may be combined with each other.

[0024] The embodiment of the present application provides a photopolymer holographic recording medium, which includes a polymerizable monomer and nanoparticles, wherein the refractive index of the nanoparticles is lower than the refractive index of the polymerizable monomer. Generally, the average refractive index of the nanoparticles is lower than 1.42, and the average refractive index of the polymerizable monomer is higher than 1.55. Under exposure, such as two-beam laser exposure, the polymerizable monomer in the coherent dark area migrates to the coherent bright area to participate in the polymerization reaction, and the nanoparticles in the coherent bright area are migrated to the coherent dark area. Finally, the refractive index of the coherent bright area is close to the refractive index of the polymerizable monomer, that is, the refractive index is high, and the refractive index of the coherent dark area is close to the refractive index of the nanoparticles, that is, the refractive index is low, thereby increasing the refractive index difference between the coherent bright area and the coherent dark area, which is beneficial for the grating to obtain a higher diffraction efficiency, for example, a diffraction efficiency greater than 97% can be obtained.

[0025] In addition, since the low-refractive-index nanoparticles are reversely migrated to the coherent dark region, the sensitivity of the photopolymer-based holographic recording medium is significantly improved, for example, at an exposure dose of less than 10 mJ / cm 2 (millijoules per square centimeter) to record the grating.

[0026] In addition, the shrinkage rate of the polymerizable monomer is high after polymerization, which can easily lead to large grating offset. The photopolymer holographic recording medium including polymerizable monomers and nanoparticles partially replaces the high-refractive-index polymerizable monomers with low-refractive-index nanoparticles, which not only reduces the amount of polymerizable monomer used, but also reduces the shrinkage rate, thereby avoiding large grating offset.

[0027] In some embodiments of the present invention, the polymerizable monomer includes at least one of alkenyl naphthalene compounds, alkenyl anthracene compounds, alkenyl benzene compounds, acrylic compounds, methacrylic compounds, acrylate compounds, methacrylate compounds, N-vinyl pyrrole, N-vinyl carbazole, N-vinylimidazole, N-vinyl indole, N-vinyl pyrrolidone, and trans-N-3-ynyl butenyl carbazole.

[0028] In some optional embodiments of the present invention, the alkenylbenzene compound can be selected from styrene, 2-chlorostyrene, 2-bromostyrene, 3-chlorostyrene, 3-bromostyrene, 4-chlorostyrene, 4-bromostyrene, p-(chloromethyl)styrene, p-(bromomethyl)styrene, etc.

[0029] In some optional embodiments of the present invention, the methacrylic compound may be methacrylic acid and its derivatives.

[0030] In some optional embodiments of the present invention, the acrylate compound can be selected from pentabromophenyl acrylate, pentachlorophenyl acrylate, phenoxyethyl acrylate, pentabromobenzyl acrylate, 2-naphthyl acrylate, 1,4-di(2-thionaphthyl)2-butyl acrylate, phenoxyethoxyethyl acrylate, bisphenol A diacrylate, tetrabromobisphenol A diacrylate, 2-phenoxyethyl acrylate, benzyl acrylate, p-chlorophenyl acrylate, 2,4,6-trichlorophenyl acrylate, p-bromophenyl acrylate, 2,4,6-tribromophenyl acrylate, propane-2,2-diylbis[(2,6-dibromo-4,1-phenylene)oxy(2-{[3,3,3-tri(4-chlorophenyl)propionyl]oxy}propane-3,1-diyl)oxyethane-2,1-diyl] diacrylate, etc.

[0031] In some optional embodiments of the present invention, the methacrylate compound can be selected from 2-phenoxyethyl methacrylate, benzyl methacrylate, p-bromophenyl methacrylate, p-chlorophenyl methacrylate, 2,4,6-trichlorophenyl methacrylate, pentabromophenyl methacrylate, pentachlorophenyl methacrylate, phenoxyethyl methacrylate, phenoxyethoxyethyl methacrylate, 1,4-di(2-thionaphthyl) 2-butyl methacrylate, pentabromobenzyl methacrylate, 2-naphthyl methacrylate, bisphenol A dimethacrylate, tetrabromobisphenol A dimethacrylate, etc.

[0032] In some optional embodiments of the present invention, the alkenyl anthracene compound may be selected from 2-vinyl anthracene, 9-vinyl anthracene and the like.

[0033] In some optional embodiments of the present invention, the alkenyl naphthalene compound can be selected from 1-vinyl naphthalene, 2-vinyl naphthalene and the like.

[0034] In some optional embodiments of the present invention, the nanoparticles are selected from calcium fluoride nanoparticles, magnesium fluoride nanoparticles, barium fluoride nanoparticles, aluminum fluoride nanoparticles, sodium hexafluoroaluminate, and the like.

[0035] In some embodiments of the present invention, the photopolymer holographic recording medium includes the following components:

[0036] The first component: polyurethane precursor;

[0037] The second component: polymerizable monomer;

[0038] The third component: nanoparticles;

[0039] The fourth component: photosensitive initiation system;

[0040] The fifth component: chain transfer agent;

[0041] The sixth component: catalyst;

[0042] Seventh component: additives or solvents.

[0043] Wherein, the first component polyurethane precursor comprises a polyisocyanate compound and a polyol. In some embodiments of the present invention, the polyisocyanate compound is a compound with a low refractive index and two or more isocyanate groups. In some optional embodiments of the present invention, the polyisocyanate compound is selected from hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, (2,4,6-trioxotriazine-1,3,5 (2H,4H,6H)-triyl) tris (hexamethylene) isocyanate, butane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate; the polyol is a low refractive index compound with two or more hydroxyl functional groups, selected from tetraethylene glycol, trimethylolethane, glycerol, triethanolamine, polyester polyol, polycarbonate polyol, polyether polyol.

[0044] The second component polymerizable monomer is as described in the above embodiments and will not be described again here.

[0045] The third component nanoparticles are as described in the above embodiments and will not be described again here.

[0046] The fourth component, the photosensitive initiation system, includes a photosensitive dye (also called a photosensitizer) and a photoinitiator, wherein the photosensitive dye can be matched with the photoinitiator to realize a visible light initiation system and adapt to lasers of different wavelengths. Under the irradiation of light in a specific wavelength range, the photosensitive dye in the photoinitiator system is activated by the corresponding light, absorbs light energy, and transfers the light energy to the photoinitiator, so that the photoinitiator can be activated under light radiation of more frequencies to generate free radicals with initiation function. The photoinitiator free radicals can initiate monomer polymerization to realize the formation of a photopolymer holographic recording medium, thereby improving the photosensitivity of the photopolymer holographic recording medium and broadening the range of optional radiation sources for light radiation.

[0047] It can be understood that, in other examples, when the present invention uses a wavelength-adapted photoinitiator, no photosensitizing dye may be added.

[0048] Exemplarily, the photosensitizing dye is a dye having a high electron transfer efficiency under illumination, including but not limited to cyanine dyes, fluorescein dyes, coumarin ketone dyes, nitrogen-containing aromatic heterocyclic compounds, aromatic amine compounds, benzylcycloalkane ketone compounds or any mixture of these compounds in any proportion. For example, it includes one or more of new methylene blue, thionine, basic yellow, chlorinated pinacol, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, lapis lazuli blue, methylene blue, Astrazon OrangeG, Darrow red, pyrrole red Y, basic red 29, quinaldine red, crystal violet, ethyl violet, brilliant green, pyri11lium I, azure A, crystal violet white nitrile, malachite green white nitrile, etc.

[0049] Exemplarily, the photoinitiator is an initiator that can be activated by actinic radiation and initiates polymerization of the corresponding polymerizable groups, including but not limited to aromatic ketone compounds, benzoin and its derivatives, benzil ketal, acylphosphine oxide, aryl ammonium borate, chromium salt, aryl diazonium salt, onium salt, organometallic compound or any mixture of these compounds. For example, it includes one or more of benzophenone, alkylbenzophenone, 4,4'-bis(dimethylamino)benzophenone, anthrone and halogenated benzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxide, phenyl dihydroxyacetate, camphorquinone, α-aminoalkylphenone, α,α-dialkoxyacetophenone, α-hydroxyalkylphenone, triphenylhexyl borate tetrabutylammonium, tri-(3-fluorophenyl)hexylborate tetrabutylammonium, tri-(3-chloro-4-methylphenyl)hexylborate tetrabutylammonium, ferrocenyl compounds, iodonium salts, sulfonium salts, hexaarylbiimidazoles, etc.

[0050] When these photoinitiators are irradiated by light within the corresponding wavelength range, they can be quickly activated and generate active free radicals, thereby initiating polymerization reactions between the components of the photopolymer holographic recording medium and achieving a difference in monomer concentration between the coherent bright area and the coherent dark area.

[0051] The fifth component chain transfer agent is a thiol compound, including but not limited to one or more of dodecyl mercaptan, mercaptoethanol, hexanethiol, phenylethyl mercaptan, 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, 4-methyl-4H-1,2,4-triazole-3-thiol, etc.

[0052] The sixth component catalyst is a tertiary amine catalyst and an organic metal catalyst, including but not limited to triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts and bismuth carboxylate catalysts.

[0053] The seventh component additives include one or more of a defoamer, a leveling agent, a plasticizer, an ultraviolet absorber, a light stabilizer and an antioxidant.

[0054] Exemplarily, the defoamer is a silicone defoamer and / or a polymer defoamer that does not contain silicone. The defoamer can reduce the surface tension of the liquid and remove bubbles, thereby improving the fluidity of the mixture of each component. For example, BYK-011, BYK-012, BYK-014, BYK-023, BYK-051N, BYK-085, BYK-1610, BYK-1707, BYK-1740, BYK-1760 produced by BYK, DC65, AFE-7820 produced by Dow Corning, or any proportion of these defoamers. BYK series defoamers have excellent defoaming performance, good compatibility with other components, and good dispersibility; among them, BYK-011, BYK-012, BYK-014 and BYK-051N are polymer defoamers that do not contain silicone. DC65 is a water-based ink that dries quickly, has good printing effects, and is not easy to fall off. AFE-7820 has efficient defoaming properties.

[0055] Exemplarily, the leveling agent is an organic silicon surface additive, such as BYK-302, BYK-306, BYK-307, BYK-327, BYK-329, BYK-333, BYK-356, BYK-358, BYK-378, BYK-3455, BYK-3566 produced by BYK, or any mixture of these surface additives. BYK series leveling agents have excellent leveling properties.

[0056] Exemplarily, the plasticizer is toluene, xylene, dimethylformamide, dimethylacetamide, glycerol, phthalate or any mixture of these compounds. The plasticizer is inserted between polymer molecular chains to weaken the stress between molecules, increase the mobility of molecular chains, and reduce crystallinity, thereby increasing the plasticity of the polymer.

[0057] Exemplarily, the ultraviolet absorber includes, but is not limited to, 2-hydroxy-4-n-octyloxybenzophenone, 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol, N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide, 2-(2H-benzotriazole-2-yl)-p-cresol, 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazole-2-yl)-4,6-di-tert-amylphenol, 2-(2H-benzotriazole-2)-4,6-di(1-methyl-1-phenylethyl)phenol, or a mixture of these additives in any proportion.

[0058] Illustratively, the light stabilizer includes, but is not limited to, light stabilizer 944, bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, light stabilizer 622, or a mixture of these additives in any ratio.

[0059] Exemplarily, the antioxidant includes, but is not limited to, Irganox 1010, Irganox 168, Irganox 1076, Irganox 1098, Irganox MD1024, Irganox 1035, BASF liquid antioxidant 1135, Irganox B225, Irganox PS800 (DLTP), Irganox B900, Irganox 3114, Irganox 245, Irganox B215, Irganox PS-802FL, Irganox Borchors Ascinin@Special, Irganox Borchors Ascinin@P, or any mixture of these additives in any proportion.

[0060] The seventh component solvent includes but is not limited to petroleum ether, methylene chloride, ethyl acetate, n-hexane, tetrahydrofuran, acetone, benzene, methyl ethyl ketone, methyl formate, methyl propionate, isobutyl formate, butyl chloride, ethyl propionate, ethylene dichloride, chloroisopentane, methyl carbonate, trichloroethane, carbon tetrachloride, ethylene dichloride, carbon disulfide, propyl alcohol 3-pentanone, dichloropropane, butanone, ethyl bromide, cyclohexane. These solvents have good compatibility with other components, so that each component is fully dissolved, and the solvent is convenient for subsequent drying and removal.

[0061] The content of each component is different. The content of polyurethane precursor and polymerizable monomer is the highest, followed by nanoparticles, and the content of photosensitive initiator system, chain transfer agent, catalyst, additive or solvent is low.

[0062] In some embodiments of the present invention, the content of the polyurethane precursor is 30% to 60% by mass percentage (based on the total mass of the photopolymer holographic recording medium), for example: 30%, 40%, 50%, 60%, etc.; the content of the polymerizable monomer is 20% to 50%, for example: 20%, 30%, 40%, 50%, etc.; the content of the nanoparticles is 5% to 20%, for example: 5%, 10%, 15%, 20%, etc.; the content of the photosensitive initiator system is 0.1% to 5%, for example: 0.1%, 1%, 3%, 5%, etc.; the content of the chain transfer agent is 0.1% to 3%, for example: 0.1%, 1%, 2%, 3%, etc.; the content of the catalyst is 0.1% to 3%, for example: 0.1%, 1%, 2%, 3%, etc.; the content of the additive or solvent is 0.1% to 15%, for example: 0.1%, 5%, 10%, 15%, etc.

[0063] It is understandable that the present invention can achieve full synergistic effect of the components by reasonably controlling the content of each component, and avoid the deterioration of the holographic performance of the final photopolymer holographic recording medium due to excessive or insufficient amount of a certain component, thereby ensuring that the comprehensive holographic performance of the final photopolymer holographic recording medium is better.

[0064] For example, by controlling the content of the polyurethane precursor to 30% to 60%, a film-forming resin is formed, thereby providing support for other components. In addition, the presence of the film-forming resin enables the photopolymer holographic recording medium to be prepared in a film state, which is conducive to mass production and use.

[0065] For example, by controlling the content of the polymerizable monomer to be 20% to 50%, the polymerizable monomer can form a writing monomer and have a higher refractive index.

[0066] For example, by controlling the content of nanoparticles to 5% to 20%, the nanoparticles have a lower refractive index. Then the first component, the second component and the third component provide a material basis for forming a photopolymer holographic recording medium with a large refractive index difference.

[0067] For example, by controlling the content of the photosensitive initiator system at 0.1% to 5%, it is possible to absorb an appropriate number of photons during exposure and control the polymerization reaction at a certain speed, so that the photopolymer holographic recording medium can be quickly formed and obtain a higher diffraction efficiency; in addition, it can also ensure that the final photopolymer holographic recording medium has the required light transmittance and that the grating prepared from the photopolymer holographic recording medium has a certain diffraction efficiency.

[0068] For example, controlling the content of the chain transfer agent to 0.1% to 3% can control the polymer chain length within a certain reasonable range and effectively prevent excessive polymerization, thereby ensuring that the final photopolymer holographic recording medium has the desired optical properties and diffraction efficiency.

[0069] For example, controlling the catalyst content at 0.1% to 3% can effectively increase the reaction rate of related components and the consumption rate of related components after exposure, thereby quickly forming a concentration difference between monomers in coherent bright areas and coherent dark areas, and achieving a refractive index difference between coherent bright areas and coherent dark areas, which is beneficial for the grating to obtain a higher diffraction efficiency.

[0070] For example, controlling the content of additives or solvents to 0.1% to 15%, taking the additive as a leveling agent as an example, can effectively improve the uniformity of the mixed liquid, improve fluidity, and reasonably control costs. If the content of the solvent is controlled within the above range, the solvent can fully wet the other components, and the components can be mutually soluble to form a relatively uniform mixed system, which is convenient for coating and making photopolymer holographic recording media.

[0071] In some optional embodiments of the present invention, when the additive includes a defoaming agent, the content of the defoaming agent is no more than 3% by mass (based on the total mass of the photopolymer holographic recording medium).

[0072] In some optional embodiments of the present invention, when the additive includes a leveling agent, the content of the leveling agent is no more than 3% by mass (based on the total mass of the photopolymer holographic recording medium).

[0073] In some optional embodiments of the present invention, when the additive includes a plasticizer, the content of the plasticizer is no more than 3% by mass (based on the total mass of the photopolymer holographic recording medium).

[0074] In some optional embodiments of the present invention, when the additive includes an ultraviolet absorber, the content of the ultraviolet absorber is no more than 3% by mass (based on the total mass of the photopolymer holographic recording medium).

[0075] In some optional embodiments of the present invention, when the additive includes an antioxidant, the content of the antioxidant is no more than 3% by mass (based on the total mass of the photopolymer holographic recording medium).

[0076] In some optional embodiments of the present invention, when the additive includes a light stabilizer, the content of the light stabilizer is no more than 3% by mass (based on the total mass of the photopolymer holographic recording medium).

[0077] See also Figure 1 , Figure 1 FIG. 1 is a schematic diagram of a method for preparing a photopolymer holographic recording medium according to an embodiment of the present application. Figure 1 As shown, the method for preparing the photopolymer holographic recording medium specifically includes steps S101 to S103.

[0078] Step S101 , weighing various components of the photopolymer holographic recording medium into a container, and stirring thoroughly until all the components are dissolved.

[0079] Step S102, filtering using a filter membrane to obtain a mixture.

[0080] Step S103: coating the mixture onto a substrate, and obtaining the photopolymer holographic recording medium after curing.

[0081] Wherein, the container includes but is not limited to a glass bottle. Exemplarily, coating the mixture onto the substrate includes but is not limited to coating the mixture onto the substrate by inkjet printing, blade coating, spin coating, etc.

[0082] As can be seen from the above, the preparation method of the photopolymer holographic recording medium proposed in the present invention has few preparation steps, simple operation, easy implementation conditions, and is convenient for obtaining a photopolymer holographic recording medium with low shrinkage, high photosensitivity, and high diffraction efficiency.

[0083] In some embodiments of the present invention, the curing is carried out in a dark room at a temperature of 10° C. to 50° C. The conditions are simple and the operation is easy.

[0084] The photopolymer holographic recording medium and the preparation method thereof of the present invention are described below with reference to specific embodiments.

[0085] Example 1

[0086] In this embodiment, the photopolymer holographic recording medium includes the following raw materials of various components:

[0087] The first component: polyurethane precursor, the content is 30%. The polyurethane precursor includes a polyisocyanate compound and a polyol, wherein the polyisocyanate compound is hexamethylene diisocyanate, the content is 20%, and the polyol is tetraethylene glycol, the content is 10%.

[0088] The second component: a polymerizable monomer, the content of which is 40%. The polymerizable monomer is 2-vinylnaphthalene.

[0089] The third component: nanoparticles, with a content of 10%. The nanoparticles are calcium fluoride nanoparticles.

[0090] The fourth component: a photosensitive initiation system, with a content of 5%. The photosensitive initiation system includes a photosensitive dye and a photoinitiator, wherein the photosensitive dye is new methylene blue, with a content of 0.7%, and the photoinitiator is benzophenone, with a content of 4.3%.

[0091] The fifth component: a chain transfer agent, the content of which is 2%. The chain transfer agent is mercaptoethanol.

[0092] The sixth component: catalyst, the content is 3%. The catalyst is triethylenediamine.

[0093] The seventh component: additives, with a content of 10%. The additives include defoamers and leveling agents, wherein the defoamer is BYK-011, with a content of 5%, and the leveling agent is BYK-302, with a content of 5%.

[0094] Example 2

[0095] In this embodiment, the photopolymer holographic recording medium includes the following raw materials of various components:

[0096] The first component: polyurethane precursor, the content is 35%. The polyurethane precursor includes a polyisocyanate compound and a polyol, wherein the polyisocyanate compound is trimethyl hexamethylene diisocyanate, the content is 21%, and the polyol is trimethylolethane, the content is 14%.

[0097] The second component: a polymerizable monomer, the content of which is 40%. The polymerizable monomer is 4-chlorostyrene.

[0098] The third component: nanoparticles, with a content of 12%. The nanoparticles are magnesium fluoride nanoparticles.

[0099] The fourth component: a photosensitive initiation system, with a content of 5%. The photosensitive initiation system includes a photosensitive dye and a photoinitiator, wherein the photosensitive dye is ethyl violet, with a content of 0.7%, and the photoinitiator is a-aminoalkylphenone, with a content of 4.3%.

[0100] The fifth component: a chain transfer agent, the content of which is 1%. The chain transfer agent is dodecyl mercaptan.

[0101] The sixth component: a catalyst, the content of which is 2%. The catalyst is bis(dimethylaminoethyl) ether.

[0102] The seventh component: additives, with a content of 5%. The additives include defoamers, leveling agents and plasticizers, wherein the defoamer BYK-085 has a content of 2%, the leveling agent is BYK-329, with a content of 2%, and the plasticizer is phthalate, with a content of 1%.

[0103] Example 3

[0104] In this embodiment, the photopolymer holographic recording medium includes the following raw materials of various components:

[0105] The first component: polyurethane precursor, the content is 40%. The polyurethane precursor includes a polyisocyanate compound and a polyol, wherein the polyisocyanate compound is (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl) tris(hexamethylene) isocyanate, the content is 13%, and the polyol is triethanolamine, the content is 27%.

[0106] The second component: polymerizable monomer, with a content of 37%. The polymerizable monomer is p-bromophenyl acrylate.

[0107] The third component: nanoparticles, with a content of 13%. The nanoparticles are barium fluoride nanoparticles.

[0108] The fourth component: a photosensitive initiation system, with a content of 2%. The photosensitive initiation system includes a photosensitive dye and a photoinitiator, wherein the photosensitive dye is quinaldine red, with a content of 0.3%, and the photoinitiator is tetra-(3-fluorophenyl)hexyl borate ammonium, with a content of 1.7%.

[0109] The fifth component: a chain transfer agent, the content of which is 1%. The chain transfer agent is 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol.

[0110] The sixth component: a catalyst, the content of which is 1%. The catalyst is stannous octoate.

[0111] The seventh component: additives, with a content of 6%. The additives include defoamers, leveling agents and plasticizers, wherein the defoamer is BYK-1760, with a content of 2%, the leveling agent is BYK-3455, with a content of 2%, and the plasticizer is dimethylacetamide, with a content of 2%.

[0112] Example 4

[0113] In this embodiment, the photopolymer holographic recording medium includes the following raw materials of various components:

[0114] The first component: polyurethane precursor, the content is 38%. The polyurethane precursor includes a polyisocyanate compound and a polyol, wherein the polyisocyanate compound is butane-1,4-diisocyanate, the content is 23%, and the polyol is glycerol, the content is 15%.

[0115] The second component: a polymerizable monomer, with a content of 30%. The polymerizable monomer is p-(bromomethyl)styrene.

[0116] The third component: nanoparticles, with a content of 12%. The nanoparticles are aluminum fluoride nanoparticles.

[0117] The fourth component: a photosensitive initiation system, with a content of 4%. The photosensitive initiation system includes a photosensitive dye and a photoinitiator, wherein the photosensitive dye is lapis lazuli blue, with a content of 0.6%, and the photoinitiator is tetrabutylammonium triphenylhexylborate, with a content of 3.4%.

[0118] The fifth component: a chain transfer agent, the content of which is 2%. The chain transfer agent is hexanethiol.

[0119] The sixth component: a catalyst, the content of which is 2%. The catalyst is dibutyltin dilaurate.

[0120] The seventh component: additives, with a content of 12%. The additives include defoamers, leveling agents and plasticizers, wherein the defoamer is BYK-1707, with a content of 5%, the leveling agent is BYK-358, with a content of 2%, and the plasticizer is glycerin, with a content of 5%.

[0121] Example 5

[0122] In this embodiment, the photopolymer holographic recording medium includes the following raw materials of various components:

[0123] The first component: polyurethane precursor, the content is 60%. The polyurethane precursor includes a polyisocyanate compound and a polyol, wherein the polyisocyanate compound is isophorone diisocyanate, the content is 40%, and the polyol is polyester polyol, the content is 20%.

[0124] The second component: a polymerizable monomer, with a content of 22%. The polymerizable monomer is 9-vinyl anthracene.

[0125] The third component: nanoparticles, with a content of 10%. The nanoparticles are aluminum fluoride nanoparticles.

[0126] The fourth component: a photosensitive initiation system, with a content of 4%. The photosensitive initiation system includes a photoinitiator, and the photoinitiator is diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, with a content of 4%.

[0127] The fifth component: a chain transfer agent, the content of which is 1%. The chain transfer agent is mercaptoethanol.

[0128] The sixth component: a catalyst, the content of which is 1%. The catalyst is N,N-bis(dimethylaminopropyl)isopropanolamine.

[0129] The seventh component: additives, with a content of 2%. The additives include a defoamer and a leveling agent, wherein the defoamer is BYK-1610, with a content of 1%, and the leveling agent is BYK-333, with a content of 1%.

[0130] Example 6

[0131] In this embodiment, the photopolymer holographic recording medium includes the following raw materials of various components:

[0132] The first component: polyurethane precursor, the content is 46%. The polyurethane precursor includes a polyisocyanate compound and a polyol, wherein the polyisocyanate compound is isophorone diisocyanate, the content is 23%, and the polyol is polycarbonate polyol, the content is 23%.

[0133] The second component: a polymerizable monomer, with a content of 32%. The polymerizable monomer is p-(chloromethyl)styrene.

[0134] The third component: nanoparticles, with a content of 10%. The nanoparticles are sodium hexafluoroaluminate.

[0135] The fourth component: a photosensitive initiation system, with a content of 4%. The photosensitive initiation system includes a photosensitive dye and a photoinitiator, wherein the photosensitive dye is eosin, with a content of 0.6%, and the photoinitiator is benzophenone, with a content of 3.4%.

[0136] The fifth component: chain transfer agent, the content of which is 2%. The chain transfer agent is dodecyl mercaptan.

[0137] The sixth component: a catalyst, the content of which is 2%. The catalyst is dibutyltin dilaurate.

[0138] The seventh component: additives, with a content of 4%. The additives include a defoamer and a plasticizer, wherein the defoamer is BYK-014, with a content of 2.8%, and the plasticizer is dimethylformamide, with a content of 1.2%.

[0139] Example 7

[0140] In this embodiment, the photopolymer holographic recording medium includes the following raw materials of various components:

[0141] The first component: polyurethane precursor, the content is 40%. The polyurethane precursor includes a polyisocyanate compound and a polyol, wherein the polyisocyanate compound is dicyclohexylmethane diisocyanate, the content is 24%, and the polyol is polyether polyol, the content is 16%.

[0142] The second component: polymerizable monomer, the content is 42%. The polymerizable monomer is styrene.

[0143] The third component: nanoparticles, with a content of 11%. The nanoparticles are sodium hexafluoroaluminate.

[0144] The fourth component: a photosensitive initiation system, with a content of 2%. The photosensitive initiation system includes a photosensitive dye and a photoinitiator, wherein the photosensitive dye is 3,3'-carbonylbis(7-diethylaminocoumarin), with a content of 0.3%, and the photoinitiator is 2-isopropylthioxanthone, with a content of 1.7%.

[0145] The fifth component: a chain transfer agent, the content of which is 1%. The chain transfer agent is hexanethiol.

[0146] The sixth component: a catalyst, the content of which is 1%. The catalyst is bis(dimethylaminoethyl) ether.

[0147] The seventh component: solvent, the content is 3%. The solvent is ethyl acetate.

[0148] In addition, comparative test examples were added to test the performance of the common photopolymer holographic recording media of Examples 1-7 and the test examples. The results are shown in Table 1.

[0149] Table 1 Holographic performance test table of each photopolymer holographic recording medium in the embodiments and test examples

[0150]

[0151]

[0152] During the test, each holographic recording medium can be exposed to lasers of different wavelengths according to its different photosensitive systems. For example, the exposure intensity is 3mW / cm2 (milliwatts per square centimeter).

[0153] The corresponding holographic performance graphs were drawn using the photopolymer holographic recording media of Examples 1, 3, 5, 7 and the test example, and the results were obtained. Figure 2 and Figure 3 .

[0154] Specifically, for the above four embodiments 1, 3, 5, 7 and the experimental example, solid lasers with wavelengths of 633nm, 532nm, 405nm, 457nm and 532nm are used as light sources, and two beams with the same light intensity and a diameter of 8mm are obtained after passing through a beam expander, a beam splitter and a half-wave plate. The two beams intersect in the prepared holographic recording medium for exposure, and the light intensity is 3mW / cm 2 The detection light source is a 785nm wavelength solid laser that does not react with the recording medium. The detection light is incident on the exposure area from the Bragg angle. The transmitted light and diffracted light are monitored in real time by the photodetector. The single grating diffraction efficiency (η) of the photopolymer holographic recording medium and the photosensitivity (S) of the photopolymer holographic recording medium are calculated by formulas (1) to (3).

[0155]

[0156] Where η is the diffraction efficiency, η max is the highest diffraction efficiency, I d is the diffracted light, I t is the transmitted light, S is the photosensitivity, E is the exposure energy, and ΔE is the exposure energy when the highest diffraction efficiency is achieved.

[0157] The UV-visible transmittance curves of Example 3 and the test example were tested by a fiber optic spectrometer, and the results were Figure 4 .

[0158] like Figure 2 As shown in the figure, it is finally measured that the diffraction efficiency of the photopolymer holographic recording medium of the present invention is greater than 95%, and the exposure amount is less than 20mJ / cm 2 , high sensitivity (greater than 50cm 2 / mJ).

[0159] And as Figure 3 As shown, the ordinary photopolymer holographic recording medium of the test example was exposed, and it was measured that the diffraction efficiency of the ordinary photopolymer holographic recording medium in the test example was less than 55%, and the required exposure amount was greater than 50mJ / cm 2 , the sensitivity is lower.

[0160] In summary, reference Figure 2 , Figure 3 , Figure 4As shown in Table 1, for the photopolymer holographic recording medium of the embodiment of the present application, the diffraction efficiency is much higher than that of the ordinary photopolymer holographic recording medium of the test example, the sensitivity is much greater than the sensitivity of the ordinary photopolymer holographic recording medium of the test example, the required exposure is much smaller than that of the ordinary photopolymer holographic recording medium of the test example, and the shrinkage rate is much smaller than that of the ordinary photopolymer holographic recording medium of the test example.

[0161] A volume holographic grating is also provided in an embodiment of the present application, and the photopolymer holographic recording medium used in the volume holographic grating includes any of the photopolymer holographic recording media described above. The volume holographic grating can be applied to display devices, wherein the display devices include but are not limited to near-eye display devices such as AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, HUD (head-up display), etc. The beneficial effects that can be achieved by the photopolymer holographic recording medium provided in the embodiments of the present application can be achieved, as detailed in the previous embodiments, which will not be repeated here.

[0162] The embodiment of the present application also provides a volume holographic optical waveguide, which includes the volume holographic grating as described above, and can achieve the beneficial effects that can be achieved by the photopolymer holographic recording medium provided in the embodiment of the present application, as detailed in the previous embodiment, which will not be repeated here.

[0163] The embodiment of the present application provides a holographic device, which includes the volume holographic optical waveguide as described above. The holographic device includes but is not limited to AR glasses, VR glasses, etc., which can achieve the beneficial effects that can be achieved by the photopolymer holographic recording medium provided in the embodiment of the present application. For details, please refer to the previous embodiment and will not be repeated here.

[0164] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0165] The above description is only a specific implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present application, and these modifications or substitutions should be included in the protection scope of the present application.

Claims

1. A photopolymer holographic recording medium, characterized in that: It includes polymerizable monomers and nanoparticles, wherein the refractive index of the nanoparticles is lower than that of the polymerizable monomers. Under exposure, the polymerizable monomers in the coherent dark area migrate to the coherent bright area to participate in polymerization reaction, and the nanoparticles in the coherent bright area migrate to the coherent dark area.

2. The photopolymer holographic recording medium according to claim 1, wherein: The polymerizable monomer includes at least one of alkenyl naphthalene compounds, alkenyl anthracene compounds, alkenyl benzene compounds, acrylic compounds, methacrylic compounds, acrylate compounds, methacrylate compounds, N-vinyl pyrrole, N-vinyl carbazole, N-vinylimidazole, N-vinyl indole, N-vinyl pyrrolidone, and trans-N-3-ynyl butenyl carbazole.

3. The photopolymer holographic recording medium according to claim 1, wherein: The nanoparticles are selected from calcium fluoride nanoparticles, magnesium fluoride nanoparticles, barium fluoride nanoparticles, aluminum fluoride nanoparticles, and sodium hexafluoroaluminate.

4. The photopolymer holographic recording medium according to claim 1, wherein: Includes the following components: The first component: polyurethane precursor; The second component: polymerizable monomer; The third component: nanoparticles; The fourth component: photosensitive initiation system; The fifth component: chain transfer agent; The sixth component: catalyst; Seventh component: additives or solvents.

5. The photopolymer holographic recording medium according to claim 4, wherein: In terms of mass percentage, the content of the polyurethane precursor is 30% to 60%, the content of the polymerizable monomer is 20% to 50%, the content of the nanoparticles is 5% to 20%, the content of the photosensitive initiator system is 0.1% to 5%, the content of the chain transfer agent is 0.1% to 3%, the content of the catalyst is 0.1% to 3%, and the content of the additive or solvent is 0.1% to 15%.

6. The photopolymer holographic recording medium according to claim 4, wherein: The polyurethane precursor comprises a polyisocyanate compound and a polyol; the polyisocyanate compound is a compound with a low refractive index and two or more isocyanate groups, selected from hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate, butane-1,4-diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate; the polyol is a compound with a low refractive index and two or more hydroxyl functional groups, selected from tetraethylene glycol, trimethylolethane, glycerol, triethanolamine, polyester polyol, polycarbonate polyol, and polyether polyol.

7. The photopolymer holographic recording medium according to claim 4, wherein: The photosensitive initiation system comprises a photosensitizing dye and a photoinitiator; the photosensitizing dye is a dye having a high electron transfer efficiency under light, including at least one of cyanine dyes, fluorescein dyes, coumarin ketone dyes, nitrogen-containing aromatic heterocyclic compounds, aromatic amine compounds, and benzylcycloalkane ketone compounds; the photoinitiator is an initiator that can be activated by actinic radiation and initiate a polymerization reaction of the corresponding polymerizable groups, including at least one of ketone compounds, benzoin and its derivatives, benzyl ketals, acylphosphine oxides, aromatic ammonium borates, chromium salts, aromatic diazonium salts, onium salts, and organic metal compounds.

8. The photopolymer holographic recording medium according to claim 4, wherein: The chain transfer agent is a thiol compound, including at least one of dodecyl mercaptan, mercaptoethanol, hexanethiol, phenylethyl mercaptan, 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, and 4-methyl-4H-1,2,4-triazole-3-thiol.

9. The photopolymer holographic recording medium according to claim 4, wherein: The catalyst is a tertiary amine catalyst and an organic metal catalyst, selected from triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts, and bismuth carboxylate catalysts.

10. The photopolymer holographic recording medium according to claim 4, wherein: The additives include at least one of a defoamer, a leveling agent, a plasticizer, a UV absorber, a light stabilizer and an antioxidant; the solvent includes at least one of petroleum ether, dichloromethane, ethyl acetate, n-hexane, tetrahydrofuran, acetone, benzene, methyl ethyl ketone, methyl formate, methyl propionate, isobutyl formate, butyl chloride, ethyl propionate, ethylene dichloride, isopentyl chloride, methyl carbonate, trichloroethane, carbon tetrachloride, ethylene dichloride, carbon disulfide, 3-propanol, dichloropropane, butanone, ethyl bromide and cyclohexane.

11. A method for preparing a photopolymer holographic recording medium according to any one of claims 1 to 10, characterized in that: The following steps are involved: Weigh each component of the photopolymer holographic recording medium into a container, and stir thoroughly until all components are dissolved; Filter the mixture using a membrane filter; The mixture is coated on a substrate and cured to obtain the photopolymer holographic recording medium.

12. A volume holographic grating, characterized in that: The photopolymer holographic recording medium used in the volume holographic grating includes the photopolymer holographic recording medium according to any one of claims 1 to 10.

13. A volume holographic optical waveguide, characterized in that: The volume holographic optical waveguide comprises the volume holographic grating as claimed in claim 12.

14. A holographic device, characterized in that: The holographic device comprises the volume holographic optical waveguide of claim 13.

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