Grating preparation method and grating

Abstract

The invention discloses a preparation method of a grating and the grating. The preparation method comprises the following steps: coating a substrate with a multi-cured photopolymer composition, and carrying out first thermal curing to obtain a substrate loaded with a dry film; covering one side, deviating from the substrate, of the dry film with a protective film, exposing, bleaching, and carrying out second thermocuring to obtain the grating; the photopolymer composition comprises the following components in parts by weight: 1-10 parts of a first curing agent with the curing temperature of 40-85 DEG C; 1-10 parts of a second curing agent with the curing temperature of 90-200 DEG C; 30 to 50 parts of polyester polyol and / or polyether polyol; 0.01 to 1 part of a polyurethane reaction catalyst; 30 to 50 parts of an acrylic ester monomer; 0.1 to 5 parts of a photoinitiator system; 10 to 40 parts of a solvent; and 1-25 parts of an auxiliary agent. Wherein the second curing agent can perform second thermal curing after exposure, so that the bonding force between the grating layer and the protective layer can be increased, and the prepared grating is more practical.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical materials, in particular to a preparation method of a grating and the grating. BACKGROUND

[0002] Volume holographic diffraction grating realizes light diffraction through three-dimensional structure of refractive index modulation, and only realizes Bragg condition at specific angle and wavelength, so that it can efficiently and conveniently diffract target wavelength, and has advantages of low power consumption, low cost, convenient setting and the like. Compared with surface relief diffraction grating, the photopolymer diffraction grating has advantages of designability, low cost and no light leakage.

[0003] In specific application, the grating is usually fixed together with other materials through lamination to form a laminated body for use. However, the photopolymer forming the grating has the characteristics of not being resistant to solvents, small molecule chemicals and adhesives, so a film piece without adhesive needs to be covered on the surface of the photopolymer as a protective layer before lamination and bonding, and then the protective layer is used as a contact surface to bond with other materials. However, the photopolymer has another characteristic of insufficient adhesion, which leads to that the bonding force between the grating layer and the protective layer in the laminated body is less than the bonding force between the protective layer and the other material layer, so that the grating layer and the protective layer are not tightly connected and are easy to fall off, and water vapor erosion in use process also causes damage to the grating and reduces the service life of the device.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] In view of the above deficiencies of the prior art, the purpose of the present application is to provide a preparation method of a grating and the grating, so as to improve the adhesion between the grating layer and the protective layer, make the photopolymer diffraction grating more practical, and obtain more extensive application.

[0006] The technical scheme of the present application is as follows: In a first aspect, a preparation method of a grating is provided, comprising the following steps: (1) coating a multiple-cured photopolymer composition on a substrate to obtain a substrate loaded with a wet film; (2) placing the substrate loaded with the wet film at 40-85℃ for 1-60min of first heat curing to obtain a substrate loaded with a dry film; (3) covering a protective film on the side of the dry film away from the substrate to obtain a holographic dry plate; (4) exposing the holographic dry plate, bleaching, and then placing it at 90-200℃ for 1-60min of second heat curing to obtain a grating; The photopolymer composition comprises, by weight fraction: 1-10 parts of a first curing agent; a second curing agent 1-10 parts; a polyester polyol and / or a polyether polyol 30-50 parts; a polyurethane reaction catalyst 0.01-1 part; an acrylate monomer 30-50 parts; a photoinitiator system 0.1-5 parts; a solvent 10-40 parts; an auxiliary agent 1-25 parts; wherein the curing temperature of the first curing agent is 40-85°C; and the curing temperature of the second curing agent is 90-200°C. Steps (1)-(3) are performed in a light-proof environment or an environment inert to the photoinitiator system.

[0007] Optionally, the material of the substrate is selected from one of cellulose triacetate, polyethylene terephthalate, thermoplastic polyurethane, polycarbonate, polyimide, silica glass, silicon carbide, and silicon nitride.

[0008] Optionally, the substrate is a film with a thickness of 20-200 μm.

[0009] Optionally, the coating method is selected from one of spin coating, wire bar coating, slot coating, pull-off coating, roll coating, and screen printing.

[0010] Optionally, the protective film is one of polyethylene terephthalate film, polyimide film, thermoplastic polyurethane film, polycarbonate film, or cellulose triacetate film. The protective film has a haze of 0.5-1% and a thickness of 30-200 μm.

[0011] Optionally, the first heat curing is performed at a temperature of 60-85°C for 3-15 min. The second heat curing is performed at a temperature of 90-120°C for 5-30 min.

[0012] Optionally, the first curing agent is selected from one or more of isocyanate, isocyanate dimer, isocyanate trimer, and isocyanate prepolymer with a molecular weight of 500-5000. The second curing agent is selected from one or more of (A)-(C) as follows: (A) one or more of blocked isocyanate, blocked isocyanate dimer, blocked isocyanate trimer, and blocked isocyanate prepolymer with a molecular weight of 500-5000; (B) amino resin and deblocking catalyst; (C) urea-formaldehyde resin and deblocking catalyst; The amount of the desealing catalyst is 0.05-1 parts by weight. The deblocking catalyst is selected from one or more of dinonylnaphthalene disulfonic acid or dinonylnaphthalene disulfonic acid amine salt formed by reacting it with an organic amine, p-toluenesulfonic acid or p-toluenesulfonic acid amine salt formed by reacting it with an organic amine, wherein the organic amine is selected from one or more of triethylamine, triethanolamine, ammonia, tributylamine, and N-methyldiethanolamine; The molecular weight of the polyester polyol and / or polyether polyol is 400-5000; The polyurethane reaction catalyst is selected from one of dibutyltin dilaurate, dioctyltin octaate, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, sodium oxalate, and calcium oxalate. The acrylate monomers are selected from 9,9-bis(methyl acrylate) fluorene, bisphenol fluorene diethoxydiacrylate, phenyl acrylate, phenyl methacrylate, p-chlorophenyl acrylate, p-chlorophenyl methacrylate, p-bromophenyl acrylate, p-bromophenyl methacrylate, 2,4,6-trichlorophenyl acrylate, 2,4,6-trichlorophenyl methacrylate, 2,4,6-tribromophenyl acrylate, 2,4,6-tribromophenyl methacrylate, pentachlorophenyl acrylate, pentachlorophenyl methacrylate, pentabromophenyl acrylate, pentabromophenyl methacrylate, pentabromobenzyl acrylate, pentabromobenzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxyethoxyethyl acrylate. The following are some of the following: esters, phenoxyethoxyethyl methacrylate, 2-phenylthioethyl acrylate, phenylthioethyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 1,4-bis(2-thionathyl)-2-butyl acrylate, 1,4-bis(2-thionathyl)-2-butyl methacrylate, propane-2,2-diylbis[(2,6-dibromo-4,1-phenylene)oxy(2-{[3,3,3-tris(4-chlorophenyl)propionyl]oxy}propane-3,1-diyl)oxyethane-2,1-diyl]diacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate, tetrabromobisphenol A diacrylate, and N-carbazole acrylate; The photoinitiator system comprises: a photosensitive dye and a co-initiator; the photosensitive dye is selected from one or more of Irgacure 784, new methylene blue, thionine, basic red 2, basic yellow, pinacyanin chloride, rhodamine 6G, cyanine, ethyl violet, Victoria blue R, azurite blue, quinaldinium red, brilliant green, basic orange G, darosin, pyronin Y, Bengal rose red, eosin Y, mifepristone, aminocoumarin, pyranoside, diiodofluorescein, anthocyanin, methylene blue, 2,5-bis{[4-(diethylamino)-2-methylphenyl]methylene}cyclopentanone, azure A, crystal violet, and malachite green; the co-initiator is selected from one or more of ethylenediamine, triethanolamine, N-methyldiethanolamine, N-butyldiethanolamine, N-phenylglycine, 2-(4-chlorophenyl)-4,5-diphenylimidazole, and ethyl 4-dimethylaminobenzoate. The solvent is selected from one or more of dichloromethane, dichloroethane, chloroform, acetone, methyl isobutyl ketone, butanone, ethanol, butanol, ethyl acetate, butyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, N-ethylpyrrolidone, and dimethyl sulfoxide.

[0013] Optionally, the adjuvant comprises one or more of the following components: Chain transfer agent 0.5-3 parts; Defoamer 0.01-0.2 parts; Leveling agent 0.1-1 part; Plasticizer 3-25 parts; The chain transfer agent is selected from one of dodecyl mercaptan, hexamethylene mercaptan, and mercaptobenzothiazole; The defoamer is selected from one or more of diethylhexanol, isooctanol, isoamyl alcohol, diisobutylmethanol, polydimethylsiloxane, nonylphenol polyoxyethylene ether, and octylphenol polyoxyethylene ether. The leveling agent is selected from one or more of polyacrylate, fluorinated polyacrylate, and modified polysiloxane; The plasticizer is selected from one or more of the following: urethane, fluorourethane, dibutyl phthalate, diisobutyl phthalate, poly(ethylene oxide) methyl ether, fluoropolyether, fluorinated polyacrylate polymer, and N,N-dimethylformamide.

[0014] Optionally, the method for preparing the photopolymer composition is carried out in a light-protected environment at 10-40°C or in an environment inert to the photoinitiator system, and includes the following steps: The polyurethane reaction catalyst, polyester polyol and / or polyether polyol, second curing agent, acrylate monomer, additives and part of the solvent are mixed evenly to obtain the first mixture. The photoinitiator system and another portion of the solvent were mixed evenly, and then filtered first to obtain a second mixture. The second mixture is added to the first mixture, then the first curing agent and the remaining solvent are added and mixed evenly. The mixture is then filtered a second time to obtain the photopolymer composition.

[0015] In a second aspect, a grating is provided, which is prepared using the preparation method described in the first aspect.

[0016] Beneficial Effects: This invention provides a method for preparing a grating and the grating itself. Compared with existing technologies, the photopolymer composition used in this invention employs an additional curing agent (a second curing agent). When preparing a grating using the photopolymer composition of this invention, the added second curing agent enables a second thermal curing after exposure, thereby increasing the adhesion between the grating layer and the protective layer, making the photopolymer diffraction grating more practical and allowing for wider applications. Furthermore, due to the increased adhesion, the grating is less likely to be damaged if the protective layer is peeled off. Therefore, the photopolymer composition proposed in this invention can be used in holographic anti-counterfeiting products. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the exposure optical path for holographic dry plate exposure in an embodiment of the present invention. Detailed Implementation

[0018] This invention provides a method for preparing a grating and the grating itself. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below.

[0019] This invention provides a method for fabricating a grating, comprising the following steps: (1) The photopolymer composition with multiple curing is coated on the substrate to obtain a substrate loaded with a wet film; (2) The substrate loaded with wet film is placed at 40-85°C for 1-60 min for the first heat curing to obtain a substrate loaded with dry film; (3) Cover the side of the dry film away from the substrate with a protective film to obtain a holographic dry plate; (4) Expose the holographic plate, bleach it, and then place it at 90-200℃ for 1-60 min for a second thermal curing to obtain a grating; The photopolymer composition comprises, by weight parts: 1-10 parts of the first curing agent; 1-10 parts of the second curing agent; 30-50 parts of polyester polyol and / or polyether polyol; 0.01-1 part of polyurethane reaction catalyst; 30-50 parts of acrylate monomers; 0.1-5 parts of photoinitiator system; Solvent 10-40 parts; 1-25 parts of auxiliary agent; The curing temperature of the first curing agent is 40-85℃; the curing temperature of the second curing agent is 90-200℃. Steps (1)-(3) are carried out in a light-protected environment or in an environment inert to the photoinitiator system.

[0020] Specifically, most photopolymer systems currently used for grating fabrication employ single-stage curing, such as directly forming a film after the macromolecular polymer solvent evaporates, followed by UV exposure to form the high-refractive-index portion; or two-stage curing, where the first stage involves thermosetting the film using an alcohol / NCO or epoxy / amine two-component system, followed by UV curing during exposure and bleaching. However, in applications, gratings fabricated using existing photopolymer systems exhibit weaker adhesion between the grating layer and the protective layer compared to the adhesion between the protective layer and other material layers. This results in a loose bond between the grating layer and the protective layer, making them prone to detachment. Furthermore, moisture erosion during use can damage the grating and reduce device lifespan.

[0021] This embodiment provides a method for preparing a grating. Compared with the prior art, the method in this embodiment uses a multi-curing photopolymer composition with an additional curing agent (second curing agent), which divides the thermal curing into two stages: before and after exposure. The first thermal curing stage (first curing): Under the action of a polyurethane reaction catalyst, polyester polyol and / or polyether polyol and the first curing agent are cured into a film at a low temperature (40-85℃). After film formation, it is easy to wind up and store, with a storage period of more than 12 months. The exposure stage (second curing): acrylate monomers undergo UV curing to obtain a common grating. The second thermal curing stage (third curing): The final thermal curing step is carried out at a high temperature (90-200℃). The second curing agent can cure with the protective layer, thereby increasing the adhesion between the grating layer and the protective layer, resulting in a grating with better performance. The preparation method of this embodiment makes photopolymer diffraction gratings more practical and allows for wider applications. Similarly, a third curing agent can be added to carry out a fourth curing at different temperatures, or even more fourth or fifth curing agents.

[0022] The curing temperature of the first curing agent is 40-85℃, preferably 60-85℃; the curing temperature of the second curing agent is 90-200℃, preferably 90-120℃. The different curing temperatures of the first and second curing agents allow the thermal curing of the photopolymer composition in this embodiment to be divided into two stages.

[0023] In some embodiments, the substrate is selected from one of triacetate cellulose (TAC), polyethylene terephthalate (PET), thermoplastic polyurethane (TPU), polycarbonate (PC), polyimide (PI), silica glass, silicon carbide, and silicon nitride.

[0024] In some embodiments, the substrate is a thin film with a thickness of 20-200 μm, preferably 30-50 μm.

[0025] In some embodiments, the substrate is ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, and then dried with nitrogen.

[0026] In some embodiments, the coating method is selected from one of spin coating, bar coating, slot coating, dip coating, roller coating, and screen printing.

[0027] In some embodiments, the protective film is one of polyethylene terephthalate (PET) film, polyimide film, thermoplastic polyurethane (TPU) film, polycarbonate (PC) film, or cellulose triacetate (TAC) film; the protective film has a haze of 0.5-1% and a thickness of 30-200 μm, preferably 30-50 μm. Optionally, the protective film may be treated with a halo method, ozonation, or plasma irradiation to give the surface of the protective film more hydrophilic groups. The purpose of covering with a protective film is to: prevent the photopolymer from coming into contact with oxygen during the exposure stage to avoid oxidation; physically block the intrusion of dust, moisture, etc., to prevent scratches, and facilitate storage.

[0028] In some embodiments, the storage conditions for the holographic dry plate include: a light-protected environment with a temperature of 10-25°C and a humidity of 30-70%; preferably, a light-protected environment with a temperature of 15-20°C and a humidity of 40-60%.

[0029] In some implementations, the exposure is performed by interferometric exposure through the construction of a laser exposure optical path, and parameters such as light intensity ratio, exposure energy, and exposure time are determined according to the characteristics of the holographic material and product design requirements.

[0030] In some embodiments, the bleaching is achieved by irradiating with LED lights, fluorescent lights, or ultraviolet lights. The purpose of bleaching is to consume the acrylate monomers in the dark areas and other areas of the holographic dry plate, ensuring the completion of the second curing reaction and fixing the grating structure.

[0031] In some embodiments, the temperature of the first thermosetting is 60-85°C and the time is 3-15 minutes.

[0032] In some embodiments, the second thermosetting temperature is 90-120°C and the time is 5-30 minutes.

[0033] In some embodiments, after obtaining the grating, the process may further include: cutting the grating into a specified size according to the product design.

[0034] In some embodiments, the first curing agent is selected from one or more of isocyanates, isocyanate dimers, isocyanate trimers, and isocyanate prepolymers with a molecular weight of 500-5000.

[0035] Specifically, the first curing agent participates in the reaction during the first thermosetting stage (first curing). Its role is to polymerize with polyester polyol and / or polyether polyol under the action of polyurethane reaction catalyst to form a film, that is, to polymerize into a matrix polymer, which serves as the "skeleton" of the grating and a low refractive index component.

[0036] In some more specific embodiments, the isocyanate is selected from one or more of toluene diisocyanate (TDI, CAS: 584-84-9), hexamethylene diisocyanate (HDI, CAS: 822-06-0), diphenylmethane-4,4'-diisocyanate (MDI, CAS: 101-68-8), and isophorone diisocyanate (IPDI, CAS: 4098-71-9); The isocyanate dimer is formed by the polymerization of one or two isocyanates; The isocyanate trimer is formed by the polymerization of one or more isocyanates; The isocyanate prepolymer is formed by polymerization of isocyanate and polyether polyol and / or polyester polyol, wherein the molecular chain ends retain free isocyanate groups (-NCO), and the molecular weight is 500-5000, preferably 1000-2000; wherein the polyester polyol is preferably one or more of polycaprolactone polyol, polyvalerol, and polycarbonate polyol.

[0037] In some embodiments, the second curing agent is selected from one or more of the following (A)-(C): (A) One or more of the following: blocked isocyanates, blocked isocyanate dimers, blocked isocyanate trimers, and blocked isocyanate prepolymers with a molecular weight of 500-5000; (B) Amino resin (CAS: 9003-08-1) and deblocking catalyst; (C) Urea-formaldehyde resin (CAS: 9011-05-6) and deblocking catalyst; The amount of the desealing catalyst is 0.05-1 parts by weight. The deblocking catalyst is selected from one or more of dinonylnaphthalene disulfonic acid (CAS: 60223-95-2) or dinonylnaphthalene disulfonic acid amine salt formed by reacting it with an organic amine, p-toluenesulfonic acid (CAS: 104-15-4) or p-toluenesulfonic acid amine salt formed by reacting it with an organic amine, wherein the organic amine is selected from one or more of triethylamine, triethanolamine, ammonia, tributylamine, and N-methyldiethanolamine.

[0038] Specifically, the second curing agent participates in the reaction during the second thermosetting stage (third curing), and its role is to increase the adhesion between the grating layer and the protective layer (such as polyethylene terephthalate (PET) film), thereby expanding the application range of photopolymer diffraction gratings.

[0039] In some more specific embodiments, when the second curing agent is (A), the blocked isocyanate is formed by the reaction of isocyanate and blocking agent, and the blocking agent can be removed at the unsealing temperature; The blocked isocyanate dimer is formed by polymerizing one or two isocyanates and reacting them with a blocking agent; The blocked isocyanate trimer is formed by polymerizing one or more isocyanates and reacting them with a blocking agent; The blocked isocyanate prepolymer is formed by polymerizing isocyanate and polyether polyol and / or polyester polyol and then reacting with a blocking agent. After polymerization, the molecular chains of isocyanate and polyether polyol and / or polyester polyol retain free isocyanate groups (-NCO) at their ends, and the molecular weight is 500-5000, preferably 1000-2000. The polyester polyol is preferably one or more of polycaprolactone polyol, polyvalerol, and polycarbonate polyol. The sealing agent is selected from one or more of the following (1)-(5): (1) Alcohols or ethers: such as isooctanol, ethylene glycol butyl ether, unsealing temperature <120℃; (2) Oximes: such as methyl ethyl oxime, the decongestion temperature is 130-150℃; (3) Pyrazoles: such as 3,5-dimethylpyrazole (DMP), with a desealing temperature of 130-150℃; (4) Phenolic compounds: such as phenol, nonylphenol, p-chlorophenol, cashew phenol, unsealing temperature >150℃; (6) Lactams: such as caprolactam, the unsealing temperature is 160℃.

[0040] In some more specific embodiments, when the second curing agent is (B), the amino resin is a methyl etherified amino resin and / or a butyl etherified amino resin. The methyl etherified amino resin can be an amino resin with the trade name CYMEL 303 LF or similar products, with a desealing temperature of 160-200°C; the methyl etherified amino resin can also be an amino resin with the trade name CYMEL 325 or similar products, with a desealing temperature of 140-180°C. The desealing catalyst is used to lower the desealing temperature, and the aforementioned desealing temperature is the lowered desealing temperature.

[0041] In some more specific embodiments, when the second curing agent is (C), the unsealing temperature of the urea-formaldehyde resin is 160-190°C. The unsealing catalyst is used to lower the unsealing temperature, which is the lowered unsealing temperature.

[0042] In some embodiments, the molecular weight of the polyester polyol and / or polyether polyol is 400-5000.

[0043] Specifically, the polyester polyol and / or polyether polyol contains functional groups that can react with the isocyanate groups (-NCO) in the first curing agent to form a matrix polymer in the presence of a polyurethane reaction catalyst. The polyester polyol and / or polyether polyol has a molecular weight of 400-5000, preferably 1000-3000, and ≥2 functional groups, preferably 2-4.

[0044] In this embodiment, the matrix polymer formed by the reaction of the polyester polyol and / or polyether polyol with the first curing agent is a polyurethane system. In this embodiment, the separation of the first curing agent and the polyester polyol and / or polyether polyol in the photopolymer composition is to reflect the multiple curing characteristics. In practice, these two components can be combined into a single matrix polymer component; regardless of the separation and description, the effect is the formation of a matrix polymer.

[0045] In some embodiments, the polyurethane reaction catalyst is selected from organotin, organobismuth, organolead, calcium salts, amine catalysts, and high molecular weight polyethyleneimine (PEI) catalysts. Examples include dibutyltin dilaurate, dioctyltin octaate, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, sodium oxalate, or calcium oxalate, but it is not limited thereto.

[0046] In some embodiments, the acrylate monomers are selected from 9,9-bis(methyl acrylate) fluorene, bisphenol fluorene diethoxydiacrylate, phenyl acrylate, phenyl methacrylate, p-chlorophenyl acrylate, p-chlorophenyl methacrylate, p-bromophenyl acrylate, p-bromophenyl methacrylate, 2,4,6-trichlorophenyl acrylate, 2,4,6-trichlorophenyl methacrylate, 2,4,6-tribromophenyl acrylate, 2,4,6-tribromophenyl methacrylate, pentachlorophenyl acrylate, pentachlorophenyl methacrylate, pentabromophenyl acrylate, pentabromophenyl methacrylate, pentabromobenzyl acrylate, pentabromobenzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxyethoxyethyl acrylate, phenoxyethoxyethyl methacrylate, phenoxyethoxyethyl methacrylate. Ethyl acrylate, 2-phenylthioethyl acrylate, phenylthioethyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 1,4-bis(2-thionathyl)-2-butyl acrylate, 1,4-bis(2-thionathyl)-2-butyl methacrylate, propane-2,2-diylbis[(2,6-dibromo-4,1-phenylene)oxy(2-{[3,3,3-tris(4-chlorophenyl)propionyl]oxy}propane-3,1-diyl)oxyethane-2,1-diyl]diacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate, tetrabromobisphenol A diacrylate, N-carbazole acrylate, or one or more of these, but not limited to these, may also be used. Other acrylate monomers capable of forming a refractive index difference with the matrix polymer may also be used.

[0047] In some embodiments, the photoinitiator system comprises a photosensitive dye and a co-initiator. Specifically, the photoinitiator system is used to expose the photopolymer composition at the wavelength required by the grating, thereby forming a high-low refractive index difference to prepare a volume holographic diffraction grating.

[0048] In some more specific embodiments, the photosensitive dye is selected from Irgacure. 784, New Methylene Blue, Thionium, Basic Red 2, Basic Yellow, Pinacyanohydrin Chloride, Rhodamine 6G, Pyrocyanine, Ethyl Violet, Victoria Blue R, Celestite Blue, Quinaldin Red, Brilliant Green, Basic Orange G, Darrocin, Pyronin Y, Bengal Rose Red, Eosin Y, Mischelone, Aminocoumarin, Pyranoside Iodine, Diiodofluorescein, Anthocyanin, Methylene Blue, 2,5-bis{[4-(diethylamino)-2-methylphenyl]methylene}cyclopentanone, Azure A, Crystal Violet, and Malachite Green, but not limited to these; other photosensitive dyes with initiation functions may also be used. The co-initiator is selected from one or more of ethylenediamine, triethanolamine, N-methyldiethanolamine, N-butyldiethanolamine, N-phenylglycine, 2-(4-chlorophenyl)-4,5-diphenylimidazole, and ethyl 4-dimethylaminobenzoate, but not limited to these; other co-initiators with similar functions may also be used.

[0049] In some embodiments, the solvent is selected from one or more of dichloromethane, dichloroethane, chloroform, acetone, methyl isobutyl ketone, butanone, ethanol, butanol, ethyl acetate, butyl acetate, N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N-methylpyrrolidone, N-ethylpyrrolidone, and dimethyl sulfoxide, but is not limited thereto. The solvent is used to ensure uniform mixing of the components and is removed by evaporation during the first curing process.

[0050] In some embodiments, the adjuvant comprises one or more of the following components: Chain transfer agent 0.5-3 parts; Defoamer 0.01-0.2 parts; Leveling agent 0.1-1 part; 3-25 parts of plasticizer, preferably 10-15 parts.

[0051] In some more specific embodiments, the chain transfer agent is selected from, but is not limited to, dodecyl mercaptan, hexamethylene mercaptan, and mercaptobenzothiazole.

[0052] In some more specific embodiments, the defoamer is selected from one or more of diethylhexanol, isooctanol, isoamyl alcohol, diisobutylmethanol, polydimethylsiloxane, nonylphenol polyoxyethylene ether, and octylphenol polyoxyethylene ether, but is not limited thereto.

[0053] In some more specific embodiments, the leveling agent is selected from one or more of polyacrylates, fluorinated polyacrylates, and modified polysiloxanes, but is not limited thereto.

[0054] In some more specific embodiments, the plasticizer is selected from one or more of urethane, fluorourethane, dibutyl phthalate, diisobutyl phthalate, poly(ethylene oxide) methyl ether, fluoropolyether, fluorinated polyacrylate polymer, and N,N-dimethylformamide, but is not limited thereto.

[0055] In some embodiments, the method for preparing the photopolymer composition is carried out in a light-protected environment at 10-40°C or in an environment inert to the photoinitiator system, and includes the following steps: The polyurethane reaction catalyst, polyester polyol and / or polyether polyol, second curing agent, acrylate monomer, additives and part of the solvent are mixed evenly to obtain the first mixture. The photoinitiator system and another portion of the solvent were mixed evenly, and then filtered first to obtain a second mixture. The second mixture is added to the first mixture, then the first curing agent and the remaining solvent are added and mixed evenly. The mixture is then filtered a second time to obtain the photopolymer composition.

[0056] In some more specific embodiments, one or more of a catalyst, chain transfer agent, defoamer, leveling agent and plasticizer are also added to the first mixture.

[0057] In some more specific embodiments, the first filtration is performed using a 0.5 μm filter element or filter screen.

[0058] In some more specific embodiments, the second filtration is performed using a 1μm filter cartridge or filter screen.

[0059] This invention provides a grating, which is prepared using the preparation method described above.

[0060] The present invention will be further described below through specific embodiments.

[0061] Example 1 In a light-protected environment at 25°C, a polyurethane reaction catalyst (0.1g dibutyltin dilaurate), polyester polyol (40g WHP-2024), a second curing agent (3g BL3175A), acrylate monomers (20g bisphenol fluorene diethoxylate and 20g 2-phenylthioethyl acrylate), leveling agent (0.5g BYK333), defoamer (0.1g BYK024), chain transfer agent (0.02g dodecyl mercaptan), plasticizer (5g diisobutyl phthalate), and a portion of the solvent (5g ethyl acetate) were mixed evenly to obtain a first mixture. Separately, a photoinitiator system (0.1g neomethylene blue, 2g 2-(4-chlorophenyl)-4,5-diphenylimidazole, 1g N-methyldiethanolamine, and 0.1g eosin Y) was dissolved in another portion of the solvent (10g... The first mixture was prepared by filtering ethyl acetate and 5g of N-methylpyrrolidone (NMP) using a 0.5μm filter to obtain a second mixture. The second mixture was then added to the first mixture and stirred until homogeneous. The first curing agent (3g N3900) was then added and mixed again until homogeneous. The viscosity was adjusted to 500-1000cps with the remaining ethyl acetate. The mixture was stirred at 500r / min for 10min and then filtered using a 1μm filter to obtain a multi-cured photopolymer composition.

[0062] In a light-proof environment with a cleanliness level below Class 1000, the above photopolymer composition was coated onto a 50μm thick PET film using a spin coating method. The PET film had a light transmittance greater than 95% and a haze of less than 1%. After coating, the film was placed in an oven and baked for 5 minutes at a temperature of 70°C, resulting in a dry film thickness of 20μm. After baking, a 50μm thick PET film was used to cover the surface of the coated layer, and then interlayer bubbles were removed with a force of 20 N to obtain a holographic dry plate. The plate was then placed in a light-proof environment for later use.

[0063] The exposure and baking processes for holographic plates are performed in a light-protected environment or under a protective lamp inert to photosensitive dye compounds. First, the holographic plate is cleaned. Exposure is then performed in a two-beam coherent light path, with the two beams angled at 40 degrees and having powers of 1mW and 0.65mW respectively. The exposure stage is placed on a vibration-resistant platform, and exposure is conducted in a Class 1000 cleanroom environment at 20-25 degrees Celsius and 40-60% relative humidity. The exposure light path is as follows... Figure 1 As shown, a holographic grating is formed, and then the image is irradiated with ultraviolet light (wavelength 365nm, power 150 mw, time 3min) until it is completely fixed and bleached. Then it is placed in an oven at 120℃ for 10min and taken out for various tests.

[0064] The preparation processes for Examples 2-3 and Comparative Examples 1-2 are the same as those for Example 1, except that the composition of the photopolymer composition is different, as detailed below. Examples 4-7 are identical to those in Example 1 except that the composition of the photopolymer composition differs from that in Example 1; the post-fixing and bleaching treatment involves baking in an oven at 150°C for 10 minutes.

[0065] The materials and formulations for all embodiments and comparative examples are shown in Tables 1 and 2.

[0066] Table 1. Materials of Examples and Comparative Examples

[0067] Table 2. Formulations of Examples and Comparative Examples

[0068] In Table 2, the unit of measurement for each substance is grams (g).

[0069] Test methods and results: The adhesion test method is based on GB / T9286-2021 and ISO2409 test standards, using the cross-cut adhesion test. A 1mm × 1mm grid is drawn, and then adhesive tape is used to pull it off. The adhesion is judged based on the number of grids that are pulled off, ranging from 0 to 5, with 0 being the best and 5 being the worst.

[0070] The double 85 test involves placing the sample in an environment of 85°C and 85% humidity for 200 hours, after which its performance is evaluated.

[0071] Table 3. Test results of the examples and comparative examples

[0072] Examples 1, 2, and 3 used different proportions of BL3175 as the second curing agent, with unsealing temperatures of 120-130℃. The results showed that adding BL3175 did not affect diffraction efficiency or transmittance, but it improved adhesion and moisture resistance. Especially after 2 hours of boiling in water and after the double 85 heat test, the diffraction efficiency did not decrease, and the adhesion remained at a high level, thus significantly improving device lifespan. In these examples, a BL3175 addition ratio of 3 parts was more suitable, allowing more curing agent to react with the residual hydroxyl groups on the PET film, thereby improving adhesion. Furthermore, the increased cross-linking degree improved resistance to solvents and moisture erosion, ultimately protecting device lifespan and facilitating subsequent processes.

[0073] Examples 4, 5, 6, and 7 used different proportions of CYMEL325 as the second curing agent, with an unsealing temperature of 150-160℃ and a baking time of 10 minutes. Compared with Comparative Examples 1 and 2, Examples 4, 5, 6, and 7 also improved adhesion and resistance to moisture erosion without reducing diffraction efficiency. Different addition ratios have different effects; a moderate amount is recommended. Increasing the amount slightly reduces transparency. Furthermore, the higher baking temperatures in Examples 4, 5, 6, and 7 resulted in better adhesion and resistance to moisture erosion with less material. In practical applications, different components and proportions can be selected as needed.

[0074] Comparative Examples 1 and 2 did not contain the second curing agent component. The remaining components and amounts of Comparative Example 1 were the same as in Example 1, while the amounts of Comparative Example 2 differed from those of Comparative Example 1. It can be seen that the diffraction efficiency and transmittance of Comparative Example 1 were the same as in Example 1, but the initial adhesion was significantly poor. After boiling in water and undergoing the double 85 test, the low adhesion led to a decrease in the protective ability of the protective film, resulting in a noticeably white appearance, damage to the grating structure, and severe attenuation of diffraction efficiency. Comparative Example 2 also exhibited the problems of low adhesion and efficiency attenuation; the change in its amount primarily altered the initial diffraction efficiency.

[0075] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for fabricating a grating, characterized in that, Including the following steps: (1) The photopolymer composition with multiple curing is coated on the substrate to obtain a substrate loaded with a wet film; (2) The substrate loaded with wet film is placed at 40-85°C for 1-60 min for the first heat curing to obtain a substrate loaded with dry film; (3) Cover the side of the dry film away from the substrate with a protective film to obtain a holographic dry plate; (4) Expose the holographic plate, bleach it, and then place it at 90-200℃ for 1-60 min for a second thermal curing to obtain a grating; The photopolymer composition comprises, by weight parts: 1-10 parts of the first curing agent; 1-10 parts of the second curing agent; 30-50 parts of polyester polyol and / or polyether polyol; 0.01-1 part of polyurethane reaction catalyst; 30-50 parts of acrylate monomers; 0.1-5 parts of photoinitiator system; Solvent 10-40 parts; 1-25 parts of auxiliary agent; in, The curing temperature of the first curing agent is 40-85℃; The curing temperature of the second curing agent is 90-200℃; Steps (1)-(3) are carried out in a light-protected environment or in an environment inert to the photoinitiator system.

2. The preparation method according to claim 1, characterized in that, The substrate is made of a material selected from cellulose triacetate, polyethylene terephthalate, thermoplastic polyurethane, polycarbonate, polyimide, silica glass, silicon carbide, and silicon nitride.

3. The preparation method according to claim 1, characterized in that, The substrate is a thin film with a thickness of 20-200 μm.

4. The preparation method according to claim 1, characterized in that, The coating method is selected from one of the following: spin coating, bar coating, slot coating, dip coating, roller coating, and screen printing.

5. The preparation method according to claim 1, characterized in that, The protective film is one of polyethylene terephthalate film, polyimide film, thermoplastic polyurethane film, polycarbonate film, or cellulose triacetate film. The protective film has a haze of 0.5-1% and a thickness of 30-200 μm.

6. The preparation method according to claim 1, characterized in that, The first thermosetting temperature is 60-85℃, and the time is 3-15 minutes; The second thermosetting temperature is 90-120℃, and the time is 5-30 minutes.

7. The preparation method according to claim 1, characterized in that, The first curing agent is selected from one or more of isocyanates, isocyanate dimers, isocyanate trimers, and isocyanate prepolymers with a molecular weight of 500-5000; The second curing agent is selected from one or more of the following (A)-(C): (A) One or more of the following: blocked isocyanates, blocked isocyanate dimers, blocked isocyanate trimers, and blocked isocyanate prepolymers with a molecular weight of 500-5000; (B) Amino resin and deblocking catalyst; (C) Urea-formaldehyde resin and desealing catalyst; The amount of the desealing catalyst is 0.05-1 parts by weight. The deblocking catalyst is selected from one or more of dinonylnaphthalene disulfonic acid or dinonylnaphthalene disulfonic acid amine salt formed by reacting it with an organic amine, p-toluenesulfonic acid or p-toluenesulfonic acid amine salt formed by reacting it with an organic amine, wherein the organic amine is selected from one or more of triethylamine, triethanolamine, ammonia, tributylamine, and N-methyldiethanolamine; The molecular weight of the polyester polyol and / or polyether polyol is 400-5000; The polyurethane reaction catalyst is selected from one of dibutyltin dilaurate, dioctyltin octaate, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, sodium oxalate, and calcium oxalate. The acrylate monomers are selected from 9,9-bis(methyl acrylate) fluorene, bisphenol fluorene diethoxydiacrylate, phenyl acrylate, phenyl methacrylate, p-chlorophenyl acrylate, p-chlorophenyl methacrylate, p-bromophenyl acrylate, p-bromophenyl methacrylate, 2,4,6-trichlorophenyl acrylate, 2,4,6-trichlorophenyl methacrylate, 2,4,6-tribromophenyl acrylate, 2,4,6-tribromophenyl methacrylate, pentachlorophenyl acrylate, pentachlorophenyl methacrylate, pentabromophenyl acrylate, pentabromophenyl methacrylate, pentabromobenzyl acrylate, pentabromobenzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxyethoxyethyl acrylate. The following are some of the following: esters, phenoxyethoxyethyl methacrylate, 2-phenylthioethyl acrylate, phenylthioethyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 1,4-bis(2-thionathyl)-2-butyl acrylate, 1,4-bis(2-thionathyl)-2-butyl methacrylate, propane-2,2-diylbis[(2,6-dibromo-4,1-phenylene)oxy(2-{[3,3,3-tris(4-chlorophenyl)propionyl]oxy}propane-3,1-diyl)oxyethane-2,1-diyl]diacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate, tetrabromobisphenol A diacrylate, and N-carbazole acrylate; The photoinitiator system comprises: a photosensitive dye and a co-initiator; the photosensitive dye is selected from one or more of Irgacure 784, new methylene blue, thionine, basic red 2, basic yellow, pinacyanin chloride, rhodamine 6G, cyanine, ethyl violet, Victoria blue R, azurite blue, quinaldinium red, brilliant green, basic orange G, darosin, pyronin Y, Bengal rose red, eosin Y, mifepristone, aminocoumarin, pyranoside, diiodofluorescein, anthocyanin, methylene blue, 2,5-bis{[4-(diethylamino)-2-methylphenyl]methylene}cyclopentanone, azure A, crystal violet, and malachite green; the co-initiator is selected from one or more of ethylenediamine, triethanolamine, N-methyldiethanolamine, N-butyldiethanolamine, N-phenylglycine, 2-(4-chlorophenyl)-4,5-diphenylimidazole, and ethyl 4-dimethylaminobenzoate. The solvent is selected from one or more of dichloromethane, dichloroethane, chloroform, acetone, methyl isobutyl ketone, butanone, ethanol, butanol, ethyl acetate, butyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, N-ethylpyrrolidone, and dimethyl sulfoxide.

8. The preparation method according to claim 1, characterized in that, The additives include one or more of the following components: Chain transfer agent 0.5-3 parts; Defoamer 0.01-0.2 parts; Leveling agent 0.1-1 part; Plasticizer 3-25 parts; The chain transfer agent is selected from one of dodecyl mercaptan, hexamethylene mercaptan, and mercaptobenzothiazole; The defoamer is selected from one or more of diethylhexanol, isooctanol, isoamyl alcohol, diisobutylmethanol, polydimethylsiloxane, nonylphenol polyoxyethylene ether, and octylphenol polyoxyethylene ether. The leveling agent is selected from one or more of polyacrylate, fluorinated polyacrylate, and modified polysiloxane; The plasticizer is selected from one or more of the following: urethane, fluorourethane, dibutyl phthalate, diisobutyl phthalate, poly(ethylene oxide) methyl ether, fluoropolyether, fluorinated polyacrylate polymer, and N,N-dimethylformamide.

9. The preparation method according to claim 1, characterized in that, The method for preparing the photopolymer composition is carried out in a light-protected environment at 10-40°C or in an environment inert to the photoinitiator system, and includes the following steps: The polyurethane reaction catalyst, polyester polyol and / or polyether polyol, second curing agent, acrylate monomer, additives and part of the solvent are mixed evenly to obtain the first mixture. The photoinitiator system and another portion of the solvent were mixed evenly, and then filtered first to obtain a second mixture. The second mixture is added to the first mixture, then the first curing agent and the remaining solvent are added and mixed evenly. The mixture is then filtered a second time to obtain the photopolymer composition.

10. A grating, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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