Holographic photopolymer and preparation method thereof

Abstract

The invention relates to a novel holographic photopolymer and a manufacturing method thereof. In some embodiments, a holographic photopolymer may include a polyurethane matrix, a write monomer, and a dye system. In some embodiments, the write monomer may include a polycyclic heteroaryl write monomer. In some embodiments, the holographic photopolymer may include an antioxidant inhibitor. In some embodiments, an augmented reality / virtual reality (AR / VR) device comprising a holographic photopolymer is described.

Description

[0001] Cross-references to related applications This application claims the benefit of US Provisional Patent Application No. 63 / 518,258, filed August 8, 2023, and US Provisional Patent Application No. 63 / 627,381, filed January 31, 2024, both of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure relates to holographic photopolymers that can be used in AR / VR glasses, optical displays, and other holographic applications, among other possibilities. This disclosure also relates to methods for manufacturing holographic photopolymers. Background Technology

[0003] As augmented reality glasses and optical displays become more prevalent, the demand for improved holographic media is increasing. Holographic media or materials can be produced from holographic gratings (e.g., volume holographic gratings). For example, US Patents No. 9,281,000 B2 and No. 8,771,904 B2 relate to a photopolymer formulation comprising a chemically cross-linked matrix polymer, a writing monomer, and a photoinitiator system for producing the holographic media via a volume holographic grating. However, the process of producing such a photopolymer formulation requires expensive nitrogen purging to remove oxygen. If oxygen is not completely removed, incomplete polymerization of the polymer may occur due to oxidation of free radicals.

[0004] Furthermore, the combination of high refractive index and low film thickness allows for the production of highly visible holograms. Existing volume grating holographic films used in AR / VR glasses may only achieve 50% reflectivity but have a thickness greater than 12 μm, resulting in low refractive index modulation. For example, increasing the refractive index modulation to greater than 0.03 could facilitate the production of holographic films with a thickness of 5–12 μm without compromising the wider field of view of AR / VR glasses.

[0005] Given the above situation, more contributions are needed in this technological field. Summary of the Invention

[0006] This disclosure generally relates to holographic photopolymers and methods for manufacturing the same. In one embodiment, the holographic photopolymer may include a polyurethane matrix, a writing monomer, and a dye system. In some forms of this embodiment, the holographic photopolymer may also include an oxygen scavenging additive. In some forms, the polyurethane matrix may conform to one of the following formulas: and .

[0007] In some forms, the polyurethane matrix can be connected to the writing monomer by a bond (e.g., a covalent bond or a non-covalent bond). In one non-limiting form, the bond can be a hydrogen bond.

[0008] In one or more forms, the polyurethane matrix can have a refractive index of about 1.44 to about 1.48. In some forms, the writing monomer can have a refractive index of about 1.45 to about 1.6, which results in a refractive index modulation (Δn) of greater than about 0.02.

[0009] In some forms, the polyurethane matrix can include one or more of a polypropylene polyol, 2-ethyl-2-(hydroxymethyl)-l,3-propanediol, an aliphatic polyether isocyanate, and dimethyl tin dineodecanoate. In one or more forms, the polyurethane matrix can have a glass transition temperature (Tg) of less than about 0 °C, although other variations are possible. In some forms, the weight ratio of the polyurethane matrix to the writing monomer can be in the range of 19: 1 to 1 :9, although other variations are contemplated and possible.

[0010] In one or more forms, the writing monomer can include a di-functional writing monomer or a mono-functional writing monomer. In some forms, the writing monomer can include one or more of bisphenol A diglycidyl ether diacrylate, bisphenol A ethoxylated diacrylate / dimethacrylate, and trimethylolpropane triacrylate. In some forms where bisphenol A di(meth)acrylate is present, it can conform to one or more of the following: , or .

[0011] In some forms, the writing monomer can include a polycyclic heteroaryl writing monomer. In some forms, the polycyclic heteroaryl writing monomer can include a di-functional writing monomer or a mono-functional writing monomer. When a polycyclic heteroaryl writing monomer is present, it can include one or more of bisphenol A diglycidyl ether diacrylate, bisphenol A ethoxylated di(meth)acrylate, trimethylolpropane triacrylate, ethoxylated fluorene diacrylate, liquid carbazole acrylate / methacrylate including alkyl sulfide chains or ether chains, m-phenoxybenzyl acrylate, and a hydroxy-functional acrylate, to provide some non-limiting examples. In some forms, the polycyclic heteroaryl writing monomer can include one of the following structures: , , , , and .

[0012] In some forms, the polycyclic heteroaryl write monomer can conform to the following formula: where X is C, Si, or Ge.

[0013] In some forms, the polycyclic heteroaryl write monomer can conform to one of the following formulas: or where X is O, S, Se, or Te.

[0014] In some forms, the polycyclic heteroaryl write monomer further includes a diluent, such as 1-vinyl-2-pyrrolidinone, although other variations are possible.

[0015] In some forms, the dye system includes a dye and a co-initiator. For example, the dye can include one or more of Erioglaucine O, methylene blue, astrazon orange G, and ethyl violet, and the co-initiator can include one or more of N-phenylglycine and hexaaryl-bisimidazolyl, to provide some non-limiting examples.

[0016] In forms where an oxygen scavenger additive is present, it can be an antioxidant inhibitor, such as triphenylphosphine, although other variations are possible. In some forms, the holographic photopolymer can further include a reactive diluent, such as [C1-C3 alkylpyrrolidinone] N-ethyl-2-pyrrolidinone, although other forms of reactive diluents are possible and contemplated.

[0017] In some forms, the transmittance of the holographic photopolymer can be greater than 90%. Additionally or alternatively, in some forms, the haze of the holographic photopolymer can be less than about 1%.

[0018] In some embodiments, an augmented reality / virtual reality (AR / VR) device includes a holographic photopolymer as described herein.

[0019] In one embodiment, a method of manufacturing a holographic photopolymer includes providing a polyurethane matrix including at least one hydroxyl group, a write monomer including at least one ether group, a dye system, and an oxygen scavenging or oxygen scavenger additive; mixing the polyurethane matrix, the write monomer, the dye system, and the oxygen scavenging or oxygen scavenger additive to form a mixture; and drying the mixture at room temperature. In some forms, the method can further include applying a vacuum to the mixture for about 1 hour. In some forms, the method includes forming a bond between the hydroxyl group and the ether group. In some forms, the method can further include polymerizing the mixture to form a photopolymer film. In some forms, the method can further include exposing the photopolymer film to a laser and bleaching the photopolymer film.

[0020] These and other embodiments are described in more detail below. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a graph showing infrared spectra of the holographic photopolymers described herein.

[0022] Figure 2 is a schematic of an experimental setup to measure properties of the holographic photopolymers described herein.

[0023] Figure 3 is a graph showing stability of the refractive efficiency of the holographic photopolymers described herein over time.

[0024] Figure 4 is a schematic of an experimental setup to measure the reflectance efficiency of the holographic photopolymers described herein.

[0025] Figure 5 is a graph showing measurement data of the reflectance efficiency and the diffraction efficiency of the holographic photopolymers described herein.

[0026] Figure 6 is a graph showing thickness of the holographic photopolymers described herein.

[0027] Figure 7A and 7B is a graph showing the reflectance efficiency, the transmittance efficiency, and the diffraction efficiency of the holographic photopolymers described herein.

[0028] Figure 8 is a graph showing transmittance of the holographic photopolymers described herein.

[0029] Figure 9 is a graph showing reflectance and transmittance of the holographic photopolymers described herein.

[0030] Figure 10A and 10B is a graph showing the reflectance efficiency, the transmittance efficiency, and the diffraction efficiency of the holographic photopolymers described herein.

[0031] Figure 11 is a graph showing reflectance and transmittance of the holographic photopolymers described herein.

[0032] Figure 12A and 12B is a graph showing the reflectance efficiency, the transmittance efficiency, and the diffraction efficiency of the holographic photopolymers described herein.

[0033] Figure 13A and 13B is a graph showing the reflectance efficiency, the transmittance efficiency, and the diffraction efficiency of the holographic photopolymers described herein.

[0034] Figure 14 This is a schematic diagram of the experimental setup used to measure the diffraction efficiency of the holographic optical polymer described in this paper. Detailed Implementation

[0035] In some aspects, this disclosure relates to holographic media that can be used in augmented reality / virtual reality (AR / VR) devices and / or optical displays, although other uses are contemplated. In one or more forms, the holographic photopolymer comprises a polyurethane matrix, a writing monomer, a dye system, and optional oxygen scavenging additives. In some aspects, the holographic photopolymer can provide high-visibility holograms for A / R 3D glasses, which can improve the user's viewing experience. Methods for manufacturing the holographic photopolymer are also described.

[0036] As used in this article, the term "bond" or "bonding" refers to a chemical bond between two atoms or between two parts when the atoms connected by a bond are considered part of a larger structure.

[0037] As used in this article, the term "part" refers to a specific segment or functional group of a molecule.

[0038] As used herein, the term "ester" refers to a chemical moiety having the formula RCOOR', where R can be an alkyl, cycloalkyl, aryl, heteroaryl (by cyclic carbon bonding), heterocyclic (by cyclic carbon bonding), or a hydrogen atom, and R' can be an alkyl or aryl.

[0039] As used herein, the term "purge-free" refers to a process or method for manufacturing the holographic photopolymer described herein, in which it is not necessary to purge gases from the local atmosphere in which the holographic photopolymer is manufactured.

[0040] This disclosure generally relates to holographic photopolymers and methods for manufacturing the same. In one or more forms, the holographic photopolymer includes a polyurethane matrix, a writing monomer, a dye system, and optionally an oxygen-scavenging additive. In some embodiments, the holographic photopolymer may also include a reactive diluent and / or may be solvent-free.

[0041] In one or more forms, the polyurethane matrix can be a chemically crosslinked aliphatic polyether polyurethane matrix. More specific, but non-limiting examples of polyurethane matrices include one or more of the following: polypropylene polyol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, aliphatic polyether isocyanate, and dimethyltin dinedecyl ester. In some forms, the polyurethane matrix conforms to one of the following formulas: or Where n = 5-70. Other variations of the polyurethane matrix are possible and anticipated. For example, in some forms where the polyurethane matrix includes dimethyltin dinedecanoate, it may include one or more aliphatic ether groups (having 2 to 5 carbon atoms), which can improve compatibility with the polypropylene polyol when the polypropylene polyol is also present in the polyurethane matrix. More specific, but non-limiting, examples of polyurethane matrices that can be used for the holographic photopolymers described herein include Sannix (Sanyo Chemical, Japan), A13084.0C (ThermoFisher Scientific, USA), Desmodur ultra E 30600 (Covestro, Germany), and Fomrez UL-28 (Galata Chemicals, USA).

[0042] In some forms, the components of the polyurethane matrix can be selected based on their molecular weight, which can affect the viscosity, flexibility, and mechanical strength of the polyurethane matrix. For example, in some forms where the polyurethane matrix includes a polypropylene polyol, the molecular weight of the polypropylene polyol can be about 2000, and in forms where the polyurethane matrix additionally or alternatively includes 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, the molecular weight of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol can be about 178. Without being bound by any particular theory, selecting the components of the polyurethane matrix based on molecular weight can yield unexpected results that optimize the reactivity and curing time of the polyurethane matrix.

[0043] In one or more forms, the glass transition temperature (Tg) of the polyurethane matrix can be less than about 0°C, about -5°C, about -10°C, about -20°C, about -30°C, about -40°C, about -50°C, about -70°C, or any temperature defined by these values, for example, -52°C. In some forms, the weight ratio of the polyurethane matrix to the writing monomer can be in the range of 19:1 to 1:9, although other variations are possible and contemplated. In some embodiments, the polyurethane matrix may have a free volume defined by the unoccupied space between matrix molecules. It is believed that a polyurethane matrix with a free volume can improve the shear modulus, thereby improving the diffusivity of the writing monomer.

[0044] In one or more forms, the monomer may include one or more of the following: bisphenol A diglycidyl ether diacrylate, bisphenol A ethoxylated diacrylate / dimethacrylate, trimethylolpropane triacrylate (TMPTA), and N-ethylpyrrolidone, to which only a few non-limiting examples are provided. In some embodiments, bisphenol A di(meth)acrylate may conform to one or more of the following formulas: , ,or .

[0045] In one or more forms, the writing monomer can be a polycyclic heteroaryl writing monomer. In these forms, the polycyclic heteroaryl writing monomer can include a bifunctional or monofunctional writing monomer. More specific, but non-limiting examples of polycyclic heteroaryl writing monomers that can be used include one or more of the following: bisphenol A diglycidyl ether diacrylate, bisphenol A ethoxylated di(meth)acrylate, trimethylolpropane triacrylate, ethoxylated cumylphenol acrylate, ethoxylated fluorene diacrylate, liquid ethoxylated fluorene diacrylate, 2-hydroxy-3-phenoxypropyl acrylate, o-phenylphenol ethyl acrylate, o-phenylphenol (EO)2 acrylate, biphenyl methacrylate, liquid carbazole acrylate / methacrylate containing an alkyl sulfide chain or ether chain, m-phenoxybenzyl acrylate, and hydroxy functional acrylate. In one or more forms, the monofunctional writing monomer can include a secondary hydroxyl functional acrylate, which can include the same organic ether unit as the polyurethane matrix. In some forms, the polycyclic heteroaryl writing monomer can include one of the following structures: , , , , and .

[0046] In some forms, the writing of polycyclic heteroaryl groups into monomers can conform to the following formula: , where X is C, Si or Ge.

[0047] In some forms, the polycyclic heteroaryl group written into the monomer can conform to one or more of the following formulas: and , where X is O, S, Se or Te.

[0048] In the heteroaryl writing monomers comprising one or more forms of bisphenol A di(meth)acrylate and TMPTA, the weight ratio of bisphenol A di(meth)acrylate to TMPTA can be from about 2:3 to about 3:1, or any ratio defined by that range. Other variations of the writing monomers are possible and contemplated, and more specific but non-limiting forms of the writing monomers include Ebercryl 3700 (Allnex, Germany) and TMPTA (Allnex, Germany). Without being bound by any particular theory, selecting writing monomers and polyurethane matrices with similar structures, and forming hydrogen bonds between the writing monomers and the polyurethane matrix, can improve miscibility.

[0049] In the form in which the monomer comprises bisphenol A diglycidyl ether diacrylate, the molecular weight of bisphenol A diglycidyl ether diacrylate can be about 484. In the form in which the monomer comprises trimethylolpropane triacrylate, the molecular weight of trimethylolpropane triacrylate can be about 296. In the form in which the monomer comprises N-ethylpyrrolidone, the molecular weight of N-ethylpyrrolidone can be about 113.

[0050] Unbound by any particular theory, using monofunctional write-monomers with a refractive index greater than 1.5, a glass transition temperature less than 40°C, and a viscosity less than 2000 cP, 1000 cP, 500 cP, or 200 cP at 25°C, and whose mobility is correlated with a specific viscosity (e.g., mobility increases with decreasing viscosity, resulting in low resistance, high shear strength, and rapid molecular flow), can increase diffusivity and facilitate the production of holographic photopolymers with Δn ≥ 0.03. In some forms, the refractive index of the monofunctional write-monomer can be greater than about 1.5, about 1.51, about 1.52, about 1.53, about 1.54, about 1.55, about 1.56, about 1.57, about 1.58, about 1.59, about 1.6, or any refractive index defined by this range, such as 1.523. In some embodiments, the glass transition temperature (Tg) of the monofunctional write-in monomer can be less than about 40°C, about 40°C, about 35°C, about 30°C, about 25°C, about 20°C, about 15°C, about 10°C, about 5°C, or any temperature defined by these values, for example, 31°C. In some embodiments, the viscosity of the monofunctional write-in monomer can be less than 200 cP at 25°C.

[0051] The polyurethane matrix can be linked to the writing monomer via one or more forms of bonds. For example, the bond can be covalent or non-covalent. In some forms where the writing monomer includes bisphenol A diglycidyl ether diacrylate, the bond can be a hydrogen bond formed between the hydroxyl group of the bisphenol A diglycidyl ether diacrylate and the ether group of the polyurethane matrix. In other forms, hydrogen bonds can be formed between the hydroxyl group of another (meth)acrylate of the writing monomer and the ether group of the polyurethane matrix. For example, in forms comprising polypropylene polyol and aliphatic polyether isocyanate, hydrogen bond formation can be promoted by ensuring that the polypropylene polyol to aliphatic polyether isocyanate reacts completely with each other at a ratio that ensures their complete reaction. As a non-limiting example, the ratio of polypropylene polyol to aliphatic polyether isocyanate can be about 1.4:1. In a non-limiting form comprising bisphenol A diglycidyl ether diacrylate and trimethylolpropane triacrylate, for example, about 1 gram to about 2 grams of bisphenol A diglycidyl ether diacrylate and about 1 gram to about 2 grams of trimethylolpropane triacrylate can be included.

[0052] Hydrogen bonds between the polyurethane matrix and the written monomers of the holographic photopolymer can be evaluated using Fourier transform infrared (FTIR) spectroscopy. For example, hydrogen bonds were evaluated on the holographic photopolymer described in this paper after the application of a holographic grating (Thermo Scientific FTIR-ATR Spectrophotometer). FTIR results are shown below. Figure 1 As shown, the absorption peaks at 2920 cm⁻¹ and 2850 cm⁻¹ are related to the OH stretching vibration. The decrease and weakening of the OH peak intensity indicate hydrogen bonding. (Y. Wang et al., Macromol. Mater. Eng. 2023, 5, 2200440).

[0053] In some forms, the refractive index of the polyurethane matrix can be from about 1.4 to about 1.5, about 1.40, about 1.41, about 1.42, about 1.43, about 1.44, about 1.45, about 1.46, about 1.47, about 1.48, about 1.49, about 1.5, or any value defined by that range, for example, 1.468. In some forms, the refractive index of the written monomer can be from about 1.5 to about 1.6, about 1.5, about 1.51, about 1.52, about 1.53, about 1.54, about 1.55, about 1.56, about 1.57, about 1.58, about 1.59, about 1.6, or any value defined by that range, for example, 1.523. Unbound by any particular theory, it is believed that writing hydrogen bonds between the monomer and the polyurethane matrix, and selecting monomers and polyurethane matrices with similar polymer chains, can increase the refractive index modulation (Δn) of the holographic photopolymer to greater than about 0.02. In some forms, the refractive index modulation of the holographic photopolymer can be greater than about 0.02, about 0.025, about 0.026, about 0.027, about 0.028, about 0.029, about 0.030, about 0.031, about 0.032, about 0.033, about 0.034, about 0.035, about 0.036, about 0.037, about 0.038, about 0.039, about 0.04, or any refractive index modulation defined by this range, such as 0.0293 or 0.0387. By achieving a refractive index modulation from about 0.02 to about 0.033, holographic photopolymer films with a thickness of less than 12 μm can be provided. Figure 2 A schematic diagram of an apparatus for measuring the refractive index modulation of a holographic polymer is shown, which is used to evaluate the holographic polymers described in the examples below. In some forms, the haze of the holographic polymers described herein may be less than about 1%, about 0.75%, about 0.5%, about 0.25%, or any haze defined by that range, for example, 0.41.

[0054] In one or more forms, the writing monomer and polyurethane matrix may include two methyl groups between the two phenyl groups. Without being limited by any particular theory, it is believed that the mechanical stability of the holographic photopolymer can be increased by selecting writing monomers and polyurethane matrices with similar structures.

[0055] In one or more forms, the dye system comprises a dye and a co-initiator. The dye may include Safranin O, Methylene Blue, Basic Orange 21, Ethyl Violet, or combinations thereof, to be provided only as non-limiting examples. The co-initiator may include N-phenylglycine, hexaarylbisimidazole, or combinations thereof, to be provided only as non-limiting examples. Other variations of the dye system are possible and contemplated. More specific, but non-limiting, examples of dye systems that may be used in this holographic photopolymer include Safranin O (available from ThermoFisher Scientific, USA, product number B21674.09 (CAS No. 477-73-6)) and N-phenylglycine (available from Sigma-Aldrich, Germany, product number 330469 (CAS No. 103-01-5)). In one or more forms, the molecular weight of the dye may be from about 300 to about 400, about 300, about 325, about 350, about 375, about 400, or any value defined by that range. In one or more forms, the molecular weight of the co-initiator can be about 100 to about 200, about 100, about 125, about 150, about 175, about 200, or any value defined by that range.

[0056] Controlling the ratio of dye to co-initiator can increase the polymerization rate and degree of polymerization. As a non-limiting example, the weight ratio of dye to co-initiator can be from about 1:2 to about 1:20, about 1:2, about 1:5 to about 1:10, about 1:15, about 1:20, about 1:10 to about 1:14, or any ratio or range defined by that range. For example, in one form, the weight ratio of dye to co-initiator can be from 1:10 to about 1:14.

[0057] As described above, in some forms, holographic photopolymers may optionally contain an oxygen scavenger additive that facilitates polymerization of the holographic photopolymer in a localized atmosphere without requiring degassing, purging, or oxygen removal of the localized atmosphere. For example, the oxygen scavenger additive may include an antioxidant inhibitor, such as triphenylphosphine, available from Sigma-Aldrich, Germany, under product number T84409. Variations of the oxygen scavenger additive are possible and contemplated; a more specific but non-limiting example of an oxygen scavenger additive that can be used with the holographic photopolymers described herein includes triphenylphosphine (CAS No. 603-35-0), available from Sigma-Aldrich, Germany, under product number T84409. Without being bound by any particular theory, it is anticipated that the type of oxygen scavenger additive may unexpectedly result in reduced oxidation of free radicals to regenerate active free radicals, thereby eliminating the need to remove oxygen from the localized atmosphere through degassing, purging, or with a gas (e.g., nitrogen), thus improving time and cost efficiency. In one or more forms, the molecular weight of the oxygen scavenger additive can be about 200 to about 300, about 200, about 225, about 250, about 275, about 300, or any value defined by that range.

[0058] When the oxygen scavenging additive is triphenylphosphine, it can reduce oxygen inhibition during the free radical polymerization of the monomer according to the following reaction scheme: As described above, in some embodiments, the holographic photopolymer may also include a diluent. For example, in some forms, the writing monomer of the holographic photopolymer may include a reactive diluent. In some forms, the reactive diluent may be a solvent, such as a low-volatility aprotic solvent. A non-limiting example of a low-volatility aprotic solvent that can be used is [C1-C3 alkylpyrrolidone]N-ethyl-2-pyrrolidone. In some forms, the diluent may include a polymerizable diluent, such as 1-vinyl-2-pyrrolidone. Among other functions, a polymerizable diluent can facilitate the dissolution and mixing of the dye system without the need for a solvent. Other variations of the diluent are also possible and contemplated. A more specific but non-limiting example of a reactive diluent that can be used with holographic photopolymers includes 1-ethyl-2-pyrrolidone, available from Sigma-Aldrich, Germany, under product number 146358.

[0059] In some forms, the reflectivity of the holographic photopolymer described herein may be greater than about 50%, about 55%, about 60%, about 65%, or any reflectivity defined by these values, for example, 61%. In one or more forms, the diffraction efficiency of the holographic photopolymer described herein may be greater than about 70%, about 75%, about 80%, about 85%, or any diffraction efficiency defined by these values, for example, 79%.

[0060] In one or more forms, the thickness of the holographic photopolymer described herein may be about 3 µm to about 12 µm, about 3 µm, about 4 µm, about 5 µm, about 6 µm, about 7 µm, about 8 µm, about 9 µm, about 10 µm, about 11 µm, about 12 µm, or any value defined by that range.

[0061] In some forms, the holographic photopolymer may also include a tin catalyst. The tin catalyst may include an organotin catalyst, 1-vinyl-2-pyrrolidone, or a combination thereof. The ratio of the organotin catalyst to 1-vinyl-2-pyrrolidone may be about 0:10, about 1:10, about 2:10, about 3:10, about 0:9, about 1:9, about 2:9, about 3:9, about 0:8, about 1:8, about 2:8, about 3:8, or any value defined by that range, for example, 1.1:9.2.

[0062] As described above, in one or more forms, the dye system may include a dye (e.g., Safranin O) and a co-initiator (e.g., hexaarylbisimidazole, N-phenylglycine, or a combination thereof). For example, in the presence of N-phenylglycine, it can be used as a hydrogen donor compatible with tin catalysts (when present) and aliphatic polyether isocyanates of a polyurethane matrix (if applicable). Combining N-phenylglycine with a visible light-absorbing photosensitizer (e.g., Safranin O) and a co-initiator (e.g., hexaarylbisimidazole) yields unexpected results, increasing transmittance to over 95%.

[0063] In a non-limiting form, the holographic photopolymer may include liquid ethoxylated fluorene diacrylate, liquid carbazole acrylate / methacrylate, monofunctional writing monomer, secondary hydroxyl-functionalized acrylate, aliphatic polyether isocyanate, and polypropylene polyol. In this form, the components exhibit high compatibility due to their similar organic ether units and the covalent bonds formed between the isocyanate and the secondary hydroxyl-functionalized acrylate. This compatibility can provide unexpected results, namely, a high transmittance of greater than 95% and a low haze of less than 1% for the holographic photopolymer.

[0064] In some embodiments, the transmittance of the holographic photopolymer described herein can be greater than about 90%. In some embodiments, the transmittance of the holographic photopolymer described herein can be greater than about 90%, greater than 91%, greater than 92%, greater than 93%, greater than 94%, greater than 95%, greater than 96%, or greater than 97% at 457 nm. In some embodiments, the transmittance of the holographic photopolymer described herein can be greater than about 90%, greater than 91%, greater than 92%, greater than 93%, greater than 94%, greater than 95%, greater than 96%, greater than 97%, greater than 98%, or greater than 99% at 532 nm. In some embodiments, the transmittance of the holographic photopolymer described herein may be greater than about 90% at 600 nm, greater than 91% at 600 nm, greater than 92% at 600 nm, greater than 93% at 600 nm, greater than 94% at 600 nm, greater than 95% at 600 nm, greater than 96% at 600 nm, greater than 97% at 600 nm, greater than 98% at 600 nm, or greater than 99% at 600 nm.

[0065] A method for manufacturing the holographic photopolymer described herein may include: providing a polyurethane matrix comprising at least one hydroxyl group; providing a writing monomer comprising at least one ether group; providing a dye system; providing an oxygen scavenging additive; mixing the polyurethane matrix, writing monomer, dye system, and oxygen scavenging additive at a temperature of about 50°C to about 70°C to form a mixture; and drying the mixture at room temperature. In some forms, the method may further include applying a vacuum to the mixture at a pressure of about -0.09 MPa to about 0.09 MPa for about 30 minutes or about 1 hour. In some forms, the application of vacuum removes defects in the mixture and occurs prior to polymerization. In some forms, the method may further include polymerizing the mixture to form a photopolymer film. In some aspects, the method includes forming hydrogen bonds between the hydroxyl and ether groups. In some embodiments, the method for manufacturing the holographic photopolymer may be purge-free. In some forms, the method may further include exposing the photopolymer film to a laser and bleaching the photopolymer film.

[0066] In some forms, methods for manufacturing holographic photopolymers may include: preparing a dye system; preparing a writing monomer; preparing a catalyst solution; mixing the dye system, the writing monomer, and a polypropylene polyol to form a first mixture; mixing the first mixture with a polyether isocyanate to form a second mixture; mixing the second mixture with the catalyst solution to form a third mixture; and applying a vacuum to the third mixture. In some forms, the step of preparing the dye system may include mixing N-ethylpyrrolidone, safranin O, N-phenylglycine, and triphenylphosphine at a temperature of about 40°C to about 70°C for about 2 to about 3 hours. In some forms, the step of preparing the writing monomer may include mixing bisphenol A diglycidyl ether diacrylate and TMPTA at a temperature of about 50°C to about 70°C for about 5 to about 7 hours. In some forms, the step of preparing the catalyst solution may include mixing the catalyst and 1-ethyl-2-pyrrolidone at a ratio of about 1:9 (catalyst: 1-ethyl-2-pyrrolidone). In some forms, the ratio of catalyst to 1-ethyl-2-pyrrolidone can be about 1:2 to about 1:20, about 1:2, about 1:5, about 1:10, about 1:15, about 1:20, or any ratio defined by that range, for example, about 1:9.

[0067] In some forms, the step of mixing the dye system, the writing monomer, and the polyurethane matrix to form a first mixture may further include mixing the dye system, the writing monomer, and the polyurethane matrix at a temperature of about 50°C to about 70°C for about 7 to about 9 hours. In some forms, the first mixture may contain about 5 wt.% to about 20 wt.% of the dye system, about 40 wt.% to about 60 wt.% of the polypropylene polyol, and about 30 wt.% to about 40 wt.% of the polyether isocyanate. In some forms, the method may further include cooling the first mixture to about 30°C to about 40°C.

[0068] In some forms, a vacuum may be applied to the third mixture at a temperature of about 20°C to about 50°C for about 10 minutes to about 1 hour, although various alternatives are possible and contemplated. For example, in a non-limiting form, a vacuum may be applied to the third mixture for about 30 minutes. The vacuum may be applied at a pressure of about 0.01 MPa to about 0.09 MPa.

[0069] In some forms, the method for manufacturing holographic photopolymers may also include a two-stage chemical process. The first stage of this method may include the step of polymerizing a third mixture to form a photopolymer film. In some forms, the photopolymer film may include a polymerized polyurethane matrix and non-polymerized writing monomers dispersed in the polymerized polyurethane matrix. In some forms, the step of polymerizing the third mixture to form the photopolymer film may further include curing the third mixture at room temperature for about 6 hours to about 12 hours.

[0070] In some implementations, the second stage may include exposing the photopolymer film to a power density of about 1 mW / cm². 2 Approximately 20 mW / cm 2 The process involves exposing the photopolymer film to a laser with a wavelength of about 532 nm for about 1 second to about 30 seconds. In some embodiments, the step of exposing the photopolymer film to the laser may further include polymerizing the writing monomer dispersed in the polymeric polyurethane matrix. In some embodiments, the second stage may further include a step of bleaching the photopolymer film, which may include exposing the photopolymer to ultraviolet light with a wavelength of about 340 nm to about 400 nm.

[0071] A two-stage chemical approach can improve holographic photopolymers because it allows for precise control over the sequence, timing, and selectivity of different chemical transformations, resulting in the efficient and high-precision synthesis of complex molecules or materials. In some embodiments, a solid host matrix comprising a polyurethane matrix and additives can be formed to produce a first photopolymer, which is then recorded into a second photopolymer comprising a dye system and a writing monomer. Furthermore, the writing monomer and polyurethane matrix can be selected based on their similar ether groups to increase the transparency of the holographic photopolymer. In some embodiments, the transmittance of the holographic photopolymer can be greater than 80%, 85%, 90%, or 95%, or any transmittance defined by these values, for example, 91%. In some forms, high transmittance can be observed in the UV-Vis spectrum.

[0072] In some embodiments, the membrane can be manufactured in an atmosphere comprising about 25% oxygen to about 0% oxygen, less than about 25% oxygen, less than about 20% oxygen, less than about 15% oxygen, less than about 10% oxygen, less than about 5% oxygen, less than about 1% oxygen, or any percentage of oxygen defined by such range, according to the methods described herein.

[0073] In some embodiments, the holographic photopolymer described herein may be a film or coating applied to a glass substrate. In some embodiments, the holographic photopolymer described herein may be applied to a plastic substrate in the form of a film or coating. In some embodiments, the holographic photopolymer described herein may be applied to a glass substrate in the form of a coating using a vacuum lamination coating method. In some embodiments, the holographic photopolymer described herein may be applied to a plastic substrate in the form of a coating using a roll-to-roll coating method.

[0074] In some implementations, the AR / VR device may include the holographic light polymer described herein. In some forms, the AR / VR device may be an AR / VR headset. In some forms, the AR / VR device may include a holographic display.

[0075] The implementation plan and methods will be described in more detail below.

[0076] Example The following examples are intended to illustrate this disclosure only and are not intended to limit the scope or basic principles of this disclosure in any way.

[0077] Example 1 Preparation of photopolymer solution 1 0.35 mg N-ethylpyrrolidone (CAS No.: 2687-91-4), 10 mg safranin O (SFH+) (CAS 477-73-6), 100 mg N-phenylglycine (CAS No.: 103-01-5), and 50 mg triphenylphosphine (CAS 603-35-0) were mixed together at 55°C for 2–3 hours to form a dye stock solution. Equal amounts of Ebecryl 3700 (Allnex, Inc.) and TMPTA (CAS No.: 15625-89-5) were then mixed together at 60°C under safe light conditions for 6 hours to form a monomer writing solution. One part of catalyst (FOMREZ® UL-28) was mixed with nine parts of 1-ethyl-2-pyrrolidone to form a 10% catalyst stock solution.

[0078] 0.51 g of dye stock solution was mixed with 2.5 g of writing monomer solution and 1.4 g of polyol at 60°C under safe light conditions for 8 hours. Then the dye stock solution / writing monomer solution was cooled to 35°C, and 1 g of isocyanate Desmodur ultra E 36000 (Covestro company) was vigorously mixed into the dye stock solution / writing monomer solution for 5-10 minutes.

[0079] 0.018 g of catalyst stock solution was mixed into dye stock solution / written monomer solution for 1 minute. The final solution was then placed under vacuum at 35°C for 30 minutes to remove defects and bubbles from the solution.

[0080] The stability of the holographic photopolymer in this embodiment was tested. After the polyurethane matrix was cured, the non-grating photopolymer sample film was stored in the ambient environment. Every two days, the sample was holographically recorded, UV bleached, and then the reflectance was measured. Figure 3 A graph is provided to describe the stability of the holographic photopolymer after two weeks of storage in the ambient environment at room temperature.

[0081] The reflection efficiency and diffraction efficiency of the holographic polymer in this embodiment were evaluated. Using... Figure 2 The apparatus shown is for measuring the refractive index modulation of a holographic polymer, and uses... Figure 4 The apparatus shown measures diffraction efficiency. In the evaluation, the signal beam passes through a recorded and developed hologram. By adjusting the angle of the hologram, the position where the reflected beam PR shows its maximum value can be found. Simultaneously, the transmitted beam PT will show its minimum value. The reflection efficiency can be calculated using the formula (PR / PT+PR) x 100%. Figure 5 Graphs of the measured reflection and diffraction efficiencies of the holographic optical polymer are provided.

[0082] The thickness of the photopolymer film can be measured by placing a recorded and UV-bleached photopolymer sample between upper and lower glass substrates. The substrates can be carefully separated using a blade, leaving the photopolymer on one substrate. The film can be removed from the holographic region using a blade. The thickness of the PP layer can be measured using a Dektak stylus profiler (Bruker.com). Figure 6 A graph showing the measured thickness of the holographic photopolymer described in this paper is provided.

[0083] Example 2 Preparation of writing monomer mixtures 2.25 g of EA-F5710 (a mixture of ethoxylated fluorene diacrylate and m-phenoxybenzyl acrylate) (OSAKA GAS Chemicals, Japan) and 0.25 g of 2-hydroxy-3-phenoxypropyl acrylate (CAS No.: 16969-10-1) were mixed in the dark at 60°C for 6 hours to provide a writing monomer mixture.

[0084] Preparation of photoinitiated mixture solution 50 mg N-phenylglycine (CAS No.: 103-01-5, co-initiator 1), 5.4 mg safranin O (photosensitizer or dye) and 16.2 mg 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-bisimidazole (HABI, CAS No.: 7189-82-4, co-initiator 2) were dissolved in the dark at 50-55°C and mixed in 0.35 g 1-ethyl-2-pyrrolidone (CAS No.: 88-12-0) for 2 hours.

[0085] Preparation of tin catalyst solution (for urethane polymerization) One part of organotin catalyst (FOMREZ UL-28, dimethyltin dinedecanoate) was mixed with nine parts of 1-ethyl-2-pyrrolidone (CAS No.: 88-12-0) at room temperature to form a 10% catalyst stock solution.

[0086] Preparation of photopolymer formulation 2 2.5 g of the monomer mixture from Example 2, 1.4 g of polypropylene polyol (SANNIX PP-2000, Sanyo Chemical), and 0.42 g of the photoinitiator mixture solution were mixed in the dark at approximately 35°C for 1 hour. Then, 1 g of isocyanate (Desmodur ultra E 30600, Covestro) was added. The mixture was then vigorously mixed at 35°C for 10 minutes. Next, 0.018 g of tin catalyst solution was added to the resulting mixture, and it was mixed at 35°C for 3 minutes. The resulting liquid solution was then placed under vacuum at 35°C to remove any bubbles generated during mixing. The reflectance and transmittance performance data were tested, and the resulting spectra are shown below. Figure 7A and 7B As shown. The transmittance in the zero-incident-angle grating region was measured using a UV-VIS spectrometer. The refractive index modulation Δn was derived from the Bragg curve obtained by Kogelnik theory analysis.

[0087] The transmittance of the photopolymer in this embodiment was measured using a UV-Vis spectrophotometer. The photopolymer film was sandwiched between two glass substrates. After UV bleaching, the transmission spectrum of the film was measured. Figure 8 The transmission spectrum of a UV bleaching film with a thickness of 13 μm is shown.

[0088] Example 3 Preparation of photoinitiated mixture solution 80 mg of tetrabutylammonium tri(3-chloro-4-methylphenyl)(hexyl)borate (CAS No.: 1147315, co-initiator) and 8.0 mg of Safranin O (photosensitizer or dye) were dissolved in the dark at 55°C and mixed in 0.35 g of 1-vinyl-2-pyrrolidone (CAS No.: 88-12-0) for 2 hours.

[0089] Preparation of tin catalyst solution (for urethane polymerization) One part of organotin catalyst (FOMREZ UL-28, dimethyltin dinedecanoate) was mixed with nine parts of 1-vinyl-2-pyrrolidone (CAS No.: 88-12-0) at room temperature to form a 10% catalyst stock solution.

[0090] Preparation of photopolymer formulations 3 2.5 g of EA-F5710 (see the monomer mixture in Example 2), 1.4 g of polypropylene polyol (SANNIX PP-2000, Sanyo Chemical), and 0.44 g of photoinitiator mixture solution were mixed in the dark at approximately 60°C for 2 hours. The solution was then cooled to 35°C, and 1 g of isocyanate (Desmodur ultra E 30600, Covestro) was added. The mixture was vigorously mixed at 35°C for 10 minutes. Then, 0.018 g of tin catalyst solution was added to the resulting mixture, and it was mixed at 35°C for 3 minutes. The resulting liquid solution was then placed under vacuum at 35°C to remove bubbles obtained through mixing. Reflectance and transmittance performance data were tested and... Figure 9 The figure shows the obtained transmittance spectra of the unexposed film, the grating region, and the UV bleached film.

[0091] Example 4 Preparation of writing monomer mixtures 1.25 g of carbazole methacrylate (synthesized according to ACS Applied Materials & Interfaces 2023, 15, 24827-24835) and 1.25 g of o-phenylphenol ethyl acrylate (MIRAMER M1142) were mixed in the dark at 60°C for 6 hours to provide a writing monomer mixture.

[0092] Preparation of photoinitiated mixture solution 80 mg tetrabutylammonium butyltriphenylborate (CAS No.: 120307-06-4, co-initiator) and 8.0 mg safranin O (photosensitizer or dye) were dissolved in the dark at 55°C and mixed in 0.35 g 1-ethyl-2-pyrrolidone (CAS No.: 88-12-0) for 2 hours.

[0093] Preparation of tin catalyst solution (for urethane polymerization) One part of organotin catalyst (FOMREZ UL-28, dimethyltin dinedecanoate) was mixed with nine parts of 1-ethyl-2-pyrrolidone (CAS No.: 88-12-0) at room temperature to form a 10% catalyst stock solution.

[0094] Preparation of photopolymer formulation 4 2.5 g of the monomer mixture from Example 4, 1.4 g of polypropylene polyol (SANNIX PP-2000, Sanyo Chemical), and 0.42 g of the photoinitiator mixture solution were mixed in the dark at approximately 35°C for 1 hour. Then, 1 g of isocyanate (Desmodur ultra E 30600, Covestro) was added. The mixture was then vigorously mixed at 35°C for 10 minutes. Next, 0.018 g of tin catalyst solution was added to the resulting mixture, and it was mixed at 35°C for 3 minutes. The resulting liquid solution was then placed under vacuum at 35°C to remove any bubbles generated during mixing. The reflectance and transmittance properties were tested, and the resulting spectra are shown below. Figure 10A As shown in Figure B, the transmittance in the zero-incident-angle grating region was measured using a UV-VIS spectrometer. The refractive index modulation Δn was derived from the Bragg curve obtained based on Kogelnik theory.

[0095] Example 5 Preparation of photoinitiator mixture stock solution 1.5 g of tetrabutylammonium tri(3-chloro-4-methylphenyl)(hexyl)borate (CAS No.: 1147315, co-initiator), 0.05 g of Basic Orange 21 (CAS No.: 3056-93-7) (photosensitizer or dye, wavelength 492 nm), 0.05 g of neomethylene blue (CAS No.: 1934-16-3) (photosensitizer or dye, wavelength 632 nm) and 0.05 g of ethyl violet (CAS No.: 2390-59-2) (photosensitizer or dye, wavelength 592 nm) were completely dissolved in the dark at 55°C and mixed in 3.5 g of 1-ethyl-2-pyrrolidone (CAS No.: 88-12-0) for 2 hours.

[0096] Preparation of tin catalyst solution (for urethane polymerization) One part of organotin catalyst (FOMREZ UL-28, dimethyltin dinedecanoate) was mixed with nine parts of 1-ethyl-2-pyrrolidone (CAS No.: 88-12-0) at room temperature to form a 10% catalyst stock solution.

[0097] Preparation of photopolymer formulations 5 2.5 g of EA-F5710 (see the monomer mixture in Example 2), 1.4 g of polypropylene polyol (SANNIX PP-2000, Sanyo Chemical), and 0.39 g of the photoinitiating mixture solution from Example 5 were mixed in the dark at approximately 60°C for 1 hour. Then, 1.2 g of isocyanate (Desmodur ultra E 30600, Covestro) was added. The mixture was vigorously mixed at 35°C for 10 minutes. Then, 0.018 g of tin catalyst solution was added to the resulting mixture and mixed at 35°C for 3 minutes. The resulting liquid solution was then placed under vacuum at 35°C to remove any bubbles generated during mixing. Reflectance and transmittance were tested, and the resulting spectra are shown below. Figure 11 As shown.

[0098] Example 6 Preparation of photoinitiator mixture stock solution 1.5 g of tetrabutylammonium tris(3-chloro-4-methylphenyl)(hexyl)borate (CAS No.: 1147315, co-initiator), 0.05 g of Safranin O (CAS No.: 477-73-6) (photosensitizer or dye, wavelength 532 nm), 0.05 g of neomethylene blue (CAS No.: 1934-16-3) (photosensitizer or dye, wavelength 632 nm), and 0.05 g of ethyl violet (CAS No.: 2390-59-2) (photosensitizer or dye, wavelength 592 nm) were completely dissolved in the dark at 55 °C and mixed in 3.5 g of 1-vinyl-2-pyrrolidone (CAS No.: 88-12-0) for 2 hours. A tin catalyst solution (for urethane polymerization) was prepared. One part of organotin catalyst (FOMREZ UL-28, dimethyltin dinedecanoate) was mixed with nine parts of 1-vinyl-2-pyrrolidone (CAS No.: 88-12-0) at room temperature to form a 10% catalyst stock solution.

[0099] Preparation of photopolymer formulations 6 2.5 g of EA-F5710 (see the monomer mixture in Example 2), 1.4 g of polypropylene polyol (SANNIX PP-2000, Sanyo Chemical), and 0.39 g of the photoinitiating mixture solution from Example 6 were mixed in the dark at approximately 60°C for 1 hour. Then, 1.2 g of isocyanate (Desmodur ultra E30600, Covestro) was added. The mixture was vigorously mixed at 35°C for 10 minutes. Then, 0.018 g of tin catalyst solution was added to the resulting mixture and mixed at 35°C for 3 minutes. The resulting liquid solution was then placed under vacuum at 35°C to remove bubbles generated during mixing. Reflectance and transmittance properties were tested, and the resulting spectra are shown below. Figure 11 As shown.

[0100] Example 7 Preparation of photoinitiator mixture stock solution 500 mg N-phenylglycine (CAS No.: 103-01-5), 50 mg safranin O (CAS No.: 477-73-6) (photosensitizer or dye, wavelength 532 nm) and 250 mg triphenylphosphine (CAS 603-35-0) were completely dissolved in the dark at 55°C and mixed in 1.75 g N-ethylpyrrolidone (CAS No.: 2687-91-4) for 2 hours.

[0101] Preparation of tin catalyst solution (for urethane polymerization) One part of organotin catalyst (FOMREZ UL-28, dimethyltin dinedecanoate) was mixed with nine parts of N-ethylpyrrolidone (CAS No.: 2687-91-4) at room temperature to form a 10% catalyst stock solution.

[0102] Preparation of writing monomer mixtures 1.25 g Ebecryl 3700 (Allnex, Inc.), 0.625 g SR590 (ethoxylated cumylphenol acrylate, Arkema, Inc.) and 0.625 g TMPTA (CAS No.: 15625-89-5) were mixed in the dark at 60°C for 6 hours to provide a writing monomer mixture.

[0103] Preparation of photopolymer formulations 7 2.5 g of the monomer mixture from Example 7, 1.4 g of polypropylene polyol (SANNIX PP-2000, Sanyo Chemical), and 0.26 g of the photoinitiator mixture solution from Example 7 were mixed in the dark at approximately 60°C for 1 hour. Then, 1.0 g of isocyanate (Desmodur ultra E 30600, Covestro) was added. The mixture was then vigorously mixed at 35°C for 10 minutes. Next, 0.018 g of tin catalyst solution was added to the resulting mixture and mixed at 35°C for 3 minutes. The resulting liquid solution was then placed under vacuum at 35°C to remove any bubbles generated during mixing. The reflectance and transmittance properties were tested, and the resulting spectra are shown below. Figure 12A and 12B As shown.

[0104] Example 8 Preparation of photoinitiator mixture stock solution 500 mg N-phenylglycine (CAS No.: 103-01-5), 50 mg safranin O (CAS No.: 477-73-6) (photosensitizer or dye, wavelength 532 nm) and 250 mg triphenylphosphine (CAS 603-35-0) were completely dissolved in the dark at 55°C and mixed in 1.75 g N-ethylpyrrolidone (CAS No.: 2687-91-4) for 2 hours.

[0105] Preparation of tin catalyst solution (for urethane polymerization) One part of organotin catalyst (FOMREZ UL-28, dimethyltin dinedecanoate) was mixed with nine parts of N-ethylpyrrolidone (CAS No.: 2687-91-4) at room temperature to form a 10% catalyst stock solution.

[0106] Preparation of writing monomer mixtures 1.25 g of SR590 (ethoxylated cumylphenol acrylate, Arkema, Inc.), 0.625 g of SR349 (ethoxylated bisphenol A diacrylate, Arkema, Inc.), 0.375 g of 2-hydroxy-3-polyoxypropylene acrylate and 0.25 g of TMPTA (CAS No.: 15625-89-5) were mixed in the dark at 60°C for 6 hours to provide a monomer mixture.

[0107] Preparation of photopolymer formulations 8 2.5 g of the monomer mixture from Example 8, 1.4 g of polypropylene polyol (SANNIX PP-2000, Sanyo Chemical), and 0.51 g of the photoinitiating mixture solution from Example 8 were mixed in the dark at approximately 60°C for 1 hour. Then, 1.0 g of isocyanate (Desmodur ultra E 30600, Covestro) was added. The mixture was then vigorously mixed at 35°C for 10 minutes. Next, 0.018 g of tin catalyst solution was added to the resulting mixture, and it was mixed at 35°C for 3 minutes. The resulting liquid solution was then placed under vacuum at 35°C to remove any bubbles generated during mixing. The reflectance and transmittance properties were tested, and the resulting spectra are shown in Figure 13.

[0108] Glass substrate coating (sample preparation for exposure) Clean and dry the glass substrate in a light-controlled (safety red light) environment. Cut the glass substrate into approximately 2”×2” squares. Wash the cut glass substrate with soap (detergent) and water, then dry it with nitrogen (N2) at room temperature for approximately 30 seconds, followed by heating to approximately 60°C. Apply a drop of synthetic photopolymer material to the glass substrate, then cover it with a second glass plate, maintaining a distance of approximately 4 µm by applying silica microspheres. Vacuum-bonding the glass laminate sample using an NPC vacuum chamber bonding machine (https: / / www.npcgroup.net / eng / solarcell / vacuum-bonding). After lamination, allow the sample to stand at 35°C. Allow the sample to stand at room temperature for curing (polymerization) for approximately 8 to 60 hours.

[0109] Holographic recording The polymer film was exposed to the Denisyuk (mirror hologram) device using a 532 nm laser at a frequency of 5-10 mW / cm². 2 The hologram is exposed at a high power density for 3-10 seconds. After exposure, it is visually inspected and then bleached under UV light. The hologram, laminated between two glass slides, is then exposed under a lamp (UVASPOT1000 RF2 from Honle UV Technology, Germany). UVASPOT is a modular, high-intensity UV unit and system that achieves very high uniformity across the entire irradiation area. Various lamp and filter configurations can produce different spectra for applications in the UVA (340 nm-400 nm) range.

[0110] Reflection efficiency measurement Experimental apparatus for measuring reflection efficiency, such as Figure 4As shown, the signal beam passes through the recorded and developed hologram. By adjusting the angle of the hologram, the position where the reflected beam PR displays its maximum value is found. Simultaneously, the transmitted beam PT will display its minimum value. The reflection efficiency can be calculated using the formula (PR / PT+PR)×100%.

[0111] Film thickness measurement Provide a sample photopolymer for recording and UV bleaching, sandwiched between an upper and lower glass substrate. Carefully separate the upper and lower glass substrates using a blade, leaving the photopolymer on one of the substrates. Remove the film from the holographic region using a blade. Measure the thickness of the PP layer using a Dektak profilometer (Bruker.com).

[0112] Refractive index modulation calculation The amplitude of refractive index modulation is measured using a transmission hologram as follows: a) Using a collimated double beam, record the hologram assuming the incident angle of the object wave is θ and the incident angle of the reference wave is 2π-θ. b) The highest diffraction efficiency value (or the diffraction efficiency value considered to be saturated) should be determined from the exposure characteristic curve and based on... Figure 14 The measurements were taken using the settings shown.

[0113] The amplitude (Δn) of the refractive index modulation should be calculated according to the following equation: According to Snell's law, the relationship between the Bragg diffraction angle θ'B and the incident angle θ of the two beams can be expressed as follows: , where n: the average refractive index of the hologram.

[0114] The use of the terms “may,” “may,” or “can” should be interpreted as shorthand for “yes” or “no,” or alternatively, “does,” “does not,” “will,” or “will not,” etc. For example, the statement “the thermally conductive composite material may also include a backing layer” should be interpreted as, for example, “in some embodiments, the thermally conductive composite material further includes a backing layer,” or “in some embodiments, the thermally conductive composite material does not further include a backing layer.” Unless otherwise indicated, all figures used in this specification and embodiments to represent the amount, properties (e.g., molecular weight), reaction conditions, etc., of components should be understood to be modified by the term "about" in all cases. As used herein, the term "about" can include any numerical value that can be varied without altering the essential function of the value. When used with a range, "about" also refers to a range defined by the absolute values ​​of its two endpoints. The term "about" can refer to plus or minus 10% of the indicated numerical value.

[0115] Therefore, unless otherwise indicated, the numerical parameters set forth in this specification and the accompanying embodiments are approximate values ​​and may vary depending on the desired performance sought. At least, no limitation is made to the application of equivalent solutions. For the scope of the embodiments, each numerical parameter should be interpreted at least according to the number of significant figures reported and by applying common rounding techniques.

[0116] For the disclosed processes and / or methods, the functions performed within the processes and methods may be implemented in different orders, as may be shown in the context. Furthermore, the outlined steps and operations are provided only as examples, and some steps and operations may be optional, may be combined into fewer steps and operations, or may be extended into additional steps and operations.

[0117] This disclosure may sometimes illustrate different components contained in or connected to different other components. The architectures described in this way are merely examples, and many other architectures that implement the same or similar functions can be implemented.

[0118] The terminology used in this disclosure and the appended embodiments is generally intended to be "open-ended" (e.g., the term "including" should be interpreted as "including, but not limited to"), the term "having" should be interpreted as "having at least", the term "include" should be interpreted as "including, but not limited to", etc.). Furthermore, if a specific number of elements are introduced, this can be interpreted as including at least the stated number, as may be indicated by the context (e.g., a simple statement of "two statements" without other modifiers includes at least two statements, or two or more statements). As used in this disclosure, any separating words and / or phrases indicating two or more alternative terms should be understood to account for the possibility of including one term, either term, or both terms. For example, the phrase "A or B" would be understood to include the possibility of "A" or "B" or "A and B".

[0119] The terminology and words used are not limited to their documentary meaning, but are merely intended to provide a clear and consistent understanding of this disclosure. The terms “a,” “an,” “the,” and similar designations used in the context of describing this disclosure (particularly in the context of the embodiments described below) should be interpreted to cover both the singular and plural, unless otherwise indicated herein or clearly contradicted by the context. The use of any and all instances or representative language provided herein (e.g., “such as”) is intended only to better clarify this disclosure and does not constitute a limitation on the scope of any embodiment. The language in this specification should not be construed as indicating any unrepresented element essential to the practice of this disclosure.

[0120] The alternative elements or embodiments disclosed herein should not be construed as limiting. Each member of a group may be mentioned and embodied individually, or in any combination with other members of that group or other elements described herein. It is foreseeable that, for convenience and / or patentability reasons, one or more members of a group may be included in a group or removed from a group. When any such inclusion or removal occurs, this specification is deemed to contain the modified group, thereby satisfying the written description of all Markush groups used in the appended embodiments.

[0121] This document describes certain embodiments, including the best mode known to the inventors for carrying out this disclosure. Of course, variations of these described embodiments will become apparent to those skilled in the art after reading the foregoing description. The inventors expect those skilled in the art to appropriately employ such variations, and the inventors intend to practice this disclosure in ways different from those specifically described herein. Therefore, embodiments include all modifications and equivalents of the subject matter described in embodiments permitted by applicable law. Furthermore, any combination of the foregoing elements in all possible variations should be considered unless otherwise indicated herein or clearly contradicted by the context. Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments. Other modifications may be employed within the scope of the embodiments. Therefore, alternative embodiments may be utilized based on the teachings herein, by way of example and not limitation. Thus, the embodiments are not limited to those precisely shown and described.

[0122] The term “substantially” means that the described characteristic, parameter, or value does not need to be precisely achieved, but deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limitations, and other suitable factors, may occur in a quantity that does not preclude the effect that the characteristic is intended to provide.

[0123] Various aspects of this disclosure may be implemented in other forms without departing from the spirit or essential characteristics of this disclosure. The described aspects are to be considered illustrative rather than restrictive in all respects. The subject matter embodied is indicated by the appended embodiments, not by the foregoing description. All variations in the meaning and scope of equivalent embodiments are included within the scope of the embodiments.

Claims

1. A holographic photopolymer, comprising: Polyurethane matrix, polycyclic aromatic hydrocarbons are incorporated into monomers and dye systems.

2. The holographic photopolymer according to claim 1, further comprising an oxygen scavenger additive.

3. The holographic photopolymer according to claim 1, wherein the polyurethane matrix is ​​connected to the polycyclic heteroaryl writing monomer by bonds.

4. The holographic photopolymer according to claim 3, wherein the bond is a covalent bond or a non-covalent hydrogen bond.

5. The holographic photopolymer according to claim 1, wherein the polyurethane matrix comprises at least one of the following: polypropylene polyol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, aliphatic polyether isocyanate, and dimethyltin dinedecyl ester.

6. The holographic photopolymer according to claim 1, wherein the polycyclic heteroaryl writing monomer comprises a bifunctional writing monomer or a monofunctional writing monomer.

7. The holographic photopolymer according to claim 1, wherein the polycyclic heteroaryl writing monomer comprises one of the following structures: , , , , and .

8. The holographic photopolymer according to claim 1, wherein the polycyclic heteroaryl writing monomer conforms to the following formula: , where X is C, Si or Ge.

9. The holographic photopolymer according to claim 1, wherein the polycyclic heteroaryl writing monomer conforms to one of the following formulas: and , where X is O, S, Se or Te.

10. The holographic photopolymer according to claim 1, wherein the polycyclic heteroaryl writing monomer comprises at least one of the following: bisphenol A diglycidyl ether diacrylate, bisphenol A ethoxylated di(meth)acrylate, trimethylolpropane triacrylate, ethoxylated fluorene diacrylate, liquid carbazole acrylate / methacrylate containing alkyl sulfide chains or ether chains, m-phenoxybenzyl acrylate, and hydroxyfunctional acrylate.

11. The holographic photopolymer according to claim 10, wherein the bisphenol A diglycidyl ether diacrylate comprises one of the following structures: , or 。 12. The holographic photopolymer of claim 1, wherein the polycyclic heteroaryl writing monomer further comprises a diluent.

13. The holographic photopolymer of claim 12, wherein the diluent comprises 1-vinyl-2-pyrrolidone.

14. The holographic photopolymer according to claim 1, wherein the dye system comprises a dye and a co-initiator.

15. The holographic photopolymer of claim 14, wherein the dye comprises at least one of safranin O, methylene blue, basic orange 21 and ethyl violet, and wherein the co-initiator comprises at least one of N-phenylglycine and hexaarylbisimidazole.

16. The holographic photopolymer of claim 14, wherein the weight ratio of the dye to the co-initiator is from about 1:10 to about 1:

14.

17. The holographic photopolymer according to claim 2, wherein the oxygen scavenging additive comprises triphenylphosphine.

18. The holographic photopolymer according to claim 1, further comprising a reactive diluent, said reactive diluent comprising [C1-C3 alkylpyrrolidone]N-ethyl-2-pyrrolidone.

19. The holographic photopolymer according to claim 1, wherein the weight ratio of the polyurethane matrix to the polycyclic heteroaryl writing monomer is in the range of 19:1 to 1:

3.

20. The holographic photopolymer according to claim 1, wherein the polyurethane matrix conforms to the following formula: and .

21. An augmented reality / virtual reality device comprising a holographic light polymer according to any one of claims 1-20.

22. A film comprising the holographic photopolymer according to any one of claims 1-20.

Images