A holographic polymer liquid crystal material, its preparation method and application

Abstract

The present invention provides a holographic polymer liquid crystal material, a preparation method thereof and an application thereof. In terms of mass percentage, the holographic polymer liquid crystal material comprises 20-50% of a nematic liquid crystal composition, 30-80% of an acrylate monomer, 1-20% of glue and 0.1-5% of a photoinitiator; the nematic liquid crystal composition comprises component A and component B; component A comprises at least one of the compounds having the structure shown in formula I; component B comprises at least one of the compounds having the structure shown in formula II; the acrylate monomer comprises at least one of the compounds having the structure shown in formula III. In the present invention, by selecting a nematic liquid crystal composition and an acrylate monomer having specific structures, the volume holographic grating comprising the material has high diffraction efficiency, low haze, and can be switched between a holographic state and a transparent state, and has a wide application range.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical materials, and particularly relates to a holographic polymer liquid crystal material, a preparation method thereof and an application thereof. Background Art

[0002] Augmented reality (AR) is a new technology that superimposes real-world information and virtual-world information onto the same picture or space in real time. By generating prompt information, virtual objects or virtual scenes through a computer and superimposing them onto the real world to be perceived by human organs, the sensory experience of augmented reality is achieved. At present, AR technology has been widely applied in fields such as games, retail, education, industry, military, and medical care.

[0003] The waveguide technologies for making AR are currently divided into three categories: array optical waveguides, surface relief optical waveguides, and volume holographic optical waves. Among them, the volume holographic optical waveguide technology has received extensive attention at home and abroad due to its advantages such as low cost and suitability for large-scale production.

[0004] Current research on volume holographic materials focuses on photopolymers. For example, CN113527143A discloses a writing monomer, a preparation method thereof, a photopolymer composition, and a grating thereof. The writing monomer is a carbamate acrylate monomer containing a fluorenyl group; the photopolymer can achieve a relatively high refractive index modulation degree and diffraction efficiency by using the carbamate acrylate monomer containing a fluorenyl group. However, since the photopolymer is not sensitive to electrical signals, it cannot be tuned after the material is exposed to form a grating.

[0005] Holographic polymer dispersed liquid crystal (HPDLC) is a new type of holographic material, which has outstanding advantages such as low cost, simple manufacturing process, high diffraction efficiency, and low haze. Compared with photopolymers (PP), since liquid crystal materials have birefringence and can be sensitive to an electric field and can be switched between no and ne, an electric signal can be used to tune the grating. When no voltage is applied, there is a large difference between the refractive index of the liquid crystal and that of the polymer, and the device presents a holographic state. When a voltage is applied, the liquid crystal deflects, and at this time, the refractive index of the liquid crystal is approximately the same as that of the polymer, and the device will no longer present a holographic state.

[0006] HPDLC components primarily include acrylate monomers, polyurethane acrylate prepolymers, photoinitiators, liquid crystals, and a small amount of additives. When the material is exposed to light, the monomers undergo polymerization. As the polymerization proceeds, the liquid crystal and polymer phase separate. The polymerization rate is a key factor influencing phase separation. If the reaction rate is too fast, the polymer cannot form a grating structure. If the reaction rate is too slow, the liquid crystal is encapsulated by the polymer, preventing complete phase separation. This results in low diffraction efficiency and increased haze. Existing HPDLC materials, due to incomplete phase separation between the liquid crystal and polymer, have low diffraction efficiency and high haze, making them currently unsuitable for volume holographic waveguide applications.

[0007] Therefore, developing a holographic polymer liquid crystal material with high diffraction efficiency and low haze is a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0008] In response to the shortcomings of the prior art, the present invention provides a holographic polymer liquid crystal material, its preparation method, and its application. By selecting a nematic liquid crystal composition with a specific structure and an acrylate monomer, the holographic polymer liquid crystal material enables a volume holographic grating comprising the material to exhibit high diffraction efficiency, low haze, and the ability to switch between a holographic state and a transparent state.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a holographic polymer liquid crystal material, which comprises, by weight percentage, 20-50% of a nematic liquid crystal composition, 30-80% of an acrylate monomer, 1-20% of a glue, and 0.1-5% of a photoinitiator; the nematic liquid crystal composition comprises component A and component B; component A comprises at least one compound having a structure represented by formula I; component B comprises at least one compound having a structure represented by formula II; and the acrylate monomer comprises at least one compound having a structure represented by formula III;

[0011]

[0012] wherein R1, R2, R3, R4, R5, and R6 are each independently any one of a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C1-C7 straight-chain or branched alkyl group, a substituted or unsubstituted C1-C7 straight-chain or branched alkoxy group, a substituted or unsubstituted C2-C7 straight-chain or branched alkenyl group, or a substituted or unsubstituted C2-C7 straight-chain or branched alkenyloxy group;

[0013] Z1 is selected from any one of substituted or unsubstituted C1-C3 alkylene, substituted or unsubstituted C2-C3 alkenylene, ethynylene, ester group or substituted or unsubstituted C1-C3 alkoxy;

[0014] Z2 and Z3 are each independently selected from any one of substituted or unsubstituted C1-C3 alkylene, substituted or unsubstituted C2-C3 alkenylene, ethynylene, ester group, substituted or unsubstituted C1-C3 alkoxy or single bond; at least one of the groups Z2 and Z3 is selected from ethynylene;

[0015] L1, L2, L3 and L4 are each independently selected from halogen or hydrogen;

[0016] L5 is selected from any one of halogen, substituted or unsubstituted C3-C6 cycloalkyl, substituted or unsubstituted C1-C7 straight-chain or branched-chain alkyl, substituted or unsubstituted C1-C7 straight-chain or branched-chain alkoxy, substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyl or substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyloxy;

[0017] A1 and A2 are each independently selected from single bond, substituted or unsubstituted C1-C6 straight-chain or branched-chain alkylene, wherein any one or more -CH2- in the alkylene are optionally substituted by -O-, -COO- or -CH=CH-;

[0018] n is 0 or 1;

[0019] p is an integer from 1 to 5; q is an integer from 0 to 4;

[0020] The substituents of the substitution include halogen.

[0021] In the present invention, in the holographic polymer liquid crystal material, the nematic liquid crystal composition selects component A and component B with specific structures, and at the same time the acrylate monomer selects a polymerizable monomer with a specific structure. The three cooperate with each other and are indispensable, so that the material is completely phase-separated after exposure, and the formed grating has both high diffraction efficiency and low haze, and can be tuned, meeting the application requirements of the volume holographic optical waveguide.

[0022] Based on mass percentage, the holographic polymer liquid crystal material comprises 20-50% of the nematic liquid crystal composition, for example, it can be 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, etc.

[0023] In terms of mass percentage, the holographic polymer liquid crystal material comprises 30-80% of acrylate monomers, for example, it can be 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 54%, 58%, 60%, 64%, 68%, 70%, 74%, 78%, etc.

[0024] In terms of mass percentage, the holographic polymer liquid crystal material comprises 1-20% of glue, for example, it can be 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, etc.

[0025] In terms of mass percentage, the holographic polymer liquid crystal material comprises 0.1-5% of photoinitiator, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc.

[0026] In the present invention, the C3-C6 cycloalkyl includes C3, C4, C5, C6 cycloalkyl, and exemplarily includes but is not limited to cyclopropyl, cyclobutyl, cyclopentyl, etc.

[0027] In the present invention, the C1-C7 straight-chain or branched-chain alkyl includes C1, C2, C3, C4, C5, C6, C7 straight-chain or branched-chain alkyl, and exemplarily includes but is not limited to methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl or heptyl, etc.

[0028] In the present invention, the C1-C7 straight-chain or branched-chain alkoxy includes C1, C2, C3, C4, C5, C6, C7 straight-chain or branched-chain alkoxy, and exemplarily includes but is not limited to methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, hexyloxy or heptyloxy, etc.

[0029] In the present invention, the C2-C7 straight-chain or branched-chain alkenyl includes C2, C3, C4, C5, C6, C7 straight-chain or branched-chain alkenyl, and exemplarily includes but is not limited to vinyl, propenyl, isopropenyl, butenyl, pentenyl, hexenyl or heptenyl, etc.

[0030] In the present invention, the C2-C7 straight-chain or branched-chain alkenyloxy includes C2, C3, C4, C5, C6, C7 straight-chain or branched-chain alkenyloxy, and exemplarily includes but is not limited to vinyloxy, propenyloxy, isopropenyloxy, butenyloxy, pentenyloxy, hexenyloxy or heptenyloxy, etc.

[0031] In the present invention, the C1-C3 alkylene groups include C1, C2, and C3 alkylene groups, and exemplarily include, but are not limited to, methylene, ethylene, etc.; the C2-C3 alkenylene groups include C2 and C3 alkenylene groups, and exemplarily include, but are not limited to, vinylidene, etc.; the C1-C3 alkoxy groups include C1, C2, and C3 alkoxy groups, and exemplarily include, but are not limited to, -CH2O-.

[0032] In the present invention, p is 1, 2, 3, 4, 5, etc.; q is 0, 1, 2, 3, 4, etc.

[0033] The halogen includes F, Cl, etc.

[0034] In the present invention, when n is 0, R1 is selected from any one of

[0035] Preferably, the component A includes at least one of the compounds having the following structures;

[0036]

[0037] Wherein, R 11 , R 21 each independently includes any one of a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkyl group, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkoxy group, a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyl group, or a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyloxy group; the substituent of the substitution includes a fluorine substituent.

[0038] Preferably, the component B includes at least one of the compounds having the following structures;

[0039]

[0040]

[0041] Wherein, R 31 , R 41 each independently includes any one of a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkyl group, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkoxy group, a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyl group, or a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyloxy group; the substituent of the substitution includes a fluorine substituent.

[0042] Preferably, the mass ratio of component A to component B in the nematic liquid crystal composition is (1 to 2.5):1, and can be, for example, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, etc.

[0043] Preferably, the acrylate monomer includes at least one of the compounds having the following structures;

[0044]

[0045] Wherein, R 51 , R 61 are each independently selected from an H atom, -CH3 or -CF3;

[0046] L 51 , L 52 are each independently selected from an F atom, a Cl atom, a C3-C6 cycloalkyl group, a C1-C7 straight-chain or branched-chain alkyl group, a C1-C7 straight-chain or branched-chain alkoxy group, a C2-C7 straight-chain or branched-chain alkenyl group or a C2-C7 straight-chain or branched-chain alkenyloxy group;

[0047] A 11 , A 21 are each independently selected from a C1-C6 straight-chain alkylene group, wherein any one or more -CH2- are optionally substituted by -O-, -COO- or -C═C-;

[0048] q1 and q2 are each independently an integer from 0 to 4.

[0049] Preferably, the glue includes at least one of a polyurethane acrylate resin glue, an epoxy acrylate glue, a polyester acrylate glue, a polyether acrylate glue or an acrylate glue.

[0050] Preferably, the photoinitiator includes bis(2,6-difluoro-3-pyrrolylphenyl)titanocene dichloride.

[0051] In a second aspect, the present invention provides a method for preparing a holographic polymer liquid crystal material according to the first aspect, the preparation method comprising:

[0052] Mix the nematic liquid crystal composition, the acrylate monomer, the glue and the photoinitiator according to the formula amount under light-shielded conditions to obtain the holographic polymer liquid crystal material.

[0053] Preferably, the temperature of the mixing is 30 to 50 °C, and can be, for example, 35 °C, 40 °C, 45 °C, etc.; the time is 20 to 40 min, and can be, for example, 25 min, 30 min, 35 min, etc.

[0054] In a third aspect, the present invention provides a volume holographic grating, and the material of the volume holographic grating comprises the holographic polymer liquid crystal material as described in the first aspect.

[0055] The numerical ranges described in the present invention include not only the above-listed point values, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] The present invention provides a holographic polymer liquid crystal material. By selecting a nematic liquid crystal composition and an acrylate monomer with a specific structure, the volume holographic grating including the material has high diffraction efficiency, low haze, and can be switched between a holographic state and a transparent state. The diffraction efficiency of the grating is ≥61%, and the haze is ≤1.3%. Detailed implementation manners

[0058] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0059] All materials used in the present invention can be prepared by commercially available or methods disclosed in the prior art, and the structures and numbers are as follows:

[0060] Component A (having the structure shown in Formula I)

[0061]

[0062] Component B (having the structure shown in Formula II)

[0063]

[0064] Acrylate monomer (having the structure shown in Formula III)

[0065]

[0066]

[0067] All the holographic polymer liquid crystal materials provided in the examples and comparative examples of the present invention include the photoinitiator bis(2,6-difluoro-3-pyrrolylphenyl)titanocene dichloride, and the dosage is 1% of the total mass of the components.

[0068] Example 1

[0069] This embodiment provides a holographic polymer liquid crystal material. Based on the total amount of the nematic liquid crystal composition, acrylate monomers, and glue being 100%, the adjustable holographic material includes 28% of the nematic liquid crystal composition, 60% of acrylate monomers, and 12% of glue NOA61; the nematic liquid crystal composition includes 3% of I-11, 5% of I-12, 5% of I-31, 5% of I-21; 5% of II-11, 5% of II-21; the acrylate monomers include 30% of III-31, 30% of III-11.

[0070] This embodiment provides a preparation method of a holographic polymer liquid crystal material, which specifically includes the following steps:

[0071] Weigh each component according to the formula amount and put them into a brown glass bottle. Add a magnetic rotor to the bottle, start stirring at a controlled temperature of 40°C, stir for 30 minutes until the material is uniform, and then cool to room temperature to obtain the holographic polymer liquid crystal material.

[0072] Example 2

[0073] This embodiment provides a holographic polymer liquid crystal material. Based on the total amount of the nematic liquid crystal composition, acrylate monomers, and glue being 100%, the adjustable holographic material includes 30% of the nematic liquid crystal composition, 60% of acrylate monomers, and 10% of glue NOA61; the nematic liquid crystal composition includes 7% of I-11, 3% of I-12, 4% of I-31, 6% of I-21; 3% of II-11, 7% of II-21; the acrylate monomers include 30% of III-31, 30% of III-11.

[0074] This embodiment provides a preparation method of a holographic polymer liquid crystal material, and the specific steps are the same as those in Example 1.

[0075] Example 3

[0076] This embodiment provides a holographic polymer liquid crystal material. Based on the total amount of the nematic liquid crystal composition, acrylate monomers, and glue being 100%, the adjustable holographic material includes 35% of the nematic liquid crystal composition, 55% of acrylate monomers, and 10% of glue NOA61; the nematic liquid crystal composition includes 10% of I-11, 10% of I-21; 5% of II-31, 5% of II-11, 5% of II-21; the acrylate monomers include 25% of III-31, 30% of III-11.

[0077] This embodiment provides a preparation method of a holographic polymer liquid crystal material, and the specific steps are the same as those in Example 1.

[0078] Example 4

[0079] This embodiment provides a holographic polymer liquid crystal material, which is only different from that of Embodiment 1 in that the total amount of the nematic liquid crystal composition remains unchanged, the composition and ratio of Component A and Component B remain unchanged, and the mass ratio of the two is 0.5:1, and other components, dosages and preparation methods are the same as those of Embodiment 1.

[0080] Example 5

[0081] This embodiment provides a holographic polymer liquid crystal material, which is only different from that of Embodiment 1 in that the total amount of the nematic liquid crystal composition remains unchanged, the composition and ratio of Component A and Component B remain unchanged, and the mass ratio of the two is 3:1, and other components, dosages and preparation methods are the same as those of Embodiment 1.

[0082] Comparative Example 1

[0083] This comparative example provides a holographic polymer liquid crystal material, which is only different from that of Embodiment 1 in that the nematic liquid crystal composition is equal masses of Compounds D1, D2, D3, and D4, and the mass ratio is 1:1:1:1, and other components, dosages and preparation methods are the same as those of Embodiment 1.

[0084] Comparative Example 2

[0085] This comparative example provides a holographic polymer liquid crystal material, which is only different from that of Embodiment 1 in that the acrylate monomer is 30% 1,6 - hexanediol diacrylate and 30% methyl methacrylate, and other components, dosages and preparation methods are the same as those of Embodiment 1.

[0086] Comparative Example 3

[0087] This comparative example provides a holographic polymer liquid crystal material, which is only different from that of Embodiment 1 in that Component A is replaced with an equal amount of Compound F, Component B is replaced with an equal amount of Compound G, and the acrylate monomer is an equal amount of Compound E, and other components, dosages and preparation methods are the same as those of Embodiment 1.

[0088] Performance Test

[0089] (1) Diffraction Efficiency

[0090] Under a light - shielded state, the holographic polymer liquid crystal material is poured into a glass cell. Due to the siphon effect, the material will slowly be sucked into the glass cell until it is completely filled. The thickness of the cavity of the glass cell is 8 μm. The glass cell filled with the holographic polymer liquid crystal material is placed in the exposure optical path for exposure. After exposure, a grating is formed in the glass cell by the holographic polymer liquid crystal material. The diffraction efficiency is measured through the test optical path; the diffraction light intensity and the incident light intensity are recorded, and the ratio of the diffraction light intensity to the incident light intensity is the diffraction efficiency; the preparation method of the grating and the diffraction efficiency measurement method can refer to the literature (Wang Xiaodie. Research on Holographic Polymer - Dispersed Liquid Crystal (H - PDLC) Gratings [D]. Southeast University.).

[0091] (2) Haze

[0092] The haze was measured using a WGT-S transmittance / haze meter.

[0093] The specific test results are shown in Table 1:

[0094] Table 1

[0095] Diffraction efficiency (%) Haze (%) Example 1 64 1 Example 2 61 1.3 Example 3 64 0.8 Example 4 52 5.4 Example 5 50 5.7 Comparative Example 1 3 20 Comparative Example 2 5 19 Comparative Example 3 8 16

[0096] As can be seen from the above table, for the holographic polymer liquid crystal material provided by the present invention, by selecting a nematic liquid crystal composition and an acrylate monomer with specific structures, the volume holographic grating including the material has high diffraction efficiency, low haze, and can be switched between the holographic state and the transparent state. From Examples 1 to 3, it can be seen that the diffraction efficiency of the grating is 61-64%, and the haze is 0.8-1.3%.

[0097] From Examples 1, 4, and 5, it can be seen that when components A and B are not within a specific mass ratio range, the diffraction efficiency is low and the haze is high; from the comparison between the examples and the comparative examples, it can be seen that when using a nematic liquid crystal composition and an acrylate monomer with non-specific structures in the present invention, the phase separation is incomplete after the material is exposed, and the obtained grating has low diffraction efficiency and high haze.

[0098] In summary, in the holographic polymer liquid crystal material, the nematic liquid crystal composition selects components A and B with specific structures, and at the same time, the acrylate monomer selects a polymerizable monomer with a specific structure. The three cooperate with each other and are indispensable, enabling the obtained grating to have both high diffraction efficiency and low haze, and meeting the application requirements of the volume holographic optical waveguide.

[0099] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A holographic polymer liquid crystal material, characterized in that, In terms of mass percentage, the holographic polymer liquid crystal material comprises 20-50% of a nematic liquid crystal composition, 30-80% of an acrylate monomer, 1-20% of glue, and 0.1-5% of a photoinitiator; The nematic liquid crystal composition comprises component A and component B; Component A comprises at least one of the compounds having the following structures; Component B comprises at least one of the compounds having the following structures; The acrylate monomer comprises at least one of the compounds having the structure shown in Formula III; Wherein, R5 and R6 each independently comprise any one of a substituted or unsubstituted C3-C6 cycloalkyl, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkyl, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkoxy, a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyl, or a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenoxy; L5 is selected from any one of a halogen, a substituted or unsubstituted C3-C6 cycloalkyl, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkyl, a substituted or unsubstituted C1-C7 straight-chain or branched-chain alkoxy, a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenyl, or a substituted or unsubstituted C2-C7 straight-chain or branched-chain alkenoxy; A1 and A2 each independently are selected from a single bond, a substituted or unsubstituted C1-C6 straight-chain or branched-chain alkylene, wherein any one or more -CH2- in the alkylene are optionally substituted by -O-, -COO-, or -CH=CH-; p is an integer from 1 to 5; q is an integer from 0 to 4; The substituent of the substitution comprises a halogen.

2. The holographic polymer liquid crystal material according to claim 1, characterized in that The mass ratio of component A to component B in the nematic liquid crystal composition is (1-2.5):

1.

3. The holographic polymer liquid crystal material according to claim 1, characterized in that, The acrylate monomer comprises at least one of the compounds having the following structures; wherein, R 51 , R 61 are each independently selected from an H atom, -CH3 or -CF3; L 51 and L 52 each independently selected from any one of an F atom, a Cl atom, a C3-C6 cycloalkyl group, a C1-C7 straight-chain or branched-chain alkyl group, a C1-C7 straight-chain or branched-chain alkoxy group, a C2-C7 straight-chain or branched-chain alkenyl group, or a C2-C7 straight-chain or branched-chain alkenyloxy group; A 11 and A 21 each independently selected from straight-chain alkylene groups having 1 to 6 carbon atoms, where any one or more of the -CH2- groups are optionally substituted with -O-, -COO-, or -C═C-; q1 and q2 each independently are integers from 0 to 4.

4. The holographic polymer liquid crystal material according to claim 1, characterized in that, The glue comprises at least one of a polyurethane acrylate glue, an epoxy acrylate glue, a polyester acrylate glue, a polyether acrylate glue, or an acrylate glue.

5. The holographic polymer liquid crystal material according to claim 1, characterized in that, The photoinitiator comprises bis(2,6-difluoro-3-pyrrolylphenyl)titanocene dichloride.

6. A method for preparing a holographic polymer liquid crystal material according to any one of claims 1 to 5, characterized in that, The preparation method comprises: According to the formulation amount, under light-shielded conditions, the nematic liquid crystal composition, the acrylate monomer, the glue, and the photoinitiator are mixed to obtain the holographic polymer liquid crystal material.

7. The preparation method according to claim 6, characterized in that, The temperature of the mixing is 30-50 °C, and the time is 20-40 min.

8. A volume holographic grating, characterized in that, The material of the volume holographic grating comprises the holographic polymer liquid crystal material according to any one of claims 1-5.

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