Photopolymer material, application thereof and volume holographic grating

Abstract

The invention discloses a photopolymer material, application thereof and a volume holographic grating, and relates to the technical field of polymer photosensitive materials. The photopolymer material comprises the following raw materials: a binder, an active monomer, a photoinitiator, a photosensitizer, a hydrogen donor and a sensitizer, the molar ratio of the active monomer to the photoinitiator is (8-12): 1; the molar ratio of the photosensitizer to the photoinitiator is 1: (15-25); the active monomer comprises a high-refractive-index monomer with the refractive index of 1.55-1.72 and a low-refractive-index monomer with the refractive index of 1.44-1.50, and the molar ratio of the high-refractive-index monomer to the low-refractive-index monomer is (0.7-1.3): 1. The photopolymer material meeting holographic recording can be prepared, and the prepared material is good in heat resistance, rapid in film forming, short in oxygen isolation exposure response time (as long as several seconds), high in refractive index modulation degree, high in sensitivity, high in diffraction efficiency, good in mechanical property and high in transmittance and can be prepared in a large area.

Description

Technical Field

[0001] This invention relates to the field of polymer photosensitive materials technology, and more specifically, to a photosensitive polymer material and its applications, and a volume holographic grating. Background Technology

[0002] Geometric waveguides transmit images through array reflection. However, the processes of coating, bonding, and parallel control between micromirror arrays are complex, easily leading to ghosting and image distortion, resulting in low product yield. SRG diffraction waveguides have high production costs and complex assembly and calibration processes. To reduce mass production costs, volume holographic grating waveguides (or holographic waveguides for short), which use volume holographic gratings as coupling elements, have received widespread attention in the HMD-AR R&D field in recent years.

[0003] Holographic techniques used to fabricate VHGs involve the interference of two coherent plane waves at a specific angle, with the interference fringes recorded in a photosensitive material. The material's refractive index changes according to the light intensity distribution, ultimately forming a two-dimensional periodic grating structure. The main challenge in fabricating VHG holographic waveguides lies in the development and formulation of the holographic photosensitive material. Typical holographic recording media include: silver halide emulsions, dichromate gelatin, photodegradable polymers, photoconductive thermoplastics, photoisomerized materials, photorefractive materials (including liquid crystals), metasurface materials, and photopolymers.

[0004] Among these, silver halide latex has a complex post-processing process and poor light transmittance; dichromate gelatin, photodegradable polymers, photoconductive thermoplastics, and photoisomerized materials have low photosensitivity and refractive index modulation; photorefractive materials require an additional external electric field, resulting in complex equipment and poor safety; and metasurface materials are difficult to construct and have complex processes. Photopolymers, on the other hand, have many advantages, including high photosensitivity, high resolution, good light transmittance, simple preparation processes, broad spectral response, and dynamic tunability. Volume holographic grating waveguides (VHGs) achieve high diffraction efficiency and large refractive index modulation through photopolymers. Bayfol® HX series polyurethane-based holographic films (Δn > 0.03, thickness 16 μm) have been introduced abroad, while the performance of domestic materials still needs improvement. Photopolymer technology is driving the development of waveguides towards high performance and low cost, but its large-scale application still requires solving problems such as material weather resistance and process compatibility.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a photopolymer material and its applications, as well as a volume holographic grating.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a photopolymer material, the raw materials of which include: a binder, an active monomer, a photoinitiator, a photosensitizer, a hydrogen donor, and a sensitizer; the molar ratio of the active monomer to the photoinitiator is 8~12:1; the molar ratio of the photosensitizer to the photoinitiator is 1:15~25; the active monomer includes a high refractive index monomer with a refractive index of 1.55~1.72 and a low refractive index monomer with a refractive index of 1.44~1.50, and the molar ratio of the high refractive index monomer to the low refractive index monomer is 0.7~1.3:1.

[0008] In an optional embodiment, the raw materials, by mass percentage, comprise: 42%-58% binder, 32%-50% active monomer, 3.0%-6.5% photoinitiator, 0.15%-0.5% photosensitizer, 0.7%-1.8% hydrogen donor, and 1.5%-2.2% sensitizer.

[0009] In an optional embodiment, the high refractive index monomer is selected from one or more of the following: benzyl acrylate, 2-phenoxyethyl acrylate, 2-(phenylmercapto)ethyl acrylate, o-phenylphenoxyethyl acrylate, phenoxybenzyl acrylate, biphenylmethanol acrylate, [1,1′-biphenyl]-4,4′-dimethylbis(2-acryloyloxyethane), 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, and N-vinylcarbazole; And / or, the low refractive index monomer is selected from one or more of the following: tetrahydrofuran acrylate, cyclotrimethylolpropane formal acrylate, methoxy polyethylene glycol acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, isobornyl acrylate, isooctadecyl acrylate, 2-acryloylethoxysuccinate, hexafluorobutyl acrylate, and 2,2,2-trifluoroethyl acrylate and lauryl acrylate; And / or, the photosensitizer is selected from one or more of Alginate B, Bengal Rose Red, Eosin Y, and Saffron Red.

[0010] In an optional embodiment, the photoinitiator is a hexaarylbisimidazole photoinitiator; the hexaarylbisimidazole photoinitiator includes one or more of o-chlorohexaarylbisimidazole (BCIM), 2,2',4,4'-tetra(2-chlorophenyl)-5,5'-bis(3,4-dimethoxyphenyl)-1,1'-diimidazole (TCTM), 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-diimidazole (TCDM), m-Me-O-Cl-HABI, p-Me-O-Cl-HABI, TFDM-HABI, and FCl-HABI.

[0011] In an optional embodiment, the adhesive is selected from one or more of polyvinyl acetate, polyvinyl alcohol, cellulose acetate, polyvinyl chloride, and acrylate polymers; And / or, the sensitizer is selected from one or more of di-n-butylamine, n-butylamine, tetraethylmielone, 9-phenylacridinium (9-PA), 5-nitroacenaphthene, N,N-dimethyltriphenylmethane, and benzoin dimethyl ether; And / or, the hydrogen donor is selected from one or more of tertiary amine hydrogen donors, thiols hydrogen donors, and secondary amine hydrogen donors; Preferably, the tertiary amine hydrogen donor includes one or more of triethanolamine, triisopropanolamine, methyldiethanolamine, N,N-dimethylaniline, N,N-dimethylaminobenzoate, and N,N-dimethylaminobenzamide; Preferably, the thiol hydrogen donor includes one or more of dodecyl mercaptan, 2-mercaptobenzothiazole, and 2-mercaptobenzimidazole; Preferably, the secondary amine hydrogen donor includes one or more of N-phenylglycine and 2,2"-(4-methylphenylimino)diethanol.

[0012] In an optional embodiment, the raw material further includes at least one of a prepolymer and an additive; the additive includes one or more of a polymerization inhibitor, a bleaching agent, and a chain transfer agent, wherein the amount of the prepolymer added accounts for 0%-7% of the total mass of the photopolymer material, and the amount of the additive added accounts for 0%-6% of the total mass of the photopolymer material.

[0013] In an optional embodiment, the prepolymer is selected from polyurethane acrylates; And / or, the polymerization inhibitor comprises one or more of hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butyl-p-methylphenol, 4,4'-dihydroxybiphenyl, bisphenol A, 1,1-diphenyl-2-trinitrophenylhydrazine, and N-nitroso-N-phenylhydroxylamine aluminum; And / or, the bleaching agent comprises one or more of tert-butyl hydroperoxide and 7-(4-chloro-6-diethylamino-1,3,5-triazine-4-amino)-3-phenylcoumarin; And / or, the chain transfer agent comprises one or more of 2-mercaptobenzoxazole, α-methylstyrene dimer, 4-cyano-4-(thiobenzoyl)valerate, 2-(dodecylthiothiocarbonylthio)-2-methylpropionic acid, 4-cyano-4-[[(dodecylthio)thiocarbonyl]thio]valerate, sodium formate, 1-mercapto-2-propanol, 4,4"-azobis(4-cyanovaleric acid), and sodium citrate; And / or, the raw material further includes a solvent, the amount of which is added such that the solid-liquid mass ratio is 1:3-6, the solvent including one or more of tetrahydrofuran, chloroform, butyl acetate, ethyl formate, ethyl acetate, dichloromethane, dichloroethane, methanol, ethanol, acetone and toluene.

[0014] In a second aspect, the present invention provides the application of the photopolymer material according to any of the foregoing embodiments in the preparation of data storage media, volume holographic gratings, anti-counterfeiting labels or display optical elements.

[0015] Thirdly, the present invention provides a volume holographic grating, the preparation method of which includes: In a dark room environment, the raw materials in the photopolymer material as described in any of the foregoing embodiments are stirred thoroughly at room temperature for 1-2 hours to obtain a homogeneous solution. In a dark room, the solution is coated onto a substrate, dried, and then a protective layer is attached and cut to obtain a holographic photosensitive material. Based on the principle of laser interference exposure, a reflective holographic recording method is used to record the phase and amplitude information of the object light wave in the holographic photosensitive material. After exposure for 10 seconds, dark reaction for 3-10 minutes, irradiation with ultraviolet lamp for 5-20 minutes, and finally heat treatment in an oven at 90-110℃ for 5-10 minutes, a holographic grating is obtained.

[0016] In an optional embodiment, the photopolymer material coating thickness is 20-70 μm; And / or, the substrate layer is a transparent plastic film, a plastic sheet, or a glass sheet; wherein the transparent plastic film or the plastic sheet is selected from one or more of polyethylene terephthalate, polycarbonate, polyethylene, polyvinyl chloride, polypropylene, polystyrene, modified polystyrene, and cellulose acetate; and the glass sheet is quartz glass, borate glass, optical glass, or tempered glass. And / or, the substrate layer has a thickness of 10 μm-2 mm and a refractive index of 1.50-1.60; And / or, the protective layer is a smooth, transparent plastic film with a thickness of 30-250 μm; And / or, the diffraction efficiency of the volume holographic grating is 80%-98%; And / or, the refractive index modulation amplitude Δn of the volume holographic grating is greater than 0.025.

[0017] The present invention has the following beneficial effects: The photopolymer material provided by this invention can effectively control the initiation efficiency and completion of the polymerization reaction by limiting the molar ratio of active monomers to photoinitiators. By limiting the molar ratio of photosensitizers and photoinitiators, the photosensitive wavelength range and photoresponse efficiency of the material can be determined. In this invention, by compounding specific high-refractive-index monomers and low-refractive-index monomers as active monomers, the macroscopic refractive index of the polymerized material can be adjusted to match the requirements of optical systems. Simultaneously, the microscopic refractive index distribution can be controlled. The compounding of these two monomers can balance the refractive index with other properties (mechanical properties, light transmittance). By controlling the molar ratios of the active monomers to photoinitiators, photosensitizers to photoinitiators, and high / low refractive-index monomers, photopolymer materials that meet the requirements of holographic recording can be prepared, avoiding problems such as photocuring failure, refractive index deviation, and mechanical embrittlement. The prepared material exhibits good heat resistance, rapid film formation, short oxygen-barrier exposure response time (only a few seconds), high refractive index modulation, high sensitivity, high diffraction efficiency, good mechanical properties, and high transmittance, and can be prepared on a large area. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The diagram illustrates the working principle of the fabricated volumetric holographic grating provided for experimental examples of this invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0021] This invention provides a photopolymer material, the raw materials of which include: a binder, an active monomer, a photoinitiator, a photosensitizer, a hydrogen donor, and a sensitizer; the molar ratio of the active monomer to the photoinitiator is 8~12:1; the molar ratio of the photosensitizer to the photoinitiator is 1:15~25; the active monomer includes a high refractive index monomer with a refractive index of 1.55~1.72 and a low refractive index monomer with a refractive index of 1.44~1.50, and the molar ratio of the high refractive index monomer to the low refractive index monomer is 0.7~1.3:1, wherein the molar ratio is calculated based on the amount of active monomer, photoinitiator, and photosensitizer added, and other components are not included in this molar ratio.

[0022] This invention provides the above-mentioned raw materials and limits the molar ratio between specific raw materials to form photopolymer holographic recording materials. The molar ratio of active monomer to photoinitiator, photosensitizer to photoinitiator, and high / low refractive index monomer are the core formulation parameters. Their regulatory effect directly determines the photopolymerization kinetics, final optical properties, mechanical properties and application adaptability of the material.

[0023] The active monomer is the "reaction host" of the photopolymerization reaction (ultimately forming the polymer network framework), while the photoinitiator is the "reaction trigger" (generating active free radicals / cations upon photoexcitation, initiating monomer polymerization). The molar ratio of the two directly determines the initiation efficiency and completion rate of the polymerization reaction. In this invention, the molar ratio of active monomer to photoinitiator is controlled at 8~12:1 to match the chemical properties of the initiator, balance polymerization kinetics and monomer diffusion, maximize refractive index modulation, and avoid defects such as over-initiation or under-initiation.

[0024] Photoinitiators have a narrow inherent photosensitive wavelength range, while photosensitizers absorb specific wavelengths of light (such as visible and near-infrared light) and transfer energy to the photoinitiator, triggering the generation of active species (i.e., "photosensitization"). The molar ratio of the two determines the photosensitive wavelength range and photoresponse efficiency of the material. In this invention, the molar ratio of photosensitizer to photoinitiator is limited to 1:15~25 to maximize the activation efficiency of the photoinitiator, achieving high material sensitivity while using low dye dosage, and optimizing the response and dynamic range of holographic exposure.

[0025] The core applications of photopolymers (such as holographic gratings, optical lenses, and anti-reflective coatings) have strict requirements on refractive index. In this invention, by compounding specific high-refractive-index monomers and low-refractive-index monomers as active monomers, the macroscopic refractive index of the polymerized material can be adjusted to match the requirements of optical systems. At the same time, the microscopic refractive index distribution can also be controlled. By compounding the two, the refractive index can be balanced with other properties (mechanical properties and light transmittance).

[0026] In this invention, by controlling the molar ratios of the aforementioned active monomers to photoinitiators, photosensitizers to photoinitiators, and high / low refractive index monomers, photopolymer materials that meet the requirements for holographic recording can be prepared, avoiding problems such as photocuring failure, refractive index deviation, and mechanical embrittlement. The prepared materials exhibit excellent properties, including high refractive index modulation, high sensitivity, high diffraction efficiency, good mechanical properties, and high transmittance, and can be prepared on a large scale.

[0027] Specifically, the amount of raw materials used varies depending on the type of raw materials selected, and the amount used will also vary while maintaining the molar ratio to meet the above requirements. In this invention, the raw materials include, by mass percentage: 42%-58% binder, 32%-50% active monomer, 3.0%-6.5% photoinitiator, 0.15%-0.5% photosensitizer, 0.7%-1.8% hydrogen donor, and 1.5%-2.2% sensitizer.

[0028] In some embodiments, the high-refractive-index monomer is selected from one or more of the following: benzyl acrylate, 2-phenoxyethyl acrylate, 2-(phenylmercapto)ethyl acrylate, o-phenylphenoxyethyl acrylate, phenoxybenzyl acrylate, biphenylmethanol acrylate, [1,1′-biphenyl]-4,4′-dimethylbis(2-acryloyloxyethane), 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, and N-vinylcarbazole.

[0029] In some embodiments, the low refractive index monomer is selected from one or more of the following: tetrahydrofuran acrylate, cyclotrimethylolpropane formal acrylate, methoxy polyethylene glycol acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, isobornyl acrylate, isooctadecyl acrylate, 2-acryloylethoxysuccinate, hexafluorobutyl acrylate, and 2,2,2-trifluoroethyl acrylate and lauryl acrylate; In some embodiments, the photoinitiator is a hexaarylbisimidazole photoinitiator; hexaarylbisimidazole photoinitiators include one or more of o-chlorohexaarylbisimidazole (BCIM), 2,2',4,4'-tetra(2-chlorophenyl)-5,5'-bis(3,4-dimethoxyphenyl)-1,1'-diimidazole (TCTM), 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-diimidazole (TCDM), m-Me-O-Cl-HABI, p-Me-O-Cl-HABI, TFDM-HABI, and FCl-HABI.

[0030] In some embodiments, the photosensitizer is selected from one or more of phycoerythrin B, Bengal rose red, eosin Y, and saffron red.

[0031] In some embodiments, the adhesive is selected from one or more of polyvinyl acetate, polyvinyl alcohol, cellulose acetate, polyvinyl chloride, and acrylate polymers; In some embodiments, the sensitizer is selected from one or more of di-n-butylamine, n-butylamine, tetraethylmielone, 9-phenylacridine (9-PA), 5-nitroacenaphthene, N,N-dimethyltriphenylmethane, and benzoin dimethyl ether; In some embodiments, the hydrogen donor is selected from one or more of tertiary amine hydrogen donors, thiols hydrogen donors, and secondary amine hydrogen donors; preferably, the tertiary amine hydrogen donor includes one or more of triethanolamine, triisopropanolamine, methyldiethanolamine, N,N-dimethylaniline, N,N-dimethylaminobenzoate, and N,N-dimethylaminobenzamide; preferably, the thiols hydrogen donor includes one or more of dodecyl mercaptan, 2-mercaptobenzothiazole, and 2-mercaptobenzimidazole; preferably, the secondary amine hydrogen donor includes one or more of N-phenylglycine and 2,2"-(4-methylphenylimino)diethanol.

[0032] In addition, in some embodiments, the raw materials of the present invention also include a prepolymer, the amount of which accounts for 0%-7% of the total mass of the photopolymer material, and the prepolymer is selected from polyurethane acrylate.

[0033] In some embodiments, the raw materials of the present invention further include additives; the additives include, but are not limited to, one or more of polymerization inhibitors, bleaching agents, and chain transfer agents, and the amount of additives added accounts for 0%-6% of the total mass of the photopolymer material. Among them, polymerization inhibitors include, but are not limited to, one or more of hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butyl-p-methylphenol, 4,4"-dihydroxybiphenyl, bisphenol A, 1,1-diphenyl-2-trinitrophenylhydrazine, and N-nitroso-N-phenylhydroxylamine aluminum; and / or, bleaching agents include, but are not limited to, tert-butyl hydroperoxide and 7-(4-chloro-6-diethylamino-1,3,5-triazine-4-amino)-3-phenylcoumarin. One or more; and / or, the chain transfer agent includes, but is not limited to, one or more of 2-mercaptobenzoxazole, α-methylstyrene dimer, 4-cyano-4-(thiobenzoyl)valerate, 2-(dodecylthiothiocarbonylthio)-2-methylpropionic acid, 4-cyano-4-[[(dodecylthio)thiocarbonyl]thio]valerate, sodium formate, 1-mercapto-2-propanol, 4,4"-azobis(4-cyanovaleric acid), and sodium citrate.

[0034] In some embodiments, the raw materials also include a solvent, the amount of which is added such that the solid-liquid mass ratio is 1:3-6. The solvent includes, but is not limited to, one or more of tetrahydrofuran, chloroform, butyl acetate, ethyl formate, ethyl acetate, dichloromethane, dichloroethane, methanol, ethanol, acetone, and toluene.

[0035] This invention also provides a method for preparing the above-mentioned photopolymer material, which only requires uniformly mixing the raw materials with a solvent. The preparation method is simple and easy to operate. The prepared photopolymer material can be widely used in the preparation of data storage media, volume holographic gratings, anti-counterfeiting labels, or display optical components.

[0036] Specifically, please refer to Figure 1The present invention provides a volume holographic grating, the preparation method of which includes: S1. In a dark room environment, the raw materials in the above photopolymer material are stirred thoroughly at room temperature for 1-2 hours to obtain a homogeneous solution. S2. In a dark room, the solution is coated onto the substrate, dried, and then a protective layer is attached and cut to obtain the holographic photosensitive material. The photopolymer material coating has a thickness of 20-70 μm; and / or, the substrate layer has a thickness of 10 μm-2 mm and an optical refractive index of 1.50-1.60; the protective layer is a smooth transparent plastic film with a thickness of 30-250 μm.

[0037] The substrate is a transparent plastic film, plastic sheet, or glass sheet; wherein the transparent plastic film or plastic sheet is selected from one or more of polyethylene terephthalate, polycarbonate, polyethylene, polyvinyl chloride, polypropylene, polystyrene, modified polystyrene, and cellulose acetate; and the glass sheet is quartz glass, borate glass, optical glass, or tempered glass. S3. Based on the principle of laser interference exposure, the phase and amplitude information of the object light wave is recorded in the holographic photosensitive material using the reflective holographic recording method. The material is exposed for 10 seconds, followed by a dark reaction for 3-10 minutes, then irradiated with an ultraviolet lamp for 5-20 minutes, and finally heat-treated in an oven at 90-110℃ for 5-10 minutes to obtain the holographic grating.

[0038] The diffraction efficiency of the prepared volume holographic grating is 80%~98%; the refractive index modulation amplitude Δn of the volume holographic grating is >0.025.

[0039] The prepared volume holographic grating (VHG) is used as the waveguide of the entrance pupil. When the incident light satisfies the Bragg diffraction condition of the volume grating, the VHG will have extremely high diffraction efficiency. However, if it deviates from the Bragg condition, the diffraction efficiency will drop rapidly. Therefore, it has good wavelength and angle selectivity.

[0040] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0041] Example 1 This embodiment provides a photopolymer material, comprising: Adhesive: Polyvinyl acetate 52.0 wt%; Prepolymer: 5 wt% polyurethane acrylate; Reactive monomers: High refractive index monomers: o-phenylphenoxyethyl acrylate 10wt% and N-vinylcarbazole 7wt%; Low refractive index monomers: polyethylene glycol diacrylate 15wt%; Photoinitiator: o-chlorohexaaryldiimidazole 4.5 wt%; Photosensitizer: Phycoerythromycin B 0.2wt%; Hydrogen donor: N-phenylglycine 0.9 wt%; Sensitizer: Tetraethylmielone 2wt%; Other additives (polymerization inhibitors, bleaching agents, chain transfer agents) 3.4 wt.

[0042] The molar ratio of active monomer to photoinitiator is 10.2:1; the molar ratio of photosensitizer to photoinitiator is 1:20.8; and the molar ratio of high refractive index monomer to low refractive index monomer is 1.18:1.

[0043] Example 2 This embodiment provides a photopolymer material, comprising: Adhesive: Polyvinyl acetate 56.0 wt%; Prepolymer: 0wt%; Reactive monomers: High refractive index monomers: fluorene diacrylate 8wt% and N-vinylcarbazole 12wt%; Low refractive index monomers: tetrahydrofuran acrylate 14wt%; Photoinitiator: o-chlorohexaaryldiimidazole 4.3 wt%; Photosensitizer: Phycoerythromycin B 0.2wt%; Hydrogen donor: N-phenylglycine 1.0 wt%; Sensitizer: Tetraethylmirlidone 2.0 wt%; Other additives (polymerization inhibitors, bleaching agents, chain transfer agents) 3.4 wt.

[0044] The molar ratio of active monomer to photoinitiator is 10.8:1; the molar ratio of photosensitizer to photoinitiator is 1:19.5; and the molar ratio of high refractive index monomer to low refractive index monomer is 1.05:1.

[0045] Example 3 This embodiment provides a photopolymer material, comprising: Adhesive: Polyvinyl acetate 50.0 wt%; Prepolymer: 0wt%; Active monomers: High refractive index monomer: N-vinylcarbazole 18wt%; Low refractive index monomer: isobornyl acrylate 18wt%; Photoinitiator: o-chlorohexaaryldiimidazole 4.2 wt%; Photosensitizer: Phycoerythromycin B 0.2wt%; Hydrogen donor: N-phenylglycine 1.0 wt%; Sensitizer: Tetraethylmirlidone 2.0 wt%; Other additives (polymerization inhibitors, bleaching agents, chain transfer agents) 3.6 wt.

[0046] The molar ratio of active monomer to photoinitiator is 11.5:1; the molar ratio of photosensitizer to photoinitiator is 1:21.2; and the molar ratio of high refractive index monomer to low refractive index monomer is 0.99:1.

[0047] Comparative Example 1 (High / Low Ratio Imbalance) This comparative example provides a photopolymer material comprising: Adhesive: Polyvinyl acetate 57.0 wt%; Prepolymer: 0wt%; Reactive monomers: High refractive index monomers: o-phenylphenoxyethyl acrylate 16wt%, N-vinylcarbazole 11.5wt%; Low refractive index monomers: polyethylene glycol diacrylate 8wt%; Photoinitiator: o-chlorohexaaryldiimidazole 4.0 wt%; Photosensitizer: Phycoerythromycin B 0.3wt%; Hydrogen donor: N-phenylglycine 0.9 wt%; Sensitizer: Tetraethylmirlidone 2.0 wt%; Other additives (polymerization inhibitors, bleaching agents, chain transfer agents) 3.3 wt%.

[0048] The molar ratio of active monomer to photoinitiator is 10.3:1; the molar ratio of photosensitizer to photoinitiator is 1:12.4; and the molar ratio of high refractive index monomer to low refractive index monomer is 2.52:1.

[0049] Comparative Example 2 (Excess Photoinitiator) This comparative example provides a photopolymer material comprising: Adhesive: Polyvinyl acetate 58.0 wt%; Prepolymer: 0wt%; Active monomers: High refractive index monomer: N-vinylcarbazole 18wt%; Low refractive index monomer: isobornyl acrylate 18wt%; Photoinitiator: o-chlorohexaaryldiimidazole 6.5 wt%; Photosensitizer: Phycoerythromycin B 0.2wt%; Hydrogen donor: N-phenylglycine 1.0 wt%; Sensitizer: Tetraethylmirlidone 2.0 wt%; Other additives (polymerization inhibitors, bleaching agents, chain transfer agents) 3.3 wt%.

[0050] The molar ratio of active monomer to photoinitiator is 5.1:1; the molar ratio of photosensitizer to photoinitiator is 1:23; and the molar ratio of high refractive index monomer to low refractive index monomer is 0.98:1.

[0051] Comparative Example 3 (Insufficient photoinitiator) This comparative example provides a photopolymer material comprising: Adhesive: Polymethyl methacrylate 57.5 wt%; Prepolymer: 0wt%; Reactive monomers: High refractive index monomers: o-phenylphenoxyethyl acrylate 12% N-vinylcarbazole 8wt%; Low refractive index monomers: tetrahydrofuran acrylate 14wt%; Photoinitiator: o-chlorohexaaryldiimidazole 1.8 wt%; Photosensitizer: Phycoerythromycin B 0.2wt%; Hydrogen donor: N-phenylglycine 0.9 wt%; Sensitizer: Tetraethylmirlidone 2.0 wt%; Other additives (polymerization inhibitors, bleaching agents, chain transfer agents) 3.6 wt.

[0052] The molar ratio of active monomer to photoinitiator is 81:1; the molar ratio of photosensitizer to photoinitiator is 1:8.3; and the molar ratio of high-refractive-index monomer to low-refractive-index monomer is 0.84:1.

[0053] Comparative Example 4 (excess dye) This comparative example provides a photopolymer material comprising: Adhesive: Polyvinyl acetate 57.5 wt%; Prepolymer: 0wt%; Active monomers: High refractive index monomer: N-vinylcarbazole 18wt%; Low refractive index monomer: isobornyl acrylate 18wt%; Photoinitiator: o-chlorohexaaryldiimidazole 4.0 wt%; Photosensitizer: Phycoerythromycin B 0.5wt%; Hydrogen donor: N-phenylglycine 1.0 wt%; Sensitizer: Tetraethylmirlidone 2.0 wt%; Other additives (polymerization inhibitors, bleaching agents, chain transfer agents) 3.0 wt.

[0054] The molar ratio of active monomer to photoinitiator is 10.5:1; the molar ratio of photosensitizer to photoinitiator is 1:9.8; and the molar ratio of high refractive index monomer to low refractive index monomer is 0.98:1.

[0055] Experimental Example The photopolymer materials provided in Examples 1-3 and Comparative Examples 1-4 were used to fabricate volume holographic gratings, and then the diffraction efficiency and refractive index modulation of the volume holographic gratings were tested.

[0056] The fabrication method of volume holographic grating includes: In a dark room environment, the raw materials of the above photopolymer material are added to the solvent in sequence and stirred thoroughly at room temperature for 2 hours to obtain the photopolymer material. In a dark room, the photopolymer material is uniformly coated onto the substrate with a coating agent to a thickness of 50 μm. After drying at room temperature for 1 hour, a protective layer is attached using a sealing machine to isolate oxygen. The material is then cut into several pieces of the required size to obtain the holographic photosensitive material. Based on the principle of laser interferometry, a reflective holographic recording method is used to record the phase and amplitude information of the object light wave onto a holographic photosensitive material. The exposure method involves using a 532nm laser, which is split into two beams, filtered, and expanded to ensure consistent polarization. These two beams are then exposed at a specific angle onto the holographic photosensitive film or holographic photosensitive plate. After 10 seconds of exposure and a 6-minute dark reaction, the material is irradiated with ultraviolet light for 5 minutes, and finally heated in a 110°C oven for 8 minutes to obtain a volume holographic grating.

[0057] The diffraction efficiency testing method includes: using a 532nm laser beam as the incident light, and placing the grating surface of the exposed volume holographic grating directly facing the incident light. After passing through the volume holographic grating, the laser beam forms directly transmitted light T0, directly reflected light R0, and diffracted transmission diffraction orders T1 and T-1, and reflection diffraction orders R1 and R-1. The optical power of R1 is measured using an optical power meter. and the optical power of the incident light I 0, the diffraction efficiency can be calculated: Please refer to Table 1 for the test results of diffraction efficiency.

[0058] The test method for refractive index modulation includes: measuring the refractive index (n1) of the holographic photosensitive material before exposure (after coating) using an ellipsometer, and the refractive index (n2) of the holographic photosensitive material after laser exposure (after coating). The difference between n1 and n2 is the refractive index modulation Δn. The distribution of refractive index variation within the material is analyzed using a rigorous finite element analysis model, based on actual test data, to calculate the refractive index modulation under different process conditions. The test results for refractive index modulation are shown in Table 1.

[0059] The test method for refractive index modulation includes: measuring the refractive index (n1) of the holographic photosensitive material before exposure (after coating) using an ellipsometer, and the refractive index (n2) of the holographic photosensitive material after laser exposure (after coating). The difference between n1 and n2 is the refractive index modulation Δn. The distribution of refractive index variation within the material is analyzed using a rigorous finite element analysis model, based on actual test data, to calculate the refractive index modulation under different process conditions. The test results for refractive index modulation are shown in Table 1.

[0060]

[0061] As can be seen from the table above, the green-sensitive photopolymer holographic recording material provided by the present invention has good diffraction efficiency and refractive index modulation, and is significantly better than comparative examples 1-4.

[0062] In summary, the photopolymer material provided by this invention can effectively control the initiation efficiency and completion of the polymerization reaction by limiting the molar ratio of the active monomer to the photoinitiator. By limiting the molar ratio of the photosensitizer and the photoinitiator, the photosensitive wavelength range and photoresponse efficiency of the material can be determined. In this invention, by compounding specific high-refractive-index monomers and low-refractive-index monomers as active monomers, the macroscopic diffraction efficiency of the polymerized material can be adjusted to match the requirements of the optical system. Simultaneously, the microscopic refractive index distribution can be controlled, improving the refractive index modulation. The compounding of these two monomers can balance the refractive index with other properties (mechanical properties, light transmittance). By controlling the molar ratios of the active monomer to the photoinitiator, the photosensitizer to the photoinitiator, and the high / low refractive-index monomers, photopolymer materials that meet the requirements of holographic recording can be prepared, avoiding problems such as photocuring failure, refractive index deviation, and mechanical embrittlement. The prepared material exhibits excellent properties, including high refractive index modulation, high sensitivity, high diffraction efficiency, good mechanical properties, and high transmittance, and can be prepared on a large scale.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A photopolymer material, characterized in that, The raw materials include: a binder, an active monomer, a photoinitiator, a photosensitizer, a hydrogen donor and a sensitizer; the molar ratio of the active monomer to the photoinitiator is 8-12:1; the molar ratio of the photosensitizer to the photoinitiator is 1:15-25; the active monomer includes a high-refractive monomer with a refractive index of 1.55-1.72 and a low-refractive monomer with a refractive index of 1.44-1.50, and the molar ratio of the high-refractive monomer to the low-refractive monomer is 0.7-1.3:1, wherein the molar ratio is calculated based on the material amount of the active monomer, the photoinitiator and the photosensitizer, and other components are not included in the molar ratio.

2. Photopolymer material according to claim 1, characterized in that The raw materials include, in percentage by mass: a binder 42%-58%, an active monomer 32%-50%, a photoinitiator 3.0%-6.5%, a photosensitizer 0.15%-0.5%, a hydrogen donor 0.7%-1.8% and a sensitizer 1.5%-2.2%.

3. The photopolymer material according to claim 1, wherein The high-refractive monomer is selected from one or more of benzyl acrylate, 2-phenoxyethyl acrylate, 2-(phenylmercapto)ethyl acrylate, o-phenylphenoxyethyl acrylate, phenoxybenzyl acrylate, diphenylmethanol acrylate, [1,1'-biphenyl]-4,4'-diylbis(2-propenoyloxyethane, 9,9-bis[4-(2-propenoyloxyethoxy)phenyl]fluorene and N-vinylcarbazole; and / or, the low-refractive monomer is selected from one or more of tetrahydrofurfuryl acrylate, cyclotrimethylolethane formal acrylate, methoxypolyethylene glycol acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, isobornyl acrylate, isooctadecyl acrylate, 2-acryloyloxyethoxy succinate, hexafluorobutyl acrylate and 2,2,2-trifluoroethyl acrylate and lauryl acrylate; and / or, the photosensitizer is selected from one or more of erythrosin B, rose bengal, eosin Y and safranin.

4. Photopolymer material according to claim 3, characterized in that The photoinitiator is a hexaarylbiimidazole photoinitiator; the hexaarylbiimidazole photoinitiator includes one or more of ortho-chlorinated hexaarylbiimidazole (BCIM), 2,2',4,4'-tetra(2-chlorophenyl)-5,5'-di(3,4-dimethoxyphenyl)-1,1'-biimidazole (TCTM), 2,2',4-tri(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-biimidazole (TCDM), m-Me-0-Cl-HABI, p-Me-0-Cl-HABI, TFDM-HABI and FCl-HABI.

5. The photopolymer material of claim 1, wherein, The binder is selected from one or more of polyvinyl acetate, polyvinyl alcohol, cellulose acetate, polyvinyl chloride and acrylate polymers; and / or, the sensitizer is selected from one or more of di-n-butylamine, n-butylamine, tetraethyl Michler's ketone, 9-phenylacridine (9-PA), 5-nitroacenaphthene, N,N-dimethyltritolylmethane and benzoin dimethyl ether; and / or, the hydrogen donor is selected from one or more of a tertiary amine hydrogen donor, a mercaptan hydrogen donor and a secondary amine hydrogen donor; Preferably, the tertiary amine hydrogen donor includes one or more of triethanolamine, triisopropanolamine, methyldiethanolamine, N,N-dimethylaniline, N,N-dimethylaminobenzoate and N,N-dimethylaminobenzamide; Preferably, the mercaptan hydrogen donor includes one or more of dodecyl mercaptan, 2-mercaptobenzothiazole and 2-mercaptobenzimidazole; Preferably, the secondary amine hydrogen donor includes one or more of N-phenylglycine and 2,2'-(4-methylphenylimino)diethanol.

6. Photopolymer material according to any of claims 1 to 5, characterized in that The raw materials further include at least one of a pre-polymer and an auxiliary agent; the auxiliary agent includes one or more of a polymerization inhibitor, a bleaching agent and a chain transfer agent, the pre-polymer is added in an amount of 0-7% of the total mass of the photopolymer material, and the auxiliary agent is added in an amount of 0-6% of the total mass of the photopolymer material.

7. Photopolymer material according to claim 6, characterized in that The pre-polymer is selected from polyurethane acrylate; and / or, the polymerization inhibitor includes one or more of hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butyl-p-cresol, 4,4'-dihydroxydiphenyl, bisphenol A, 1,1-diphenyl-2-trinitrophenylhydrazine and N-nitroso-N-phenylhydroxylamine aluminum; and / or, the bleaching agent includes one or more of tert-butyl hydroperoxide and 7-(4-chloro-6-diethylamino-1,3,5-triazin-4-amino)-3-phenylcoumarin; and / or, the chain transfer agent includes one or more of 2-mercaptobenzoxazole, α-methylstyrene dimer, 4-cyano-4-(thiobenzoyl)valeric acid, 2-(dodecylthiothiocarbonylthio)-2-methylpropionic acid, 4-cyano-4-[[(dodecylthio)thiocarbonyl]thio]valeric acid, sodium formate, 1-mercapto-2-propanol, 4,4'-azobis(4-cyanovaleric acid) and sodium citrate; and / or, the raw materials further include a solvent, the solvent is added in an amount such that the solid-liquid mass ratio is 1:3-6, and the solvent includes one or more of tetrahydrofuran, chloroform, butyl acetate, ethyl formate, ethyl acetate, dichloromethane, dichloroethane, methanol, ethanol, acetone and toluene.

8. Use of the photopolymer material according to any one of claims 1-7 in the preparation of a data storage medium, a volume holographic grating, an anti-counterfeiting label or a display optical element.

9. A volume holographic grating, characterized by The preparation method comprises: In a darkroom environment, the raw materials in the photopolymer material according to any one of claims 1-7 are fully stirred at room temperature for 1-2 hours to obtain a uniform solution, In a darkroom, the solution is coated on a substrate layer, dried and then attached to a protective layer and cut to obtain a holographic photosensitive material; Based on the principle of laser interference exposure, the phase and amplitude information of the object light wave are recorded in the holographic photosensitive material by using a reflection type holographic recording method, exposed for 10 seconds, dark reacted for 3-10 minutes, then irradiated with an ultraviolet lamp for 5-20 minutes, and finally heat treated in an oven at 90-110°C for 5-10 minutes to obtain a volume holographic grating.

10. Volume holographic grating according to claim 9, characterized in that The photopolymer material coating thickness is 20-70 μm; And / or, the substrate layer is a transparent plastic film, a plastic sheet or a glass sheet; wherein the transparent plastic film or the plastic sheet is selected from one or more of polyethylene terephthalate, polycarbonate, polyethylene, polyvinyl chloride, polypropylene, polystyrene, modified polystyrene and cellulose acetate; and the glass sheet is quartz glass, borate glass, optical glass or tempered glass; And / or, the substrate layer has a thickness of 10 μm-2 mm and a refractive index of 1.50-1.60; And / or, the protective layer is a smooth transparent plastic film with a thickness of 30-250 μm; And / or, the volume holographic grating has a diffraction efficiency of 80%-98%; And / or, the volume holographic grating has a refractive index modulation amplitude Δn > 0.025.

Images