Fluororesin and preparation method thereof, holographic recording medium and holographic optical element

Abstract

The present application discloses a hydroxyl-terminated fluororesin and a preparation method thereof, a photopolymer-type holographic recording medium and a holographic optical element. The hydroxyl-terminated fluororesin has a structural formula such as G1-G4; the photopolymer-type holographic recording medium comprises a film-forming resin, and the film-forming resin comprises at least one of the hydroxyl-terminated fluororesins G1-G4 and a polyisocyanate compound. In this way, the refractive index difference between the film-forming resin and the writing monomer can be increased, and the holographic recording performance of the photopolymer can be effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of optical functional materials, and in particular to a hydroxyl-terminated fluororesin and a preparation method thereof, a photopolymer holographic recording medium and a holographic optical element. Background Art

[0002] With the rapid development of augmented reality (AR) technology, photopolymers, as an advanced polymer material, have shown great application potential in the AR field. Their unique properties and adjustability make photopolymers an ideal choice in the AR field. The holographic waveguide system constructed by volume holographic grating (VHG) prepared by photopolymers is one of the preferred technical routes in the AR field.

[0003] The VHG diffraction efficiency is determined by the refractive index difference between the photopolymer film-forming resin and the writing monomer. Increasing the refractive index difference between the film-forming resin and the writing monomer can effectively improve the holographic recording performance of the photopolymer. The current refractive index difference between the photopolymer film-forming resin and the writing monomer needs to be improved. Summary of the invention

[0004] Based on this, the present application provides a hydroxyl-terminated fluororesin and a preparation method thereof, a photopolymer-type holographic recording medium and a holographic optical element, which can increase the refractive index difference between the film-forming resin and the writing monomer, and effectively improve the holographic recording performance of the photopolymer.

[0005] In a first aspect, the present application provides a hydroxyl-terminated fluororesin, wherein the structural formula of the hydroxyl-terminated fluororesin is as follows G1-G4:

[0006]

[0007] In the formula, R1 and R3 each independently represent H or methyl, R2 and R4 each independently represent H or F, m1 is 1 or 2, m2 is 1 or 2, n1 represents an integer of 0-15, n2 represents an integer of 0-15, x represents an integer of 1-200, y represents an integer of 1-200, and q represents an integer of 1-20.

[0008] In a second aspect, the present application provides a method for preparing the hydroxyl-terminated fluororesin as described above, the preparation method comprising:

[0009] (1) Synthesis of hydroxyl-terminated fluororesin G1:

[0010] S1-1, control compound 1 and ethylene glycol bromide isobutyrate are polymerized by atom transfer radical polymerization to obtain oligomer P1;

[0011]

[0012] S1-2, controlling the oligomer P1 to undergo atom transfer radical polymerization to obtain a hydroxyl-terminated fluororesin G1;

[0013]

[0014] (2) Synthesis of hydroxyl-terminated fluororesin G2:

[0015] S2-1, controlling the oligomer P1 and the compound 2 to undergo atom transfer radical polymerization to obtain an oligomer P2;

[0016]

[0017] S2-2, controlling the oligomer P2 to undergo atom transfer radical polymerization to obtain a hydroxyl-terminated fluororesin G2;

[0018]

[0019] (3) Synthesis of hydroxyl-terminated fluororesin G3:

[0020] The oligomer P1 and compound 3 are controlled to react to obtain a hydroxyl-terminated fluororesin G3.

[0021]

[0022] (4) Synthesis of hydroxyl-terminated fluororesin G4:

[0023] The oligomer P2 and compound 3 are controlled to react to obtain a hydroxyl-terminated fluororesin G4.

[0024]

[0025] In a third aspect, the present application provides a photopolymer holographic recording medium, wherein the photopolymer holographic recording medium comprises a film-forming resin, wherein the film-forming resin comprises at least one of the hydroxyl-terminated fluororesins G1 to G4 as described above and a polyisocyanate-based compound.

[0026] In a fourth aspect, the present application provides a holographic optical element, wherein the raw material of the holographic optical element includes the photopolymer holographic recording medium as described above.

[0027] The embodiments of the present application provide a hydroxyl-terminated fluororesin and a preparation method thereof, a photopolymer-type holographic recording medium and a holographic optical element. The hydroxyl-terminated fluororesin contains fluorine atoms, which have extremely small polarizability and extremely low refractive index (about 1.0) and low viscosity. The hydroxyl-terminated fluororesin can be used as a component of a film-forming resin of a photopolymer. Therefore, fluorine elements can be introduced into the film-forming resin of the photopolymer through the hydroxyl-terminated fluororesin, which can significantly reduce the refractive index of the film-forming resin, increase the refractive index difference between the film-forming resin and the writing monomer, and effectively improve the holographic recording performance of the photopolymer. The preparation method of the hydroxyl-terminated fluororesin starts from fluorine-containing acrylate by atom transfer radical polymerization (ATRP, Atom Transfer Radical Polymerization), and polymerizes the hydroxyl-terminated fluororesin of the desired molecular weight; ATRP can accurately control the molecular weight of the polymer through the action of a transition metal catalyst; in addition, due to the active polymerization characteristics of ATRP, the chain termination reaction (such as double radical termination) is effectively suppressed during the polymerization process, so that the molecular weight distribution of the polymer product is narrow, that is, the polydispersity index (PDI, Polydispersity Index) is low. Therefore, the hydroxyl-terminated fluororesin obtained by the preparation method has a controllable molecular weight, a narrow molecular weight distribution, and an easy-to-regulate structure. Since the refractive index difference between the film-forming resin and the writing monomer increases after the hydroxyl-terminated fluororesin is added to the photopolymer, the photosensitivity of the photopolymer is significantly improved, and the diffraction efficiency of the recorded transmission / reflection volume holographic grating is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 are holographic exposure characteristic curves of holographic recording media 1-1, 2-2, 3-3, 4-4 and a comparative example;

[0029] Figure 2 These are the holographic exposure characteristic curves of holographic recording media 1-1, 2-2, 3-3, and 4-4. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0032] In the subsequent description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present application, and have no special meanings. Therefore, "module", "component" or "unit" can be used in a mixed manner.

[0033] With the rapid development of augmented reality (AR) technology, photopolymers, as an advanced polymer material, have shown great application potential in the AR field. Their unique properties and adjustability make photopolymers an ideal choice in the AR field. The holographic waveguide system constructed by volume holographic grating (VHG) prepared by photopolymers is one of the preferred technical routes in the AR field.

[0034] The VHG diffraction efficiency is determined by the refractive index difference between the photopolymer film-forming resin and the writing monomer. Increasing the refractive index difference between the film-forming resin and the writing monomer can effectively improve the holographic recording performance of the photopolymer. The refractive index difference between the current photopolymer film-forming resin and the writing monomer needs to be improved, and the material's resistance to high temperature, low temperature, oil, and chemical media (such as strong acid, strong alkali, organic solvents, etc.) also needs to be improved.

[0035] In order to solve the above-mentioned problems, the embodiments of the present application provide a hydroxyl-terminated fluororesin and a preparation method thereof, a photopolymer-type holographic recording medium and a holographic optical element. The hydroxyl-terminated fluororesin contains fluorine atoms, which have extremely small polarizability and extremely low refractive index (about 1.0) and low viscosity. The hydroxyl-terminated fluororesin can be used as a component of a film-forming resin of a photopolymer. Therefore, fluorine elements can be introduced into the film-forming resin of the photopolymer through the hydroxyl-terminated fluororesin, which can significantly reduce the refractive index of the film-forming resin, increase the refractive index difference between the film-forming resin and the writing monomer, and effectively improve the holographic recording performance of the photopolymer. The preparation method of the hydroxyl-terminated fluororesin starts from fluorine-containing acrylate by atom transfer radical polymerization (ATRP, Atom Transfer Radical Polymerization), and polymerizes the hydroxyl-terminated fluororesin of the desired molecular weight; ATRP can accurately control the molecular weight of the polymer through the action of a transition metal catalyst; in addition, due to the active polymerization characteristics of ATRP, the chain termination reaction (such as double radical termination) is effectively suppressed during the polymerization process, so that the molecular weight distribution of the polymer product is narrow, that is, the polydispersity index (PDI, Polydispersity Index) is low. Therefore, the hydroxyl-terminated fluororesin obtained by the preparation method has a controllable molecular weight, a narrow molecular weight distribution, and an easy-to-regulate structure. Since the refractive index difference between the film-forming resin and the writing monomer increases after the hydroxyl-terminated fluororesin is added to the photopolymer, the photosensitivity of the photopolymer is significantly improved, and the diffraction efficiency of the recorded transmission / reflection volume holographic grating is significantly improved.

[0036] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0037] The present application provides a hydroxyl-terminated fluororesin, and the structural formula of the hydroxyl-terminated fluororesin is as follows G1-G4:

[0038]

[0039] In the formula, R1 and R3 each independently represent H or methyl, R2 and R4 each independently represent H or F, m1 is 1 or 2, m2 is 1 or 2, n1 represents an integer of 0-15, for example, n1 is 0, 1, 2, 3, 5, 6, 7, 9, 10, 12, 14, 15, etc., n2 represents an integer of 0-15, for example, n2 is 0, 1, 2, 3, 5, 6, 7, 9, 10, 12, 14, 15, etc., x represents an integer from 1 to 200, for example, x is 1, 20, 30, 50, 70, 100, 120, 150, 180, 200, etc., y represents an integer from 1 to 200, for example, y is 1, 20, 30, 50, 70, 100, 120, 150, 180, 200, etc., q represents an integer from 1 to 20, for example, q is 1, 2, 5, 7, 9, 10, 12, 14, 15, 17, 20, etc.

[0040] The hydroxyl-terminated fluororesin of the embodiment of the present application contains fluorine atoms, which have extremely small polarizability and extremely low refractive index (about 1.0) and low viscosity. The hydroxyl-terminated fluororesin can be used as a component of the film-forming resin of the photopolymer. Therefore, the fluorine element can be introduced into the film-forming resin of the photopolymer through the hydroxyl-terminated fluororesin, which can significantly reduce the refractive index of the film-forming resin, increase the refractive index difference between the film-forming resin and the writing monomer, and effectively improve the holographic recording performance of the photopolymer.

[0041] In some embodiments, n1 represents an integer of 0-10, for example, n1 is 0, 1, 2, 3, 5, 6, 7, 9, 10, etc., n2 represents an integer of 0-10, for example, n2 is 0, 1, 2, 3, 5, 6, 7, 9, 10, etc., x represents an integer of 1-100, for example, x is 1, 20, 30, 50, 70, 100, etc., y represents an integer of 1-100, for example, y is 1, 20, 30, 50, 70, 100, etc.

[0042] The present application also provides a method for preparing a hydroxyl-terminated fluororesin as described above, the preparation method comprising the synthesis of hydroxyl-terminated fluororesins G1-G4, which is specifically described as follows.

[0043] (1) Synthesis of hydroxyl-terminated fluororesin G1:

[0044] S1-1, control compound 1 and ethylene glycol bromide isobutyrate are polymerized by atom transfer radical polymerization to obtain oligomer P1.

[0045]

[0046] Atom transfer radical polymerization mainly relies on the balance between the growth active center (active species) formed by the macromolecular active center and the halogen atom under the participation of the catalyst and the macromolecular chain free radical (dormant species) reversibly terminated by the halogen to control the polymerization. It can inhibit the chain termination reaction, control the polymerization rate to ensure simultaneous growth, and ultimately control the molecular weight and distribution, and realize the design of the macromolecular structure.

[0047] The system of atom transfer radical polymerization has the following components:

[0048] Monomer: There are many types of monomers that are suitable, and it is best if they have groups that can stabilize free radicals.

[0049] Solvent: Commonly used solvents such as toluene, xylene, chloroform, N,N-dimethylformamide, dimethyl sulfoxide, water, etc. can be used.

[0050] Initiator: To achieve controllable activity in polymerization, a relatively fast initiation rate is required so that all macromolecular chains begin to grow at almost the same time to ensure a narrow molecular weight distribution. At the same time, due to the mechanism of atom transfer radical polymerization, organic halides are generally used as initiators, and the most commonly used are alkyl halides. Both alkyl bromides and alkyl chlorides can better control the molecular weight of the polymer, but alkyl bromides have stronger activity.

[0051] Catalyst: It is an important component in ATRP, which determines the reaction rate and the distribution of product molecular weight to a certain extent. If the catalyst is fed less, the concentration of active species will be high, which is conducive to accelerating the reaction rate, but it will increase side reactions such as double base termination, which is not conducive to the preparation of polymers with narrow molecular weight distribution. Catalyst systems include cuprous halide / bipyridine system (heterogeneous catalytic system), introducing oil-soluble long chains into bipyridine to become a homogeneous catalytic system, Fe, Ru, Ni system, etc.

[0052] Ligand: The ligand forms a complex with the catalyst to solve the problem of catalyst solubility in the organic phase.

[0053] In some embodiments, step S1-1 may specifically be: CuBr (catalyst), compound 1 (fluorine-containing compound) and toluene (solvent) are charged into a three-necked round-bottom flask; the reaction mixture is evacuated with argon or nitrogen in an ice bath for multiple times (e.g., three times) to place the entire system in an inert gas environment; N,N,N',N",N"-pentamethyldiethylenetriamine (ligand) is added, and the solution is stirred until a copper complex is formed; the mixture is then frozen with liquid nitrogen, and degassed by multiple (e.g., three) freeze-evacuation-thaw cycles; the flask is immersed in a constant temperature oil bath at 60°C, and ethylene glycol bromide (initiator) is added to the system within 2 minutes to start the reaction. The reaction is monitored by gas chromatography, and the solution is cooled and diluted with tetrahydrofuran to stop the reaction. The solvent is removed by rotary evaporation, and the resulting reaction mixture is purified by a neutral alumina column to obtain oligomer P1.

[0054] S1-2, controlling the oligomer P1 to undergo atom transfer radical polymerization to obtain a hydroxyl-terminated fluororesin G1.

[0055]

[0056] In some embodiments, step S1-2 may specifically be: placing oligomer P1, CuBr and toluene in a three-necked round-bottom flask; evacuating the reaction mixture with argon or nitrogen in an ice bath for multiple times (e.g., three times) to place the entire system in an inert gas environment; adding N,N,N',N",N"-pentamethyldiethylenetriamine, then freezing the mixture with liquid nitrogen, and degassing through multiple (e.g., three) freeze-evacuation-thaw cycles; then adding nano-sized copper (diameter d in the range of 30-150 nm) to the reaction, and then placing the flask in an oil bath and stirring at 70°C; monitoring the change in the molecular weight of the system by gas chromatography. After the reaction is completed, the solution is cooled and the solvent is removed by rotary evaporation, and the resulting reaction mixture is purified by a neutral alumina column to obtain the product G1.

[0057] (2) Synthesis of hydroxyl-terminated fluororesin G2:

[0058] S2-1, controlling the oligomer P1 and the compound 2 to undergo atom transfer radical polymerization to obtain an oligomer P2;

[0059]

[0060] In some embodiments, step S2-1 may specifically be: adding oligomer P1 and compound 2 to a three-necked round-bottom flask; degassing by multiple (e.g., three) freeze-pump-thaw cycles; then adding CuBr and N,N,N',N",N"-pentamethyldiethylenetriamine (1:1 molar ratio) to the mixture under argon or nitrogen; placing the flask in a constant temperature oil bath at 100°C, monitoring the reaction by gas chromatography, cooling the solution and diluting with tetrahydrofuran to stop the reaction. The solvent is removed by rotary evaporation, and the resulting reaction mixture is purified by a neutral alumina column to obtain oligomer P2.

[0061] S2-2, controlling the oligomer P2 to undergo atom transfer radical polymerization to obtain a hydroxyl-terminated fluororesin G2.

[0062]

[0063] In some embodiments, step S2-2 may specifically be: oligomer P2, CuBr and toluene are charged into a three-necked round-bottom flask; the reaction mixture is evacuated multiple times (e.g., three times) with argon or nitrogen in an ice bath to place the entire system in an inert gas environment. N,N,N',N",N"-pentamethyldiethylenetriamine is added, and the mixture is then frozen with liquid nitrogen and degassed through multiple (e.g., three) freeze-evacuation-thaw cycles; nanosized copper (diameter d in the range of 30-150 nm) is then added to the reaction, and the flask is then placed in an oil bath and stirred at 70°C; changes in the molecular weight of the system are monitored by gas chromatography. After the reaction is completed, the solution is cooled and the solvent is removed by rotary evaporation, and the resulting reaction mixture is purified by a neutral alumina column to obtain product G2.

[0064] (3) Synthesis of hydroxyl-terminated fluororesin G3:

[0065] S3-1. Control the oligomer P1 and compound 3 to react to obtain a hydroxyl-terminated fluororesin G3.

[0066]

[0067] In some embodiments, step S3-1 may specifically be: adding compound 3 and oligomer P1 to a round-bottom flask; stirring the reaction system at 25° C., and monitoring the reaction of the system by gas chromatography. After the reaction is completed, extracting the sample solution with a water / chloroform mixture, collecting the chloroform phase, drying it with anhydrous magnesium sulfate, and purifying the obtained reaction mixture by a neutral alumina column to obtain product G3.

[0068] (4) Synthesis of hydroxyl-terminated fluororesin G4:

[0069] S4-1. Control the oligomer P2 and compound 3 to react to obtain a hydroxyl-terminated fluororesin G4.

[0070]

[0071] The embodiment of the present application also provides a photopolymer holographic recording medium, which includes a film-forming resin, and the film-forming resin includes at least one of the hydroxyl-terminated fluororesins G1-G4 as described above and a polyisocyanate compound (ie, a multifunctional isocyanate).

[0072] In some embodiments, the polyisocyanate-based compound is a compound with a low refractive index and two or more isocyanate groups, for example, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate, butane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, etc.

[0073] In some embodiments, the content of the film-forming resin is 40%-50% by mass percentage; for example: 40%, 42.5%, 45%, 47.5%, 50%, etc., wherein the content of the hydroxyl-terminated fluororesin and the polyisocyanate-based compound can be determined according to the content of hydroxyl groups in the hydroxyl-terminated fluororesin and the content of isocyanate in the polyisocyanate-based compound. The photopolymer holographic recording medium also includes: a writing monomer, a photosensitive initiator system, a chain transfer agent, a catalyst and an additive.

[0074] The writing monomer has a higher refractive index and can be a polymerizable monomer / oligomer.

[0075] The polymerizable monomer / oligomer is selected from at least one of alkenyl naphthalene compounds, alkenyl anthracene compounds, alkenyl benzene compounds, acrylic compounds, methacrylic compounds, acrylate compounds, methacrylate compounds, N-vinyl pyrrole, N-vinyl carbazole, N-vinylimidazole, N-vinyl indole, N-vinyl pyrrolidone, and trans-N-3-ynyl butenyl carbazole.

[0076] Illustratively, the alkenylbenzene compound can be selected from styrene, 2-chlorostyrene, 2-bromostyrene, 3-chlorostyrene, 3-bromostyrene, 4-chlorostyrene, 4-bromostyrene, p-(chloromethyl)styrene, p-(bromomethyl)styrene, and the like.

[0077] Exemplarily, the methacrylic acid compound can be methacrylic acid and its derivatives; Exemplarily, the acrylate compound can be selected from pentabromophenyl acrylate, pentachlorophenyl acrylate, phenoxyethyl acrylate, pentabromobenzyl acrylate, 2-naphthyl acrylate, 1,4-di(2-thionaphthyl)2-butyl acrylate, phenoxyethoxyethyl acrylate, bisphenol A diacrylate, tetrabromobisphenol A diacrylate, 2-phenoxyethyl acrylate, benzyl acrylate, p-chlorophenyl acrylate, 2,4,6-trichlorophenyl acrylate, p-bromophenyl acrylate, 2,4,6-tribromophenyl acrylate, propane-2,2-diylbis[(2,6-dibromo-4,1-phenylene)oxy(2-{[3,3,3-tri(4-chlorophenyl)propionyl]oxy}propane-3,1-diyl)oxyethane-2,1-diyl] diacrylate, etc.

[0078] Exemplarily, the methacrylate compound can be selected from 2-phenoxyethyl methacrylate, benzyl methacrylate, p-bromophenyl methacrylate, p-chlorophenyl methacrylate, 2,4,6-trichlorophenyl methacrylate, pentabromophenyl methacrylate, pentachlorophenyl methacrylate, phenoxyethyl methacrylate, phenoxyethoxyethyl methacrylate, 1,4-di(2-thionaphthyl) 2-butyl methacrylate, pentabromobenzyl methacrylate, 2-naphthyl methacrylate, bisphenol A dimethacrylate, tetrabromobisphenol A dimethacrylate, and the like.

[0079] For example, the alkenyl anthracene compound may be selected from 2-vinyl anthracene, 9-vinyl anthracene, and the like.

[0080] For example, the alkenyl naphthalene compound may be selected from 1-vinyl naphthalene, 2-vinyl naphthalene and the like.

[0081] The photosensitive initiation system may include a photosensitizer (also called a photosensitizer dye) and a photoinitiator, or may not include a photosensitizer. Different wide-band responses can be achieved by regulating the type of photosensitizer. When a photoinitiator with an adapted wavelength is selected in the photopolymer holographic recording medium raw material of the embodiment of the present application, the photosensitizer may not be added. Exemplarily, the photosensitizer is a dye with a high electron transfer efficiency under illumination, including but not limited to cyanine dyes, fluorescein dyes, coumarin ketone dyes, nitrogen-containing aromatic heterocyclic compounds, aromatic amine compounds, benzylcycloalkane ketone compounds, or any mixture of these compounds in any proportion. For example, it includes one or more of new methylene blue, thionine, basic yellow, pinacol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, lapis lazuli blue, methylene blue, Astrazon Orange G, Darrow red, pyrrole red Y, basic red 29, quinaldine red, crystal violet, ethyl violet, brilliant green, pyri11lium I, azure A, crystal violet white nitrile, malachite green white nitrile, etc.

[0082] The photoinitiator is an initiator that can be activated by actinic radiation and initiates polymerization of the corresponding polymerizable groups, including but not limited to aromatic ketone compounds, benzoin and its derivatives, benzil ketal, acylphosphine oxide, aryl ammonium borate, chromium salt, aryl diazonium salt, onium salt, organometallic compound or any mixture of these compounds. For example, it includes one or more of benzophenone, alkylbenzophenone, 4,4'-bis(dimethylamino)benzophenone, anthrone and halogenated benzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxide, phenyl dihydroxyacetate, camphorquinone, α-aminoalkylphenone, α,α-dialkoxyacetophenone, α-hydroxyalkylphenone, triphenylhexyl borate tetrabutylammonium, tri-(3-fluorophenyl)hexylborate tetrabutylammonium, tri-(3-chloro-4-methylphenyl)hexylborate tetrabutylammonium, ferrocenyl compounds, iodonium salts, sulfonium salts, hexaarylbiimidazoles, etc.

[0083] The chain transfer agent is a thiol compound, including but not limited to one or more of dodecyl mercaptan, mercaptoethanol, hexanethiol, phenylethyl mercaptan, 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, 4-methyl-4H-1,2,4-triazole-3-thiol, etc.

[0084] The catalyst is a tertiary amine catalyst or an organic metal catalyst, including but not limited to triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts and bismuth carboxylate catalysts.

[0085] The additives include one or more of a defoamer, a leveling agent, a plasticizer and a water remover.

[0086] The defoamer is an organosilicon defoamer, such as BYK-011, BYK-012, BYK-014, BYK-023, BYK-051N, BYK-085, BYK-1610, BYK-1707, BYK-1740, BYK-1760 produced by BYK, DC65, AFE-7820 produced by Dow Corning, or a mixture of these defoamers in any proportion.

[0087] The leveling agent is an organic silicon surface additive, such as BYK-302, BYK-306, BYK-307, BYK-327, BYK-329, BYK-333, BYK-356, BYK-358, BYK-378, BYK-3455, BYK-3566 produced by BYK, or a mixture of these surface additives in any proportion.

[0088] The plasticizer is toluene, xylene, dimethylformamide, dimethylacetamide, glycerol, phthalate or a mixture of these compounds in any proportion.

[0089] The dehydrating agent includes but is not limited to p-toluenesulfonyl isocyanate, triethyl orthoformate, CUWR-WB20 dehydrating agent of Guangzhou Yourun Synthetic Materials Co., Ltd., ALT-201 dehydrating agent of Anxiang Elite Chemical Co., Ltd., PCCI dehydrating agent of Shanghai Ruhr Chemical Trading Co., Ltd., etc.

[0090] In some embodiments, the content of the writing monomer is 40%-50%, for example 40%, 42.5%, 45%, 47.5%, 50%, etc., the content of the photosensitive initiator system is 0.01%-8%, for example 0.01%, 0.05%, 1%, 3%, 5%, 6%, 7%, 8%, etc., the content of the chain transfer agent is 0.05%-5%, for example 0.05%, 1%, 2%, 3%, 4%, 5%, etc., the content of the catalyst is 0.001%-3%, for example 0.001%, 0.005%, 0.01%, 0.05%, 1%, 2%, 3%, etc., the content of the additive is 0.1%-10%, for example 0.1%, 0.5%, 1%, 3%, 5%, 7%, 9%, 10%, etc.

[0091] In some embodiments, the film-forming resin further comprises a compound having a plurality of isocyanate-reactive functional groups. The compound having a plurality of isocyanate-reactive functional groups helps the film-forming resin to form a network-like polymer structure.

[0092] Among the compounds having multiple isocyanate-reactive functional groups, the isocyanate-reactive functional groups are hydroxyl groups; the compounds having multiple isocyanate-reactive functional groups can be selected from compounds with a low refractive index and two or more hydroxyl functional groups, for example, tetraethylene glycol, trimethylolethane, glycerol, triethanolamine, polyester polyols with a molecular weight of 200-2000, polycarbonate polyols, polyether polyols, etc.

[0093] When the film-forming resin also includes a compound having multiple isocyanate-reactive functional groups, the total content of hydroxyl-terminated fluororesin, the compound having multiple isocyanate-reactive functional groups, and the polyisocyanate-based compound is 40%-50%; the respective contents of the hydroxyl-terminated fluororesin (providing hydroxyl groups), the compound having multiple isocyanate-reactive functional groups (providing hydroxyl groups), and the polyisocyanate-based compound (providing isocyanate groups) can be determined based on the content of hydroxyl groups in the hydroxyl-terminated fluororesin, the content of hydroxyl groups in the compound having multiple isocyanate-reactive functional groups, and the content of isocyanate in the polyisocyanate-based compound.

[0094] The embodiment of the present application also provides a holographic optical element, wherein the raw material of the holographic optical element comprises any of the above-mentioned photopolymer holographic recording media. The holographic optical element includes but is not limited to a volume holographic grating.

[0095] The embodiments of the present application are described below through specific examples.

[0096] Example 1. Synthesis of hydroxyl-terminated fluororesins G1-1 to G1-5:

[0097] 1. Charge CuBr, compound 1-1 and toluene into a three-necked round-bottom flask. Pump and degas the reaction mixture three times with argon or nitrogen in an ice bath to place the entire system in an inert gas environment. Add N,N,N',N",N"-pentamethyldiethylenetriamine and stir the solution until a copper complex is formed. Then freeze the mixture with liquid nitrogen and degas it through three freeze-pump-thaw cycles. Immerse the flask in a constant temperature oil bath at 60°C and add ethylene glycol bromide isobutyrate to the system within 2 minutes to start the reaction. Monitor the change in the molecular weight of the system by gas chromatography, cool the solution and dilute it with tetrahydrofuran to stop the reaction. Remove the solvent by rotary evaporation, and purify the resulting reaction mixture through a neutral alumina column to obtain oligomer P1-1.

[0098] According to the same method, compound 1-1 was replaced by compound 1-2, compound 1-3, compound 1-4 and compound 1-5 to obtain oligomer P1-2, oligomer P1-3, oligomer P1-4 and oligomer P1-5, as shown in Table 1.

[0099]

[0100] 2. Charge oligomer P1-1, CuBr and toluene into a three-necked round-bottom flask. Pump and deflate the reaction mixture three times with argon or nitrogen in an ice bath to place the entire system in an inert gas environment. Add N,N,N',N",N"-pentamethyldiethylenetriamine, then freeze the mixture with liquid nitrogen and degas it through three freeze-pump-thaw cycles. Then add nanosized copper (d ~ 30-150nm) to the reaction, and then place the flask in an oil bath and stir at 70°C. Monitor the changes in the molecular weight of the system by gas chromatography. After the reaction is completed, cool the solution and remove the solvent by rotary evaporation, and purify the resulting reaction mixture through a neutral alumina column to obtain the product G1-1.

[0101] According to the same method, oligomer P1-1 was replaced by oligomer P1-2, oligomer P1-3, oligomer P1-4 and oligomer P1-5 to obtain product G1-2, product G1-3, product G1-4 and product G1-5, as shown in Table 1.

[0102]

[0103] Table 1

[0104]

[0105] Example 2: Synthesis of hydroxyl-terminated fluororesins G2-1 to G2-5:

[0106] 1. Add oligomer P1-1 and compound 2-1 to a three-necked round-bottom flask. Degas by three freeze-pump-thaw cycles. Then add CuBr and N,N,N',N",N"-pentamethyldiethylenetriamine (1:1 molar ratio) to the mixture under argon or nitrogen. Place the flask in a constant temperature oil bath at 100°C, monitor the reaction by gas chromatography, cool the solution and dilute with tetrahydrofuran to stop the reaction. Remove the solvent by rotary evaporation, and purify the resulting reaction mixture by a neutral alumina column to obtain oligomer P2-1.

[0107] According to the same method, oligomer P1-1 was replaced by oligomer P1-2, oligomer P1-3, oligomer P1-4 and oligomer P1-5, and compound 2-1 was replaced by compound 2-2, compound 2-3, compound 2-4 and compound 2-5, to obtain oligomer P2-2, oligomer P2-3, oligomer P2-4 and oligomer P2-5, as shown in Table 2.

[0108]

[0109] 2. Charge oligomer P2-1, CuBr and toluene into a three-necked round-bottom flask. Pump and degas the reaction mixture three times with argon or nitrogen in an ice bath to place the entire system in an inert gas environment. Add N,N,N',N",N"-pentamethyldiethylenetriamine, then freeze the mixture with liquid nitrogen and degas it through three freeze-pump-thaw cycles. Then add nanosized copper (d ~ 30-150nm) to the reaction, and then place the flask in an oil bath and stir at 70°C. Monitor the changes in the molecular weight of the system by gas chromatography. After the reaction is completed, cool the solution and remove the solvent by rotary evaporation, and purify the resulting reaction mixture through a neutral alumina column to obtain the product G2-1.

[0110] According to the same method, oligomer P2-1 was replaced by oligomer P2-2, oligomer P2-3, oligomer P2-4 and oligomer P2-5 to obtain product G2-2, product G2-3, product G2-4 and product G2-5, respectively, as shown in Table 2.

[0111]

[0112] Table 2

[0113]

[0114]

[0115] Example 3: Synthesis of hydroxyl-terminated fluororesins G3-1 to G3-5:

[0116] Compound 3-1 and oligomer P1-1 were added to a round-bottom flask. The reaction system was stirred at 25°C and the reaction was monitored by gas chromatography. After the reaction was completed, the sample solution was extracted with a water / chloroform mixture, the chloroform phase was collected, and dried over anhydrous magnesium sulfate. The obtained reaction mixture was purified by a neutral alumina column to obtain the product G3-1.

[0117] According to the same method, compound 3-1 was replaced by compound 3-2, compound 3-3, compound 3-4 and compound 3-5, and oligomer P1-1 was replaced by oligomer P1-2, oligomer P1-3, oligomer P1-4 and oligomer P1-5, to obtain product G3-2, product G3-3, product G3-4 and product G3-5, as shown in Table 3.

[0118]

[0119] Table 3

[0120]

[0121] Example 4: Synthesis of hydroxyl-terminated fluororesins G4-1 to G4-5:

[0122] Add oligomer P2-1 and compound 3-1 to a round-bottom flask. Stir the reaction system at 25°C and monitor the reaction of the system by gas chromatography. After the reaction is completed, extract the sample solution with a water / chloroform mixture, collect the chloroform phase, dry it with anhydrous magnesium sulfate, and purify the obtained reaction mixture through a neutral alumina column to obtain the product G4-1.

[0123] According to the same method, compound 3-1 was replaced by compound 3-2, compound 3-3, compound 3-4 and compound 3-5, and oligomer P2-1 was replaced by oligomer P2-2, oligomer P2-3, oligomer P2-4 and oligomer P2-5, to obtain product G4-2, product G4-3, product G4-4 and product G4-5, as shown in Table 4.

[0124]

[0125] Table 4

[0126]

[0127]

[0128] Example 5: Preparation of photopolymer holographic recording media 1-1 to 1-5 using hydroxyl-terminated fluororesins G1-1 to G1-5:

[0129] The specific components of the photopolymer holographic recording media 1-1 to 1-5 are shown in Table 5:

[0130] Table 5

[0131]

[0132]

[0133] Example 6: Preparation of photopolymer holographic recording media 2-1 to 2-5 using hydroxyl-terminated fluororesins G2-1 to G2-5:

[0134] The specific components of the photopolymer holographic recording media 2-1 to 2-5 are shown in Table 6:

[0135] Table 6

[0136]

[0137]

[0138]

[0139] Example 7: Preparation of photopolymer holographic recording media 3-1 to 3-5 using hydroxyl-terminated fluororesins G3-1 to G3-5:

[0140] The specific components of the photopolymer holographic recording media 3-1 to 3-5 are shown in Table 7:

[0141] Table 7

[0142]

[0143]

[0144] Example 8: Preparation of photopolymer holographic recording media 4-1 to 4-5 using hydroxyl-terminated fluororesins G4-1 to G4-5:

[0145] The specific components of the photopolymer holographic recording media 4-1 to 4-5 are shown in Table 8:

[0146] Table 8

[0147]

[0148]

[0149] For the specific components of the comparative example and the photopolymer holographic recording medium prepared in the comparative example, please refer to Table 9:

[0150] Table 9

[0151]

[0152] Test example:

[0153] The performance of the holographic recording media of Examples 5-8 and Comparative Examples was tested. The results are as follows: Figure 1-2 , Table 10.

[0154] The test method includes the following steps:

[0155] Solid-state lasers with wavelengths of 405nm, 532nm, and 633nm were used as light sources. After passing through a beam expander, beam splitter, and half-wave plate, two beams with the same light intensity and a diameter of 8mm were obtained. The two beams intersected in the prepared holographic recording medium for exposure, and the light intensity was 2.91mW / cm 2 The detection light source is a 785nm wavelength solid laser that does not react with the recording medium. The detection light is incident on the exposure area from the Bragg angle. The transmitted light and diffracted light are monitored in real time by the photodetector. The single grating diffraction efficiency (η) of the photopolymer sample and the photosensitivity (S) of the recording medium are calculated by formulas (1) to (3).

[0156]

[0157]

[0158]

[0159] Where η is the diffraction efficiency, η max is the highest diffraction efficiency, I d is the diffracted light, I t is the transmitted light, S is the photosensitivity, E is the exposure energy, and ΔE is the exposure energy when the highest diffraction efficiency is achieved.

[0160] The performance of the photopolymer holographic recording media of Examples 7-12 and Comparative Example was evaluated according to the above test method. The results are as follows: Figure 1-2 As shown in Table 10.

[0161] Table 10

[0162]

[0163] from Figure 1 to Figure 2 (The holographic recording media 1-1, 2-2, 3-3, and 4-4 are taken as examples in the figure) and Table 10 show that the exposure amount of the holographic recording media of Examples 5 to 8 of the present application is much smaller than the exposure amount of the comparative example, the diffraction efficiency of the holographic recording media of Examples 5 to 8 of the present application is much greater than the diffraction efficiency of the comparative example, and the sensitivity of the holographic recording media of Examples 5 and 8 of the present application is much greater than the sensitivity of the comparative example.

[0164] It should be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0165] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0166] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A hydroxyl-terminated fluororesin, characterized in that: The structural formula of the hydroxyl-terminated fluororesin is as follows G1-G4: In the formula, R1 and R3 each independently represent H or methyl, R2 and R4 each independently represent H or F, m1 is 1 or 2, m2 is 1 or 2, n1 represents an integer of 0-15, n2 represents an integer of 0-15, x represents an integer of 1-200, y represents an integer of 1-200, and q represents an integer of 1-20.

2. The fluororesin according to claim 1, characterized in that n1 represents an integer from 0 to 10, n2 represents an integer from 0 to 10, x represents an integer from 1 to 100, and y represents an integer from 1 to 100.

3. A method for preparing a hydroxyl-terminated fluororesin according to any one of claims 1 to 2, characterized in that: The preparation method comprises: (1) Synthesis of hydroxyl-terminated fluororesin G1: S1-1, control compound 1 and ethylene glycol bromide isobutyrate are polymerized by atom transfer radical polymerization to obtain oligomer P1; S1-2, controlling the oligomer P1 to undergo atom transfer radical polymerization to obtain a hydroxyl-terminated fluororesin G1; (2) Synthesis of hydroxyl-terminated fluororesin G2: S2-1, controlling the oligomer P1 and the compound 2 to undergo atom transfer radical polymerization to obtain an oligomer P2; S2-2, controlling the oligomer P2 to undergo atom transfer radical polymerization to obtain a hydroxyl-terminated fluororesin G2; (3) Synthesis of hydroxyl-terminated fluororesin G3: The oligomer P1 and compound 3 are controlled to react to obtain a hydroxyl-terminated fluororesin G3. (4) Synthesis of hydroxyl-terminated fluororesin G4: The oligomer P2 and compound 3 are controlled to react to obtain a hydroxyl-terminated fluororesin G4.

4. A photopolymer holographic recording medium, characterized in that: The photopolymer type holographic recording medium comprises a film-forming resin comprising at least one of the hydroxyl-terminated fluororesins G1 to G4 as claimed in any one of claims 1 to 2 and a polyisocyanate-based compound.

5. The photopolymer holographic recording medium according to claim 4, characterized in that: The content of the film-forming resin is 40%-50% by mass percentage; The photopolymer holographic recording medium further comprises: a writing monomer, a photosensitive initiation system, a chain transfer agent, a catalyst and additives.

6. The photopolymer holographic recording medium according to claim 5, characterized in that: In terms of mass percentage, the content of the writing monomer is 40%-50%, the content of the photosensitive initiator system is 0.01%-8%, the content of the chain transfer agent is 0.05%-5%, the content of the second catalyst is 0.001%-3%, and the content of the additive is 0.1%-10%.

7. The photopolymer holographic recording medium according to any one of claims 4 to 6, characterized in that: The film-forming resin also includes a compound having a plurality of isocyanate-reactive functional groups.

8. A holographic optical element, characterized in that: The raw material of the holographic optical element comprises the photopolymer holographic recording medium as claimed in any one of claims 4 to 7.

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