Holographic recording medium, its preparation and use

Abstract

The application discloses a holographic recording medium and preparation and application thereof, and the holographic recording medium is characterized by comprising a high-glass-transition-temperature and high-refractive-index base, a low-refractive-index monomer and a photoinitiating system, and adding plasticizers and leveling agents according to needs; the glass transition temperature of the base is above 100 DEG C. Under the irradiation of coherent laser, the holographic recording medium has a coherent bright area, the photoinitiating system rapidly generates active centers, the low-refractive-index monomer is attacked by the active centers to initiate polymerization, the monomer in the coherent bright area is consumed, the monomer between the coherent bright area and a coherent dark area generates a concentration difference, the monomer is driven to diffuse from the coherent dark area to the coherent bright area and participate in the polymerization reaction of the coherent bright area, the plasticizers and the base move to the coherent dark area due to the increase of potential energy of the coherent bright area, and finally, the refractive index variation of the low-refractive-index coherent bright area and the high-refractive-index coherent dark area is formed, thereby generating a periodic refractive index difference.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical materials, and more particularly relates to a holographic recording medium and a preparation method and application thereof. BACKGROUND

[0002] A holographic recording medium is a carrier for recording holograms, and can store all information such as amplitude and phase of light waves through coherent laser exposure technology, and generally has a periodic ordered structure. As the most promising holographic recording medium, holographic plastic has the characteristics of light weight, easy processing, large information storage capacity, and strong light modulation ability, and has shown broad application prospects in naked-eye three-dimensional display, augmented reality (AR), high-end anti-counterfeiting, high-density holographic data storage, and holographic sensors.

[0003] Holographic plastic is mainly composed of a matrix, a photopolymer monomer, and a photoinitiating system, wherein the photoinitiating system includes a dye and a co-initiator. The dye absorbs visible light and reacts with the co-initiator to produce active centers, and the active centers react with the photopolymer monomer to initiate polymerization, so that the monomer and the matrix undergo phase separation, forming a holographic grating with a periodic distribution of refractive index. The performance of holographic plastic includes refractive index modulation, light transmittance, diffraction efficiency, and photosensitivity. Among them, increasing the refractive index modulation is conducive to increasing the diffraction efficiency and reducing the thickness of the holographic recording material (Holographic Polymer Materials, Science Press, 2020). It is generally believed that the refractive index modulation determines the performance of the grating and is the most important performance parameter of holographic plastic.

[0004] The refractive index modulation of holographic plastic is determined by the degree of phase separation of the matrix and the photopolymer monomer and the refractive index difference. The degree of phase separation of the matrix and the photopolymer monomer is related to the viscosity of the system. Generally speaking, the smaller the viscosity of the system, the more conducive to the migration of the photopolymer monomer, and the more conducive to improving the degree of phase separation. In addition, since the period of the reflective grating is smaller, the photopolymer monomer migrates a shorter distance compared to the transmissive grating, so the refractive index modulation of the reflective grating is higher.

[0005] At present, the preparation of holographic plastics, the base is mostly low glass transition temperature polymer. The advantage of this is that the base has better solubility, which is convenient for subsequent processing into a film, and at room temperature, the base has a larger free volume or even the chain segment of the base polymer has a certain movement ability, which facilitates the diffusion of photopolymer monomers and improves the phase separation degree. However, the holographic plastics prepared by using such base often do not have good environmental weatherability, and under high temperature conditions, the diffraction peak of the grating will drift, the haze of the grating will increase and other problems will occur. Therefore, how to use a high glass transition temperature base to prepare a reverse diffusion photopolymerization holographic plastic system, so as to prepare a holographic plastic with high refractive index modulation is still a challenge. SUMMARY

[0006] In view of the above defects or improvement needs of the prior art, the purpose of the present application is to provide a holographic recording medium and its preparation and application, so as to solve the problem of monomer diffusion difficulty when the base with high glass transition temperature exists in the holographic plastic. The holographic recording medium is constructed by using a base with high glass transition temperature and high refractive index, a low refractive index monomer, a photoinitiating system, and adding a leveling agent or a plasticizer as needed. The preparation method of the holographic recording medium is: (1) mixing the base with high glass transition temperature and high refractive index, the low refractive index monomer and the photoinitiating system under light shielding condition to obtain a mixed solution; the mixing process can selectively add an appropriate amount of organic solvent, plasticizer or leveling agent; (2) under light shielding condition, the mixed solution obtained in step (1) is scraped and coated on a substrate to form a film, thereby obtaining the holographic recording medium. The holographic recording medium is exposed to coherent laser, thereby forming a photopolymerization holographic plastic with periodic distribution of refractive index, in which the coherent bright area is low refractive index and the coherent dark area is high refractive index. The grating structure generated based on the present application can be either transmissive or reflective.

[0007] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0008] A holographic recording medium, characterized in that it comprises a base with high glass transition temperature and high refractive index, a low refractive index monomer and a photoinitiating system.

[0009] The glass transition temperature of the base is above 100℃.

[0010] According to an embodiment of the present application, the holographic recording medium further comprises a plasticizer.

[0011] According to an embodiment of the present application, the holographic recording medium further comprises a leveling agent.

[0012] According to an embodiment of the present application, the base with high glass transition temperature and high refractive index is at least one of polyimide, polyurea, polythiourea and polyimino ketone, preferably polyimide; the polyimide can have the following chemical structure:

[0013]

[0014] wherein 2≤(n+m)≤50, m is an integer equal to or greater than 0 and less than 50, X1 is at least one of sulfur, selenium, and tellurium, and X2 is at least one of carbon, oxygen, and sulfur.

[0015] According to an embodiment of the present application, the polyimide has a number average molecular weight of 2,000 to 50,000, preferably 8,000 to 40,000.

[0016] According to an embodiment of the present application, the substrate has a refractive index of greater than 1.5, preferably a refractive index of 1.55 or greater, more preferably a refractive index of 1.6 or greater, for example 1.6 to 1.8, and for example 1.6 to 1.7. The substrate has good solution processing properties and a high glass transition temperature, and the thin film thereof has a high light transmittance.

[0017] According to an embodiment of the present application, the substrate thin film has a light transmittance of 70% or greater at 400 nm, preferably 80% or greater.

[0018] According to an embodiment of the present application, the substrate is soluble in an organic solvent. Preferably, the organic solvent is at least one selected from the group consisting of tetrahydrofuran, dichloromethane, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0019] According to an embodiment of the present application, the substrate has a glass transition temperature of 150°C or greater, for example 150 to 230°C, and for example 150 to 190°C.

[0020] According to an embodiment of the present application, the low refractive index monomer has a refractive index of less than 1.55; preferably, the low refractive index monomer has a refractive index of 1.50 or less; more preferably 1.46 or less.

[0021] According to an embodiment of the present application, the low refractive index monomer has a viscosity of less than 200 mPa·s at 20°C, preferably a viscosity of less than 100 mPa·s at 20°C.

[0022] According to an embodiment of the present application, the plasticizer has a refractive index of 1.50 or greater, preferably a refractive index of 1.55 or greater, more preferably a refractive index of 1.60 or greater, for example 1.55 to 1.80, and for example 1.60 to 1.80.

[0023] According to an embodiment of the present application, the difference between the refractive index of the substrate and the low refractive index monomer is greater than 0.02, preferably not less than 0.06.

[0024] According to an embodiment of the present application, the holographic recording medium comprises, in mass parts, 15-90% of the high glass transition temperature and high refractive index base, 9-70% of the low refractive index monomer and 0-50% of the plasticizer;

[0025] wherein the photoinitiating system accounts for 0.1-10% of the total mass of the base, the low refractive index monomer and the plasticizer; and the leveling agent accounts for 0-2% of the total mass of the base, the low refractive index monomer and the plasticizer.

[0026] Preferably, the holographic recording medium comprises, in mass parts, 30-60% of the high glass transition temperature and high refractive index base, 30-60% of the low refractive index monomer and 0-20% of the plasticizer; and the photoinitiating system accounts for 0.5-5% of the total mass of the base, the low refractive index monomer and the plasticizer.

[0027] Preferably, the leveling agent accounts for 0-1% of the total mass of the base, the low refractive index monomer and the plasticizer.

[0028] Preferably, the holographic recording medium comprises, in mass parts, 30-60% of the high glass transition temperature and high refractive index base, 30-60% of the low refractive index monomer and 5-20% of the plasticizer; and the photoinitiating system accounts for 0.5-5% of the total mass of the base, the low refractive index monomer and the plasticizer.

[0029] According to an embodiment of the present application, the low refractive index monomer is at least one of acrylate, methacrylate, acrylamide, methacrylamide; preferably, one or both of acrylate and acrylamide; more preferably, acrylate.

[0030] Preferably, the acrylate includes, but is not limited to, at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-octyl acrylate, decyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-ethoxyethyl acrylate, 2-cyanoethyl acrylate, cyclohexyl acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, tricyclo[5.2.1.0 2,6]decane diacrylate, urethane dimethacrylate, 2-phenoxyethyl acrylate, (5-ethyl-13-dioxane-5-yl)methyl acrylate, tetrahydrofuran-2-yl methacrylate, cyclopentyl methacrylate, etc.

[0031] Preferably, the acrylamide includes, but is not limited to, at least one of N,N-dimethyl acrylamide, N,N-diethyl acrylamide, N-methyl acrylamide, N-ethyl acrylamide, diacetone acrylamide, methylol acrylamide, N-phenyl acrylamide, m-xylene diacrylamide, N-hydroxyethyl acrylamide, N-t-octyl acrylamide, N-t-butyl acrylamide, hexamethylene bisacrylamide, N-dodecyl acrylamide, N-p-hydroxyphenyl acrylamide, 4-(acrylamido)benzoic acid, and the like.

[0032] According to an embodiment of the present application, the photoinitiating system comprises a photoinitiator; the photoinitiator includes, but is not limited to, at least one of bisacyl phosphine oxide, organic borate, organic metal compound, light absorbing amine, purine dye, thiazine dye, acridine dye, phenoxazine dye, phenoxazine dye, fluorescent dye, phenoxazole dye, thiazole dye, iodonium salt, ketone derivative, diaryl imidazole derivative, coumarin and coumarin ketone derivative, pyridine and thio pyridine salt, and the like. For example, the photoinitiator is at least one of safranin O, tetrapropyl ammonium fluoroborate, erythrosin, benzyl tetrafluoroborate ammonium, tetra-n-butyl ammonium tetraphenyl borate, bis(4-t-butylphenyl) iodonium hexafluorophosphate, tetrapropyl ammonium fluoroborate.

[0033] According to an embodiment of the present application, the plasticizer is at least one of oxacyclic compound, azacyclic compound, thiacyclic compound, liquid crystal, bromonaphthalene, bromobenzene, iodine naphthalene. Preferably, the oxacyclic compound, azacyclic compound, more preferably, the oxacyclic compound. Preferably, the plasticizer is selected from at least one of epoxy chloropropane, diphenyl glycidyl ether, epoxy cyclohexane, butyl oxirane, ethyl oxirane, epoxy propyl phenyl ether, m-oxirane chlorobenzene, 1,2-epoxy octane, epoxy propyl guaiacol ether, epoxy styrene, 4-epoxy propoxy carbazole, epoxy propyl phenyl ether, 2-phenyl-3-methyl cycloaziridine, 3-hydroxy-1-benzhydryl cycloaziridine, 2-methyl cyclothioethane, 2-methyl cyclothiopropane, 2-(chloromethyl) cyclothioethane, cyclohexyl-4-thiomorpholinyl-methyl mercaptan, and the like.

[0034] According to an embodiment of the present application, the leveling agent is selected from at least one of leveling agent 310, leveling agent 313, leveling agent 333, leveling agent 354, leveling agent 381, and the like.

[0035] The present application also provides a preparation method of the above-mentioned holographic recording medium, characterized in that the method is prepared by the following steps:

[0036] (1) mixing the high glass transition temperature and high refractive index matrix, low refractive index monomer, photoinitiating system under light-proof condition to obtain a mixed solution;

[0037] (2) The mixture obtained in step (1) is coated on a substrate to form a film under light-proof conditions to obtain a holographic recording medium.

[0038] According to an embodiment of the present application, at least one of a plasticizer, an organic solvent or a leveling agent can be further added in step (1).

[0039] For example, when at least one of the matrix and the low refractive index monomer is a liquid, the mixture can be directly mixed uniformly by the liquid substance. Alternatively, when at least one of the high refractive index resin and the low refractive index monomer is a liquid, the mixture can also be additionally used with an organic solvent.

[0040] For example, when neither the matrix nor the low refractive index monomer is a liquid, the uniform reaction mixture is formed by using an organic solvent.

[0041] Preferably, the organic solvent is at least one of tetrahydrofuran, dichloromethane, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0042] According to an embodiment of the present application, in step (2), the film thickness of the holographic recording medium is below 8 μm.

[0043] The present application also provides a photopolymerized holographic plastic, characterized in that the photopolymerized holographic plastic is a grating structure with periodic refractive index distribution formed by the above-mentioned holographic recording medium under coherent laser irradiation.

[0044] According to an embodiment of the present application, the refractive index modulation of the holographic plastic is not less than 0.02, preferably not less than 0.03, preferably not less than 0.04, and more preferably not less than 0.045.

[0045] According to an embodiment of the present application, the haze of the holographic plastic is not higher than 4%, preferably not higher than 3%, and more preferably not higher than 2%.

[0046] The present application also provides a preparation method of the above-mentioned photopolymerized holographic plastic, which comprises:

[0047] The above-mentioned holographic recording medium is subjected to holographic exposure to obtain the photopolymerized holographic plastic.

[0048] According to an embodiment of the present application, the wavelength of the light applied to the holographic recording medium is 400-800 nm.

[0049] The present application also provides the above-mentioned holographic recording medium or photopolymerized holographic plastic for use in anti-counterfeiting, virtual reality, augmented reality or data storage.

[0050] It should be noted that: in the present application, if there is no special description, all the embodiments and preferred embodiments mentioned in the present application can be combined to form new technical solutions. In this application, if there is no special description, all the technical features and preferred features mentioned in the application can be combined to form new technical solutions. In the present application, if there is no special description, the percentage (%) or the part refers to the percentage by weight or the weight part of the composition. In the present application, unless otherwise specified, the numerical range "a~b" represents a brief representation of any real number combination between a and b, and includes a and b, where a and b are real numbers. For example, the numerical range "1~5" means that all real numbers between "1~5" have been listed in the present application, and "1~5" is only a brief representation of these numerical combinations. The lower limit and upper limit of the range disclosed in the present application can be one or more lower limits and one or more upper limits, respectively. The beneficial effects of the present application:

[0051] The photopolymerization holographic plastic of the present application not only has a higher refractive index modulation and a lower haze, but also uses a high glass transition temperature and a high refractive index matrix (such as polyimide) to prepare a holographic plastic for the first time, which has good environmental weather resistance.

[0052] Specific analysis:

[0053] (1) In the present application, the principle of grating formation is that under the irradiation of coherent laser, the holographic recording medium, the coherent bright area, the photo-initiation system rapidly produces active centers, and the low refractive index monomer is attacked by the active center to initiate polymerization. The monomer in the coherent bright area is consumed, and the monomer between the coherent bright area and the coherent dark area produces a concentration difference, which drives the monomer to diffuse from the coherent dark area to the coherent bright area and participate in the polymerization reaction of the coherent bright area. Due to the increase of potential energy, the plasticizer and the matrix move to the coherent dark area, and finally the refractive index change of the coherent bright area low refractive index and the coherent dark area high refractive index is formed, thereby producing a periodic refractive index difference. By adding a suitable plasticizer, the diffusion ability of the photopolymer monomer in the matrix is given, the difficult processing problem of the holographic plastic with high glass transition temperature matrix is solved, and the phase separation degree and the refractive index modulation of the holographic plastic are greatly improved.

[0054] (2) The matrix (such as polyimide) used in the holographic recording medium of the present application is self-synthesized, which has the characteristics of solution processing and high refractive index, and the thin film has the characteristics of high light transmittance.

[0055] (3) Based on the present application, the obtained grating structure can be either transmissive or reflective. Generally, the reflective grating has a smaller period and the photopolymer monomer migrates a shorter distance compared to the transmissive grating, so the refractive index modulation of the reflective grating is higher.

[0056] (4) The holographic plastic obtained by the present application has high refractive index modulation and low haze, and for the first time, a high glass transition temperature polymer is used as the matrix, which has high glass transition temperature and good thermal stability. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 is a graph of the refractive index modulation (n) versus the haze of the holographic plastic obtained in Examples 1-5.

[0058] Figure 2 is a photograph of the products of Example 1 and Example 2; wherein, Figure 2 (a) in corresponds to the product of Example 1, Figure 2 (b) in corresponds to the product of Example 2. DETAILED DESCRIPTION

[0059] The technical solutions of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0060] The polyimides used in the following examples are all self-synthesized; the remaining drugs, except as specifically described, are commercially available. The substrate can be a glass substrate, and the protective film can be a polyethylene terephthalate protective film, according to actual needs.

[0061] Example 1:

[0062] The holographic recording medium contains 40% polyimide, 55% acrylic acid (5-ethyl-13-dioxane-5-yl) methyl ester, and 5% diphenyl glycidyl ether, based on 100% by mass;

[0063] The photoinitiating system is safranin O and tetrapropylammonium fluoroborate, which accounts for 0.1% and 0.7% of the total mass of the matrix, low refractive index monomer and plasticizer, respectively.

[0064] The glass transition temperature of the polyimide is 163°C, and the T 400 The light transmittance is 80.03%, the refractive index is 1.62, the number average molecular weight is 32000 (unit g / mol, same below), and the structure is:

[0065]

[0066] The low refractive index monomer has a refractive index of 1.46 and a viscosity of 10 mPa-s at 20°C.

[0067] The plasticizer has a refractive index of 1.581.

[0068] The preparation method is as follows:

[0069] (1) The above polyimide, low refractive index monomer, photoinitiating system and plasticizer are mixed under light-proof condition, an appropriate amount of tetrahydrofuran is added, and magnetic stirring is performed to obtain a uniform reaction mixture;

[0070] (2) The mixture prepared in step (1) is coated on a substrate using a coating machine under light-proof condition to form a film, and the solvent is volatilized to obtain a holographic recording medium;

[0071] (3) A beam of 532 nm laser is divided into two coherent beams with equal intensity, which are incident from the two sides of the holographic recording medium prepared in step (2) with an angle of 180°, and exposure is performed to prepare a holographic plastic with a thickness of 4 μm, a refractive index modulation of 0.047 and a haze of 2.7%. The holographic plastic can be stored stably at 70°C for 24 h.

[0072] Example 2:

[0073] The holographic recording medium contains 35% of polyimide, 55% of tetrahydrofuran-2-yl methacrylate and 10% of bromonaphthalene, based on 100% by mass.

[0074] The photoinitiating system is erythrosin and benzyl tetrafluoroborat, which accounts for 0.2% and 1.2% of the total mass of the matrix, low refractive index monomer and plasticizer, respectively.

[0075] The glass transition temperature of the polyimide is 186°C, and the T 400 The light transmittance is 86.5%, the refractive index is 1.62, the number average molecular weight is 28000 (unit g / mol, the same below), and the structure is:

[0076]

[0077] The low refractive index monomer has a refractive index of 1.45 and a viscosity of 5 mPa-s at 20°C.

[0078] The plasticizer has a refractive index of 1.656.

[0079] The preparation method is as follows:

[0080] (1) The above polyimide, low refractive index monomer, photoinitiating system and plasticizer are mixed under light-proof condition, and an appropriate amount of dichloromethane is added for magnetic stirring to obtain a uniform reaction mixture;

[0081] (2) The mixture prepared in step (1) is coated on a substrate using a coater under light-proof condition to form a film, and the solvent is volatilized to obtain a holographic recording medium;

[0082] (3) A 532 nm laser beam is divided into two coherent beams with equal intensity, which are incident from opposite sides of the holographic recording medium prepared in step (2) with an included angle of 180°, and exposure is performed to prepare a holographic grating with a thickness of 4 μm, a refractive index modulation of 0.041, and a haze of 2.4%. The holographic plastic can be stored stably at 70°C for 24 h.

[0083] Example 3:

[0084] The holographic recording medium contains 50% of polyimide, 40% of tetrahydrofurfuryl acrylate and 10% of bromobenzene, based on 100% by mass.

[0085] The photoinitiating system is safranin O and tetra-n-butylammonium tetraphenylborate, which accounts for 0.4% and 2% of the total mass of the matrix, low refractive index monomer and plasticizer, respectively.

[0086] The glass transition temperature of the polyimide is 179°C, and the T 400 The light transmittance is 83.41%, the refractive index is 1.62, the molecular weight is 36000 (unit g / mol, same below), and the structure is:

[0087]

[0088] The refractive index of the low refractive index monomer is 1.48, and the viscosity at 20°C is 15 mPa·s.

[0089] The refractive index of the plasticizer is 1.556.

[0090] The preparation method is as follows:

[0091] (1) The above polyimide, low refractive index monomer, photoinitiating system and plasticizer are mixed under light-proof condition, and an appropriate amount of tetrahydrofuran is added for magnetic stirring to obtain a uniform reaction mixture;

[0092] (2) The mixture prepared in step (1) is coated on a substrate using a coater under light-proof condition to form a film, and the solvent is volatilized to obtain a holographic recording medium;

[0093] (3) A 532 nm laser beam is divided into two coherent beams with equal intensity, which are incident from both sides of the holographic recording medium prepared in step (2) with an angle of 180°, to perform exposure, thereby preparing a holographic grating with a thickness of 4 μm, a refractive index modulation of 0.031, and a haze of 0.9%. The holographic plastic can be stored stably at 70 °C for 24 h.

[0094] Example 4

[0095] The holographic recording medium comprises, in parts by mass, 45% of polyimide, 45% of cyclopentyl methacrylate, and 10% of iodine naphthalene;

[0096] The photoinitiating system is safranin O and bis (4-tert-butylphenyl) iodonium hexafluorophosphate, which accounts for 0.5% and 3% of the total mass of the matrix, the low-refractive monomer, and the plasticizer, respectively.

[0097] The glass transition temperature is 188 °C, the film T 400 The light transmittance is 88.76%, the refractive index of the polyimide is 1.62, the molecular weight is 38000 (unit g / mol, the same below), and the structure is:

[0098]

[0099] The refractive index of the low-refractive monomer is 1.46, and the viscosity at 20 °C is 25 mPa·s.

[0100] The refractive index of the plasticizer is 1.712.

[0101] The preparation method is as follows:

[0102] (1) The polyimide, the low-refractive monomer, the photoinitiating system, and the plasticizer are mixed under light-proof conditions, an appropriate amount of tetrahydrofuran is added, and magnetic stirring is performed to obtain a uniform reaction mixture;

[0103] (2) The mixture prepared in step (1) is coated on a substrate using a coating machine under light-proof conditions, and a film is obtained after volatilizing the solvent, thereby obtaining a holographic recording medium;

[0104] (3) A 532 nm laser beam is divided into two coherent beams with equal intensity, which are incident from both sides of the holographic recording medium prepared in step (2) with an angle of 180°, to perform exposure, thereby preparing a holographic grating with a thickness of 4 μm, a refractive index modulation of 0.035, and a haze of 1.1%. The holographic plastic can be stored stably at 70 °C for 24 h.

[0105] Example 5

[0106] A holographic recording medium comprising, in mass proportions, 40 wt.% of polyimide, 50 wt.% of acrylic (5-ethyl-13-dioxane-5-yl) methyl ester, 5 wt.% of diurethane dimethacrylate, 5 wt.% of diphenyl glycidyl ether, and a photoinitiating system in an amount of 1.6 wt.% of the total mass of polyimide, low refractive index monomer and plasticizer.

[0107] The holographic recording medium comprises, in mass proportions of 100%, 40% of polyimide, 50% of acrylic (5-ethyl-13-dioxane-5-yl) methyl ester, 5 wt.% of diurethane dimethacrylate and 5% of diphenyl glycidyl ether;

[0108] The photoinitiating system is safranin O and tetrapropyl ammonium fluoroborate, in amounts of 0.1% and 0.7% of the total mass of the matrix, low refractive index monomer and plasticizer, respectively.

[0109] The glass transition temperature of the polyimide is 163°C, and the Tg of the film thereof is 163°C. 400 The light transmittance is 80.03%, the refractive index is 1.62, the number average molecular weight is 32000 (unit g / mol, same below), and the structure is:

[0110]

[0111] The refractive indices of the low refractive index monomers are 1.46 (acrylic (5-ethyl-13-dioxane-5-yl) methyl ester) and 1.47 (diurethane dimethacrylate), respectively, and the viscosities at 20°C are 10 mPa·s and 50 mPa·s, respectively.

[0112] The refractive index of the plasticizer is 1.581.

[0113] The preparation method is as follows:

[0114] (1) The polyimide, low refractive index monomer, photoinitiating system and plasticizer are mixed under light shielding conditions, an appropriate amount of tetrahydrofuran is added, and magnetic stirring is performed to obtain a uniform reaction mixture;

[0115] (2) The mixture prepared in step (1) is coated on a substrate using a coating machine under light shielding conditions, and after the solvent is volatilized, a holographic recording medium is obtained;

[0116] (3) A beam of 532 nm laser light is divided into two coherent beams of equal intensity, which are incident from opposite sides of the holographic recording medium prepared in step (2) at an angle of 180°, and exposure is performed to obtain a holographic plastic with a thickness of 4 μm, a refractive index modulation of 0.045, and a haze of 2.4%. The holographic plastic can be stored stably at 85°C for 96 h.

[0117] Example 6:

[0118] The holographic recording medium comprises 45% of polyimide and 55% of acrylic (5-ethyl-13-dioxane-5-yl) methyl ester, without adding plasticizer, with 100% of mass fraction;

[0119] The photoinitiating system is safranin O and tetrapropyl ammonium fluoroborate, and the mass fractions of the two in the total mass of the matrix and the low refractive monomer are 0.1% and 0.7% respectively.

[0120] The glass transition temperature of the polyimide is 163℃, and the T 400 The light transmittance is 80.03%, the refractive index is 1.62, the number average molecular weight is 32000 (unit: g / mol, the same below), and the structure is as follows:

[0121]

[0122] The refractive index of the low refractive monomer is 1.46, and the viscosity at 20℃ is 10 mPa·s.

[0123] The preparation method is as follows:

[0124] (1) The polyimide, the low refractive monomer and the photoinitiating system are mixed under light shielding condition, and an appropriate amount of tetrahydrofuran is added, and magnetic stirring is performed to obtain a uniform reaction mixture;

[0125] (2) The mixture prepared in step (1) is coated on a substrate using a coating machine under light shielding condition, and after volatilizing the solvent, a holographic recording medium is obtained;

[0126] (3) A beam of 532nm laser is divided into two beams of coherent light with equal intensity, and the two beams are incident from the two sides of the holographic recording medium prepared in step (2) with an angle of 180°, and exposure is performed to obtain a holographic plastic with a thickness of 4μm, a refractive index modulation degree of 0.011 and a haze of 2.3%. The holographic plastic can be stored stably at 70℃ for 24h.

[0127] The above has exemplarily described the embodiments of the present application. However, the protection scope of the present application is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A holographic recording medium, characterized by, It comprises a high glass transition temperature and high refractive index matrix, a low refractive index monomer and a photoinitiating system; The glass transition temperature of the matrix is 150-230 ℃; The high glass transition temperature and high refractive index matrix is at least one of polyimide, polyurea, polythiourea and polyimino ketone; The refractive index of the matrix is greater than 1.5; The refractive index of the low refractive index monomer is less than 1.55; The high glass transition temperature and high refractive index matrix is polyimide; the polyimide has the following chemical structure: Wherein, 2≤(n+m)≤50, m is an integer greater than or equal to 0 and less than 50, X1 is at least one of sulfur, selenium or tellurium element, X2 is at least one of carbon, oxygen or sulfur element.

2. The holographic recording medium according to claim 1, characterized in that, The holographic recording medium further comprises a plasticizer.

3. The holographic recording medium according to claim 2, wherein, The holographic recording medium further comprises a leveling agent.

4. The holographic recording medium according to claim 1, wherein, The number average molecular weight of the polyimide is 2000-50000.

5. The holographic recording medium according to claim 2, wherein The refractive index of the plasticizer is above 1.

50.

6. The holographic recording medium according to claim 3, wherein The holographic recording medium comprises 15-90% of the high glass transition temperature and high refractive index matrix, 9-70% of the low refractive index monomer and 0-50% of the plasticizer, with the total mass being 100%. Wherein, the photoinitiating system accounts for 0.1-10% of the total mass of the matrix, the low refractive index monomer and the plasticizer; the leveling agent accounts for 0-2% of the total mass of the matrix, the low refractive index monomer and the plasticizer.

7. The holographic recording medium according to claim 1, wherein The low refractive index monomer is at least one of acrylate, methacrylate, acrylamide or methacrylamide.

8. The holographic recording medium according to claim 1, wherein, The photoinitiating system comprises a photoinitiator; the photoinitiator is selected from at least one of bisacyl phosphine oxide, organic borate, organic metal compound, light absorbing amine, purine dye, thiazine dye, acridine dye, phenazine dye, phenoxazine dye, fluorescent dye, phenoxazole dye, thiazole dye, iodonium salt, ketone derivative, diaryl imidazole derivative, coumarin and coumarin ketone derivative, pyridine and thio pyridine salt.

9. The holographic recording medium according to claim 2, wherein, The plasticizer is at least one of oxygen heterocyclic compound, nitrogen heterocyclic compound, sulfur heterocyclic compound, liquid crystal, bromonaphthalene, bromobenzene and iodine naphthalene.

10. The holographic recording medium according to claim 3, wherein, The leveling agent is selected from at least one of leveling agent 310, leveling agent 313, leveling agent 333, leveling agent 354 and leveling agent 381.

11. The method of producing a holographic recording medium according to any one of claims 1 to 10, characterized in that, The method is prepared by the following steps: (1) mixing the high glass transition temperature and high refractive index matrix, the low refractive index monomer and the photoinitiating system under light-proof condition to obtain a mixed solution; (2) coating the mixed solution obtained in step (1) on a substrate under light-proof condition to form a film and obtain a holographic recording medium.

12. The method of claim 11, wherein, At least one of the plasticizer, organic solvent or leveling agent is further added in step (1).

13. A photopolymerized holographic plastic, characterized in that, The photopolymerized holographic plastic is a grating structure with periodic refractive index distribution formed by the holographic recording medium of any one of claims 1-10 under coherent laser irradiation.

14. The method for preparing the photopolymerizable holographic plastic according to claim 13, characterized in that, The method comprises: The holographic recording medium is subjected to holographic exposure to obtain the photopolymerized holographic plastic.

15. The holographic recording medium of any one of claims 1-10 or the photopolymerized holographic plastic of claim 13 is applied in anti-counterfeiting, virtual reality, augmented reality or data storage.

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