Liquid crystal composition and holographic polymer-dispersed liquid crystal grating

Abstract

This invention discloses a liquid crystal composition comprising at least one compound of general formula I and at least one compound of general formula II. The liquid crystal composition provided by this invention has a high birefringence and exhibits a smectic phase. Furthermore, as phase separation proceeds, the liquid crystal molecules are arranged in a layered structure, maintaining their ordered nature. Under a specified electric field, the layered liquid crystal molecules can align different layers along different directions. Moreover, once arranged in a certain manner, the liquid crystal molecules can stably maintain their alignment without the need for an external electric field. This invention also discloses a holographic polymer-dispersed liquid crystal grating, comprising the liquid crystal composition provided by this invention. After phase separation, the grating not only exhibits high light transmittance but also high diffraction efficiency for both S- and P-beams, providing a better effect for two-dimensional pupil expansion.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal technology, specifically relating to a liquid crystal composition and a holographic polymer-dispersed liquid crystal grating. Background Technology

[0002] Liquid crystals are organic compounds whose molecules arrange themselves in an ordered manner within a certain temperature range, existing in a state between liquid and crystalline. Liquid crystal technology is a common display technology widely used in various electronic devices, such as mobile phones, televisions, and computers. The principle of liquid crystal technology is to utilize the photoelectric properties of liquid crystal molecules to control the transmission and blocking of light, thereby displaying images. As a modern display technology, liquid crystal displays have wide applications in daily life, and with the gradual development of liquid crystal display technology, people's requirements for liquid crystal displays are also increasing.

[0003] Birefringence is a crucial physical characteristic of liquid crystals. The formula for calculating the focal length of a liquid crystal lens is f = r² / (2Δn*d), where r represents half the grid pitch, Δn represents the birefringence of the liquid crystal, and d represents the thickness of the liquid crystal cell. Given a fixed focal length and grid pitch, materials with higher birefringence are advantageous for reducing the thickness of the liquid crystal cell. However, the birefringence of liquid crystals currently used in liquid crystal display technology is generally between 0.08 and 0.2, and this relatively low birefringence limits the further development of liquid crystal lenses.

[0004] In typical liquid crystal compositions, the liquid crystal molecules are not arranged in layers, but rather maintain a parallel arrangement along their long axes. During the exposure process of grating fabrication, as phase separation proceeds, the molecules become more orderly and parallel in the formed liquid crystal droplets. Therefore, gratings fabricated from existing liquid crystal compositions can only achieve high diffraction efficiency for S-light or P-light. Summary of the Invention

[0005] The purpose of this invention is to provide a liquid crystal composition and a holographic polymer-dispersed liquid crystal grating, so as to provide a liquid crystal composition with high birefringence and exhibiting a smectic phase, and a grating with high diffraction efficiency for both S-rays and P-rays.

[0006] The present invention achieves the above-mentioned objectives through the following technical solutions.

[0007] In a first aspect, the present invention provides a liquid crystal composition comprising:

[0008] At least one of the compounds of general formula I;

[0009] as well as

[0010] At least one of the compounds of general formula II;

[0011] The compound of general formula I is:

[0012]

[0013] R1 is selected from any one of alkyl and alkoxy groups having 3-9 carbon atoms;

[0014] R2 is selected from any one of alkyl and alkoxy groups having 3-9 carbon atoms, -F, -OCF3, and -CN; X1 and X2 are selected from any one of H, F, methyl, and ethyl groups, either individually or simultaneously.

[0015] Selected independently

[0016] Any one of them;

[0017] m1 and m2 represent 0, 1, 2 or 3 respectively or simultaneously, and m1+m2≠0;

[0018] The compound of general formula II is:

[0019]

[0020] R3 is selected from alkyl and alkoxy groups having 3-12 carbon atoms;

[0021] Y is selected from any one of -F, -OCF3, and -CN;

[0022] X3 and X4 are selected independently or simultaneously from one of H and F;

[0023] Selected from Any one of them;

[0024] m3 represents 1 or 2.

[0025] The liquid crystal composition provided by this invention has a high birefringence and exhibits a smectic phase. Furthermore, as phase separation proceeds, the liquid crystal molecules are arranged in a layered structure, maintaining their ordered nature. Under a specified electric field, the layered liquid crystal molecules can align different layers in different directions. Moreover, once arranged in a certain configuration, the liquid crystal molecules can stably maintain their alignment without the need for an external electric field. Therefore, the holographic polymer-dispersed liquid crystal grating containing this liquid crystal composition exhibits high diffraction efficiency for both S- and P-beams. Simultaneously, the ordered layered arrangement allows the holographic polymer-dispersed liquid crystal grating containing this liquid crystal composition to maintain high light transmittance.

[0026] Furthermore, by mass percentage, it includes: 40%-70% of the compound of general formula I; and 30%-60% of the compound of general formula II.

[0027] Furthermore, the liquid crystal composition also includes additives.

[0028] Furthermore, the additives include one or more of the following: hexadecyltetraammonium hexafluoroborate, tetradecylammonium bromide, tetrabutylammonium bromide, hexadecylpyridinium bromide, tetrabutylamine hexafluorophosphate, hexadecyltrimethylammonium bromide, hexadecyltriethylammonium bromide, 2-isopropylquinoline bromide, and hexadecyltrimethylammonium perchlorate.

[0029] Furthermore, by mass percentage, the composition includes: 40%-70% of the compound of general formula I; 30%-60% of the compound of general formula II; and 0%-4% of the additive.

[0030] Furthermore, by mass percentage, it comprises: 39.99%-70% of the compound of general formula I; 29.99%-60% of the compound of general formula II; and 0.01%-1% of the additive.

[0031] Furthermore, the compound of general formula I may be at least one of the following compounds:

[0032]

[0033] Furthermore, the compound of general formula II may be at least one of the following compounds:

[0034]

[0035]

[0036] In a second aspect, the present invention provides a holographic polymer-dispersed liquid crystal grating, comprising a photopolymerizable monomer, a photoinitiator composition, and the liquid crystal composition provided in the first aspect above.

[0037] Furthermore, by weight, it comprises: 30-70 parts of the photopolymerizable monomer; 0.1-10 parts of the photoinitiator composition; and 20-60 parts of the liquid crystal composition.

[0038] The holographic polymer-dispersed liquid crystal grating provided by the present invention includes the liquid crystal composition provided by the present invention. After phase separation, the grating not only has a high light transmittance, but also has a high diffraction efficiency for both S-rays and P-rays, providing a better effect for two-dimensional pupil expansion of the grating. Detailed Implementation

[0039] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0040] First Embodiment

[0041] This invention provides a liquid crystal composition comprising at least one compound of general formula I and at least one compound of general formula II. In other words, the liquid crystal composition provided by this invention comprises a compound of general formula I and a compound of general formula II, and the compound of general formula I in the liquid crystal composition may be one, two, or more, and the compound of general formula II may be one, two, or more.

[0042] Specifically, the compound of general formula I is: Wherein, R1 is selected from any one of alkyl and alkoxy groups having 3-9 carbon atoms; R2 is selected from any one of alkyl and alkoxy groups having 3-9 carbon atoms, -F, -OCF3, -CN; X1 and X2 are selected from any one of H, F, methyl, and ethyl groups, respectively or simultaneously. Selected independently

[0043] Any one of the following; m1 and m2 represent 0, 1, 2 or 3 respectively or simultaneously, and m1+m2≠0;

[0044] The compound of general formula II is: Wherein, R3 is selected from one of alkyl and alkoxy groups having 3-12 carbon atoms; Y is any one of -F, -OCF3, and -CN; X3 and X4 are selected independently or simultaneously from one of H and F; Selected from Any one of them; m3 represents 1 or 2.

[0045] In this embodiment of the invention, R1 is selected from any one of alkyl and alkoxy groups with 3-9 carbon atoms, and R2 is selected from any one of alkyl and alkoxy groups with 3-9 carbon atoms, -F, -OCF3, and -CN. The selection of alkyl chains of R1 and R2 can significantly increase the solubility of liquid crystal molecules and reduce the viscosity of the composition. The selection of terminal -F, -OCF3, and -CN polar groups can increase the dielectric constant of liquid crystal molecules, making the liquid crystal composition easier to drive. X1 and X2 are selected from any one of H, F, methyl, and ethyl groups, respectively or simultaneously. The introduction of side groups can increase the solubility of liquid crystal molecules. At the same time, the introduction of different side chain groups can change the arrangement of liquid crystal molecules, so that the liquid crystal composition does not present a single ordered arrangement. The selection of the groups, i.e., different combinations of rigid groups in liquid crystal molecules, can increase the diversity of liquid crystal composition. For example, cyclohexyl groups can improve the clearing point of liquid crystal molecules while ensuring good solubility. The introduction of benzene rings and heterocycles can increase the conjugated system of liquid crystal molecules, significantly improve the birefringence of liquid crystal molecules, improve the clearing point, and widen the phase transition temperature range of liquid crystal molecules. For example, the introduction of pyridine and pyrimidine heterocycles makes the liquid crystal molecules more inclined to a smectic texture. m1 and m2 represent 0, 1, 2 or 3 respectively or simultaneously, and m1+m2≠0, representing different numbers of structures. When the value is small, it ensures good solubility of liquid crystal molecules, and when the value is large, it provides higher birefringence for liquid crystal molecules.

[0046] In embodiments of the present invention, the compound of general formula I can be at least one of the following compounds:

[0047]

[0048]

[0049] It should be noted that the above compounds are only a part of the examples of compounds of general formula I and should not be construed as limiting the compounds of general formula I.

[0050] Meanwhile, the compound of general formula II is: Wherein, R3 is selected from alkyl or alkoxy groups having 3-12 carbon atoms; Y is any one of -F, -OCF3, and -CN; X3 and X4 are selected independently or simultaneously from one of H and F; Selected from Any one of them; m3 represents 1 or 2.

[0051] In this embodiment of the invention, R3 is selected from one of alkyl and alkoxy groups having 3-12 carbon atoms. The selection of the alkyl chain of R3 can significantly increase the solubility of liquid crystal molecules and reduce the viscosity of the composition. Y is selected from any one of -F, -OCF3, and -CN. The selection of polar groups such as -F, -OCF3, and -CN can increase the dielectric constant of liquid crystal molecules, making the liquid crystal composition easier to drive. X3 and X4 are selected independently or simultaneously from one of H and F. The introduction of side groups can increase the solubility of liquid crystal molecules. At the same time, the introduction of different side chain groups can change the arrangement of liquid crystal molecules, so that the liquid crystal composition does not exhibit a single ordered arrangement. The selection of m3, i.e., different combinations of rigid groups in liquid crystal molecules, can increase the diversity of liquid crystal composition. Furthermore, the introduction of benzene rings and heterocycles can increase the conjugated system of liquid crystal molecules, significantly improve the birefringence of liquid crystal molecules, improve the clearing point of liquid crystal molecules, and widen the phase transition temperature range of liquid crystal molecules. m3 represents 1 or 2, indicating different numbers of structures. When the value is small, it ensures that the liquid crystal molecules have good solubility. When the value is large, it provides higher birefringence for the liquid crystal molecules.

[0052] In embodiments of the present invention, the compound of general formula II can be at least one of the following compounds:

[0053]

[0054]

[0055] It should be noted that the above compounds are only a part of the examples of compounds of general formula II and should not be construed as limiting the compounds of general formula II.

[0056] As a further improvement of the embodiments of the present invention, the liquid crystal composition provided by the embodiments of the present invention comprises 40%-70% of the compound of general formula I and 30%-60% of the compound of general formula II by mass percentage. In preferred embodiments, the proportion of the compound of general formula I can be 40%, 45%, 50%, 55%, 60%, 65%, or 70%, and the proportion of the compound of general formula II can be 30%, 35%, 40%, 45%, 50%, 55%, or 60%. The liquid crystal composition provided by the embodiments of the present invention, by controlling the proportions of the compounds of general formula I and general formula II in the liquid crystal composition, can precisely control the birefringence of the liquid crystal composition and improve the light transmittance and diffraction efficiency of the holographic polymer-dispersed liquid crystal grating containing the liquid crystal composition as well as the diffraction efficiency for S-rays and P-rays.

[0057] As a further improvement of this invention, the liquid crystal composition further includes additives. After adding the additives, the alignment of the liquid crystal can be controlled by applying an electrical signal, which helps to drive the liquid crystal to move under an electric field.

[0058] As a further improvement of the embodiments of the present invention, the additive includes one or more of the following: hexadecyltetraammonium hexafluoroborate, tetradecylammonium bromide, tetrabutylammonium bromide, hexadecylpyridinium bromide, tetrabutylamine hexafluorophosphate, hexadecyltrimethylammonium bromide, hexadecyltriethylammonium bromide, 2-isopropylquinoline bromide, and hexadecyltrimethylammonium perchlorate. In a preferred embodiment, hexadecyltrimethylammonium perchlorate is selected as the additive, which can achieve a more effective driving effect with a smaller amount added under an electric field.

[0059] As a further improvement of the embodiments of the present invention, the liquid crystal composition comprises, by weight percentage: 40%-70% of the compound of general formula I; 30%-60% of the compound of general formula II; and 0%-4% of the additive. The liquid crystal composition provided by the embodiments of the present invention, by controlling the proportions of the compound of general formula I, the compound of general formula II, and the additive in the liquid crystal composition, can precisely control the birefringence of the liquid crystal composition, and improve the light transmittance and diffraction efficiency for S- and P-light in holographic polymer-dispersed liquid crystal gratings containing the liquid crystal composition. Furthermore, tunable liquid crystal gratings can be fabricated using this liquid crystal composition.

[0060] As another improvement to the embodiments of the present invention, the composition, by mass percentage, includes: 39.99%-70% of compound of general formula I; 29.99%-60% of compound of general formula II; and 0.01%-4% of additives.

[0061] The liquid crystal composition provided in the embodiments of the present invention will be specifically described below through several sub-examples.

[0062] Table 1 shows the components (compounds of general formula I, example compounds of general formula II, and additives) and their proportions (by mass percentage) of the liquid crystal compositions in each sub-example:

[0063] Table 1

[0064]

[0065] Each sub-example is weighed according to the above component ratio, placed in a sample bottle, heated to 50°C, magnetic stirring is turned on, stirred for 10 minutes, and then allowed to stand and stored under a nitrogen atmosphere for later use.

[0066] It should be noted that the components of the liquid crystal composition in each sub-example use the example compounds from the compounds of general formula I and general formula II described above, and are represented by the codes to the right of the example compounds to simplify the table examples. The additives used are the example additives described above. For example, sub-example 1 uses example compounds I-1, I-3, I-7, I-10, and I-13 from general formula I, and example compounds II-2, II-6, II-7, and II-10 from general formula II. The additive used is hexadecyltrimethylammonium perchlorate. Of course, the above sub-examples do not illustrate all embodiments, nor do they use all example compounds or other compounds from general formula I or general formula II besides the example compounds, or other additives besides the example additives described above. The above six sub-examples are only some examples of the liquid crystal composition in this invention and should not be construed as limiting the liquid crystal composition in this invention.

[0067] The liquid crystal compositions provided in the sub-examples of this invention have a higher birefringence than the commercially available liquid crystal composition E7, and the liquid crystal compositions exhibit a smectic phase. This can improve the light transmittance and diffraction efficiency of holographic polymer-dispersed liquid crystal gratings containing any of the liquid crystal compositions provided in the above-mentioned sub-examples.

[0068] Second Embodiment

[0069] This invention provides a holographic polymer-dispersed liquid crystal grating, comprising a photopolymerizable monomer, a photoinitiator composition, and the liquid crystal composition provided in Example 1 above.

[0070] As a further improvement to this invention, the photopolymerization monomers include hydroxyethyl methacrylate, polydipentaerythritol pentaacrylate, hydroxyethyl acrylate, polydipentaerythritol tetraacrylate, glycidyl methacrylate, polyethylene glycol diacrylate, pentanediol diacrylate, etc. The photoinitiator composition includes a co-initiator and a photosensitizer. The photosensitizer includes Bengal rose red, tetraiodofluorescein B, etc., and the co-initiator includes N-phenylglycine, triethylamine, triethanolamine, 2,6-diisopropyl-N,N-dimethylaniline, etc.

[0071] As a further improvement of this invention, the photopolymerization monomers are hydroxyethyl methacrylate and polydipentaerythritol pentaacrylate; the photoinitiator composition includes a co-initiator and a photosensitizer, wherein the photosensitizer is Bengal rose red and the co-initiator is N-phenylglycine. In the photoinitiator composition, the weight ratio of the co-initiator to the photosensitizer is 2:1 to 20:1. The liquid crystal composition includes at least one of the compounds of general formula I provided in the first embodiment above, and at least one of the compounds of general formula II.

[0072] Preferably, the liquid crystal composition includes at least one of the compounds of general formula I, at least one of the compounds of general formula II, and at least one of the additives provided in the first embodiment above.

[0073] As a further improvement of the embodiments of the present invention, the composition comprises, by weight parts: 30-70 parts of photopolymerizable monomer; 0.1-10 parts of photoinitiator composition; and 20-60 parts of liquid crystal composition.

[0074] Furthermore, the holographic polymer-dispersed liquid crystal grating provided in this embodiment of the invention allows the raw materials with the above-mentioned component ratio to be placed in a sample vial, and after being magnetically stirred at 20-30°C for 10-15 minutes to mix evenly, it is then poured into a 3µm liquid crystal cell, and then subjected to a laser with a wavelength of 532nm and a light intensity of 3.5mW / cm². 2 The grating is exposed to coherent laser light for 90-120 seconds, and then bleached with 365nm ultraviolet light to obtain a holographic polymer-dispersed liquid crystal grating.

[0075] The holographic polymer-dispersed liquid crystal grating provided in this embodiment of the invention, by employing the liquid crystal composition of the layered liquid crystal molecules provided above, ensures not only high light transmittance of the grating after phase separation, but also high diffraction efficiency for both S-rays and P-rays, thus providing a better effect for two-dimensional pupil expansion of the grating.

[0076] The holographic polymer-dispersed liquid crystal grating provided in the embodiments of the present invention will be specifically described below through sub-examples and comparative examples.

[0077] Sub-example 7

[0078] Table 2 shows the composition and proportions of the holographic polymer-dispersed liquid crystal grating in sub-example 7:

[0079] Table 2

[0080] raw material Content (parts by weight) Hydroxyethyl methacrylate 40 Polydipentaerythritol pentaacrylate 18.9 Bengal Rose 0.1 N-Phenylglycine 1 Liquid crystal composition (Sub-example 1) 40

[0081] The photopolymerization monomers in this sub-example are hydroxyethyl methacrylate and polydipentaerythritol pentaacrylate; the photoinitiator composition includes a co-initiator and a photosensitizer, the photosensitizer is Bengal rose red, and the co-initiator is N-phenylglycine; the liquid crystal composition adopts the above-described sub-example 1.

[0082] The raw materials with the above-mentioned component ratio were placed in a sample vial and magnetically stirred at 25°C for 10 minutes to mix thoroughly. The mixture was then poured into a 3µm liquid crystal cell, and a laser with a wavelength of 532nm and an intensity of 3.5mW / cm² was used for analysis. 2The grating was exposed to coherent laser light for 90 seconds, and then bleached with 365nm ultraviolet light to obtain a holographic polymer-dispersed liquid crystal grating. The transmittance and diffraction efficiency of the prepared grating were measured.

[0083] The holographic polymer-dispersed liquid crystal grating prepared in this embodiment has a light transmittance of 95%, an S-ray diffraction efficiency of 75%, and a P-ray diffraction efficiency of 71%.

[0084] Sub-example 8

[0085] As shown in Table 3, the composition and proportions of the holographic polymer-dispersed liquid crystal grating in sub-example 8 are illustrated:

[0086] Table 3

[0087] raw material Content (parts by weight) Hydroxyethyl methacrylate 40 Polydipentaerythritol pentaacrylate 18.9 Bengal Rose 0.1 N-Phenylglycine 1 Liquid crystal composition (Sub-example 3) 40

[0088] The photopolymerization monomers in this sub-example are hydroxyethyl methacrylate and polydipentaerythritol pentaacrylate; the photoinitiator composition includes a co-initiator and a photosensitizer, the photosensitizer is Bengal rose red, and the co-initiator is N-phenylglycine; the liquid crystal composition adopts the above-described sub-example 3.

[0089] The raw materials with the above-mentioned component ratio were placed in a sample vial and magnetically stirred at 25°C for 10 minutes to mix thoroughly. The mixture was then poured into a 3µm liquid crystal cell, and a laser with a wavelength of 532nm and an intensity of 3.5mW / cm² was used for analysis. 2 The grating was exposed to coherent laser light for 90 seconds, and then bleached with 365nm ultraviolet light to obtain a holographic polymer-dispersed liquid crystal grating. The transmittance and diffraction efficiency of the prepared grating were measured.

[0090] The holographic polymer-dispersed liquid crystal grating prepared in this embodiment has a light transmittance of 90%, an S-ray diffraction efficiency of 85%, and a P-ray diffraction efficiency of 77%.

[0091] Sub-example 9

[0092] As shown in Table 4, the composition and proportions of the holographic polymer-dispersed liquid crystal grating in Sub-Example 9 are illustrated:

[0093] Table 4

[0094] raw material Content (parts by weight) Hydroxyethyl methacrylate 40 Polydipentaerythritol pentaacrylate 18.9 Bengal Rose 0.1 N-Phenylglycine 1 Liquid crystal composition (Sub-example 5) 40

[0095] The photopolymerization monomers in this sub-example are hydroxyethyl methacrylate and polydipentaerythritol pentaacrylate; the photoinitiator composition includes a co-initiator and a photosensitizer, the photosensitizer is Bengal rose red, and the co-initiator is N-phenylglycine; the liquid crystal composition adopts the above sub-example 5.

[0096] The raw materials with the above-mentioned component ratio were placed in a sample vial and magnetically stirred at 25°C for 10 minutes to mix thoroughly. The mixture was then poured into a 3µm liquid crystal cell, and a laser with a wavelength of 532nm and an intensity of 3.5mW / cm² was used for analysis. 2 The grating was exposed to coherent laser light for 90 seconds, and then bleached with 365nm ultraviolet light to obtain a holographic polymer-dispersed liquid crystal grating. The transmittance and diffraction efficiency of the prepared grating were measured.

[0097] The holographic polymer-dispersed liquid crystal grating prepared in this embodiment has a light transmittance of 87%, an S-ray diffraction efficiency of 87%, and a P-ray diffraction efficiency of 81%.

[0098] Comparative Examples

[0099] Table 5 shows the composition and proportions of the holographic polymer-dispersed liquid crystal grating in the comparative examples:

[0100] Table 5

[0101] raw material Content (parts by weight) Hydroxyethyl methacrylate 40 Polydipentaerythritol pentaacrylate 18.9 Bengal Rose 0.1 N-Phenylglycine 1 Liquid crystal composition (E7) 40

[0102] The polymer initiation system in this comparative example is the same as that in sub-examples 7, 8 and 9, except that the liquid crystal composition uses the commercially available formulation E7.

[0103] The raw materials with the above-mentioned component ratio were placed in a sample vial and magnetically stirred at 25°C for 10 minutes to mix thoroughly. The mixture was then poured into a 3µm liquid crystal cell, and a laser with a wavelength of 532nm and an intensity of 3.5mW / cm² was used for analysis. 2 The grating was exposed to coherent laser light for 90 seconds, and then bleached with 365nm ultraviolet light to obtain a holographic polymer-dispersed liquid crystal grating. The transmittance and diffraction efficiency of the prepared grating were measured.

[0104] The holographic polymer-dispersed liquid crystal grating prepared in this comparative embodiment has a light transmittance of 85%, an S-ray diffraction efficiency of 91%, and a P-ray diffraction efficiency of 6.7%.

[0105] Compared with the comparative examples, the sub-examples 7, 8, and 9 provided by this invention, under the same polymer initiation system, exhibit higher birefringence and smectic properties due to the liquid crystal compositions in sub-examples 7, 8, and 9. Furthermore, as phase separation proceeds, the liquid crystal molecules are arranged in layers, maintaining their order. Under a specified electric field, different layers of liquid crystal molecules can be aligned in different directions. Moreover, once aligned, the liquid crystal molecules can stably maintain their alignment without an external electric field. This results in holographic polymer-dispersed liquid crystal gratings containing these liquid crystal compositions having higher light transmittance and higher diffraction efficiency for both S- and P-beams. For example, the grating in sub-example 9 has a light transmittance of 87%, an S-beam diffraction efficiency of 87%, and a P-beam diffraction efficiency of 81%.

[0106] The holographic polymer-dispersed liquid crystal grating provided by this invention, compared with the comparative embodiment, shows significant improvement in diffraction efficiency of S-rays and P-rays, and provides a good solution for two-dimensional pupil expansion of the grating.

[0107] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A liquid crystal composition, characterized in that, It consists of five compounds of general formula I, four compounds of general formula II, and additives. The five compounds of general formula I are: The four compounds of general formula II are as follows: The additive is hexadecyltrimethylammonium perchlorate; The proportions of compounds of general formula I, general formula II, and additives in the liquid crystal composition, by weight percentage, are shown in the table below:

2. A liquid crystal composition, characterized in that, It consists of five compounds of general formula I, four compounds of general formula II, and additives. The five compounds of general formula I are: The four compounds of general formula II are as follows: The additive is hexadecyltrimethylammonium perchlorate; The proportions of compounds of general formula I, general formula II, and additives in the liquid crystal composition, by weight percentage, are shown in the table below:

3. A liquid crystal composition, characterized in that, It consists of five compounds of general formula I, four compounds of general formula II, and additives. The five compounds of general formula I are: The four compounds of general formula II are as follows: The additive is hexadecyltrimethylammonium perchlorate; The proportions of compounds of general formula I, general formula II, and additives in the liquid crystal composition, by weight percentage, are shown in the table below:

4. A liquid crystal composition, characterized in that, It consists of five compounds of general formula I, three compounds of general formula II, and additives. The five compounds of general formula I are: The four compounds of general formula II are as follows: The additive is hexadecyltrimethylammonium perchlorate; The proportions of compounds of general formula I, general formula II, and additives in the liquid crystal composition, by weight percentage, are shown in the table below:

5. A liquid crystal composition, characterized in that, It consists of five compounds of general formula I and four compounds of general formula II. The five compounds of general formula I are: The four compounds of general formula II are as follows: The proportions of compounds of general formula I and general formula II in the liquid crystal composition, by mass percentage, are shown in the table below:

6. A liquid crystal composition, characterized in that, It consists of five compounds of general formula I, two compounds of general formula II, and additives. The five compounds of general formula I are: The two compounds of general formula II are: The additive is hexadecyltrimethylammonium perchlorate; The proportions of compounds of general formula I, general formula II, and additives in the liquid crystal composition, by weight percentage, are shown in the table below:

7. A holographic polymer-dispersed liquid crystal grating, characterized in that, include: Photopolymerizable monomers, photoinitiator compositions, and liquid crystal compositions according to any one of claims 1 to 6.

8. The holographic polymer-dispersed liquid crystal grating according to claim 7, characterized in that, The composition comprises, by weight, 30-70 parts of the photopolymerizable monomer, 0.1-10 parts of the photoinitiator composition, and 20-60 parts of the liquid crystal composition.

9. The holographic polymer-dispersed liquid crystal grating according to claim 8, characterized in that, The photopolymerizable monomers are hydroxyethyl methacrylate and polydipentaerythritol pentaacrylate; the photoinitiator composition includes a co-initiator and a photosensitizer, the photosensitizer is Bengal rose red, and the co-initiator is N-phenylglycine; in the photoinitiator composition, the weight ratio of the co-initiator to the photosensitizer is 2:1-20:

1.

10. The holographic polymer-dispersed liquid crystal grating according to claim 9, characterized in that, Weigh the liquid crystal composition according to the specified ratio and place it in a sample bottle. Heat to 50°C, turn on magnetic stirring, stir for 10 minutes, and then let stand. Store under a nitrogen atmosphere for later use. Place the photopolymerizing agent monomer, photoinitiator composition and liquid crystal composition in the sample bottle according to the above-mentioned proportions, and stir magnetically at 20-30°C for 10-15 minutes to mix evenly. Then pour it into a 3µm liquid crystal cell, and expose it with a coherent laser with a wavelength of 532nm and a light intensity of 3.5mW / cm2 for 90-120 seconds. Then bleach the grating with 365nm ultraviolet light to obtain a holographic polymer-dispersed liquid crystal grating.

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