Application of modified dye in holographic material, photopolymer composition, holographic grating and holographic display system

Abstract

The invention provides an application of a modified dye in a holographic material, a photopolymer composition, a holographic grating and a holographic display system. The modified dye provided by the invention comprises the following raw materials: epoxy resin and a small molecule dye, wherein the small molecule dye comprises at least one group capable of performing ring-opening reaction with an epoxy group. The modified dye applied to the holographic material is formed by connecting epoxy resin and small molecules through a ring-opening reaction, and according to similar intermiscibility of a molecular structure, the modified dye is easy to disperse in a non-solvent organic system due to the fact that the modified dye has an epoxy polymer side chain with a large molecular weight, so that the modified dye is easy to disperse in the non-solvent organic system; therefore, the solubility and dispersity of the modified dye in the photopolymer material are improved, the improvement of the photopolymerization rate of the polymeric monomer is promoted, and the diffraction efficiency, refractive index modulation, uniformity and stability of the holographic material are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical materials, and in particular to an application of a modified dye in a holographic material, a photopolymer composition, a holographic grating and a holographic display system. Background Art

[0002] In actual photopolymerization reactions, photosensitive monomers generally do not participate in the polymerization reaction autonomously. Therefore, dyes that are sensitive to light in certain wavelengths and initiators that drive the polymerization reaction must be added to the material to enable the monomers to quickly participate in the polymerization reaction. Dyes and initiators constitute a photosensitive initiation system, which is an indispensable and important component of photopolymer materials. The dye absorbs photons in the corresponding wavelength range, transitions to an excited state, and transfers the energy of its excited state to the initiator through energy transfer or electron transfer. The initiator obtains electrons or energy to generate free radicals, which then react with the monomers and begin to polymerize continuously. During the entire photochemical reaction process, the dye itself will not be consumed or produce structural changes. It mainly plays a photocatalytic role to accelerate the speed of the photopolymerization process. A faster polymerization rate is not only conducive to the increase of the polymerization degree of the monomers in the bright area, thereby increasing the diffraction efficiency of the material. It also helps to increase the monomer concentration difference between the bright area and the dark area, thereby increasing the movement speed of the monomers and the degree of phase separation of the polymer, and the refractive index modulation of the photopolymer material is also improved.

[0003] At present, most photosensitive dyes are conjugated compounds and their ionized salts, which usually have poor solubility and dispersibility in organic systems. Too little dye added to the system is not conducive to improving the rate of photopolymerization reaction, thereby affecting the diffraction efficiency and refractive index modulation of the holographic material. In addition, poor dye dispersibility will cause uneven distribution of dyes in the holographic film, with excessive or insufficient local dye distribution. Too high or too low dye concentration is not conducive to the conversion of double bonds. If the dye concentration is too high, the number of free radicals generated in the initial stage of the reaction is too large, and the sample solidifies quickly, which is not conducive to the subsequent monomer movement, resulting in low diffraction efficiency; if the dye concentration is too low, the number of free radicals generated after illumination is small, resulting in low polymerization rate and double bond conversion rate in the initial stage of the reaction, and then the diffraction efficiency of the material will also be low.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The main purpose of the present invention is to provide an application of a modified dye in a holographic material, a photopolymer composition, a holographic grating and a holographic display system, so as to solve the problem that most of the existing photosensitive dyes are conjugated compounds and their ionized salts, which usually have poor solubility and dispersibility in organic systems, and it is difficult to take into account both the double bond conversion efficiency and the diffraction efficiency when they are added to the photopolymer material system.

[0006] To achieve the above object, according to one aspect of the present invention, a modified dye for use in a holographic material is provided, wherein the raw materials of the modified dye include epoxy resin and a small molecule dye, wherein the small molecule dye contains at least one group capable of undergoing a ring-opening reaction with an epoxy group.

[0007] Furthermore, the epoxy resin is an epoxy resin containing at least two epoxy groups, preferably including at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, epoxidized olefin compound, and cyanuric acid epoxy resin.

[0008] Furthermore, the epoxy resin is an aliphatic glycidyl ether epoxy resin, and more preferably, the number average molecular weight of the aliphatic glycidyl ether is 1,000 to 5,000.

[0009] Furthermore, the group capable of undergoing a ring-opening reaction with the epoxy group includes at least one of an amino group, an imino group, a hydroxyl group or a carboxyl group.

[0010] Furthermore, the small molecule dye includes at least one of new methylene blue, toluene cyanol O, basic blue, nel blue sulfate, Nile blue, acid blue 25, Coomassie blue, acid blue 113, aniline blue, acid blue sodium salt No. 3, rogertin 6G, red methylene blue, basic fuchsin, acid red 94, basic red 9, erythrosine, nuclear fast red, rhodamine, methyl red, acridinium yellow hydrochloride, Bismarck brown R, basic brown 1, brilliant yellow, lemon yellow, fluorescent yellow, curcumin, acridinium yellow, and sunset yellow.

[0011] Furthermore, the epoxy resin is selected from at least one of polypropylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether. Preferably, the number average molecular weight of polypropylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether is independently 500 to 8000, and more preferably 1000 to 5000.

[0012] Furthermore, the small molecule dye is selected from at least one of the compounds represented by the following formula (I) to formula (V),

[0013]

[0014]

[0015] In order to achieve the above-mentioned object, according to another aspect of the present invention, a photopolymer composition is provided, which comprises, by mass percentage, 30-65% of a polymerizable monomer, 0.5-5% of a dye, 0.5-5% of a photoinitiator and 30-65% of a film-forming agent, wherein the dye is any one of the modified dyes provided in the first aspect above.

[0016] Furthermore, the raw materials of the film-forming agent include epoxy monomer and curing agent, and the mass ratio of the two is (29-60):(1-5); wherein the epoxy monomer is an epoxy compound containing an epoxy group, and the refractive index of the epoxy compound is preferably ≤1.45.

[0017] Further, the epoxy compound includes at least one of propylene oxide, ethylene oxide, 1,2-propylene oxide, n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, cresol glycidyl ether, tertiary carboxylic acid glycidyl ether, diglycidyl ester, polyethanol diglycidyl ether, polypropylene glycol diglycidyl ether, butanediol diglycidyl ether, and glycerol triglycidyl ether.

[0018] Furthermore, the epoxy compound is a fluorinated epoxy compound, and the fluorinated epoxy compound includes at least one of bisphenol hexafluoropropane diglycidyl ether, 4,4-bis(2,2-epoxypropylene)octafluorobiphenyl, 1,3-bis[1-(2,3-epoxypropylene)-1-trifluoromethyl-2,2,2-trifluoroethyl]benzene, and 1,4-bis(hydroxyhexafluoroisopropanol)benzene diglycidyl ether.

[0019] Further, the curing agent includes at least one of a C1-C10 straight-chain tertiary amine, tetramethylamine, a tertiary alkyl monoamine, triethanolamine, piperidine, N,N-dimethylpiperazine, triethylenediamine, benzyldimethylamine, pyridine, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-undecylimidazole, chloride of 1-undecyl-2-methyl-3-benzylimidazole, boron trifluoride-monoethylamine, boron trifluoride-n-butylammonium, boron trifluoride-benzylamine, boron trifluoride-triethylamine, boron trifluoride-aniline, and boron trifluoride-piperidine.

[0020] Furthermore, the polymerizable monomer is an acrylate monomer, and preferably the refractive index of the acrylate monomer is ≥1.55, and more preferably the refractive index of the acrylate monomer is ≥1.57.

[0021] Further, the acrylate monomer includes at least one of an acrylate monomer having an aromatic group or a polyurethane acrylate monomer, wherein the acrylate monomer having an aromatic group includes at least one functional group.

[0022] Furthermore, the photoinitiator includes a mixture of one or more of onium salts, bisimidazoles, organometallic compounds, borates, benzophenone and its derivatives, thioxanthone and its derivatives, acetophenone derivatives, α-amino ketone derivatives, α-hydroxy ketone derivatives, benzoylformates, acylphosphine oxides, anthraquinone and its derivatives.

[0023] Furthermore, the photopolymer composition further comprises an additive, and the content of the additive is 0.1-5% based on the total mass of the photopolymer composition.

[0024] Furthermore, the additive includes at least one of a polar solvent, a plasticizer, an inhibitor, a light stabilizer, a chain transfer agent, a leveling agent, a wetting agent, a defoaming agent, a tackifier, an oligomer, a compound having a hydrophilic group, and an oxygen-containing compound.

[0025] According to a third aspect of the present invention, a holographic grating is provided. The holographic grating comprises a polymer film having a grating structure, and the material of the polymer film having the grating structure is any one of the photopolymer compositions provided in the second aspect.

[0026] Furthermore, the method for preparing a polymer film with a grating structure includes the following steps: step S1, mixing a polymerization monomer, a dye, a photoinitiator, a film-forming agent and optional additives to obtain a mixture; step S2, forming the mixture into a film and forming a grating structure at least in part to obtain a polymer film with a grating structure.

[0027] Further, step S2 includes the step of performing exposure using coherent light.

[0028] According to a fourth aspect of the present invention, there is provided a holographic display system, which comprises the holographic grating provided by the third aspect.

[0029] By applying the technical solution of the present application, the modified dye used in the holographic material provided by the present application is formed by connecting epoxy resin and small molecules through a ring-opening reaction. According to the similar solubility of the molecular structure, the modified dye will be easily dispersed in a non-solvent organic system due to the epoxy polymer side chain with a large molecular weight, thereby improving the solubility and dispersibility of the modified dye in the photopolymer material, promoting the increase of the photopolymerization rate of the polymerization monomer, and further improving the diffraction efficiency, refractive index modulation, uniformity and stability of the holographic material. DETAILED DESCRIPTION

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0031] As analyzed in the background technology of this application, most of the existing photosensitive dyes are conjugated compounds and their ionized salts, which usually have poor solubility and dispersibility in organic systems. When added to a photopolymer material system, it is difficult to take into account both the double bond conversion efficiency and the diffraction efficiency. In order to solve this problem, this application provides an application of a modified dye in a holographic material, a photopolymer composition, a holographic grating, and a holographic display system.

[0032] In a first typical embodiment of the present application, a modified dye for use in a holographic material is provided, wherein the raw materials of the modified dye include epoxy resin and a small molecule dye, wherein the small molecule dye contains at least one group capable of undergoing a ring-opening reaction with an epoxy group.

[0033] The modified dye used in the holographic material provided in the present application is formed by connecting epoxy resin and small molecules through a ring-opening reaction. According to the similar solubility of the molecular structure, the modified dye will be easier to disperse in a non-solvent organic system due to the epoxy polymer side chain with a larger molecular weight, thereby improving the solubility and dispersibility of the modified dye in the photopolymer material, promoting the increase of the photopolymerization rate of the polymerization monomer, and further improving the diffraction efficiency, refractive index modulation, uniformity and stability of the holographic material.

[0034] [Small molecule dyes]

[0035] The groups contained in the above-mentioned small molecule dyes that can undergo ring-opening reaction with epoxy groups are not specifically limited, and any groups that can react with epoxy groups can be used, including but not limited to amino groups, imino groups, hydroxyl groups, carboxyl groups, etc. At present, most of the photosensitizing dyes are conjugated compounds and their ionized salts with poor solubility and dispersibility, and most of the molecular structures usually contain one or more of amino groups (-NH2), imino groups (-NH-), hydroxyl groups (-OH), and carboxyl groups (-COOH) with active hydrogen.

[0036] The modified dye in the present application is obtained by using an epoxy resin containing an epoxy group and a small molecule dye containing at least one of an amino group, an imine group, a hydroxyl group, and a carboxyl group to undergo a ring-opening reaction, and grafting an epoxy polymer onto the small molecule dye. The specific reaction principle is as follows:

[0037]

[0038] Wherein Dye represents a small molecule dye, Epoxy resin represents an epoxy resin, and R represents a group that can undergo a ring-opening reaction with an epoxy group, including but not limited to an amino group, an imino group, a hydroxyl group, and a carboxyl group.

[0039] In some embodiments of the present application, the above-mentioned small molecule dye is specifically selected from a mixture of one or more of new methylene blue, toluene cyanol O, basic blue, nel blue sulfate, Nile blue, acid blue 25, Coomassie blue, acid blue 113, aniline blue, acid blue sodium salt No. 3, rogertin 6G, red methylene blue, basic fuchsin, acid red 94, basic red 9, erythrosine, nuclear fast red, rhodamine, methyl red, acridinium yellow hydrochloride, Bismarck brown R, basic brown 1, brilliant yellow, lemon yellow, fluorescent yellow, curcumin, acridinium yellow, and sunset yellow.

[0040] [Epoxy resin]

[0041] The epoxy resin mentioned above refers to an epoxy resin containing at least one epoxy group, preferably an epoxy resin containing two or more epoxy groups, so that it is more conducive to still containing unopened epoxy groups after reacting with small molecule dyes, so as to facilitate reaction with film-forming agents and the like.

[0042] In some embodiments of the present application, epoxy resin includes but is not limited to any one or a mixture of two or more of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol type glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, epoxidized olefin compound, cyanuric acid epoxy resin. Especially when epoxy resin is aliphatic glycidyl ether epoxy resin, since this type of epoxy resin is mostly long-chain molecules, it is directly connected to aliphatic chains by two or more epoxy groups, and there are no structures such as benzene rings, alicyclic rings and heterocyclic rings in the molecular structure, so the viscosity of aliphatic glycidyl ether epoxy resin will be low, and the molecular chain is flexible and has better dispersibility with organic systems. In addition, the number average molecular weight of aliphatic glycidyl ethers will also affect the dispersibility of the modified dye formed by it in organic systems. The larger the molecular weight of aliphatic glycidyl alcohol, the longer the molecular chain, and the easier it is for the modified dye to be miscible with the organic system. However, when the molecular weight is too large, the viscosity of the modified dye is too high, which will weaken its solubility. When the molecular weight is too small, the lipophilicity of the modified dye is not significantly improved and it is still difficult to disperse. Especially when the number average molecular weight of aliphatic glycidyl ether is 1000-5000, it is more conducive to the dispersion of the formed modified dye in the organic system.

[0043] In some embodiments of the present application, the epoxy resin forming the modified dye is selected from any one of polypropylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether, and the small molecule dye is selected from any one of the compounds represented by the following formula (I) to formula (V). Preferably, when the number average molecular weight of polypropylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether is independently 500 to 8000, and more preferably 1000 to 5000, the modified dye formed has better dispersibility in the organic system.

[0044]

[0045]

[0046] In the present application, in the raw materials of the modified dye, the molar ratio of epoxy resin and small molecule dye is 1 to 4:1 (such as 1:1, 2:1, 3:1, 4:1), wherein the epoxy resin is measured by the molar amount of epoxy groups, and the small molecule dye is measured by the molar amount of groups that can undergo ring-opening reaction with epoxy groups.

[0047] In a second typical embodiment of the present application, a photopolymer composition is also provided, in which the photopolymer includes, by mass percentage, 30-65% of a polymerizable monomer, 0.5-5% of a dye, 0.5-5% of a photoinitiator and 30-65% of a film-forming agent, wherein the dye is any modified dye provided in the above-mentioned first typical embodiment.

[0048] Typically but not limitatively, in the photopolymer composition provided in the present application, the mass content of the polymerized monomer is 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or a range consisting of any two numerical values; the mass content of the dye is 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5% or a range consisting of any two numerical values; the mass content of the photoinitiator is 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5% or a range consisting of any two numerical values; the mass content of the film-forming agent is 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or a range consisting of any two numerical values.

[0049] The photopolymer composition provided in the present application adopts the modified dye provided in the above-mentioned first typical embodiment as a dye, which is more conducive to the uniform dispersion of the modified dye in the non-solvent organic system, thereby improving the solubility and dispersibility of the modified dye in the photopolymer material, promoting the increase of the photopolymerization rate of the polymerization monomer, and further improving the diffraction efficiency, refractive index modulation, uniformity and stability of the holographic material.

[0050] [Polymerization monomer]

[0051] The above-mentioned polymerizable monomer is a commonly used polymerizable monomer for holographic materials. From the perspective of increasing the refractive index, it is preferably an acrylate monomer, so as to improve the diffraction efficiency and refractive index modulation of the diffraction grating. For the acrylate monomer with a high refractive index suitable for the present application, in some specific embodiments, it has a refractive index of 1.55 or more, and more preferably has a refractive index of 1.57 or more.

[0052] For the acrylate monomer, it is preferred to use one or a mixture of two or more of an acrylate monomer with an aromatic group and a polyurethane acrylate monomer; wherein the acrylate monomer with an aromatic group contains at least one functional group, such as a monofunctional or polyfunctional acrylate monomer with an aromatic group.

[0053] [Photoinitiator]

[0054] In the present application, the specific type of the photoinitiator is not limited, and it can be matched with the corresponding polymerization monomer. In some embodiments of the present application, the initiator is selected from a mixture of one or more of onium salts, bisimidazoles, organometallic compounds, borates, benzophenone and its derivatives, thioxanthone and its derivatives, acetophenone derivatives, α-amino ketone derivatives, α-hydroxy ketone derivatives, benzoyl formate, acylphosphorus oxides, anthraquinone and its derivatives.

[0055] [Film-forming agent]

[0056] In order to further improve the uniformity of the dispersion of the modified dye in the photopolymer material, the raw materials of the film-forming agent preferably include an epoxy monomer and a curing agent, and then the epoxy monomer and the curing agent react under heating conditions to form a film-forming agent. During the reaction process, the epoxy group in the modified dye can also participate in the reaction process of the film-forming agent, thereby fixing the dye on the film-forming matrix in the form of a chemical bond, effectively avoiding the agglomeration of the modified dye, and further improving the uniformity and stability of the dispersion of the modified dye in the composition.

[0057] The epoxy monomer is a low molecular weight epoxy compound containing an epoxy group, and its specific type is not particularly limited. From the perspective of increasing the refractive index modulation degree of the photopolymer, in some embodiments of the application, an epoxy compound with a relatively low refractive index is preferred, including but not limited to any one of propylene oxide, ethylene oxide, 1,2-propylene oxide, n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, cresol glycidyl ether, tertiary carboxylic acid glycidyl ester, diglycidyl ester, polyethanol diglycidyl ether, butanediol diglycidyl ether, and glycerol triglycidyl ether, or a mixture of at least two or more thereof.

[0058] In other embodiments of the present application, the epoxy monomer is a fluorinated epoxy compound to increase the refractive index difference between the polymerized monomer and the film-forming agent, thereby improving the refractive index modulation and the diffraction efficiency of the grating product. In some specific embodiments, the fluorinated epoxy monomer includes but is not limited to any one of bisphenol hexafluoropropane diglycidyl ether, 4,4-bis(2,2-epoxypropylene) octafluorobiphenyl, 1,3-bis[1-(2,3-epoxypropylene)-1-trifluoromethyl-2,2,2-trifluoroethyl]benzene, and 1,4-bis(hydroxyhexafluoroisopropanol)benzene diglycidyl ether, or a mixture of two or more thereof.

[0059] The specific type of the above-mentioned curing agent is not limited, and it can be applied to epoxy monomers, including but not limited to addition curing agents (polyamines, acid anhydrides, etc.), catalytic curing agents (tertiary amines, boron trifluoride and boron amine complexes, etc.) or curing agents with both polymerization and catalytic effects (imidazole curing agents, etc.).

[0060] In some specific embodiments of the present application, the curing agent is selected from any one of C1-C10 straight-chain tertiary amines, tetramethylamine, tertiary alkyl monoamines, triethanolamine, piperidine, N,N-dimethylpiperazine, triethylenediamine, benzyldimethylamine, pyridine, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-undecylimidazole, 1-undecyl-2-methyl-3-benzylimidazole chloride, boron trifluoride-monoethylamine, boron trifluoride-n-butylammonium, boron trifluoride-benzylamine, boron trifluoride-triethylamine, boron trifluoride-aniline, and boron trifluoride-piperidine, or a mixture of two or more thereof.

[0061] In some embodiments of the present application, from the perspective of improving the performance of the film-forming agent, the mass ratio of the epoxy monomer to the curing agent is preferably (29-60): (1-5). Based on the total mass of the photopolymer composition, the mass content of the epoxy monomer is 29-60% (such as 29%, 35%, 40%, 45%, 50%, 55%, 60%), and the mass content of the curing agent is 1-5% (such as 1%, 2%, 3%, 4%, 5%).

[0062] [additive]

[0063] In the present application, as long as the technical effect of the present application is not affected, additives commonly used in the art may be used according to actual production needs. These additives include, but are not limited to, polar solvents, plasticizers, inhibitors, light stabilizers, chain transfer agents, leveling agents, wetting agents, defoamers, tackifiers, oligomers, compounds with hydrophilic groups (such as salts and / or polyethylene oxide), oxygen-containing compounds (such as acetals, epoxides, oxetanes, oxazolines, dioxolanes) and any one or a mixture of two or more thereof.

[0064] From the perspective of improving the performance of photopolymers, in some embodiments of the present application, the content of the additive is 0.1-5%, such as 0.1%, 0.2%, 0.8%, 1%, 2%, 5% or a range consisting of any two values, based on the total mass of the photopolymer composition.

[0065] In a third typical embodiment of the present application, a holographic grating is further provided. The holographic grating includes a polymer film having a grating structure. The material of the polymer film having the grating structure is the photopolymer composition provided in the second typical embodiment.

[0066] In the holographic grating provided in the present application, the polymer film having a grating structure is obtained by curing the above-mentioned photopolymer composition. Since the modified dye is easily dispersed in a non-solvent organic system, the concentration and dispersion uniformity of the modified dye in the polymer film are improved, and the photopolymerization rate of the polymerized monomer is promoted, thereby improving the diffraction efficiency, refractive index modulation, uniformity and stability of the holographic grating.

[0067] In some embodiments of the present application, the above-mentioned polymer film with a grating structure is prepared according to the following steps: step S1, mixing a polymerization monomer, a dye, a photoinitiator, a film-forming agent and optional additives to obtain a mixture; step S2, forming the mixture into a film and forming a grating structure at least in part to obtain a polymer film with a grating structure.

[0068] In some preferred embodiments of the present application, in the above step S1, the mixing temperature is 10-80°C to improve the mixing efficiency, and more preferably the mixing temperature is 30-80°C to further improve the mixing efficiency.

[0069] In order to improve the efficiency of forming the grating structure, it is preferred that step S2 includes a step of using coherent light for exposure to facilitate the formation of the grating structure. In some specific embodiments, two beams of coherent light can be used to simultaneously perform an exposure operation from one side of the film (transmission grating). In other specific embodiments, two beams of coherent light are used to perform an exposure operation from both sides of the film (reflection grating).

[0070] In some specific embodiments of the present application, the specific steps of forming a polymer film having a grating structure are as follows:

[0071] (1) In a dark room or a protected environment, a mixed solution formed by the photopolymer composition is coated on a glass or a high-transmittance plastic film substrate with a light transmittance greater than 90% to obtain a wet film; the coating method is not specifically limited, and a device known to those skilled in the art such as a doctor blade device or a slit nozzle can be used;

[0072] (2) placing the wet film in an oven at a preset temperature for heating and curing, wherein the curing temperature is 50 to 100° C., preferably 70 to 90° C.;

[0073] (3) After the wet film is cured, another layer of glass substrate or high-transmittance plastic protective film is covered on the surface of the film to obtain a photopolymer dry plate;

[0074] (4) exposing the photopolymer dry plate by laser interference in a dual-beam optical path, wherein a high laser intensity and short exposure time mode is preferably used;

[0075] (5) The exposed dry plate is irradiated with an LED lamp, a fluorescent lamp or an ultraviolet lamp until it is completely fixed and bleached to obtain a polymer film with a grating structure.

[0076] In a fourth typical embodiment of the present application, a holographic display system is further provided. The holographic display system includes the holographic grating provided in the third typical embodiment.

[0077] The holographic display system provided by the present application includes a holographic grating, which can be used alone or in combination with other optical elements. It is particularly suitable for augmented reality (AR) head-mounted display devices (such as AR display glasses, etc.) that have strict requirements on diffraction efficiency, refractive index modulation, light transmittance, etc., as well as head-up displays (HUDs) of automobiles or aircraft.

[0078] The holographic display system provided in the present application adopts the above-mentioned holographic grating, thereby having better imaging quality and a larger field of view, and has a broader application prospect.

[0079] The beneficial effects of the present application will be further illustrated below with reference to embodiments and comparative examples.

[0080] Examples 1 to 6

[0081] Examples 1 to 6 respectively provide a modified dye, and the raw material composition thereof is shown in Table 1 below.

[0082] Table 1

[0083]

[0084]

[0085] Note: The above molar ratio refers to the molar ratio of small molecule dye to epoxy resin.

[0086] The preparation method of the modified dye comprises the following steps: (1) dissolving a small molecule dye in ethanol at a solubility of 1 wt %;

[0087] (2) Add epoxy resin to the ethanol solution of the above small molecule dye, and stir thoroughly at room temperature for 1 to 2 hours to obtain a macromolecular modified dye suspension.

[0088] (3) Finally, the dye suspension is dried under reduced pressure at 50° C. to obtain a dry macromolecular modified dye (powder or waxy solid or highly viscous liquid with substantially no fluidity at room temperature).

[0089] Embodiment 11

[0090] This embodiment provides a holographic grating, the material of which is a photopolymer composition. The composition of the photopolymer composition is shown in Table 2 below.

[0091] Table 2

[0092] composition Quality content o-Phenylphenoxyethyl acrylate 18.3％ 9,9-Di(methylacrylate-9)fluorene 36％ 2,4,6-Trimethylbenzoyldiphenylphosphine oxide 1.2％ Modified dye provided in Example 2 1％ Bisphenol hexafluoropropane diglycidyl ether 40％ 2-Undecyl imidazole 3％ Antioxidant 1010 0.5％

[0093] The holographic grating is prepared according to the following steps:

[0094] (1) Add o-phenylphenoxyethyl acrylate, 9,9-di(methyl acrylate-9)fluorene, bisphenol hexafluoropropane diglycidyl ether, 2-undecyl imidazole, and antioxidant 1010 to a sample bottle, heat and stir at 60°C until completely clear, then add 2,4,6-trimethylbenzoyldiphenylphosphine oxide and modified macromolecular dye 2 in a dark or green light environment and stir for 30 minutes to obtain a uniform and clear photopolymer solution;

[0095] (2) Coating the photopolymer solution on a glass or high-transmittance plastic film substrate in a dark or green light environment, placing the coated wet film in an oven at 90° C. and heating it for 40 minutes to completely cure the film-forming agent, and then covering the surface of the dry film with another layer of glass substrate or high-transmittance plastic protective film to obtain a photopolymer dry plate.

[0096] (3) The photopolymer dry plate was exposed to a double beam light path with an energy density of 15 mJ / cm 2 The 639nm laser interference exposure is followed by UV lamp irradiation for about 30 minutes for fixing and bleaching to form a (reflective) holographic grating.

[0097] Example 12

[0098] The difference between this embodiment and embodiment 11 is that the modified dye provided in embodiment 4 is used to replace the modified dye provided in embodiment 2.

[0099] Example 13

[0100] The difference between this embodiment and embodiment 11 is that the modified dye provided in embodiment 2 is replaced by the modified dye provided in embodiment 5.

[0101] Embodiment 14

[0102] The difference between this embodiment and embodiment 11 is that the modified dye provided in embodiment 1 is used to replace the modified dye provided in embodiment 2.

[0103] Embodiment 15

[0104] The difference between this embodiment and embodiment 11 is that the modified dye provided in embodiment 3 is used to replace the modified dye provided in embodiment 2.

[0105] Embodiments 16 to 20

[0106] The difference between Examples 16 to 20 and Example 11 is that the modified dyes provided in Example 2 are replaced by the modified dyes provided in Examples 6 to 10, respectively.

[0107] Embodiment 21

[0108] The difference between this embodiment and embodiment 13 is that the composition of the photopolymer composition for preparing the holographic grating provided in this embodiment is shown in Table 3 below.

[0109] Table 3

[0110] composition Quality content o-Phenylphenoxyethyl acrylate 16.3％ 9,9-Di(methylacrylate-9)fluorene 36.0％ 2,4,6-Trimethylbenzoyldiphenylphosphine oxide 1.2％ Modified dye provided in Example 5 3.0％ Bisphenol hexafluoropropane diglycidyl ether 40.0％ 2-Undecyl imidazole 3.0％ Antioxidant 1010 0.5％

[0111] Embodiment 22

[0112] The difference between this embodiment and embodiment 13 is that the composition of the photopolymer composition for preparing the holographic grating provided in this embodiment is shown in Table 4 below.

[0113] Table 4

[0114]

[0115]

[0116] Comparative Example 1

[0117] The difference between this comparative example and Example 13 is that toluidine blue O is used to replace the modified dye provided in Example 2.

[0118] Test Example 2

[0119] The holographic gratings provided in the embodiments and comparative examples were tested for diffraction efficiency and refractive index modulation at different positions (9 test points evenly distributed were selected on the holographic grating), and the average diffraction efficiency, the deviation between the diffraction efficiency at different positions and the average diffraction efficiency, the average refractive index modulation at different positions, and the deviation between the refractive index modulation at different positions and the average refractive index modulation were calculated. The results are shown in Table 6 below.

[0120] The wavelengths of the test light sources used in the embodiments and comparative examples are shown in Table 5 below.

[0121] The specific test method is carried out according to the following steps: using LED point light source as the test light source, using a turntable to change the angle between the grating and the test beam, testing the relative diffraction efficiency at different angles. In order to characterize the uniformity of the holographic film, the diffraction efficiency will be tested at 9 different positions in the same holographic film.

[0122] Table 5

[0123]

[0124]

[0125] Table 6

[0126]

[0127] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0128] The modified dye used in the holographic material provided in the present application is formed by connecting epoxy resin and small molecules through a ring-opening reaction. According to the similar solubility of the molecular structure, the modified dye will be easily dispersed in a non-solvent organic system due to the epoxy polymer side chain with a large molecular weight, thereby improving the solubility and dispersibility of the modified dye in the photopolymer material, promoting the increase of the photopolymerization rate of the polymerization monomer, and further improving the diffraction efficiency, refractive index modulation, uniformity and stability of the holographic material.

[0129] In addition, when the epoxy resin forming the modified dye is an aliphatic glycidyl ether epoxy resin and has a molecular weight of 1000 to 5000, the modified dye formed by it and the small molecule dye is easier to disperse in the organic solvent system, which is more conducive to improving the diffraction efficiency, refractive index modulation, uniformity and stability of the holographic material. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Application of a modified dye in a holographic material, characterized in that: The raw materials of the modified dye include epoxy resin and small molecule dye, and the small molecule dye contains at least one group that can undergo a ring-opening reaction with an epoxy group.

2. The use according to claim 1, characterized in that: The epoxy resin is an epoxy resin containing at least two epoxy groups, preferably including at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, epoxidized olefin compound, and cyanuric acid epoxy resin; Preferably, the epoxy resin is the aliphatic glycidyl ether epoxy resin, and more preferably, the number average molecular weight of the aliphatic glycidyl ether epoxy resin is 1000-5000.

3. The use according to claim 1, characterized in that: The group capable of undergoing a ring-opening reaction with the epoxy group includes at least one of an amino group, an imino group, a hydroxyl group or a carboxyl group.

4. The use according to any one of claims 1 to 3, characterized in that The epoxy resin is selected from at least one of polypropylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether, and preferably the number average molecular weight of the polypropylene glycol diglycidyl ether and the polyethylene glycol diglycidyl ether is independently 500 to 8000, and more preferably 1000 to 5000; Preferably, the small molecule dye is selected from at least one of the compounds represented by the following formula (I) to formula (V):

5. A photopolymer composition for holographic grating, characterized in that: The photopolymer composition comprises, by mass percentage, 30-65% of polymerizable monomers, 0.5-5% of dyes, 0.5-5% of photoinitiators and 30-65% of film formers, wherein the dyes are the modified dyes described in any one of claims 1 to 4.

6. The photopolymer composition according to claim 5, characterized in that The raw materials of the film-forming agent include epoxy monomer and curing agent, and the mass ratio of the two is (29-60):(1-5); wherein the epoxy monomer is an epoxy compound containing an epoxy group, and preferably the refractive index of the epoxy compound is ≤1.

45. Preferably, the curing agent includes at least one of polyamine, acid anhydride, tertiary amine, boron trifluoride, boron amine complex or imidazole curing agent.

7. The photopolymer composition according to claim 5, characterized in that The polymerizable monomer is an acrylate monomer, and preferably the refractive index of the acrylate monomer is ≥1.55, and more preferably the refractive index of the acrylate monomer is ≥1.57; Preferably, the acrylate monomer includes at least one of an acrylate monomer having an aromatic group or a urethane acrylate monomer, wherein the acrylate monomer having an aromatic group includes at least one functional group.

8. The photopolymer composition according to any one of claims 5 to 7, characterized in that The composition further comprises an additive, wherein the content of the additive is 0.1 to 5% based on the total mass of the photopolymer composition; Preferably, the additive includes at least one of a polar solvent, a plasticizer, an extender, an inhibitor, a light stabilizer, a chain transfer agent, a leveling agent, a wetting agent, a defoamer, a tackifier, an oligomer, a compound having a hydrophilic group, and an oxygen-containing compound.

9. A holographic grating, characterized in that: The holographic grating comprises a polymer film having a grating structure, and the material of the polymer film is the photopolymer composition according to any one of claims 5 to 8; Preferably, the method for preparing the polymer film comprises the following steps: Step S1, mixing the polymerizable monomer, the dye, the photoinitiator, the film-forming agent and the optional additives to obtain a mixture; Step S2, forming the mixture into a film and forming a grating structure at least partially to obtain the polymer film having the grating structure; Preferably, step S2 includes the step of performing exposure using coherent light.

10. A holographic display system, characterized in that: The holographic display system comprises the holographic grating according to claim 9.

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