Compound, holographic composition, holographic medium and optical device

Abstract

The invention discloses a compound, a holographic composition, a holographic medium and an optical device, and belongs to the technical field of optical materials. The compound comprises a first group, a second group, a third group and an acrylate group, wherein the second group comprises carbonyl, and a first end group and a second end group which are respectively connected to the carbonyl. The first end groups of the plurality of second groups are respectively connected with different sites of the first group, a part of the second end groups in the plurality of second groups are connected with the acrylate group, and the rest of the second end groups are connected with the third group. When the compound provided by the embodiment of the invention is used as a photopolymerization monomer, volume shrinkage of the photopolymerization monomer in a photopolymerization process is effectively inhibited by introducing a steric hindrance group, a multiple hydrogen bond structure and a rigid side group with a high refractive index, so that a diffraction peak drifting phenomenon in a holographic exposure process is inhibited, and meanwhile, the photopolymerization efficiency is improved. And the refractive index of the photopolymer is improved, so that the diffraction efficiency of the grating is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical materials, and particularly relates to compounds, holographic compositions, holographic media, and optical devices. Background Art

[0002] Holography is based on the interference principle and can record the amplitude, phase, and polarization state information of coherent light, enabling the storage of three-dimensional images in a two-dimensional plane. Holographic polymer materials store the information of coherent light with polymers as the medium and are widely used due to their good chemical stability, wide sources of raw materials, and easy processing.

[0003] In related technologies, holographic polymer materials include a polymer matrix, a photopolymerizable monomer, and a photoinitiator. The holographic polymer material can be exposed under coherent light. The photopolymerizable monomer located in the coherent bright region undergoes a photopolymerization reaction under the initiation of the photoinitiator to generate a photopolymer. As the photopolymerization reaction proceeds, the photopolymerizable monomer located in the coherent dark region diffuses to the coherent bright region and continues to participate in the photopolymerization reaction, thereby forming a holographic grating based on the phase separation of the photopolymer and the polymer matrix.

[0004] However, currently known photopolymerizable monomers have a volume shrinkage phenomenon during the photopolymerization reaction, which reduces the grating spacing of the holographic grating, resulting in an obvious diffraction peak drift phenomenon in the holographic grating.

[0005] Disclosure

[0006] Embodiments of the present disclosure provide compounds, holographic compositions, holographic media, and optical devices, which can solve the technical problems in related technologies.

[0007] On the one hand, embodiments of the present disclosure provide a compound, which includes: a first group, a second group, a third group, and an acrylate group. The second group includes a carbonyl group, a first end group and a second end group respectively connected to the carbonyl group. The first end groups of multiple second groups are respectively connected to different sites of the first group. The second end groups of a part of the multiple second groups are connected to the acrylate group, and the second end groups of the remaining part are connected to the third group;

[0008] The first group includes a steric hindrance group;

[0009] The first end group of the second group and the second end group of the second group are each independently selected from an oxygen atom, a sulfur atom, a selenium atom, a hydroxyl group, a mercapto group, a selenhydryl group, or a secondary amino group;

[0010] The third group includes at least one of an aryl group and a heteroaryl group, and the heteroatoms in the heteroaryl group include at least one of a bromine atom, an iodine atom, a sulfur atom, and a nitrogen atom.

[0011] The compound provided by the embodiments of the present disclosure can be used as a photopolymerizable monomer to carry out a photopolymerization reaction under the action of a photoinitiator system. The first group serves as the core of the compound and includes a steric hindrance group. The steric hindrance group maintains a stable volume during the exposure process to support the overall spatial structure of the photopolymerizable monomer, facilitating the suppression of the volume shrinkage problem of the photopolymerizable monomer during the photopolymerization process. The second group includes a carbonyl group and a first end group and a second end group connected to the carbonyl group. The first end group and the second end group are each independently selected from an oxygen atom, a sulfur atom, a selenium atom, a hydroxyl group, a mercapto group, a selenyl hydrogen group, or a secondary amino group, which makes the second group a hydrogen-bond-forming group. A plurality of second groups are located outside the first group, thereby forming a multiple hydrogen bond structure in the compound. The introduction of the multiple hydrogen bonds enables the photopolymerizable monomers to approach each other sufficiently before the photopolymerization reaction, thereby suppressing the problem of the increase in the distance between monomers caused by the photopolymerization reaction and effectively suppressing the obvious volume shrinkage phenomenon of the photopolymerizable monomer during the photopolymerization reaction. The compound provided by the embodiments of the present disclosure further includes an acrylate group and a third group located outside. Among them, the acrylate group has an active site to undergo a photopolymerization reaction. The third group includes an aryl group and a heterocyclic group containing at least one of a bromine atom, an iodine atom, a sulfur atom, and a nitrogen atom, which makes the third group not only a high refractive index group but also capable of serving as a rigid side group. The high refractive index group is conducive to increasing the refractive index of the photopolymer formed by the photopolymerizable monomer, and the rigid side group further suppresses the volume shrinkage phenomenon of the monomer during the photopolymerization reaction. It can be seen that when the compound provided by the embodiments of the present disclosure is used as a photopolymerizable monomer, by introducing a steric hindrance group, a multiple hydrogen bond structure, and a rigid side group with a high refractive index, the volume shrinkage of the photopolymerizable monomer during the photopolymerization process is effectively suppressed, thereby suppressing the diffraction peak drift phenomenon during the holographic exposure process. At the same time, it is also conducive to increasing the refractive index of the photopolymer, thereby improving the grating diffraction efficiency.

[0012] In some possible implementation manners, the steric hindrance group includes: an alkane group having a side chain, a cycloalkane group having a side chain, a heterocyclic group having a side chain, an aryl group having a side chain, an adamantyl group having a side chain, and a siloxane group.

[0013] In some possible implementation manners, the chemical structural formula of the compound is as follows:

[0014]

[0015] Wherein, M is the first group;

[0016] R 1 is the first end group of the second group, and R 2 is the second end group of the second group;

[0017] N is the third group;

[0018] P is the acrylate group.

[0019] In some possible implementation manners, the first group is represented by any of the following chemical structural formulas:

[0020]

[0021] In some possible implementation manners, the third group is represented by any of the following chemical structural formulas:

[0022]

[0023] On the other hand, embodiments of the present disclosure provide a photopolymerizable monomer system, and the photopolymerizable monomer system is any of the compounds described above.

[0024] When the compound provided by the embodiments of the present disclosure is used as a photopolymerizable monomer, by optimizing its chemical structure, it can effectively inhibit volume shrinkage during the photopolymerization process, and further inhibit the diffraction peak drift phenomenon during the holographic exposure process, thereby preparing a photopolymer with a low volume shrinkage rate and a high refractive index.

[0025] On yet another aspect, embodiments of the present disclosure provide a holographic composition, and the holographic composition includes a polymer matrix, a photopolymerizable monomer system, and a photoinitiator system;

[0026] The photopolymerizable monomer system includes any of the compounds described above or a photopolymerizable monomer.

[0027] The holographic composition provided by the embodiments of the present disclosure has all the advantages of the above compounds or photopolymerizable monomers, which is conducive to obtaining a holographic grating with a low diffraction peak drift value.

[0028] In some possible implementation manners, the photopolymerizable monomer system includes at least two photopolymerizable monomers, and the at least two photopolymerizable monomers are any of the compounds described above.

[0029] In some possible implementation manners, the polymer matrix includes a linear polyurethane resin having an epoxy side chain, and the end group of the epoxy side chain is an epoxy group.

[0030] In some possible implementation manners, the weight of the epoxy side chain is 0.1% - 20% of the weight of the polymer matrix.

[0031] By using a linear polyurethane resin having an epoxy side chain as the polymer matrix in the embodiments of the present disclosure, there are at least the following advantages:

[0032] First, the linear polyurethane resin can form a film directly and has a low volume shrinkage rate before and after exposure (for example, 0.1%-2%), which not only endows the holographic composition material with processing characteristics such as flexible coating, but also endows the film layer with good mechanical strength.

[0033] Second, the introduction of an epoxy side chain containing an epoxy group of C3-C20 makes the compatibility between the linear polyurethane resin and the photopolymerizable monomer with multiple hydrogen bonds better, thereby improving the compatibility of the holographic composition, and can also inhibit the crystallization of the polyurethane segment, which is beneficial for the holographic composition to obtain an excellent refractive index modulation amount, a higher light transmittance, and a lower haze.

[0034] Third, there is a large refractive index difference between the linear polyurethane resin with an epoxy side chain and the photopolymerizable monomer with multiple hydrogen bonds, which is beneficial for the holographic grating formed by the holographic composition to obtain a higher diffraction efficiency.

[0035] In some possible implementation manners, the photoinitiator system includes a co-initiator and a photosensitizer.

[0036] In some possible implementation manners, the weight portion of the polymer matrix is 20 parts to 80 parts, the weight portion of the photopolymerizable monomer system is 20 parts to 80 parts, and the weight portion of the photoinitiator system is 0.1 part to 5 parts.

[0037] On the other hand, a holographic medium is provided, and the holographic medium includes: a transparent substrate and a holographic photosensitive film located on the transparent substrate, and the holographic photosensitive film is prepared by using any one of the above-mentioned holographic compositions.

[0038] In some possible implementation manners, the holographic medium further includes an optical protective film, and the optical protective film covers the surface of the holographic photosensitive film facing away from the transparent substrate.

[0039] In some possible implementation manners, the excitation wavelength range of the coherent light used by the holographic medium is 400nm to 800nm, and the excitation intensity of the coherent light used is 0.001mW / cm 2 ~500mW / cm 2 .

[0040] On the other hand, an optical device is provided, and the optical device includes any one of the above-mentioned holographic media.

[0041] The optical device provided by the embodiments of the present disclosure can be applied to scenarios such as in-vehicle head-up display (Headup Display, HUD), AR glasses, and holographic 3D projection. Description of the Drawings

[0042] Figure 1Schematic diagram of holographic recording based on holographic polymer materials provided by embodiments of the present disclosure;

[0043] Figure 2 Schematic diagram of the structure of an exemplary holographic medium provided by embodiments of the present disclosure;

[0044] Figure 3 Schematic diagram of the layout of an exemplary optical path system based on a holographic medium provided by embodiments of the present disclosure;

[0045] Figure 4 1H NMR spectrum of an exemplary linear polyurethane resin provided by embodiments of the present disclosure;

[0046] Figure 5 UV-Vis absorption spectrum of an exemplary reflective holographic grating provided by embodiments of the present disclosure;

[0047] Figure 6 UV-Vis absorption spectrum of the holographic medium provided in Example 1 of the present disclosure;

[0048] Figure 7 UV-Vis absorption spectrum of the holographic medium provided in Example 2 of the present disclosure;

[0049] Figure 8 UV-Vis absorption spectrum of the holographic medium provided in Example 3 of the present disclosure;

[0050] Figure 9 Variable-temperature infrared curve of the holographic composition provided by embodiments of the present disclosure before and after exposure in the first wavelength range;

[0051] Figure 10 Variable-temperature infrared curve of the holographic composition provided by embodiments of the present disclosure before and after exposure in the second wavelength range.

[0052] Among them, Figures 6 - 8 Multiple transmittance curves are shown, which means that multiple holographic medium samples belonging to the same holographic medium but different batches are used, and ultraviolet-visible absorption spectroscopy tests are respectively performed on these different batches of holographic medium samples to Figure 8 For example, multiple transmittance curves correspond to multiple holographic medium samples of different batches in Example 1.

[0053] Figure 9 and Figure 10Multiple variable-temperature infrared curves are shown in both the pre-exposure and post-exposure images. For the multiple variable-temperature infrared curves in the same image, the test temperatures corresponding to the multiple variable-temperature infrared curves are different from each other. Along the direction from top to bottom, the test temperatures corresponding to the multiple curves gradually increase, which are 303K, 313K, 323K, 333K, 343K, 353K, 363K, 373K, 383K, and 393K respectively.

[0054] The reference numerals respectively represent:

[0055] 100, transparent substrate;

[0056] 200, holographic photosensitive film;

[0057] 300, optical protective film. Detailed implementation manners

[0058] Holography is based on the interference principle and can record the amplitude, phase, and polarization state information of coherent light simultaneously, making it possible to store three-dimensional images in a two-dimensional plane. It is widely used in fields such as holographic optical elements, data storage, high-end anti-counterfeiting, 3D display, and sensors.

[0059] Holographic recording refers to the process of recording all information such as the amplitude and phase of coherent light through a photopolymerization reaction under the irradiation of coherent excitation light. Holographic recording materials are the key to supporting the application and development of holographic technology, including silver halide emulsions, dichromated gelatin, holographic photorefractive materials, holographic photochromic materials, holographic polymer materials, etc. Holographic polymer materials refer to materials that store all information such as the amplitude and phase of light waves with polymers as the medium, and are widely used due to their advantages such as good chemical stability, wide sources of raw materials, and easy processing.

[0060] Holographic polymer materials include a polymer matrix, a photopolymerizable monomer, a photoinitiator, and a solvent. Combining Figure 1 it can be known that the holographic polymer material can be placed under coherent light for exposure. The photopolymerizable monomers in the coherent bright area undergo a photopolymerization reaction under the initiation of the photoinitiator to generate a photopolymer. As the photopolymerization reaction proceeds, the photopolymerizable monomers in the coherent dark area diffuse to the coherent bright area and continue to participate in the photopolymerization reaction. The photopolymer and the polymer matrix form a phase-separated structure, thereby forming a holographic grating based on phase separation.

[0061] According to the grating vector In terms of the direction, holographic gratings include transmissive holographic gratings and reflective holographic gratings. Transmissive holographic gratings reproduce the recorded information of an object through light diffraction. Color holographic patterns are recorded by exposure with monochromatic light, but color distortion occurs in the recorded holographic patterns, with a large deviation from the colors of the actual object. Reflective holographic gratings reproduce object information through light reflection, and the grating only reflects light of the corresponding wavelength. Compared with transmissive holographic gratings, reflective holographic gratings have the advantages of good wavelength selectivity and little influence from ambient light. Therefore, reflective holographic gratings are usually prepared using holographic polymer materials at present.

[0062] However, for currently known photopolymerizable monomers, during the photopolymerization reaction, the intermolecular forces between monomer molecules usually change from van der Waals forces to covalent bonds. The range of action of van der Waals forces is smaller than the bond length of covalent bonds. This reduction in intermolecular distance causes an obvious volume shrinkage phenomenon in the photopolymerizable monomers during the photopolymerization reaction, thereby reducing the grating pitch of the holographic grating. Since the reconstruction wavelength of the reflective holographic grating is proportional to the grating pitch, therefore, obvious diffraction peak drift occurs in the holographic grating, and the magnitude of its diffraction peak drift depends on the magnitude of the monomer volume shrinkage rate.

[0063] In view of the technical problems existing in the related art, on the one hand, embodiments of the present disclosure provide a compound, which includes: a first group, a second group, a third group, and an acrylate group. The second group includes a carbonyl group, a first end group and a second end group respectively connected to the carbonyl group. The first end groups of multiple second groups are respectively connected to different sites of the first group, and the second end groups of a part of the multiple second groups are connected to the acrylate group, and the second end groups of the remaining part are connected to the third group.

[0064] Among them, the number of second groups can be 2, 3, 4, 5 or 6. Exemplarily, the number of second groups is 3.

[0065] The first group includes a steric hindrance group; the first end group and the second end group of the second group are each independently selected from an oxygen atom, a sulfur atom, a selenium atom, a hydroxyl group, a mercapto group, a selenyl hydrogen group or a secondary amine group; the third group includes at least one of an aryl group and a heteroaryl group, and the heteroatoms in the heteroaryl group include at least one of a bromine atom, an iodine atom, a sulfur atom and a nitrogen atom.

[0066] The compound provided by the embodiments of the present disclosure can be used as a photopolymerizable monomer to carry out a photopolymerization reaction under the action of a photoinitiator system. The first group serves as the core of the compound and includes a steric hindrance group, and the volume of the steric hindrance group remains stable during the exposure process to support the overall spatial structure of the photopolymerizable monomer, which is conducive to suppressing the volume shrinkage problem of the photopolymerizable monomer during the photopolymerization process. The second group includes a carbonyl group and a first end group and a second end group connected to the carbonyl group, and the first end group and the second end group are each independently selected from an oxygen atom, a sulfur atom, a selenium atom, a hydroxyl group, a mercapto group, a selenohydryl group or a secondary amino group, which makes the second group a hydrogen bond-forming group. A plurality of second groups are located outside the first group, thereby forming a multiple hydrogen bond structure in the compound. The introduction of the multiple hydrogen bonds enables the photopolymerizable monomers to approach each other sufficiently before the photopolymerization reaction, thereby suppressing the problem of the increase in the distance between monomers caused by the photopolymerization reaction and effectively suppressing the obvious volume shrinkage phenomenon of the photopolymerizable monomer during the photopolymerization reaction. The compound provided by the embodiments of the present disclosure further includes an acrylate group and a third group located outside. Among them, the acrylate group has an active site to carry out a photopolymerization reaction, and the third group includes an aryl group and a heterocyclic group containing at least one of a bromine atom, an iodine atom, a sulfur atom, and a nitrogen atom, which makes the third group not only a high refractive index group but also capable of serving as a rigid side group. The high refractive index group is conducive to increasing the refractive index of the photopolymer formed by the photopolymerizable monomer, and the rigid side group further suppresses the volume shrinkage phenomenon of the monomer during the photopolymerization reaction. It can be seen that when the compound provided by the embodiments of the present disclosure is used as a photopolymerizable monomer, by introducing a steric hindrance group, a multiple hydrogen bond structure and a rigid side group with a high refractive index, the volume shrinkage of the photopolymerizable monomer during the photopolymerization process is effectively suppressed, and further the diffraction peak drift phenomenon during the holographic exposure process is suppressed. At the same time, it is also conducive to increasing the refractive index of the photopolymer, thereby improving the grating diffraction efficiency.

[0067] It should be noted that by introducing multiple hydrogen bonds into the compound in the embodiments of the present disclosure, the intermolecular interaction of the compound changes from van der Waals force to hydrogen bond interaction, thereby shortening the distance between the compound molecules. When the compound is used as a photopolymerizable monomer to carry out a photopolymerization reaction, the photopolymerizable monomers can approach each other sufficiently before the photopolymerization reaction. Even during the photopolymerization reaction, when the intermolecular interaction force between the monomer molecules changes to a covalent bond, this reduction in the intermolecular distance will not be obvious, thereby avoiding the obvious volume shrinkage phenomenon of the photopolymerizable monomer during the photopolymerization reaction.

[0068] The first group of the compound includes a steric hindrance group. Some applicable steric hindrance groups include an alkane group with a side chain, a cycloalkane group with a side chain, a heterocyclic group with a side chain, an aryl group with a side chain, an adamantyl group with a side chain, and a siloxane group.

[0069] Exemplarily, the alkane group includes but is not limited to: methane, ethane, propane, butane, pentane, hexane, etc. The cycloalkane group includes but is not limited to: cyclobutane, cyclopentane, cyclohexane, etc. Among them, the cycloalkane group can be unsubstituted or substituted. For example, the substituent can be O.

[0070] Exemplarily, the heterocyclic group can be an aromatic heterocycle or an aliphatic heterocycle, and the heterocyclic group can be a four-membered heterocycle, a five-membered heterocycle, a six-membered heterocycle, a benzheterocycle, etc. The heteroatoms contained in the heterocyclic group include but are not limited to nitrogen atoms, sulfur atoms, oxygen atoms, etc. For example, some heterocyclic groups in the form of aromatic heterocycles include but are not limited to: furan, thiophene, pyrrole, pyridine, pyrimidine, indole, quinoline, pyran, pyridazine, pyrazine, quinoline, isoquinoline, benzofuran. Some heterocyclic groups in the form of aliphatic heterocycles can be such that one or more carbons in cyclobutane, cyclopentane, cyclohexane are replaced by heteroatoms. Among them, the heterocyclic group can be unsubstituted or substituted. For example, the substituent can be O.

[0071] Exemplarily, the aryl group includes but is not limited to: phenyl, tolyl, o-phenyl, naphthyl, etc.

[0072] Some steric hindrance groups include side chains. For example, the side chain includes but is not limited to: ethyl, n-propyl, butyl, pentyl, etc. By setting the above side chains in the steric hindrance group, the compatibility of the compound as a photopolymerizable monomer in the holographic composition system can be adjusted, and at the same time, it is beneficial to the balance between the flexibility and refractive index of the photopolymerizable monomer.

[0073] Exemplarily, the first group can be represented by any of the following chemical structural formulas, and * in the following chemical structural formulas all represents the chemical bonding site:

[0074]

[0075] The third group of the compound is a high refractive index group, which includes at least one of aryl and heteroaryl, and the heteroatoms in the heteroaryl include at least one of bromine atom, iodine atom, sulfur atom, nitrogen atom.

[0076] Exemplarily, the aryl group involved here includes but is not limited to: phenyl, tolyl, o-phenyl, naphthyl, etc., and the number of aryl groups can be one or more.

[0077] The heteroaryl involved here can be a five-membered heteroaryl, a six-membered heteroaryl, a benzheterocycle, a heterocyclic-fused heterocycle, etc. Exemplarily, this includes but is not limited to: thiophene, benzothiophene, dibenzothiophene, pyrrole, thiazole, imidazole, pyrazole, pyridine, pyrimidine, quinoline, carbazole, etc.

[0078] Exemplarily, the third group is represented by any of the following chemical structural formulas, where * in the following chemical structural formulas all represents a chemical bonding site, and the value of n involved can be 1, 2, 3, or 4.

[0079]

[0080] By introducing the third group into the compound, not only can the refractive index of the compound be improved, but also based on the fact that the third group is a rigid group and its synergistic effect with multiple hydrogen bond groups (i.e., the second group), the volume shrinkage of the photopolymerizable monomer during the photopolymerization process can be further inhibited, thereby suppressing the diffraction peak drift phenomenon during the holographic exposure process.

[0081] In some implementation manners, the chemical structural formula of the compound provided by the embodiments of the present disclosure is as follows:

[0082]

[0083] Wherein, M is the first group; N is the third group; P is an acrylate group; R 1 is the first end group of the second group, and R 2 is the second end group of the second group.

[0084] For the acrylate group, it includes but is not limited to: ethyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, ethyl acrylate, ethoxyethyl acrylate, ethoxyethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, hexyl acrylate, hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butoxyethyl acrylate, butoxyethyl methacrylate, lauryl acrylate, lauryl methacrylate, etc.

[0085] Exemplarily, the acrylate group is ethyl acrylate. Correspondingly, the chemical structural formula of the compound is as follows:

[0086]

[0087] Exemplarily, the first group M is represented by any of the following chemical structural formulas:

[0088]

[0089] Exemplarily, the third group N is represented by any of the following chemical structural formulas:

[0090]

[0091] Any of the compounds involved in the above embodiments of the present disclosure can be used as a photopolymerizable monomer. Further, the photopolymerizable monomer can be used in holographic polymer materials to initiate a photopolymerization reaction by a photoinitiator system under the exposure of coherent light, thereby generating a photopolymer.

[0092] On the other hand, embodiments of the present disclosure provide a photopolymerizable monomer system, which includes any of the above-mentioned compounds.

[0093] When the compound provided by the embodiments of the present disclosure is used as a photopolymerizable monomer, by optimizing its chemical structure, it can effectively inhibit volume shrinkage during the photopolymerization process, thereby inhibiting the diffraction peak drift phenomenon during the holographic exposure process, and thus preparing a photopolymer with a low volume shrinkage rate and a high refractive index.

[0094] In some examples, in the photopolymerizable monomer system, the number of photopolymerizable monomers can be one, or two, three, four or more.

[0095] All the photopolymerizable monomers in the photopolymerizable monomer system can all adopt the above different compounds, or only some of the polymerizable monomers adopt the above different compounds.

[0096] In some examples, all the photopolymerizable monomers in the photopolymerizable monomer system all adopt the different types of compounds involved above.

[0097] When the photopolymerizable monomer system uses a combination of multiple photopolymerizable monomers, according to parameters such as the viscosity, refractive index, chromaticity value, and number of functional groups of different types of photopolymerizable monomers, the relevant parameters of the photopolymerizable monomer system are adjusted to make it have properties such as low viscosity, high refractive index, low chromaticity, and multiple functional groups.

[0098] On yet another aspect, embodiments of the present disclosure provide a holographic composition, which includes a polymer matrix, a photopolymerizable monomer system, a photoinitiator system, and a solvent; the photopolymerizable monomer system includes any of the above-mentioned compounds or photopolymerizable monomers.

[0099] The holographic composition provided by the embodiments of the present disclosure has all the advantages of the above-mentioned compounds or photopolymerizable monomers, which is conducive to obtaining a holographic grating with a lower diffraction peak drift value.

[0100] In some examples, the photopolymerizable monomer system includes at least two photopolymerizable monomers, and at least one of the at least two photopolymerizable monomers adopts the photopolymerizable monomer provided by the embodiments of the present disclosure.

[0101] One example is that at least two photoinitiating monomers in the photoinitiating monomer system are both the above-mentioned compounds provided by the embodiments of the present disclosure (the types of the compounds are different). Among them, the mass ratio of at least two photoinitiating monomers can be adaptively adjusted according to actual needs. For example, it includes but is not limited to using them in equal proportions.

[0102] When a plurality of photoinitiating monomers are used in combination in the photoinitiating monomer system, relevant parameters of the photoinitiating monomer system are adjusted according to parameters such as the viscosity, refractive index, chromaticity value, and number of functional groups of different types of photoinitiating monomers, so as to make it have properties such as low viscosity, high refractive index, low chromaticity, and multiple functional groups.

[0103] In the embodiments of the present disclosure, the polymer matrix is a linear polyurethane resin with epoxy side chains, and the end groups of the epoxy side chains are epoxy groups. That is to say, the polymer matrix can be considered as randomly connecting epoxy side chains at the connection sites on the polyurethane resin network.

[0104] In the polymer matrix, the number of epoxy side chains is determined according to the amount of epoxy-containing polyol doped. The epoxy side chain includes a main chain segment and an epoxy group end group connected to one end of the main chain segment. In some examples, the number of carbon atoms in the epoxy side chain can be 3 to 20, such as 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.

[0105] In some examples, the embodiments of the present disclosure provide a linear polyurethane resin with epoxy side chains as the polymer matrix, and the chemical structural formula of the linear polyurethane resin with epoxy side chains is as follows:

[0106]

[0107] Among them, R 1 ~R 5 each independently selected from an alkyl chain, and the number of carbon atoms in the alkyl chain can be 1 to 20, including but not limited to: methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, etc.

[0108] The chemical structural formula of R 6 is as follows:

[0109] Or

[0110] Among them, x, y, z, n 1 、n 2 are all the numbers corresponding to the respective repeating units. For example, they are each independently selected from integers from 1 to 100.

[0111] The embodiments of the present disclosure adopt a linear polyurethane resin with epoxy side chains as the polymer matrix, having at least the following advantages:

[0112] Firstly, the linear polyurethane resin can directly form a film, and has a relatively low volume shrinkage rate before and after exposure (for example, 0.1%-2%). This not only endows the holographic composition material with processing characteristics such as flexible coating, but also endows the film layer with good mechanical strength.

[0113] Secondly, the introduction of epoxy side chains containing epoxy groups of C3-C20 makes the compatibility between the linear polyurethane resin and the photopolymerizable monomer with multiple hydrogen bonds better, thereby improving the compatibility of the holographic composition. Moreover, it can also inhibit the crystallization of the polyurethane segment, which is beneficial for the holographic composition to obtain excellent refractive index modulation amount, high light transmittance, and low haze.

[0114] Thirdly, there is a large refractive index difference between the linear polyurethane resin with epoxy side chains and the photopolymerizable monomer with multiple hydrogen bonds, which is beneficial for the holographic grating formed by the holographic composition to obtain a high diffraction efficiency.

[0115] The holographic composition provided by the embodiments of the present disclosure forms a holographic grating after exposure. In some examples, it is tested that the diffraction peak drift value of the holographic grating is 6.2 nm under red light, and the volume shrinkage rate is 0.97%; the diffraction peak drift value is 4.5 nm under green light, and the volume shrinkage rate is 0.85%; the diffraction peak drift value is 2.8 nm under blue light, and the volume shrinkage rate is 0.61%. The overall light transmittance ≥80%, and the haze <4%.

[0116] In some examples, the linear polyurethane resin satisfies that there are absorption peaks of the α-hydrogen of three characteristic functional groups between 2.5 ppm and 3.2 ppm, and the peak area ratio is 1:1:1. This linear polyurethane does not crosslink before the photopolymerizable monomer is exposed, which is beneficial for the diffusion of the photopolymerizable monomer, and thus a higher refractive index modulation degree is formed. After the photopolymerizable monomer is exposed and a grating is formed, this linear polyurethane can significantly improve the weather resistance of the material system.

[0117] In some examples, the weight of the epoxy side chains in the linear polyurethane resin is 0.1%-20% of the weight of the polymer matrix (i.e., the linear polyurethane resin), which includes but is not limited to 1%-20%, 5%-20%, 10%-20%, 15%-20%, etc. When the proportion of the epoxy side chains is set as above, it will not cause a significant increase in the glass transition temperature (Tg) of the polymer matrix, which is beneficial for the diffusion of the photopolymerizable monomer. Moreover, after the crosslinking of its epoxy groups, it is beneficial to improve the weather resistance of the crosslinked system.

[0118] In some examples, the number-average molecular weight of the linear polyurethane resin can be from 10,000 to 200,000.

[0119] In the embodiments of the present disclosure, the photo-polymerizable monomer undergoes a photo-polymerization reaction under a photoinitiator system to form a photopolymer. In some examples, a photosensitizer and a co-initiator are used in combination to form a photoinitiator system, wherein the photosensitizer is a photosensitizer sensitive to the excitation wavelength that excites the photo-polymerization of the photo-polymerizable monomer. Among them, the mass ratio of the photosensitizer to the co-initiator can be any ratio, for example, an equal ratio.

[0120] Under light illumination conditions, the photosensitizer is activated by actinic radiation, and under the synergistic action of the co-initiator, it induces the photo-polymerizable monomer to undergo a photo-polymerization reaction to form a photopolymer, which is beneficial to improving the photo-polymerization reaction rate.

[0121] On the premise that the photoinitiator system is a combination of a photosensitizer and a co-initiator, the photosensitizer and the co-initiator can be selected and combined from the following components: pyrromethene 597, coumarin 6, N-methyldiethanolamine, rhodamine 6G, rhodamine B, methylene blue, N-phenylglycine, diphenyliodonium hexafluorophosphate, tris(3-chloro-4-methylphenyl)hexylborate tetrabutylammonium, 3,3'-carbonylbis(7-diethylaminocoumarin).

[0122] In the holographic composition provided by the embodiments of the present disclosure, by weight, the weight portion of the polymer matrix is 20 parts to 80 parts, the weight portion of the photo-polymerizable monomer system is 20 parts to 80 parts, and the weight portion of the photoinitiator system is 0.1 part to 5 parts.

[0123] When each component acts synergistically in the above ratio, the content of the photopolymer formed by the photo-polymerization reaction of the photo-polymerizable monomer and the polymer matrix is controlled within a reasonable range, which is not only beneficial to the film-forming property of the holographic composition, but also beneficial to improving the diffraction efficiency and light transmittance of the holographic composition.

[0124] Exemplarily, the weight portions of the polymer matrix include but are not limited to 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, etc., the weight portions of the photo-polymerizable monomer system include but are not limited to 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, etc., and the weight portions of the photoinitiator system include but are not limited to 0.1 part, 0.5 part, 1 part, 1.5 parts, 2 parts, 3.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0125] In some examples, the sum of the parts by weight of the polymer matrix and the photo-polymerizable monomer system can be 100 parts. Some exemplary examples can be as follows: 80 parts of the polymer matrix and 20 parts of the photo-polymerizable monomer system, 75 parts of the polymer matrix and 25 parts of the photo-polymerizable monomer system, 70 parts of the polymer matrix and 30 parts of the photo-polymerizable monomer system, 60 parts of the polymer matrix and 40 parts of the photo-polymerizable monomer system, 50 parts of the polymer matrix and 50 parts of the photo-polymerizable monomer system, 40 parts of the polymer matrix and 60 parts of the photo-polymerizable monomer system, 30 parts of the polymer matrix and 70 parts of the photo-polymerizable monomer system, 20 parts of the polymer matrix and 80 parts of the photo-polymerizable monomer system, etc.

[0126] The holographic composition provided by the embodiments of the present disclosure contains a solvent to adjust the viscosity of the holographic composition and improve its film-forming property. Some suitable solvents include but are not limited to: at least one of ethyl acetate, acetone, xylene, toluene, methyl ethyl ketone, tetrahydrofuran, dichloromethane, and chloroform.

[0127] The holographic composition provided by the embodiments of the present disclosure can be prepared by the following method: Under light-shielded conditions, according to the ratio of each component, the polymer matrix, photo-polymerizable monomer, initiator, and photosensitizer are respectively weighed and placed in a light-shielded container. A solvent is added to the light-shielded container and stirred and mixed to form a holographic composition with a uniform texture. Before use, the holographic composition can be stored in the dark.

[0128] Any of the above-mentioned holographic compositions provided by the embodiments of the present disclosure can be applied to fields such as data storage, anti-counterfeiting images, holographic optical elements, holographic displays, etc. For example, the holographic composition of the embodiments of the present disclosure can be used to prepare a reflective holographic grating. In addition, any of the above-mentioned holographic compositions provided by the embodiments of the present disclosure can also be applied to 3D printing, near-infrared light curing (modifying the absorption wavelength of the photosensitizer), and deep light curing of dry films (thickness of mm level), because its absorption band is relatively long, and the dissipation of light source in deep curing is much improved compared with the UV band.

[0129] On the other hand, the embodiments of the present disclosure provide a holographic medium, as shown in the appendix Figure 2 The holographic medium includes: a transparent substrate 100 and a holographic photosensitive film 200 located on the transparent substrate 100, and the holographic photosensitive film 200 is prepared by using any of the above-mentioned holographic compositions.

[0130] The holographic medium provided by the embodiments of the present disclosure has all the advantages of the holographic composition provided by the embodiments of the present disclosure.

[0131] In some examples, the holographic medium provided by the embodiments of the present disclosure is prepared by the following method: coating a holographic composition on a transparent substrate, and after drying until the solvent in the holographic composition volatilizes, a holographic photosensitive film is formed on the transparent substrate to obtain the holographic medium. It should be noted that the holographic photosensitive film involved here has not been subjected to relevant light interference treatment, and the photopolymerizable monomers therein have not undergone photopolymerization reactions.

[0132] The methods of coating the holographic composition on the transparent substrate include but are not limited to: knife coating, casting, printing, spraying, inkjet printing, etc. The equipment used for coating the holographic composition on the transparent substrate includes but is not limited to: spin coater, gravure coater, comma coater, rod coater, etc.

[0133] In some examples, the thickness of the holographic photosensitive film can be 5 μm to 100 μm, and further can be 10 μm to 100 μm. For example, this includes but is not limited to 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0134] In the embodiments of the present disclosure, the transparent substrate can be transparent glass or a transparent flexible polymer substrate. Among them, the materials of the transparent flexible polymer substrate include but are not limited to: polyethylene terephthalate, cellulose triacetate, polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl chloride, polyvinyl alcohol, polymethyl methacrylate, polyethersulfone, polyetheretherketone, polyamide, polyimide, etc.

[0135] In some implementation manners, as shown in the appended Figure 2 figure, the holographic medium further includes an optical protective film 300, and the optical protective film 300 covers the surface of the holographic photosensitive film 200 facing away from the transparent substrate 100. The optical protective film 300 is a transparent film.

[0136] Protecting the holographic photosensitive film through the optical protective film is beneficial to enabling the holographic photosensitive film to be stably stored. Of course, in order to stably store the holographic medium, it can be stored in a light-shielded, light-tight environment such as a light-tight box.

[0137] In some examples, the material of the optical protective film can be polyethylene terephthalate or cellulose triacetate.

[0138] In some examples, the thickness of the optical protective film is 10 μm to 50 μm, so as not to affect the optical performance of the holographic photosensitive film while playing a protective role.

[0139] When the holographic medium includes the optical protection film 300, correspondingly, the holographic medium can be prepared by the following method: coating the holographic composition on a transparent substrate, drying until the solvent in the holographic composition volatilizes, and forming a holographic photosensitive film on the transparent substrate. Attaching the optical protection film to the surface of the holographic photosensitive film facing away from the transparent substrate to obtain the holographic medium.

[0140] In the embodiments of the present disclosure, after the prepared holographic medium is obtained and before it is exposed, the holographic medium is placed in the dark and stored away from light for standby.

[0141] In the holographic medium provided by the embodiments of the present disclosure, during the coherent light interference and subsequent curing process, the photopolymerizable monomers in the holographic photosensitive film polymerize to form a photopolymer, and the photopolymer is phase-separated from the polymer matrix, thereby generating a holographic grating.

[0142] On the other hand, the embodiments of the present disclosure also provide an optical device, which includes any one of the above holographic media.

[0143] The optical device provided by the embodiments of the present disclosure has all the advantages of the holographic medium involved in the embodiments of the present disclosure.

[0144] The holographic medium can exist in an unexposed form or an exposed form in the optical device. For the exposed form of the holographic medium, the photopolymerizable monomers in the holographic photosensitive film polymerize to form a photopolymer, and the photopolymer is phase-separated from the polymer matrix, thereby generating a holographic grating (which can also be considered as a holographic photosensitive film recording holographic information) recording holographic information.

[0145] Figure 3 Shows the layout of the optical device containing the holographic medium provided by the embodiments of the present disclosure, as shown in the appendix Figure 3 As shown, the optical device includes a laser, a beam expander, a lens, an optical element, and a mirror. The laser generates a laser beam that satisfies the coherence condition. The beam expander is used to adjust the beam diameter and divergence angle of the laser beam. The lens is used to collimate the expanded laser beam. The mirror is used to control the propagation direction of the coherent light.

[0146] The laser beam (i.e., coherent laser) that satisfies the coherence condition generated by the laser is expanded by the beam expander and then collimated by the lens. The collimated coherent light is reflected by the mirror and then irradiates the holographic medium, thereby obtaining a reflective holographic grating and realizing holographic recording.

[0147] In the embodiments of the present disclosure, the interference mode of the coherent light used in the exposure process of the holographic medium can be double-beam interference or single-beam interference, where Figure 3 Illustrates the single-beam interference mode.

[0148] The excitation wavelength range of the coherent light used in the holographic medium provided by the embodiments of the present disclosure can be 400 nm to 800 nm. Exemplarily, the excitation wavelength can be 450 nm to 480 nm, 500 nm to 560 nm, or 605 nm to 700 nm. The excitation light in these three ranges is a commonly used light wave band in holographic recording scenarios. By selecting a photoinitiator system sensitive to the excitation light in the above bands, the photopolymerization between the photopolymerizable monomers can be effectively excited, expanding the application scenarios.

[0149] The excitation intensity of the coherent light used in the holographic medium provided by the embodiments of the present disclosure is 0.001 mW / cm 2 ~500 mW / cm 2 Some examples of the excitation intensity include but are not limited to the following: 1 mW / cm 2 ~500 mW / cm 2 ,10 mW / cm 2 ~500 mW / cm 2 ,100 mW / cm 2 ~500 mW / cm 2 ,200 mW / cm 2 ~500 mW / cm 2 ,300 mW / cm 2 ~500 mW / cm 2 ,400 mW / cm 2 ~500 mW / cm 2 ,100 mW / cm 2 ~200 mW / cm 2 ,200 mW / cm 2 ~300 mW / cm 2 ,300 mW / cm 2 ~400 mW / cm 2 etc.

[0150] The illumination time of the excitation light of the coherent light used in the holographic medium provided by the embodiments of the present disclosure is 1 s to 900 s, including but not limited to: 60 s, 100 s, 150 s, 200 s, 250 s, 300 s, 450 s, 500 s, 550 s, 600 s, 650 s, 700 s, 750 s, 800 s, 850 s, 900 s, etc.

[0151] The exposure energy of the holographic medium provided by the embodiments of the present disclosure can be 20 mJ / cm 2 ~50 mJ / cm 2 ,including but not limited to: 20 mJ / cm 2 ,25 mJ / cm 2 ,30 mJ / cm 2 ,35 mJ / cm2 , 40 mJ / cm 2 , 45 mJ / cm 2 , 50 mJ / cm 2 etc.

[0152] Performing exposure processing for the above time under the above exposure parameters can efficiently activate the photoinitiator system, promote the photopolymerization reaction between photopolymerizable monomers, and improve the production efficiency of photopolymers.

[0153] As described above, the holographic medium is exposed under coherent light radiation conditions, and the polymerizable groups in the photopolymerizable monomers undergo photopolymerization to form photopolymers. In some examples, the present disclosure embodiments may further perform a curing process on the exposed holographic medium, and the curing process includes light treatment and / or heat treatment.

[0154] Through the curing process, unreacted photopolymerizable monomers can be further fully reacted, enabling further phase separation of the photopolymers and the polymer matrix, and effectively improving the diffraction efficiency of the holographic grating.

[0155] For light treatment, the light irradiation methods include but are not limited to: ultraviolet light irradiation, high-pressure mercury lamp irradiation, white light irradiation, etc., and the light irradiation time can be 1 minute to 30 minutes. Among them, white light irradiation can make unreacted photopolymerizable monomers fully react. Due to the photosensitizer being photoactivated by light radiation and decolorizing, the influence of the residual photosensitizer on the light transmittance of the holographic photosensitive film is reduced.

[0156] In some examples, performing a curing process on the holographic photosensitive film recording holographic information includes: first performing white light irradiation on the holographic photosensitive film recording holographic information, and then performing high-pressure mercury lamp irradiation.

[0157] For heat treatment, the temperature of the heat treatment can be 50 °C to 100 °C, and the time of the heat treatment can be 5 min to 30 min.

[0158] In summary, in the optical device provided by the present disclosure embodiments, after the holographic medium is exposed, it is partitioned through photopolymers and the polymer matrix, and then a phase-separated holographic grating is obtained and used as an optical element. Based on the use of the photopolymerizable monomers and the polymer matrix provided by the present disclosure embodiments, the two work together, significantly weakening the diffraction peak drift of the holographic grating, and the holographic grating also has high light transmittance and low haze.

[0159] It should be noted that the light transmittance represents the ability of light to pass through a medium, which is the percentage of the light flux passing through a transparent or translucent body to its incident light flux. Haze refers to the percentage of the transmitted light intensity deviating from the incident light by more than 2.5° in the total transmitted light intensity. The greater the haze, the lower the gloss and transparency of the film.

[0160] In some examples, the holographic grating obtained after the holographic medium is exposed is a reflection holographic grating, which has the advantages of good wavelength selectivity and little influence of ambient light.

[0161] The holographic medium according to the embodiments of the present disclosure has infrared characteristic absorption peaks in two bands of 3400 cm -1 ~3300 cm -1 and 1650 cm -1 ~1550 cm -1 before and after it is exposed, respectively corresponding to the characteristic peaks of hydrogen bond bonding. It can be seen that as the temperature rises, the hydrogen bond gradually breaks and its absorption peak gradually decreases.

[0162] The optical device provided by the embodiments of the present disclosure can be applied to scenarios such as in-vehicle head-up display (Head-up Display, HUD), AR glasses, holographic 3D projection, etc. For example, when the optical device is used in AR glasses or in-vehicle head-up display, it is clamped on the windshield / attached to the glass, and through holographic exposure, the holographic medium records all the information of light, thereby realizing the projection of a 3D stereoscopic effect, and further realizing the combination of virtual and reality.

[0163] The exemplary embodiments of the present disclosure will be described in more detail below. Although the exemplary embodiments of the present disclosure are described below, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. For those where specific techniques or conditions are not indicated in the examples, the techniques or conditions described in the literature in the relevant field or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0164] The polymer matrix involved in the following embodiments is the above-mentioned linear polyurethane resin with epoxy side chains, and its chemical structural formula is as follows:

[0165]

[0166] Among them, the chemical structural formula of the M group is as follows:

[0167]

[0168] R 1 is n-hexyl, R 2 is n-pentyl, R 3 is n-propyl, R 4 is n-pentyl, R 5 is n-hexyl.

[0169] In the above linear polyurethane resin with epoxy side chains, the weight of the epoxy side chains is 4% of the weight of the linear polyurethane resin, and the nuclear magnetic resonance hydrogen spectrum of the linear polyurethane resin with epoxy side chains is as Figure 4 shown.

[0170] The chemical structural formulas of the photopolymerizable monomers involved in the following examples are as shown below:

[0171]

[0172] Among them, the first group M is shown by any of the following chemical structural formulas, and * in the following chemical structural formulas all represents a chemical bonding site:

[0173]

[0174] The third group N is shown by any of the following chemical structural formulas, and * in the following chemical structural formulas all represents a chemical bonding site:

[0175]

[0176] Example 1

[0177] This Example 1 provides a holographic composition, a holographic medium, and a reflective holographic optical element. Among them, the formulation of the holographic composition is shown in Table 1.

[0178] Table 1

[0179]

[0180] The holographic composition provided in Example 1 is prepared by the following method:

[0181] By weight, take the above components and place them in a brown sample bottle, then add ethyl acetate as a solvent and stir. After stirring until it is uniform and clear, store it in a light-proof environment for later use. Among them, the amount of the solvent is such that the concentration of the polymer matrix reaches 0.2 g / ml.

[0182] Based on its holographic composition, Example 1 prepares a holographic medium. The holographic medium includes a glass substrate, a holographic photosensitive film, and an optical protective film made of polyethylene terephthalate, which are arranged in layers in sequence. The holographic medium is prepared by the following method:

[0183] Use a doctor blade to scrape the holographic composition onto the glass substrate. Among them, the height of the doctor blade is 100 μm, and the scraping speed is 200 mm / min, so as to form a wet film on the glass substrate. Dry the wet film at 45°C for 10 min to evaporate the solvent therein and form a holographic photosensitive film. Attach an optical protective film with a thickness of 50 μm on the holographic photosensitive film to prepare a holographic medium, and store it in a light-proof environment for later use.

[0184] Example 1 A reflective holographic optical element was prepared based on its holographic medium, and it was exposed according to the optical device arrangement shown below. The excitation light was a blue laser with a wavelength of 460 nm and an exposure energy of 30 mJ / cm Figure 3 as shown. After the exposure treatment, the holographic medium was further cured by irradiating it under a high-pressure mercury lamp for 5 minutes to obtain a reflective holographic optical element. 2

[0185] Example 2

[0186] Example 2 provides a holographic composition, a holographic medium, and a reflective holographic optical element. The formulation of the holographic composition is shown in Table 2.

[0187] Table 2

[0188]

[0189] The preparation method of the holographic composition provided in Example 2 can refer to Example 1 and will not be elaborated here. Example 2 prepared a holographic medium based on its holographic composition. The structure and preparation method of this holographic medium can both refer to Example 1 and will not be elaborated here.

[0190] Example 2 prepared a reflective holographic optical element based on its holographic medium, and it was exposed according to the optical device arrangement shown below. The excitation light was a green laser with a wavelength of 532 nm and an exposure energy of 30 mJ / cm Figure 3 as shown. After the exposure treatment, the holographic medium was further cured by irradiating it under a high-pressure mercury lamp for 5 minutes to obtain a reflective holographic optical element. 2

[0191] Example 3

[0192] Example 3 provides a holographic composition, a holographic medium, and a reflective holographic optical element. The formulation of the holographic composition is shown in Table 3.

[0193] Table 3

[0194]

[0195] The preparation method of the holographic composition provided in Example 3 can refer to Example 1 and will not be elaborated here. Example 3 prepared a holographic medium based on its holographic composition. The structure and preparation method of this holographic medium can both refer to Example 1 and will not be elaborated here.

[0196] Example 3 prepared a reflective holographic optical element based on its holographic medium, and it was exposed according to the optical device arrangement shown below. Figure 3 ​​The optical device arrangement shown is subjected to an exposure process, where the excitation light is a red laser with a wavelength of 640 nm and an exposure energy of 30 mJ / cm 2 . After the exposure process, the holographic medium is further cured by irradiating it under a high-pressure mercury lamp for 5 minutes to obtain a reflective holographic optical element.

[0197] Example 4

[0198] Example 4 provides a holographic composition, a holographic medium, and a reflective holographic optical element. Among them, the formulation of the holographic composition is shown in Table 4.

[0199] Table 4

[0200]

[0201] The preparation method of the holographic composition provided in Example 4 can refer to Example 1 and will not be elaborated here. Based on its holographic composition, Example 4 prepares a holographic medium, and the structure and preparation method of this holographic medium can both refer to Example 1 and will not be elaborated here.

[0202] Based on its holographic medium, Example 4 prepares a reflective holographic optical element and subjects it to an exposure process according to the Figure 3 optical device arrangement shown, where the excitation light is a green laser with a wavelength of 532 nm and an exposure energy of 30 mJ / cm 2 . After the exposure process, the holographic medium is further irradiated under a high-pressure mercury lamp for 5 minutes to obtain a reflective holographic optical element.

[0203] Example 5

[0204] Example 5 provides a holographic composition, a holographic medium, and a reflective holographic optical element. Among them, the formulation of the holographic composition is shown in Table 5.

[0205] Table 5

[0206]

[0207] The preparation method of the holographic composition provided in Example 5 can refer to Example 1 and will not be elaborated here. Based on its holographic composition, Example 5 prepares a holographic medium, and the structure and preparation method of this holographic medium can both refer to Example 1 and will not be elaborated here.

[0208] Based on its holographic medium, Example 5 prepares a reflective holographic optical element and subjects it to an exposure process according to the Figure 3 optical device arrangement shown, where the excitation light is a blue laser with a wavelength of 460 nm and an exposure energy of 30 mJ / cm 2After the exposure treatment, the holographic medium was irradiated under a high-pressure mercury lamp for 5 minutes to prepare a reflective holographic optical element.

[0209] In addition, the temperature-variable infrared curves of the holographic matrix provided in Example 5 before and after the exposure treatment were tested. The test results can be seen in Figure 9 and Figure 10 , and the holographic matrix has infrared characteristic absorption peaks in two bands of 3400 cm -1 ~3300 cm -1 and 1650 cm -1 ~1550 cm -1 , respectively corresponding to the characteristic peaks of hydrogen bond bonding. It can be seen that as the temperature increases, the hydrogen bond gradually breaks and its absorption peak gradually decreases.

[0210] Example 6

[0211] This Example 6 provides a holographic composition, a holographic medium and a reflective holographic optical element. Among them, the formulation of the holographic composition is shown in Table 6.

[0212] Table 6

[0213]

[0214] The preparation method of the holographic composition provided in Example 6 can refer to Example 1 and will not be elaborated here. Based on its holographic composition, Example 6 prepared a holographic medium. The structure and preparation method of this holographic medium can both refer to Example 1 and will not be elaborated here.

[0215] Based on its holographic medium, Example 6 prepared a reflective holographic optical element and carried out an exposure treatment on it according to the optical device arrangement shown in Figure 3 . Its excitation light is a red laser with a wavelength of 640 nm and an exposure energy of 30 mJ / cm 2 . After the exposure treatment, the holographic medium was irradiated under a high-pressure mercury lamp for 5 minutes to prepare a reflective holographic optical element.

[0216] Example 7

[0217] This Example 7 provides a holographic composition, a holographic medium and a reflective holographic optical element. Among them, the formulation of the holographic composition is shown in Table 7.

[0218] Table 7

[0219]

[0220] The preparation method of the holographic composition provided in Example 7 can refer to Example 1 and will not be elaborated here. Based on its holographic composition, a holographic medium was prepared in Example 7. The structure and preparation method of this holographic medium can both refer to Example 1 and will not be elaborated here.

[0221] Based on its holographic medium, a reflective holographic optical element was prepared in Example 7, and it was exposed according to the optical device arrangement shown in Figure 3 . The excitation light was a blue laser with a wavelength of 460 nm, and the exposure energy was 30 mJ / cm 2 . After the exposure treatment, the holographic medium was irradiated under a high-pressure mercury lamp for 5 min to prepare the reflective holographic optical element.

[0222] Test Example

[0223] In this test example, the transmittance, haze, diffraction efficiency, average diffraction peak drift value, and volume shrinkage rate of the holographic optical elements provided in Examples 1 - 7 were tested.

[0224] Among them, for the transmittance test, the transmittance value of each holographic optical element at the 400 nm band was measured using a UV-visible spectrophotometer, which is simply abbreviated as T 400 . For the haze test, a spectrophotometer was used to measure the haze of each holographic optical element.

[0225] For the diffraction efficiency, the acquisition method is as follows: The transmittance of each holographic optical element at the 400 - 750 nm band was measured using a UV-visible spectrophotometer. Then, based on the Figure 5 shown drawings, the minimum transmittance (T B ) of the diffraction peak and the transmittance (T A ) of the baseline were respectively obtained, and the diffraction efficiency η was calculated according to Equation (1).

[0226]

[0227] For the volume shrinkage rate, based on the Figure 1 shown drawings, the abscissa of point B, that is, the reconstruction wavelength (λ r ) of the holographic grating, was obtained. Combining with the laser wavelength used for exposure, the writing wavelength (λ w ) was obtained. Then, the calculation formula for the effective volume shrinkage rate (S eff ) of the holographic grating in the holographic optical element is shown in Equation (2).

[0228]

[0229] The average diffraction peak drift value is obtained by the following method: after the holographic optical element is exposed, there is at least one absorption peak, and the corresponding Tmin (the wavelength of the lowest transmittance, that is, the wavelength of the maximum absorption peak) is taken as λ 实验 , during actual exposure, red, green, and blue lasers are used for exposure, and the corresponding λ 激光器 are 640 nm, 532 nm, and 460 nm respectively. The diffraction peak drift value is λ 激光器 -λ 实验 . The average diffraction peak drift value is the average of the diffraction peak drift values obtained from samples made with the same formulation, using exactly the same exposure method and post-treatment process, so as to exclude the influence of experimental errors.

[0230] The test data of the holographic optical elements corresponding to Examples 1-7 are all shown in Table 8. In addition, the ultraviolet-visible absorption spectra of the holographic media provided in Examples 1, 2, and 3 are respectively referred to Figure 6 , Figure 7 and Figure 8 .

[0231] Table 8

[0232]

[0233] Combined with Table 8, and Figure 6 , Figure 7 and Figure 8 it can be seen that the holographic composition provided by the embodiments of the present disclosure has excellent light transmittance, haze, and diffraction efficiency, and both the diffraction peak drift and the volume shrinkage rate are low.

[0234] The above description is only for the convenience of those skilled in the art to understand the technical solutions of the present disclosure, and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A compound, characterized in that, the compound comprises: a first group, a second group, a third group and an acrylate group, the second group comprises a carbonyl group, a first end group and a second end group respectively connected to the carbonyl group, the first end groups of a plurality of the second groups are respectively connected to different sites of the first group, the second end groups of a part of the plurality of the second groups are connected to the acrylate group, and the second end groups of the remaining part are connected to the third group; the first group comprises a steric hindrance group; the first end group of the second group and the second end group of the second group are each independently selected from an oxygen atom, a sulfur atom, a selenium atom, a hydroxyl group, a mercapto group, a selenohydryl group or a secondary amino group; the third group comprises at least one of an aryl group and a heteroaryl group, and the heteroatoms in the heteroaryl group comprise at least one of a bromine atom, an iodine atom, a sulfur atom and a nitrogen atom.

2. The compound according to claim 1, characterized in that, the steric hindrance group comprises: an alkane group having a side chain, a cycloalkane group having a side chain, a heterocyclic group having a side chain, an aryl group having a side chain, an adamantyl group having a side chain, a siloxane group.

3. The compound according to claim 1, characterized in that, the chemical structural formula of the compound is as follows: wherein, M is the first group; R 1 is the first end group of the second group, R 2 is the second end group of the second group; N is the third group; P is the acrylate group.

4. The compound according to any one of claims 1-3, characterized in that, the first group is shown as any one of the following chemical structural formulas:

5. The compound according to any one of claims 1-4, characterized in that, the third group is shown as any one of the following chemical structural formulas:

6. A photopolymerizable monomer system, characterized in that, the photopolymerizable monomer system comprises the compound according to any one of claims 1-5.

7. A holographic composition, characterized in that, the holographic composition comprises a polymer matrix, a photopolymerizable monomer system and a photoinitiator system; the photopolymerizable monomer system comprises the compound according to any one of claims 1-5 or the photopolymerizable monomer system according to claim 6.

8. The holographic composition according to claim 7, characterized in that, the photopolymerizable monomer system comprises at least two photopolymerizable monomers, and the at least two photopolymerizable monomers are each selected from the compound according to any one of claims 1-5.

9. The holographic composition according to claim 7, characterized in that, the polymer matrix comprises a linear polyurethane resin having an epoxy side chain, and the end group of the epoxy side chain is an epoxy group.

10. The holographic composition according to claim 9, characterized in that, the weight of the epoxy side chain is 0.1% to 20% of the weight of the polymer matrix.

11. The holographic composition according to claim 7, characterized in that, the photoinitiator system comprises a co-initiator and a photosensitizer.

12. The holographic composition according to any one of claims 7-11, characterized in that, The weight parts of the polymer matrix are 20 parts to 80 parts, the weight parts of the photo-polymerizable monomer system are 20 parts to 80 parts, and the weight parts of the photoinitiator system are 0.1 part to 5 parts.

13. A holographic medium, characterized in that the holographic medium comprises: a transparent substrate and a holographic photosensitive film located on the transparent substrate, and the holographic photosensitive film is prepared from the holographic composition according to any one of claims 7-12.

14. The holographic medium according to claim 13, characterized in that the holographic medium further comprises an optical protective film, and the optical protective film covers the surface of the holographic photosensitive film facing away from the transparent substrate.

15. The holographic medium according to any one of claims 13-14, characterized in that The excitation wavelength range of the coherent light used in the holographic medium is 400 nm to 800 nm, and the excitation intensity of the coherent light used is 0.001 mW / cm 2 to 500 mW / cm 2 .

16. An optical device, characterized in that the optical device comprises the holographic medium according to any one of claims 13-15.

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