Photopolymer type holographic recording medium, grating and preparation method and equipment thereof

Abstract

The invention discloses a photopolymer type holographic recording medium, a volume holographic grating, a preparation method of the volume holographic grating and holographic equipment, and relates to the technical field of holographic materials. The photopolymer type holographic recording medium comprises a compound with a plurality of isocyanate reactive functional groups, a polyisocyanate group compound, a polymerizable monomer, a photosensitive initiation system, a chain transfer agent, a catalyst and an additive, wherein the number of the isocyanate reactive functional groups is different from the number of isocyanate groups in the polyisocyanate group compound. According to the volume holographic grating and the manufacturing method thereof, the manufactured volume holographic grating has high refractive index modulation degree for red light, green light and blue light while a laminating process is avoided.

Description

Technical Field

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

[0002] Augmented Reality (AR) technology based on holographic waveguide systems has great application potential. The core optical element of holographic waveguide systems is volume holographic gratings. In order to achieve color display, the volume holographic grating needs to be sensitive to red, green and blue light.

[0003] In the related art, three gratings sensitive to red, green and blue light are first prepared using photopolymers, and then the three gratings are bonded together to achieve color display. However, the bonding accuracy of the three gratings is high, which increases the complexity of the process and results in low preparation efficiency and yield of the photopolymer. Summary of the invention

[0004] Based on this, the present application provides a photopolymer holographic recording medium, a volume holographic grating and a preparation method and a holographic device, which can avoid the use of a lamination process while making the prepared volume holographic grating have a higher refractive index modulation degree for red, green and blue light.

[0005] In a first aspect, the present application provides a photopolymer holographic recording medium, the photopolymer holographic recording medium comprising a compound having multiple isocyanate-reactive functional groups, a polyisocyanate-based compound, a polymerizable monomer, a photosensitive initiation system, a chain transfer agent, a catalyst, and an additive;

[0006] Wherein, the number of the isocyanate reactive functional groups is different from the number of isocyanate groups in the polyisocyanate-based compound.

[0007] In a second aspect, the present application provides a volume holographic grating, wherein the photopolymer holographic recording medium used in the volume holographic grating includes the photopolymer holographic recording medium as described above.

[0008] In a third aspect, the present application provides a volume holographic grating, wherein the volume holographic grating comprises a red light photosensitive photopolymer film, a green light photosensitive photopolymer film, and a blue light photosensitive photopolymer film;

[0009] The red light photosensitive photopolymer film, the green light photosensitive photopolymer film and the blue light photosensitive photopolymer film are stacked, and adjacent film layers are connected via covalent bonds generated by isocyanate reactive functional groups or isocyanate groups.

[0010] In a fourth aspect, the present application provides a method for preparing a volume holographic grating, the method comprising:

[0011] Providing a mixed solution of three photopolymer holographic recording media, wherein the photopolymer holographic recording medium is the photopolymer holographic recording medium described above, and the photosensitive initiation systems of the three photopolymer holographic recording media are a red light photosensitive initiation system, a green light photosensitive initiation system, and a blue light photosensitive initiation system, respectively;

[0012] Providing a substrate, and evenly distributing a mixed solution of a first photopolymer holographic recording medium on the surface of the substrate, so that the first photopolymer holographic recording medium forms a first photopolymer film on the surface of the substrate;

[0013] The mixed solution of the second photopolymer holographic recording medium is uniformly distributed on the surface of the first photopolymer film, so that the second photopolymer holographic recording medium forms a second photopolymer film on the surface of the first photopolymer film, and the residual isocyanate reactive functional groups or isocyanate groups in the first photopolymer film and the second photopolymer film react to connect the first photopolymer film to the second photopolymer film in a covalent bond manner;

[0014] Evenly distributing a mixed solution of a third photopolymer holographic recording medium on the surface of the second photopolymer film, so that the third photopolymer holographic recording medium forms a third photopolymer film on the surface of the second photopolymer film, and the residual isocyanate reactive functional groups or isocyanate groups in the second photopolymer film and the third photopolymer film react to connect the second photopolymer film to the third photopolymer film in a covalent bond manner;

[0015] The multi-layer photopolymer film is exposed to produce a volume holographic grating.

[0016] In a fifth aspect, the present application provides a holographic device, wherein the holographic device comprises the volume holographic grating as described above.

[0017] The present application provides a photopolymer holographic recording medium, a volume holographic grating, a preparation method thereof and a holographic device. The photopolymer holographic recording medium includes a compound having multiple isocyanate-reactive functional groups, a polyisocyanate-based compound, a polymerizable monomer, a photosensitive initiator system, a chain transfer agent, a catalyst and an additive; wherein the number of isocyanate-reactive functional groups is different from the number of isocyanate groups in the polyisocyanate-based compound. Since the number of isocyanate reactive functional groups is different from the number of isocyanate groups, after the isocyanate reactive functional groups in the photopolymer holographic recording medium react with the isocyanate groups, there will still be residual isocyanate reactive functional groups or isocyanate groups. These residual functional groups can react with the residual functional groups in another photopolymer holographic recording medium, so that the photopolymer films are connected by covalent bonds, thereby avoiding the use of a lamination process for grating lamination. At the same time, since each layer of photopolymer film is independent of each other, each layer of photopolymer film can use the refractive index modulation degree of the corresponding layer of photopolymer, without sharing the refractive index modulation degree of a layer of photopolymer, so that the prepared volume holographic grating has a higher refractive index modulation degree and diffraction efficiency for red, green and blue light, thereby improving the display brightness of the AR device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic flow chart of the steps of a method for preparing a volume holographic grating provided in the present application.

[0019] Figure 2 This is a schematic diagram of the UV-visible transmittance curve of sample 1 after recording three types of gratings. DETAILED DESCRIPTION

[0020] 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 only 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.

[0021] 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.

[0022] In the subsequent description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present application, and have no special meanings. Therefore, "module", "component" or "unit" can be used in a mixed manner.

[0023] Augmented reality (AR) is a technology that overlays virtual information onto the real world. It has been widely used in many fields such as gaming, education, retail, and industrial manufacturing. AR devices with color display functions (AR glasses, head-up displays (HUD)) can provide users with a more realistic and rich interactive experience.

[0024] Holographic waveguide technology is one of the development directions of AR devices. It has the obvious advantages of simple preparation process and low cost. In addition, its high transparency and high diffraction efficiency make it easy to achieve a large field of view while maintaining a light and thin structure. The core optical element of the holographic waveguide system is the volume holographic grating. In order to achieve color display, the volume holographic grating needs to be sensitive to red, green and blue light. .

[0025] In the related art, a method of preparing three gratings sensitive to red, green and blue light in the same layer of photopolymer is also provided. However, this solution requires the three gratings to share a layer of photopolymer with a refractive index modulation, which will make the diffraction efficiency of the three gratings low, resulting in low display brightness of the final AR device.

[0026] In order to solve the above-mentioned problems, the embodiments of the present application provide a photopolymer holographic recording medium, a volume holographic grating and a preparation method thereof, and a holographic device, which can avoid the use of a bonding process for grating bonding, and the prepared volume holographic grating has a high refractive index modulation degree and diffraction efficiency for red, green and blue light, and can also improve the display brightness of AR devices.

[0027] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0028] An embodiment of the present application provides a photopolymer holographic recording medium, which includes a compound having multiple isocyanate-reactive functional groups, a polyisocyanate-based compound, a polymerizable monomer, a photosensitive initiator system, a chain transfer agent, a catalyst, and an additive; wherein the number of isocyanate-reactive functional groups is different from the number of isocyanate groups in the polyisocyanate-based compound.

[0029] It should be noted that the photopolymer holographic recording medium material usually contains a film-forming resin with a low refractive index and a writing monomer with a high refractive index. In the embodiment of the present application, the compound having multiple isocyanate reactive functional groups and the polyisocyanate compound can form the film-forming resin, and the polymerizable monomer is equivalent to the writing monomer.

[0030] In the embodiment of the present application, by controlling the number of isocyanate reactive functional groups and the number of isocyanate groups to be different, after the isocyanate reactive functional groups in each photopolymer holographic recording medium react with the isocyanate groups, there will be residual unreacted isocyanate reactive functional groups or isocyanate groups. The residual unreacted functional groups in one photopolymer holographic recording medium will react with the residual unreacted functional groups in another photopolymer holographic recording medium, so that the photopolymer films are connected in a covalent bond manner, thereby avoiding the use of a lamination process for grating lamination. At the same time, since each layer of photopolymer film is independent of each other, each layer of photopolymer film can use the refractive index modulation of the corresponding layer of photopolymer, without sharing the refractive index modulation of a layer of photopolymer, so that the prepared volume holographic grating has a high refractive index modulation and diffraction efficiency for red, green and blue light, thereby improving the display brightness of the AR device.

[0031] In some embodiments, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups is 1:(1.01-1.5) or (1.01-1.5): 1. This can control the number of residual unreacted functional groups in the photopolymer holographic recording medium to avoid a large number of unreacted functional groups remaining, thereby affecting the holographic recording performance.

[0032] Illustratively, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups can be 1:1.01, 1:1.35, 1:1.5, 1.01:1, 1.35:1, 1.5:1, and is not specifically limited herein.

[0033] In some embodiments, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups is 1: (1.01-1.3) or (1.01-1.3): 1. This can control the number of residual unreacted functional groups in the photopolymer holographic recording medium, thereby making each layer of the photopolymer film well connected and having better holographic recording performance.

[0034] Illustratively, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups can be 1:1.01, 1:1.2, 1:1.3, 1.01:1, 1.2:1, 1.3:1, and is not specifically limited herein.

[0035] In some embodiments, the mass ratio of the compound having multiple isocyanate-reactive functional groups, the polyisocyanate-based compound, the polymerizable monomer, the photosensitive initiator system, the chain transfer agent, the catalyst and the additive is (30-70): (10-50): (0.1-60): (0.1-4): (0.1-3): (0.1-3): (0.1-7).

[0036] The raw materials of each component in the photopolymer holographic recording medium are described below by taking parts by weight as an example.

[0037] For example, the compound having a plurality of isocyanate-reactive functional groups may be present in an amount of 30 parts to 70 parts, such as 30 parts, 40 parts, 50 parts, 60 parts, or 70 parts.

[0038] Exemplarily, the polyisocyanate compound may be in an amount of 10 parts to 50 parts, such as 10 parts, 20 parts, 30 parts, 40 parts, or 50 parts.

[0039] Illustratively, the polymerizable monomer may be 0.1 parts to 60 parts, such as 0.1 parts, 10 parts, 30 parts, 50 parts, or 60 parts.

[0040] Exemplarily, the photosensitive initiator system may be 0.1 parts to 4 parts, such as 0.1 parts, 1 parts, 2.5 parts, 3 parts, or 4 parts.

[0041] Exemplarily, the chain transfer agent may be 0.1 parts to 3 parts, such as 0.1 parts, 1 parts, 2 parts, 2.5 parts, or 3 parts.

[0042] Exemplarily, the catalyst may be in an amount of 0.1 to 3 parts, such as 0.1, 1, 2, 2.5 or 3 parts.

[0043] Exemplarily, the additive may be 0.1 parts to 7 parts, such as 0.1 parts, 1 parts, 3 parts, 5.5 parts, or 7 parts.

[0044] It is understandable that the present application can achieve full synergistic effect of the components by reasonably controlling the addition amount of each component, and will not cause the holographic performance of the final photopolymer holographic recording medium to deteriorate due to too much or too little of a certain component, thereby ensuring that the comprehensive holographic performance of the final photopolymer holographic recording medium is better.

[0045] For example, by controlling the amount of the compound having multiple isocyanate-reactive functional groups to 30 to 70 parts and the amount of the polyisocyanate-based compound to 10 to 50 parts, the compound having multiple isocyanate-reactive functional groups can react with the polyisocyanate-based compound to form a film-forming resin, thereby providing support for the other components.

[0046] For example, by controlling the polymerizable monomer to be between 0.1 and 60 parts, the polymerizable monomer can form a writing monomer with a relatively high refractive index, thereby providing a material basis for forming a volume holographic grating with refractive index modulation.

[0047] For example, by controlling the photosensitive initiator system to 0.1 to 4 parts, it can absorb an appropriate number of photons during exposure and control the polymerization reaction at a certain speed, so that the grating can be formed quickly and obtain a higher diffraction efficiency. In addition, it can also ensure that the final holographic recording medium has the required light transmittance and that the grating has a certain diffraction efficiency.

[0048] For example, by controlling the chain transfer agent to 0.1 to 3 parts, the polymer chain length can be controlled within a certain reasonable range and the degree of polymerization can be effectively prevented, thereby ensuring that the final holographic recording medium has the required optical properties and diffraction efficiency.

[0049] For example, controlling the catalyst at 0.1 to 3 parts 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 the monomers in the bright and dark areas and realizing a refractive index modulated phase-type volume holographic grating.

[0050] For example, controlling the additive to 0.1 to 7 parts, 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.

[0051] In some embodiments, the photosensitive initiation system includes a component photosensitizer and / or photoinitiator. Photosensitizer is also called dye, photosensitizer dye.

[0052] In some embodiments, the mass ratio of photosensitizer to photoinitiator is (0.001-1):(0.1-3). By controlling the mass ratio of photosensitizer to photoinitiator within the above range, the concentration of photosensitizer can be effectively controlled, so that during holographic exposure, the number of absorbed photons is controlled within a suitable range, the speed of polymerization reaction is controlled within a reasonable range, and the speed of grating formation is controlled within a certain range, so as to ensure the light transmittance of photopolymer holographic recording medium and obtain excellent diffraction efficiency. In a more specific example, the mass of photosensitizer is 1 / 10 to 1 / 3 of the mass of photoinitiator, such as 1 / 10, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, 1 / 4 or 1 / 3, etc.

[0053] Exemplarily, the photosensitive initiation system may be composed of a photosensitizer, a photoinitiator and a co-initiator; wherein, for photosensitive initiation systems of different wavelengths, the photosensitive initiation system may be composed of a photosensitizer and a photoinitiator, or may be composed of a photosensitizer and a co-initiator. Different wide-band responses may also be achieved by adjusting the type of photosensitizer. It should be noted that when a photoinitiator with an adapted wavelength is selected in the raw material of the photopolymer type holographic recording medium, the photosensitizer may not be added.

[0054] Exemplarily, the photosensitizer is a dye with high electron transfer efficiency under light, 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.

[0055] Exemplarily, the photoinitiator is an initiator that can be activated by actinic radiation and initiate 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 salts, aryl diazonium salts, onium salts, organometallic compounds or any mixture of these compounds in any proportion.

[0056] For example: the photoinitiator includes one or more of benzophenone, alkyl benzophenone, 4,4'-bis(dimethylamino)benzophenone, anthrone and halogenated benzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxide, phenyl dihydroxyacetate, camphorquinone, α-aminoalkyl phenone, α,α-dialkoxyacetophenone, α-hydroxyalkyl phenone, triphenylhexyl borate tetrabutylammonium, tri-(3-fluorophenyl)hexyl borate tetrabutylammonium, tri-(3-chloro-4-methylphenyl)hexyl borate tetrabutylammonium, ferrocenyl compounds, iodonium salts, sulfonium salts, and hexaarylbiimidazoles.

[0057] Exemplarily, the co-initiator is mainly an amine substance, including but not limited to ethylenediamine, propylenediamine, isopropylenediamine, urea oxide, triethanolamine, triisopropanolamine, N-methyldiethanolamine, N,N-dimethylaniline and its variants, N-phenylglycine, and L-cysteine.

[0058] In some embodiments, the photosensitive initiation system includes a red light photosensitive initiation system, a green light photosensitive initiation system or a blue light photosensitive initiation system, the photosensitizer of the red light photosensitive initiation system includes a red light photosensitizing dye, the photosensitizer of the green light photosensitive initiation system includes a green light photosensitizing dye, and the photosensitizer of the blue light photosensitive initiation system includes a blue light photosensitizing dye.

[0059] In the embodiments of the present application, if the prepared photopolymer holographic recording medium needs to be sensitive to red light, the photosensitive initiation system adopts a red light photosensitive initiation system; if the prepared photopolymer holographic recording medium needs to be sensitive to green light, the photosensitive initiation system adopts a green light photosensitive initiation system; if the prepared photopolymer holographic recording medium needs to be sensitive to blue light, the photosensitive initiation system adopts a blue light photosensitive initiation system.

[0060] In some embodiments, the red light photosensitizing dye can be selected from one or more of methylene blue, cyanine dye, squaryl cyanine dye, porphine dye, and porphyrin dye; the green light photosensitizing dye can be selected from one or more of benzylcycloalkane ketone compounds, erythrosine, rose bengal, eosin, and rhodamine B; the blue light photosensitizing dye can be selected from one or more of benzylcycloalkane ketone compounds, 3,3′-carbonylbis(7-diethylaminocoumarin), and 5'-riboflavin monophosphate sodium salt.

[0061] It should be noted that, in some specific cases, the photosensitizer of the green light photosensitizer system may not include the green light photosensitizer dye, and the photosensitizer of the blue light photosensitizer system may not include the blue light photosensitizer dye, so that the prepared photopolymer holographic recording medium can be sensitive to green and blue light.

[0062] In some embodiments, the isocyanate-reactive functional group is a hydroxyl group or a thiol group, and the compound having multiple isocyanate-reactive functional groups includes a compound having a refractive index less than that of the polymerizable monomer and having two or more isocyanate-reactive functional groups.

[0063] For example, the refractive index of the compound having multiple isocyanate-reactive functional groups is generally less than or equal to 1.55.

[0064] In some embodiments, the compound having multiple isocyanate-reactive functional groups can be selected from 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1,6-hexanediol, 2,5-hexanediol, 1,4-cyclohexanediol, 1,8-octanediol, 1,7-heptanediol, 1,3-butanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol, 1,3-cyclopentanediol, tetraethylene glycol, trimethylolethane, trimethylol One or more of propane, glycerol, triethanolamine, polyester polyols with a molecular weight of 100 to 2000, polycarbonate polyols, polyether polyols, 2,3-dithio (2-mercapto)-1-propanethiol, 1,2-octanedithiol, 2,5-dimethylmercapto-1,4-dithiane, 1,2-butanethiol, 1,3-butanethiol, 3,7-dithia-1,9-nonanethiol, and 2,3-butanethiol.

[0065] In some embodiments, the polyisocyanate-based compound includes a compound having a refractive index lower than that of the polymerizable monomer and having two or more isocyanate groups.

[0066] For example, the refractive index of the polyisocyanate-based compound is generally less than or equal to 1.55.

[0067] In some embodiments, the polyisocyanate compound can be selected from one or more of hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate, butane-1,4-diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0068] In some embodiments, the polymerizable monomer can be selected from 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.

[0069] For example, the alkenylnaphthalene compound may be 1-vinylnaphthalene, 2-vinylnaphthalene, and the like.

[0070] For example, the alkenyl anthracene compound may be 2-vinyl anthracene, 9-vinyl anthracene, or the like.

[0071] Exemplarily, 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 and the like.

[0072] Exemplarily, the methacrylic acid compound can be selected from methacrylic acid and its derivatives; exemplary, 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.

[0073] Exemplarily, 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, and the like.

[0074] In some embodiments, the 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, and 4-methyl-4H-1,2,4-triazole-3-thiol. Controlling a certain amount of the chain transfer agent can control the polymer chain length within a certain reasonable range and effectively prevent excessive polymerization, thereby ensuring that the final holographic recording medium has the desired optical properties and diffraction efficiency.

[0075] In some embodiments, the 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. Controlling a certain amount of catalyst can effectively increase the reaction rate of related components and increase the consumption rate of related components after exposure, thereby quickly forming a concentration difference of monomers in bright and dark areas to produce a photopolymer.

[0076] In some embodiments, the additive includes one or more of a defoamer, a leveling agent, a plasticizer, and a water scavenger.

[0077] For example, when the additive includes a defoaming agent, the content of the defoaming agent is no more than 3% based on the total mass of the photopolymer-type holographic recording medium.

[0078] Exemplarily, when the additive includes a leveling agent, the content of the leveling agent is no more than 3% based on the total mass of the photopolymer-type holographic recording medium.

[0079] Exemplarily, when the additive includes a plasticizer, the content of the plasticizer is no more than 3% based on the total mass of the photopolymer-type holographic recording medium.

[0080] Exemplarily, the defoaming agent is a silicone defoaming agent, such as 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 a mixture of these defoaming agents in any proportion.

[0081] Exemplarily, the leveling agent is an organosilicon 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 a mixture of these surface additives in any proportion.

[0082] Exemplarily, the plasticizer is toluene, xylene, dimethylformamide, dimethylacetamide, glycerol, phthalate or a mixture of these compounds in any ratio.

[0083] Exemplary dehydrating agents include, but are not limited to, p-toluenesulfonyl isocyanate, triethyl orthoformate, CUWR-WB20 dehydrating agent of Guangzhou Yourun Synthetic Materials Co., Ltd., ALT-201 dehydrating agent of Anxiang Elite Chemical Co., Ltd., PCCI dehydrating agent of Shanghai Ruhr Chemical Trading Co., Ltd., and the like.

[0084] The following describes a method for preparing the photopolymer holographic recording medium of the present application comprising the aforementioned multiple components.

[0085] like Figure 1 As shown, the embodiment of the present application also provides a method for preparing a volume holographic grating, comprising the following steps:

[0086] S101, providing a mixed solution of three photopolymer holographic recording media, wherein the photosensitive initiation systems of the three photopolymer holographic recording media are a red light photosensitive initiation system, a green light photosensitive initiation system, and a blue light photosensitive initiation system;

[0087] S102, providing a substrate, and evenly distributing a mixed solution of a first photopolymer holographic recording medium on a surface of the substrate to form a first photopolymer film on the surface of the substrate;

[0088] S103, uniformly distributing the mixed solution of the second photopolymer holographic recording medium on the surface of the first photopolymer film to form a second photopolymer film on the surface of the first photopolymer film, and the residual isocyanate reactive functional groups or isocyanate groups in the first photopolymer film and the second photopolymer film react to connect the first photopolymer film to the second photopolymer film in a covalent bond manner;

[0089] S104, uniformly distributing the mixed solution of the third photopolymer holographic recording medium on the surface of the second photopolymer film to form a third photopolymer film on the surface of the second photopolymer film, and the residual isocyanate reactive functional groups or isocyanate groups in the second photopolymer film and the third photopolymer film react to connect the second photopolymer film to the third photopolymer film in a covalent bond manner;

[0090] S105, performing exposure processing on the multilayer photopolymer film to obtain a volume holographic grating.

[0091] In the embodiment of the present application, the first photopolymer holographic recording medium, the second photopolymer holographic recording medium and the third photopolymer holographic recording medium have different photosensitive initiation systems. The composition of the photopolymer holographic recording medium can refer to the above embodiment and will not be repeated here.

[0092] Exemplarily, the photosensitive initiation systems of the first photopolymer holographic recording medium, the second photopolymer holographic recording medium and the third photopolymer holographic recording medium can be a red light photosensitive initiation system, a green light photosensitive initiation system and a blue light photosensitive initiation system, respectively, or can be a blue light photosensitive initiation system, a red light photosensitive initiation system and a green light photosensitive initiation system, respectively, that is, the order of forming the photopolymer film on the substrate and the stacking order can be determined according to the coating order, and are not specifically limited herein.

[0093] Exemplarily, two beams of light are used for coherent exposure, and after the exposure, polymerization is performed by ultraviolet light. After the polymerization is completed, a volume holographic grating can be produced.

[0094] It should be noted that residual isocyanate reactive functional groups or isocyanate groups exist in the first photopolymer film, the second photopolymer film and the third photopolymer film.

[0095] From the above, it can be seen that the method for preparing the volume holographic grating proposed in this application has few preparation steps, simple operation, and easy implementation conditions, and is convenient for preparing a volume holographic grating with high refractive index modulation and diffraction efficiency for red, green and blue light.

[0096] An embodiment of the present application provides a volume holographic grating, wherein the photopolymer holographic recording medium used in the volume holographic grating includes the photopolymer holographic recording medium described in any of the above embodiments or is prepared by the preparation method of the volume holographic grating described in any of the above embodiments.

[0097] The embodiment of the present application further provides a volume holographic grating, which includes a red light photosensitive photopolymer film, a green light photosensitive photopolymer film, and a blue light photosensitive photopolymer film.

[0098] The red light photosensitive photopolymer film, the green light photosensitive photopolymer film and the blue light photosensitive photopolymer film are stacked, and adjacent films are connected via covalent bonds generated by isocyanate reactive functional groups or isocyanate groups.

[0099] Exemplarily, the stacking order of the red light photosensitive photopolymer film, the green light photosensitive photopolymer film and the blue light photosensitive photopolymer film can be determined according to the coating order. For example, the stacking order from bottom to top can be: substrate—red light photosensitive photopolymer film—green light photosensitive photopolymer film—blue light photosensitive photopolymer film, or it can be substrate—blue light photosensitive photopolymer film—red light photosensitive photopolymer film—green light photosensitive photopolymer film, which is not specifically limited here.

[0100] In some embodiments, the red light photosensitive photopolymer film, the green light photosensitive photopolymer film, and the blue light photosensitive photopolymer film all include different numbers of isocyanate reactive functional groups and isocyanate groups.

[0101] In some embodiments, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups is 1:(1.01-1.5) or (1.01-1.5): 1. This can control the number of residual unreacted functional groups in the photopolymer holographic recording medium to avoid a large number of unreacted functional groups remaining, thereby affecting the holographic recording performance.

[0102] Illustratively, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups can be 1:1.01, 1:1.35, 1:1.5, 1.01:1, 1.35:1, 1.5:1, and is not specifically limited herein.

[0103] In some embodiments, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups is 1: (1.01-1.3) or (1.01-1.3): 1. This can control the number of residual unreacted functional groups in the photopolymer holographic recording medium, thereby making each layer of the photopolymer film well connected and having better holographic recording performance.

[0104] Illustratively, the ratio of the number of isocyanate reactive functional groups to the number of isocyanate groups can be 1:1.01, 1:1.2, 1:1.3, 1.01:1, 1.2:1, 1.3:1, and is not specifically limited herein.

[0105] As can be seen from the above, the volume holographic grating proposed in this application has a structure of three layers of photosensitive photopolymer films, and the photopolymer films are connected by covalent bonds. At the same time, the volume holographic grating has a high refractive index modulation and diffraction efficiency for red, green and blue light.

[0106] An embodiment of the present application further provides a holographic device, which includes the volume holographic grating described in any of the above embodiments.

[0107] The embodiments of the present application are described below through specific examples.

[0108] Embodiment 1: Six kinds of photopolymer holographic recording media 1-6 are provided. The preparation method of the photopolymer holographic recording media is to mix all the above-provided components uniformly. The raw material components are shown in Table 1-Table 6.

[0109] Table 1

[0110]

[0111] Table 2

[0112]

[0113] Table 3

[0114]

[0115]

[0116] Table 4

[0117]

[0118] Table 5

[0119]

[0120] Table 6

[0121]

[0122] It should be noted that, in the component a) compound having multiple isocyanate-reactive functional groups and the component b) polyisocyanate-based compound of the photopolymer-type holographic recording media in Tables 1 to 6, the number of isocyanate-reactive functional groups is different from the number of isocyanate groups. Moreover, the photosensitive initiation system of the photopolymer-type holographic recording media in Tables 1 and 2 is a red light photosensitive initiation system, the photosensitive initiation system of the photopolymer-type holographic recording media in Tables 3 and 4 is a green light photosensitive initiation system, and the photosensitive initiation system of the photopolymer-type holographic recording media in Tables 5 and 6 is a blue light photosensitive initiation system.

[0123] Example 2: Samples 1-8 are prepared using photopolymer holographic recording media 1-6, wherein the photopolymer includes a first photopolymer film, a second photopolymer film and a third photopolymer film respectively formed by a mixed solution of any one of the above-mentioned photopolymer holographic recording media 1-6.

[0124] The first photopolymer film is disposed on a substrate, and the first photopolymer film, the second photopolymer film and the third photopolymer film are stacked in sequence, and adjacent films are connected by covalent bonds, see Table 7 for details.

[0125] Table 7

[0126]

[0127] Comparative Example:

[0128] Comparative Example Samples 9-16 were prepared using photopolymer holographic recording media 7-12, see Table 8 for details.

[0129] Among them, the components used in the photopolymer holographic recording medium 7-12 and the photopolymer holographic recording medium 1-6 basically correspond to each other, except that in component a) the compound having multiple isocyanate-reactive functional groups and component b) the polyisocyanate-based compound, the number of isocyanate-reactive functional groups is the same as the number of isocyanate groups, that is, the photopolymer film formed by the photopolymer holographic recording medium 7-12 has no residual isocyanate-reactive functional groups and isocyanate groups.

[0130] Table 8

[0131]

[0132]

[0133] Since the photopolymer films formed by the photopolymer holographic recording media 7-12 have no residual isocyanate reactive functional groups and isocyanate groups, the first photopolymer film, the second photopolymer film and the third photopolymer film formed by the photopolymers 9-16 are all connected by a bonding process.

[0134] Test example:

[0135] The holographic performance parameters of samples 1 to 6 in Example 2 were tested, and the results are shown in Tables 9 and Figure 2 The adhesion between adjacent photopolymer films in samples 1-16 was tested, and the results are shown in Table 10.

[0136] (1) The method for testing the performance of the holographic recording medium comprises the following steps:

[0137] Solid-state lasers with wavelengths of 633nm, 532nm, and 457nm were used as light sources. After passing through a beam expander, beam splitter, and half-wave plate, two beams with the same light intensity and a diameter of 8mm were obtained. The two beams intersected in the prepared holographic recording medium for exposure, and the light intensity was 2.91mW / cm 2 For each group of samples, exposure was performed at 633 nm, 532 nm, and 457 nm in sequence. After exposure, the UV-visible transmittance curve of the photobleaching test sample was obtained, and the single grating diffraction efficiency (η) of the photopolymer sample with different wavelength sensitivity was calculated by formula (1).

[0138]

[0139] Where η is the diffraction efficiency, I d is the diffracted light, I t For transmitted light.

[0140] (2) The adhesion between adjacent photopolymer films in a photopolymer is tested using a cross-sectional test.

[0141] The 100-grid test is the most common method for testing the adhesion of paint films. According to international standards, it can be divided into 6 levels, with units of 0B, 1B, 2B, 3B, 4B, and 5B. The higher the level, the stricter the requirements. Level 5B means that the edge of the line is smooth, and there is no paint film falling off at the edge and intersection of the line. Level 4B means that there are small pieces of paint film falling off at the intersection of the line, and the total falling area is less than 5%. Level 3B means that there are small pieces of paint film falling off at the edge and intersection of the line, and the total falling area is between 5% and 15%. Level 2B means that there are pieces of paint film falling off at the edge and intersection of the line, and the total falling area is between 15% and 35%. Level 1B means that there are pieces of paint film falling off at the edge and intersection of the line, and the total falling area is between 35% and 65%. Level 0B means that the falling area exceeds the 1B standard.

[0142] The Baige test method includes the following steps:

[0143] Use a grid cutter to cut a cross grid pattern on the coating, and make the cut to the photopolymer film; use a brush to brush five times in each diagonal direction, stick tape on the cut and then pull it apart (it is specified to use 3M600 or 610 tape to stick in the grid and quickly pull up the 3M tape); observe the situation of the grid area, and use a magnifying glass to observe the amount of tape stuck.

[0144] Table 9

[0145]

[0146] Table 10

[0147] sample Adhesion between photopolymer films Sample 1 5B Sample 2 5B Sample 3 5B Sample 4 5B Sample 5 5B Sample 6 5B Sample 7 5B Sample 8 5B Sample 9 0B Sample 10 0B Sample 11 0B Sample 12 0B Sample 13 0B Sample 14 0B Sample 15 0B Sample 16 0B

[0148] The photopolymer holographic recording medium provided in the embodiment of the present application has high sensitivity. Specifically, the diffraction efficiency of the holographic recording medium can be adjusted between 10% and 100% according to actual needs, and the exposure amount is less than 30mJ / cm 2 , and the layers of photopolymer films in the volume holographic grating provided in the embodiment of the present application are connected by covalent bonds, and each layer of the photopolymer film is independent of each other and can use the refractive index modulation degree of the photopolymer of the corresponding layer, such as Figure 2 As shown, the volume holographic grating pair provided by the present application has a relatively high refractive index modulation degree and diffraction efficiency for red, green and blue light.

[0149] It should be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0150] 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.

[0151] The above is only a specific embodiment 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 replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A photopolymer holographic recording medium, characterized in that: The photopolymer holographic recording medium comprises a compound having multiple isocyanate-reactive functional groups, a polyisocyanate-based compound, a polymerizable monomer, a photosensitive initiation system, a chain transfer agent, a catalyst and an additive; Wherein, the number of the isocyanate reactive functional groups is different from the number of isocyanate groups in the polyisocyanate-based compound.

2. The photopolymer holographic recording medium according to claim 1, wherein: The ratio of the number of the isocyanate reactive functional groups to the number of the isocyanate groups is 1:(1.01-1.5) or (1.01-1.5):

1.

3. The photopolymer holographic recording medium according to claim 2, wherein: The ratio of the number of the isocyanate reactive functional groups to the number of the isocyanate groups is 1:(1.01-1.3) or (1.01-1.3):

1.

4. The photopolymer holographic recording medium according to claim 1, wherein: The mass ratio of the compound having multiple isocyanate-reactive functional groups, the polyisocyanate-based compound, the polymerizable monomer, the photosensitive initiator system, the chain transfer agent, the catalyst and the additive is (30-70): (10-50): (0.1-60): (0.1-4): (0.1-3): (0.1-3): (0.1-7).

5. The photopolymer holographic recording medium according to claim 1, wherein: The photosensitive initiation system includes a photosensitizer and / or a photoinitiator; When the photosensitive initiation system includes a photosensitizer and a photoinitiator, the mass ratio of the photosensitizer to the photoinitiator is (0.001-1):(0.1-3).

6. The photopolymer holographic recording medium according to claim 5, characterized in that: The photosensitive initiation system includes a red light photosensitive initiation system, a green light photosensitive initiation system or a blue light photosensitive initiation system, the photosensitizer of the red light photosensitive initiation system includes a red light photosensitizing dye, the photosensitizer of the green light photosensitive initiation system includes a green light photosensitizing dye, and the photosensitizer of the blue light photosensitive initiation system includes a blue light photosensitizing dye; Wherein, the red light photosensitizing dye is at least one of methylene blue, cyanine dye, squarylium cyanine dye, porphine dye and porphyrin dye; The green light photosensitizing dye is at least one of benzalkyne cycloalkane ketone compounds, erythrosine, rose bengal, eosin, and rhodamine B; The blue light photosensitizing dye is at least one of benzalkyne cycloalkane ketone compounds, 3,3'-carbonyl bis(7-diethylaminocoumarin), and 5'-riboflavin monophosphate sodium salt.

7. The photopolymer holographic recording medium according to claim 1, wherein: The isocyanate reactive functional group is a hydroxyl group or a mercapto group, and the compound having multiple isocyanate reactive functional groups includes a compound having a refractive index less than that of the polymerizable monomer and having two or more isocyanate reactive functional groups.

8. The photopolymer holographic recording medium according to claim 7, characterized in that: The compound having multiple isocyanate-reactive functional groups is 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1,6-hexanediol, 2,5-hexanediol, 1,4-cyclohexanediol, 1,8-octanediol, 1,7-heptanediol, 1,3-butanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol, 1,3-cyclopentanediol, tetraethylene glycol, trimethylolethane, trimethylolpropane, At least one of glycerol, triethanolamine, polyester polyol with a molecular weight of 100 to 2000, polycarbonate polyol, polyether polyol, 2,3-dithio(2-mercapto)-1-propanethiol, 1,2-octanedithiol, 2,5-dimethylmercapto-1,4-dithiane, 1,2-butanethiol, 1,3-butanethiol, 3,7-dithia-1,9-nonanethiol, and 2,3-butanethiol.

9. The photopolymer holographic recording medium according to claim 1, wherein: The polyisocyanate-based compound includes a compound having a refractive index lower than that of the polymerizable monomer and having two or more isocyanate groups.

10. The photopolymer holographic recording medium according to claim 9, wherein: The polyisocyanate compound is at least one of 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.

11. A method for preparing a volume holographic grating, characterized in that: The method comprises: Providing a mixed solution of three photopolymer holographic recording media, wherein the photopolymer holographic recording medium is the photopolymer holographic recording medium according to any one of claims 1 to 10, and the photosensitive initiation systems of the three photopolymer holographic recording media are a red light photosensitive initiation system, a green light photosensitive initiation system and a blue light photosensitive initiation system respectively; Providing a substrate, and uniformly distributing a mixed solution of a first photopolymer type holographic recording medium on the surface of the substrate to form a first photopolymer film on the surface of the substrate; The mixed solution of the second photopolymer holographic recording medium is uniformly distributed on the surface of the first photopolymer film to form a second photopolymer film on the surface of the first photopolymer film, and the residual isocyanate reactive functional groups or isocyanate groups in the first photopolymer film and the second photopolymer film react to connect the first photopolymer film to the second photopolymer film in a covalent bond manner; The mixed solution of the third photopolymer holographic recording medium is uniformly distributed on the surface of the second photopolymer film to form a third photopolymer film on the surface of the second photopolymer film, and the residual isocyanate reactive functional groups or isocyanate groups in the second photopolymer film and the third photopolymer film react to connect the second photopolymer film to the third photopolymer film in a covalent bond manner; The multi-layer photopolymer film is exposed to produce a volume holographic grating.

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 as described in any one of claims 1 to 10 or is prepared by the method for preparing a volume holographic grating as described in claim 11.

13. A volume holographic grating, characterized in that: The volume holographic grating comprises a red light photosensitive photopolymer film, a green light photosensitive photopolymer film and a blue light photosensitive photopolymer film; The red light photosensitive photopolymer film, the green light photosensitive photopolymer film and the blue light photosensitive photopolymer film are stacked, and adjacent films are connected via covalent bonds generated by isocyanate reactive functional groups or isocyanate groups.

14. The volume holographic grating according to claim 13, characterized in that: The red light photosensitive photopolymer film, the green light photosensitive photopolymer film and the blue light photosensitive photopolymer film all include different numbers of isocyanate reactive functional groups and isocyanate groups.

15. The volume holographic grating according to claim 13, characterized in that: The ratio of the number of the isocyanate reactive functional groups to the number of the isocyanate groups is 1:(1.01-1.5) or (1.01-1.5):

1.

16. The volume holographic grating according to claim 15, characterized in that: The ratio of the number of the isocyanate reactive functional groups to the number of the isocyanate groups is 1:(1.01-1.3) or (1.01-1.3):

1.

17. A holographic device, characterized in that: The holographic device comprises a volume holographic grating as claimed in any one of claims 12-16.

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