Liquid crystal compound and preparation method therefor, liquid crystal composition and use

Abstract

Provided in the embodiments of the present application are a liquid crystal compound and a preparation method therefor, a liquid crystal composition and the use. The liquid crystal compound has a general structural formula as represented by formula (I): formula (I), wherein the ring A is selected from the following formulas. The addition of the compound to the liquid crystal composition allows the composition to have a relatively high birefringence, a relatively large dielectric anisotropy, a relatively wide nematic phase temperature range, relatively strong UV resistance, etc.

Description

Liquid crystal compounds, preparation method thereof, liquid crystal composition and application

[0001] The present application claims priority to the Chinese patent application No. 202410465301.5, filed on April 17, 2024, and titled "Liquid crystal compounds, preparation method thereof, liquid crystal composition and application", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of liquid crystal materials, in particular to a liquid crystal compound, a preparation method thereof, a liquid crystal composition and application. BACKGROUND

[0003] Liquid crystal materials have adjustable electro-optical properties, and liquid crystal devices made of liquid crystal materials have been widely used in display, communication and other fields. With the development of technology, liquid crystal materials used in the above application scenarios should theoretically have a wide nematic phase temperature range, high birefringence, large dielectric anisotropy value, etc. However, the liquid crystal compounds commonly used in the industry or the liquid crystal composition formed by compounding multiple liquid crystal compounds cannot meet the above multiple performance requirements. Therefore, it is necessary to provide a liquid crystal composition and a liquid crystal compound used therein that can better meet the above multiple performance requirements. SUMMARY

[0004] In view of this, the present application provides a liquid crystal compound, a preparation method thereof, a liquid crystal composition and application. The liquid crystal compound with the unique structure has a wide nematic phase temperature range, a large dielectric anisotropy value, a high birefringence and good ultraviolet resistance, so that the liquid crystal composition using the same can simultaneously meet the above multiple performance requirements, and a liquid crystal device with excellent performance can be obtained.

[0005] The first aspect of the present application provides a liquid crystal compound, which has the following general structure shown in formula (I):

[0006] wherein ring A is selected from any one of the following structures:

[0007] wherein R1 is selected from one of halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy; X1-X8 are independently selected from one of hydrogen atom, halogen atom, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy; X9 is selected from one of halogen atom, cyano, isothiocyanato, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy.

[0008] One end of the liquid crystal compound's molecular chain has a substituted polythiophene ring, which can increase the conjugated structure of the liquid crystal compound and its birefringence, while also broadening its nematic phase temperature range and maintaining a relatively high dielectric anisotropy value. Furthermore, the introduction of the polythiophene ring can enhance the liquid crystal compound's UV resistance. Furthermore, the polythiophene ring and the adjacent benzene ring are connected by an acetylenic bond, which also facilitates broadening the nematic phase temperature range and increasing the birefringence of the liquid crystal compound. Therefore, adding the liquid crystal compound to a liquid crystal composition can ensure that the liquid crystal composition can achieve a wide nematic phase temperature range, a high birefringence, a large dielectric anisotropy value, and good UV resistance, thereby facilitating the application of the liquid crystal composition in liquid crystal devices.

[0009] In the embodiment of the present application, the halogenated or unsubstituted linear alkyl group is a fluorinated or unsubstituted C1-C 10 Straight-chain alkyl; the halogenated or unsubstituted straight-chain alkoxy is a fluorinated or unsubstituted C1~C 10 Straight chain alkoxy; the halogenated or unsubstituted chain alkenyl is a fluorinated or unsubstituted C2~C 10 Chain alkenyl; the halogenated or unsubstituted chain alkenyloxy is a fluorinated or unsubstituted C2~C 10 Each group has a suitable number of carbon atoms, which not only makes the compound represented by the above formula (I) easier to prepare, but also allows the dielectric anisotropy value to be adjusted within a wider range.

[0010] In some embodiments of the present application, in formula (I), at least one of X1 and X4 is a hydrogen atom, at least one of X2 and X3 is a hydrogen atom, at least one of X5 and X8 is a hydrogen atom, and at least one of X6 and X7 is a hydrogen atom. This avoids the introduction of too many substituents into the molecular structure of the same liquid crystal compound, thereby maintaining its rod-like structure and retaining its liquid crystal properties.

[0011] In some embodiments of the present application, X1, X2, X4, X5, and X6 are all hydrogen atoms; X3 and X7 are all fluorine atoms; and X8 is a hydrogen atom or a fluorine atom. In this case, the material represented by formula (I) is easier to synthesize and has a higher birefringence and high dielectric anisotropy.

[0012] In some embodiments of the present application, the liquid crystal compound represented by formula (I) has a birefringence of greater than 0.30, a dielectric anisotropy of greater than 9, and a nematic phase temperature range greater than or equal to 60°C. This liquid crystal compound can achieve a high birefringence, a large dielectric anisotropy, and a wide nematic phase temperature range, and has good overall performance.

[0013] The second aspect of the embodiment of the present application provides a preparation method of a liquid crystal compound, comprising the following steps:

[0014] (1) reacting an alkyne represented by the following formula (i) with an aryl halide represented by formula (ii) to obtain a substance represented by formula (iii);

[0015] (2) reacting the substance represented by formula (iii) with an aryl boronic acid represented by formula (iv) to obtain a liquid crystal composition represented by formula (I):

[0016] wherein ring A is selected from any one of the following structures:

[0017] R1 is selected from one of halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, and halogenated or unsubstituted chain alkenyloxy; X1-X8 are independently selected from one of hydrogen atom, halogen atom, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, and halogenated or unsubstituted chain alkenyloxy; and X9 is selected from one of halogen atom, cyano, isothiocyanato, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, and halogenated or unsubstituted chain alkenyloxy.

[0018] The preparation method of the liquid crystal compound is simple in operation, high in yield, and can prepare the liquid crystal composition represented by formula (I) with good comprehensive performance.

[0019] The third aspect of the embodiment of the present application provides a liquid crystal composition, which comprises at least one liquid crystal compound according to the first aspect of the embodiment of the present application.

[0020] The liquid crystal compound provided by the first aspect of the present application can effectively improve the birefringence and dielectric anisotropy of the liquid crystal composition, and make it have a wider nematic phase temperature range and stronger ultraviolet resistance, thereby facilitating the application of the liquid crystal composition in liquid crystal devices.

[0021] In the liquid crystal composition, the total mass percentage content of the liquid crystal compound is in the range of 0.5%-80%. The appropriate addition of the first liquid crystal compound in the liquid crystal composition helps to fully exert the above-mentioned effects, and makes the comprehensive performance of the liquid crystal composition better. In some embodiments of the present application, the total mass percentage content of the liquid crystal compound provided by the first aspect of the present application in the liquid crystal composition is 5%-70%.

[0022] In some embodiments of the present application, the liquid crystal composition further comprises at least one second liquid crystal compound, wherein the at least one second liquid crystal compound comprises one or more of the following formula (II-1) to formula (II-7):

[0023] wherein R2, R4, R6, R8, R 10 , R 14 are independently selected from one of halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy, halogenated or unsubstituted chain alkenyloxy, substituted or unsubstituted cycloalkyl; R3, R5, R7, R9, R 11 , R 13 , R 15 are independently selected from one of fluorine atom, cyano, isothiocyanato, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy, substituted or unsubstituted cycloalkyl; X 10 ~ X 40 are independently selected from one of hydrogen atom, halogen atom, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy, unsubstituted cycloalkyl.

[0024] The liquid crystal composition contains both the specific liquid crystal compound provided by the first aspect of the present application and the second liquid crystal composition, and has good low room temperature viscosity, high birefringence, wide nematic phase temperature range, high dielectric anisotropy, etc., and has good application prospects.

[0025] In some embodiments of the present application, in formula (II-4), at least one of X 21 and X 23 is a hydrogen atom; in formula (II-6), at least one of X 32 and X 34 is a hydrogen atom. This helps to ensure that the substances represented by formula (II-4) and formula (II-6) maintain a rod-like structure, so that they have good liquid crystal properties, and their mixture with the first liquid crystal compound has good liquid crystal properties and a wide nematic phase temperature range.

[0026] In the embodiments of the present application, the substituents in the substituted cycloalkyl group include one or more of halogen atoms, halogenated or unsubstituted straight-chain alkyl groups, halogenated or unsubstituted straight-chain alkoxy groups, halogenated or unsubstituted chain alkenyl groups, halogenated or unsubstituted chain alkenyloxy groups, and unsubstituted cycloalkyl groups substituted with at least one of halogenated or unsubstituted straight-chain alkyl groups, straight-chain alkoxy groups, chain alkenyl groups, and chain alkenyloxy groups. The cycloalkyl group has various substituents, which can make the types of the second liquid crystal compounds described above more diverse, obtain compound products with slightly different properties, and better achieve applications.

[0027] In the embodiments of the present application, the mass percentage content of the second liquid crystal compound in the liquid crystal composition is in the range of 0.5% to 90%. In the presence of the liquid crystal compound provided in the first aspect of the embodiments of the present application, the appropriate addition of the second liquid crystal compound described above can ensure that the liquid crystal composition containing them has good liquid crystal properties, strong fluidity, and high birefringence, etc. In some embodiments of the present application, the total mass percentage content of the second liquid crystal compound in the liquid crystal composition is in the range of 5% to 70%.

[0028] In some embodiments of the present application, the mass percentage content of the second liquid crystal compound in the liquid crystal composition is greater than the mass percentage content of the liquid crystal compound provided in the first aspect of the embodiments of the present application. This is more conducive to the liquid crystal composition having a higher birefringence, a larger dielectric anisotropy value, and a lower room temperature viscosity.

[0029] In some embodiments of the present application, the mass ratio of the second liquid crystal compound to the liquid crystal compound represented by formula (I) is (1.1-5.0):1. In this case, the birefringence, dielectric anisotropy value, nematic phase temperature range, room temperature viscosity, and other properties of the liquid crystal composition described above can be well balanced.

[0030] In some embodiments of the present application, the liquid crystal composition further includes an additive, which includes one or more of ultraviolet absorbers, ultraviolet stabilizers, antioxidants, and voltage stabilizers. The presence of the additive can help improve one or more of the ultraviolet resistance, high-temperature stability, and chemical oxidation resistance of the liquid crystal composition described above. The additive described above can be added as needed.

[0031] In the embodiments of the present application, the birefringence of the liquid crystal composition is 0.30 or higher, the dielectric anisotropy is 5 or higher, the crystallization point is 0°C or lower, and the clearing point is in the range of 110-165°C. The comprehensive performance of the liquid crystal composition is better, which is more convenient for applications.

[0032] The fourth aspect of the embodiments of the present application provides application of the liquid crystal compound provided in the first aspect of the present application and the liquid crystal composition provided in the third aspect of the embodiments of the present application in a liquid crystal device. The liquid crystal compound and the liquid crystal composition can be used in a liquid crystal layer of the liquid crystal device to improve the performance and use reliability of the liquid crystal device.

[0033] In the embodiments of the present application, the liquid crystal device is used in a wavelength selective switch, a microwave antenna, a liquid crystal optical waveguide, a liquid crystal grating, a dynamic focusing lens, a laser radar, a laser projection, an optical projection system, an intelligent vehicle lamp, a flat panel display, a holographic display, optical communication, or wireless communication. The application range of the liquid crystal device is wide, and the performance of various devices using the liquid crystal device is also good.

[0034] The fifth aspect of the embodiments of the present application provides a liquid crystal device, which comprises a liquid crystal layer, and the liquid crystal layer comprises the liquid crystal compound provided in the first aspect of the present application or the liquid crystal composition provided in the third aspect of the embodiments of the present application.

[0035] Based on the good performance of the liquid crystal compound or the liquid crystal composition, the performance of the liquid crystal device is good, and the market competitiveness is outstanding.

[0036] In some embodiments of the present application, the liquid crystal device comprises a silicon-based backplane, a cover plate with a transparent electrode layer, and the liquid crystal layer arranged between the silicon-based backplane and the cover plate with the transparent electrode layer. The liquid crystal device in this case can be an LCoS device, and is particularly suitable for use in a wavelength selective switch. BRIEF DESCRIPTION OF DRAWINGS

[0037] FIG. 1 is a structural schematic diagram of a liquid crystal device provided in the embodiments of the present application.

[0038] FIG. 2 is a structural schematic diagram of a wavelength selective switch provided in the embodiments of the present application. DETAILED DESCRIPTION

[0039] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0040] Liquid crystal materials have adjustable electro-optical properties, and liquid crystal devices (which can also be referred to as "electro-optical adjustment devices") made of liquid crystal materials have been widely used in various fields, such as laser projection, vehicle head-up display, optical communication, wireless communication, etc. Among them, liquid crystal devices (which can be referred to as LCoS devices) made based on liquid crystal on silicon (LCoS) technology are widely used. FIG. 1 is a schematic structural diagram of a liquid crystal device provided in an embodiment of the present application. In some embodiments, the liquid crystal device shown in FIG. 1 can be an LCoS device, which can be used in wavelength selective switches (WSSs) and the like, and can be used as an optical switching engine of a WSS to implement a phase modulation function.

[0041] Referring to FIG. 1, the liquid crystal device 100 includes a cover plate 10 with a transparent electrode layer, a silicon-based back plate 20, and a liquid crystal layer 30 disposed between the two. The liquid crystal layer 30 includes a plurality of liquid crystal molecules (represented by black oval rods in FIG. 1). The liquid crystal molecules can be deflected under certain voltage conditions to achieve phase modulation of a light beam.

[0042] The cover plate 10 can include a transparent substrate 11 and a transparent electrode layer 12 disposed on one side surface of the transparent substrate 11. The transparent substrate 11 is usually glass, which can be used to protect the liquid crystal layer 30 and allow light signals to pass through, and can also support the transparent electrode layer 12. The transparent electrode layer 12 can be an indium tin oxide (ITO) layer or an indium zinc oxide (IZO) layer, which has good conductivity and transparency, and is used to transmit light signals and conduct electricity.

[0043] The silicon-based back plate 20 can include a silicon substrate 21 and a reflective layer 22 laminated on one side surface of the silicon substrate 21. The silicon substrate 21 can be a CMOS (complementary metal oxide semiconductor) integrated circuit chip coated with liquid crystal silicon. It can be understood that the silicon substrate 21 includes a control circuit. The silicon-based back plate 20 can also be referred to as a CMOS substrate. The material of the reflective layer 22 can be aluminum, which is used to improve the reflectivity of the silicon substrate 21, and the reflective layer is usually plated. In some embodiments, the silicon-based back plate 20 further includes a back plate electrode layer and a pixel array, which can also be integrated in the silicon substrate 21.

[0044] In some embodiments, the transparent electrode layer 12 can further be provided with a first alignment layer 13 on the side facing away from the transparent substrate 11. The silicon-based backplane 20 can further be provided with a second alignment layer 23, specifically on the side of the reflective layer 22 facing away from the silicon substrate 21. When the cover plate 10 and the silicon-based backplane 20 are assembled into the liquid crystal device 100, they are oppositely arranged, and the liquid crystal layer 30 is located between the first alignment layer 13 and the second alignment layer 23. In this case, the liquid crystal device 100 described above comprises the transparent substrate 11, the transparent electrode layer 12, the first alignment layer 13, the liquid crystal layer 30, the second alignment layer 23, the reflective layer 22 and the silicon substrate 21 which are sequentially stacked. It should be understood that the size, position and the like of each layer of the liquid crystal device 100 in FIG. 1 are illustrative and do not limit the present application.

[0045] The first alignment layer 13 on the cover plate 10 and the second alignment layer 23 on the silicon-based backplane 20 can fix the arrangement direction of the liquid crystal molecules in the liquid crystal layer 30 under zero voltage. In some embodiments, when no voltage is applied to the liquid crystal layer 30, the first alignment layer 13 and the second alignment layer 23 control the parallel arrangement of the liquid crystal molecules. When a certain voltage is applied between the transparent electrode layer 12 and the silicon substrate 21 through the driving circuit in the silicon-based backplane 20, the liquid crystal molecules in the liquid crystal layer 30 will rotate under the action of the voltage. Since the liquid crystal molecules produce birefringence under the action of the electric field, different electric field strengths can cause the liquid crystal molecules to rotate to different degrees, thereby changing the refractive index and achieving the purpose of phase adjustment of the light beam transmitted through the liquid crystal molecules.

[0046] The liquid crystal layer 30 is generally formed by filling a liquid crystal composition into the space between the oppositely arranged cover plate 10 and silicon-based backplane 20, and the liquid crystal composition is usually prepared by mixing a plurality of liquid crystal compounds (also referred to as liquid crystal monomers). With the development of science and technology, the requirements for the liquid crystal device 100 are getting higher and higher, and the requirements for the liquid crystal composition used to form the liquid crystal layer 30 are getting higher and higher. For example, in order to meet the requirement of using the liquid crystal device 100 in a wider temperature range, it is required that the liquid crystal composition has a wider nematic phase temperature range (i.e. has a lower crystallization point and a higher clearing point). In addition, in order to realize a smaller driving voltage and lower power consumption of the liquid crystal device 100, it is generally desired that the liquid crystal composition has a larger dielectric anisotropy value. Furthermore, in order to reduce the thickness of the liquid crystal device 100 and shorten the response time, it is also desired that the liquid crystal composition used has a higher birefringence. However, there are very few liquid crystal compositions that can simultaneously meet the requirements of a wider nematic phase temperature range, a larger dielectric anisotropy value and a higher birefringence. It is of great application value to develop a liquid crystal composition that can simultaneously meet the above requirements. Therefore, the embodiments of the present application provide a liquid crystal compound which can be used in a liquid crystal composition, so that the liquid crystal composition using the same can simultaneously meet the requirements of a wider nematic phase temperature range, a larger dielectric anisotropy value and a higher birefringence, etc.

[0047] Firstly, the embodiment of the present application provides a liquid crystal compound which can be used in a liquid crystal composition, having a general structure shown in the following formula (I):

[0048] wherein, ring A is selected from any of the following structures:

[0049] R1 is selected from one of halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy; X1-X8 are independently selected from one of hydrogen atom, halogen atom, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy; X9 is selected from one of halogen atom, cyano (-CN), isothiocyanato (-NCS), halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy.

[0050] The above liquid crystal compound includes two benzene rings arranged in a linear manner and one polynuclear thiophene ring (ring A) with a non-hydrogen substituent R1, and the polynuclear thiophene ring with the non-hydrogen substituent R1 is located at one end of the molecular chain of the liquid crystal compound, the polynuclear thiophene ring has a longer conjugated structure than the benzene ring, which can better increase the conjugated structure of the liquid crystal compound, increase its birefringence, and at the same time, the nematic phase temperature range of the liquid crystal compound can be widened, and its dielectric anisotropy value is still at a high level and does not decrease significantly. In addition, the introduction of the polynuclear thiophene ring can improve the UV resistance of the liquid crystal compound. Furthermore, in the above liquid crystal compound, the alkynyl bond is used as the linking group between the polynuclear thiophene ring and the benzene ring adjacent thereto, which is also conducive to widening the nematic phase temperature range of the liquid crystal compound and improving its birefringence. In addition, the presence of the non-hydrogen substituent R1 on the polynuclear thiophene ring can make the structure of the liquid crystal compound more stable. In addition, the selection of X1-X9 on the two benzene rings can realize the regulation of the dielectric anisotropy value of the above liquid crystal compound.

[0051] Therefore, the addition of the above liquid crystal compound to the liquid crystal composition can make the liquid crystal composition have higher birefringence, larger dielectric anisotropy value, wider nematic phase temperature range, and stronger UV resistance.

[0052] In the present application, "halo-" refers to any one or more hydrogen atoms in a group being replaced by a halogen atom, i.e., the substituent in the group is a halogen atom. For example, halo-straight chain alkyl specifically refers to a straight chain alkyl group being replaced by a halogen atom. Similarly, halo-straight chain alkoxy refers to a straight chain alkoxy group being replaced by a halogen atom; halo-straight chain alkenyl refers to a straight chain alkenyl group being replaced by a halogen atom; and halo-straight chain alkenyloxy refers to a straight chain alkenyloxy group being replaced by a halogen atom. The introduction of halogen substituents can result in a larger dielectric anisotropy value of the liquid crystal compound, and make the compound more diverse. In the present application, "halo-" can be partial halo- or full halo-. "Full halo-" refers to all hydrogen atoms in the group being replaced by a halogen atom. "Partial halo-" refers to some of the hydrogen atoms in the group being replaced by a halogen atom. The halogen atom can be one or more of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), and is more commonly fluorine. In some embodiments, each of the halo- groups is specifically fluoro-.

[0053] In the present application, the halo- or unsubstituted straight chain alkyl is straight chain, wherein "straight chain" specifically refers to all carbon atoms constituting the alkyl group being in the same carbon chain. The halo- or unsubstituted straight chain alkyl can result in a more ordered anisotropic arrangement of the liquid crystal compound, and make the compound have liquid crystal properties. Similarly, the liquid crystal compound with halo- or unsubstituted straight chain alkoxy can also exhibit good liquid crystal properties. The term "liquid crystal properties" refers to the substance having the flowability of a liquid and the anisotropic ordered arrangement of a crystalline substance at a certain temperature.

[0054] In the embodiments of the present application, the halo- or unsubstituted straight chain alkyl can specifically be halo- or unsubstituted C1-C9 straight chain alkyl, halo- or unsubstituted C1-C6 straight chain alkyl, halo- or unsubstituted C1-C4 straight chain alkyl, etc. For example, it can specifically be halo- or unsubstituted methyl, halo- or unsubstituted ethyl, halo- or unsubstituted n-propyl, halo- or unsubstituted n-butyl, halo- or unsubstituted n-pentyl, halo- or unsubstituted n-hexyl, halo- or unsubstituted n-heptyl, halo- or unsubstituted n-octyl, etc. In some embodiments, the halo- or unsubstituted straight chain alkyl is fluoro- or unsubstituted C1-C9 straight chain alkyl, fluoro- or unsubstituted C1-C6 straight chain alkyl, fluoro- or unsubstituted C1-C4 straight chain alkyl, etc. For example, it can specifically be fluoro- or unsubstituted methyl, fluoro- or unsubstituted ethyl, fluoro- or unsubstituted n-propyl, fluoro- or unsubstituted n-butyl, fluoro- or unsubstituted n-pentyl, fluoro- or unsubstituted n-hexyl, fluoro- or unsubstituted n-heptyl, fluoro- or unsubstituted n-octyl, etc. 10 straight chain alkyl. In some embodiments, the halo- or unsubstituted straight chain alkyl is halo- or unsubstituted C1-C9 straight chain alkyl, halo- or unsubstituted C1-C6 straight chain alkyl, halo- or unsubstituted C1-C4 straight chain alkyl, etc. For example, it can specifically be halo- or unsubstituted methyl, halo- or unsubstituted ethyl, halo- or unsubstituted n-propyl, halo- or unsubstituted n-butyl, halo- or unsubstituted n-pentyl, halo- or unsubstituted n-hexyl, halo- or unsubstituted n-heptyl, halo- or unsubstituted n-octyl, etc. In some embodiments, the halo- or unsubstituted straight chain alkyl is fluoro- or unsubstituted C1-C9 straight chain alkyl, fluoro- or unsubstituted C1-C6 straight chain alkyl, fluoro- or unsubstituted C1-C4 straight chain alkyl, etc. For example, it can specifically be fluoro- or unsubstituted methyl, fluoro- or unsubstituted ethyl, fluoro- or unsubstituted n-propyl, fluoro- or unsubstituted n-butyl, fluoro- or unsubstituted n-pentyl, fluoro- or unsubstituted n-hexyl, fluoro- or unsubstituted n-heptyl, fluoro- or unsubstituted n-octyl, etc. 10 straight chain alkyl. For example, the halo- straight chain alkyl can be trifluoromethyl (-CF3), difluoroethyl (-C2F2H3), perfluoroethyl (-C2F5), perfluoropropyl (-C3F7), perfluoro-n-butyl (-C4F9), perfluoro-n-pentyl (-C5F 11 ) and the like.

[0055] In the present application, the halogenated or unsubstituted straight-chain alkoxy group can be regarded as the structure of the halogenated or unsubstituted straight-chain alkyl group connected with an oxygen atom (O). Therefore, the number of carbon atoms of the halogenated or unsubstituted straight-chain alkoxy group can refer to the description of the halogenated or unsubstituted straight-chain alkyl group in the foregoing. In the embodiments of the present application, the halogenated or unsubstituted straight-chain alkoxy group can be a halogenated or unsubstituted C1-C9 straight-chain alkoxy group, a halogenated or unsubstituted C1-C8 straight-chain alkoxy group, or a halogenated or unsubstituted C1-C6 straight-chain alkoxy group, etc. In some embodiments, the halogenated or unsubstituted straight-chain alkoxy group is a fluorinated or unsubstituted C1-C9 straight-chain alkoxy group, a fluorinated or unsubstituted C1-C8 straight-chain alkoxy group, or a fluorinated or unsubstituted C1-C6 straight-chain alkoxy group, etc. 10 The straight-chain alkoxy group can further be a halogenated or unsubstituted C1-C9 straight-chain alkoxy group, a halogenated or unsubstituted C1-C8 straight-chain alkoxy group, or a halogenated or unsubstituted C1-C6 straight-chain alkoxy group, etc. In some embodiments, the halogenated or unsubstituted straight-chain alkoxy group is a fluorinated or unsubstituted C1-C9 straight-chain alkoxy group, a fluorinated or unsubstituted C1-C8 straight-chain alkoxy group, or a fluorinated or unsubstituted C1-C6 straight-chain alkoxy group, etc. 10 The straight-chain alkoxy group can further be a halogenated or unsubstituted C1-C9 straight-chain alkoxy group, a halogenated or unsubstituted C1-C8 straight-chain alkoxy group, or a halogenated or unsubstituted C1-C6 straight-chain alkoxy group, etc. In some embodiments, the halogenated or unsubstituted straight-chain alkoxy group is a fluorinated or unsubstituted C1-C9 straight-chain alkoxy group, a fluorinated or unsubstituted C1-C8 straight-chain alkoxy group, or a fluorinated or unsubstituted C1-C6 straight-chain alkoxy group, etc.

[0056] In the embodiments of the present application, the halogenated or unsubstituted chain alkenyl group can be a halogenated or unsubstituted C2-C 10 The chain alkenyl group can be a straight-chain alkenyl group or a branched-chain alkenyl group. In some embodiments, the halogenated or unsubstituted chain alkenyl group is a halogenated or unsubstituted C2-C 20 The straight-chain alkenyl group can be a straight-chain alkenyl group or a branched-chain alkenyl group. In some embodiments, the halogenated or unsubstituted chain alkenyl group is a halogenated or unsubstituted C2-C 10 The chain alkenyl group can be a straight-chain alkenyl group or a branched-chain alkenyl group. In some embodiments, the halogenated or unsubstituted chain alkenyl group is a halogenated or unsubstituted C2-C

[0057] In the embodiments of the present application, the halogenated or unsubstituted chain alkenyloxy group can be a straight-chain alkenyloxy group or a branched-chain alkenyloxy group, and the straight-chain alkenyloxy group is preferred. The halogenated or unsubstituted chain alkenyloxy group can be regarded as the structure of the halogenated or unsubstituted chain alkenyl group connected with an oxygen atom. Therefore, the number of carbon atoms of the halogenated or unsubstituted chain alkenyloxy group can refer to the description of the halogenated or unsubstituted chain alkenyl group in the present application. In the embodiments of the present application, the halogenated or unsubstituted chain alkenyloxy group can be a halogenated or unsubstituted C2-C 10alkenyl, or C2-C6 alkenyl, etc. In some embodiments, the above-mentioned halogenated or un-substituted chain alkenyloxy is a fluorinated or un-substituted chain alkenyloxy. Illustratively, the halogenated or un-substituted alkenyloxy can be a vinylloxy (e.g., CH2=CH-O-), difluorovinyloxy (CF2=CH-O-), perfluorovinyloxy (CF2=CF-O-), fluorinated or un-substituted propenyloxy, fluorinated or un-substituted butenyloxy, etc.

[0058] The above-mentioned substituents of the present application have suitable number of carbon atoms, which can make the liquid crystal compound of the above-mentioned formula (I) more easily prepared, and regulate the dielectric anisotropy values of the liquid crystal compound of the above-mentioned formula (I) in a larger range.

[0059] In some embodiments of the present application, X1-X8 are independently selected from one of hydrogen atom (H), halogen atom, halogenated or un-substituted C1-C6 straight chain alkyl, halogenated or un-substituted C1-C6 straight chain alkoxy, halogenated or un-substituted C2-C6 straight chain alkenyl, and halogenated or un-substituted C2-C6 straight chain alkenyloxy. Further, in some embodiments, X1-X8 are independently selected from one of hydrogen atom (H), fluorine atom (F), fluorinated or un-substituted C1-C6 straight chain alkyl, fluorinated or un-substituted C1-C6 straight chain alkoxy, fluorinated or un-substituted C2-C6 straight chain alkenyl, and fluorinated or un-substituted C2-C6 straight chain alkenyloxy. In particular, when X1-X8 are selected from fluorine atom or the above-mentioned fluorinated groups, the liquid crystal compound of the formula (I) has larger dielectric anisotropy value.

[0060] In some embodiments of the present application, X9 is selected from one of fluorine atom (F), fluorinated or un-substituted C1-C6 straight chain alkyl, fluorinated or un-substituted C1-C6 straight chain alkoxy, fluorinated or un-substituted C2-C6 straight chain alkenyl, and fluorinated or un-substituted C2-C6 straight chain alkenyloxy. In this case, the liquid crystal composition using the liquid crystal compound of the formula (I) with such X9 has lower viscosity at room temperature, and has strong applicability. In addition, when X9 is fluorine atom or the above-mentioned fluorinated groups, the liquid crystal compound of the formula (I) has larger dielectric anisotropy value.

[0061] In some embodiments of the present application, at least one of X1 and X4 is hydrogen atom, at least one of X2 and X3 is hydrogen atom; at least one of X5 and X8 is hydrogen atom, and at least one of X6 and X7 is hydrogen atom. In this case, the liquid crystal compound of the formula (I) does not introduce too many non-hydrogen substituents on the two benzene rings, which can ensure that the liquid crystal compound of the formula (I) is more easily prepared, and the liquid crystal compound of the formula (I) basically maintains the rod-like structure, still has good liquid crystal characteristics, and further the liquid crystal composition using the liquid crystal monomer also has good liquid crystal characteristics.

[0062] wherein at least one of X2and X3is a hydrogen atom, i.e. X2and X3are not simultaneously the above-mentioned non-hydrogen groups (such as halogen atoms, and halogenated or unsubstituted straight-chain alkyl, straight-chain alkoxy, chain alkenyl, chain alkenyloxy, etc.). For example, when X3is the above-mentioned non-hydrogen group, X2is a hydrogen atom, X4may be a hydrogen atom, and X1may be a non-hydrogen group or a hydrogen atom; or X4is a non-hydrogen group, and X1is a hydrogen atom. For another example, when X3is a hydrogen atom, X2is a non-hydrogen group, X1is a non-hydrogen group or a hydrogen atom, and X4is a hydrogen atom; for another example, X1-X4are all hydrogen atoms.

[0063] Similarly, when X7is a non-hydrogen group, X6is a hydrogen atom, X8may be a hydrogen atom, and X5may be a non-hydrogen group or a hydrogen atom; or X8is a non-hydrogen group, and X5is a hydrogen atom. For another example, when X7is a hydrogen atom, X6is a non-hydrogen group, X5is a non-hydrogen group or a hydrogen atom, and X8is a hydrogen atom. For another example, X5-X8are all hydrogen atoms.

[0064] Further, in some embodiments, in formula (I), at least one of X2and X4is a hydrogen atom, and at least one of X6and X8is a hydrogen atom. This is also conducive to the preparation of the liquid crystal compound shown in formula (I).

[0065] In some embodiments of the present application, in formula (I), X1, X2, X5, and X6are all hydrogen atoms. In this case, formula (I) is specifically:

[0066] Further, X3and X7are independently selected from the above-mentioned non-hydrogen groups, and X4and X8are selected from the above-mentioned non-hydrogen groups. In some examples, X1, X2, X4, X5, and X6are all hydrogen atoms, X8is a hydrogen atom or a fluorine atom, and X3and X7are both fluorine atoms. In this case, the substance shown in formula (I) is easier to synthesize, and has a higher birefringence and a higher dielectric anisotropy.

[0067] As an example, the substance shown in formula (I) can be selected from one or more of the following compounds.

[0068] The above-mentioned liquid crystal compound provided by the embodiments of the present application has a higher birefringence, a wider nematic phase temperature range, a larger dielectric anisotropy value, and excellent UV resistance.

[0069] In the embodiments of the present application, the birefringence Δn of the liquid crystal compound represented by the above formula (I) is greater than or equal to 0.30. The liquid crystal compound has a high birefringence, which is conducive to increasing the birefringence of a liquid crystal composition using the same, and is further conducive to applications in optical communication, wireless communication, and display fields with high display requirements. In some embodiments, the birefringence Δn of the liquid crystal compound represented by formula (I) is greater than or equal to 0.35, for example, specifically 0.350, 0.355, 0.358, 0.360, 0.370, 0.380, 0.385, 0.390, 0.40, 0.41, 0.42, 0.43, 0.45, etc.

[0070] The Δn of the liquid crystal compound can be obtained by testing the birefringence of a mixture of the liquid crystal compound and a standard liquid crystal (also referred to as a "mother crystal") with a known birefringence at a certain mass ratio at 25°C and 589 nm, and then calculating the Δn of the added liquid crystal compound at 25°C and 589 nm.

[0071] In the embodiments of the present application, the dielectric anisotropy value Δε of the liquid crystal compound represented by the above formula (I) is greater than or equal to 9. In some embodiments, the Δε is in the range of 12-25, for example, specifically 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 15.5, 16.0, 16.5, 17.0, 17.5, 18.0, 18.5, 19.0, 19.5, 20.0, 21.0, 22.0, 23.0, 24.0, 24.5, etc. The Δε is measured at 25°C and 1KHz, specifically by testing the dielectric anisotropy value of a mixture of the liquid crystal compound and a standard liquid crystal (also referred to as a "mother crystal") with a known birefringence at a certain mass ratio at 25°C and 1KHz, and then calculating the Δε of the liquid crystal compound.

[0072] In the embodiments of the present application, the temperature width of the nematic phase temperature range of the liquid crystal compound represented by the above formula (I) is greater than or equal to 60°C. The "temperature width" here refers to the difference between the endpoint temperatures of the nematic phase temperature range, specifically the difference between the clearing point T2 of the liquid crystal compound and the crystallization point T1 of the liquid crystal compound. Accordingly, the nematic phase temperature range is represented as T1-T2. The above temperature width specifically refers to ΔT=T2-T1. When the environmental temperature is less than T1, the liquid crystal compound is in a solid state; when the environmental temperature is between T1 and T2, the compound is in a nematic phase of liquid crystal state (which can have the flowability of a liquid and the anisotropic ordered arrangement of a crystalline state substance). When the environmental temperature is greater than T2, the compound is a normal clear liquid and does not have the ordered arrangement characteristics.

[0073] In some embodiments, the liquid crystal compound of formula (I) can have a nematic phase temperature range of greater than or equal to 70°C, greater than or equal to 80°C, or greater than or equal to 90°C, etc.

[0074] The present application also provides a method for preparing the liquid crystal compound of formula (I), comprising the following steps:

[0075] (1) reacting an alkyne compound of formula (i) with an aryl halide of formula (ii) to obtain a compound of formula (iii);

[0076] (2) reacting the compound of formula (iii) with an aryl boronic acid of formula (iv) to obtain the liquid crystal compound of formula (I):

[0077] wherein ring A is selected from any one of the following structures:

[0078] R1is selected from one of halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy; X1to X8are independently selected from one of hydrogen atom, halogen atom, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy; X9is selected from one of halogen atom, cyano, isothiocyanato, halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy. The specific meaning of each symbol can be referred to the description of the foregoing.

[0079] In step (1), the coupling reaction of the terminal alkyne compound of formula (i) with the aryl halide of formula (ii) can be referred to as a Sonogashira coupling reaction, which is usually carried out in the presence of a metal catalyst. Exemplary metal catalysts can be palladium catalysts, copper catalysts, etc., such as specifically bis(triphenylphosphine)palladium dichloride, cuprous iodide, etc. The reaction in step (2) is a cross-coupling reaction between the aryl boronic acid of formula (iv) and the compound of formula (iii) with halogenated aromatic compounds, which can be referred to as a Suzuki coupling reaction, which is usually carried out under the catalysis of zero-valent palladium complexes.

[0080] Generally, after obtaining the corresponding reaction product in each step, the reaction product can also be subjected to purification treatment, wherein the purification method includes but is not limited to one or more of rectification, sublimation, recrystallization, adsorption, chromatography, etc.

[0081] The synthesis route of the liquid crystal compound shown in the above formula (I) can be as follows:

[0082] The preparation method of the liquid crystal compound shown in the above formula (I) is simple to operate and has a high yield.

[0083] The application also provides a liquid crystal composition, which comprises a liquid crystal monomer, and the liquid crystal monomer comprises at least one liquid crystal compound shown in the above formula (I).

[0084] The addition of one or more liquid crystal compounds shown in the above formula (I) as a liquid crystal monomer to the liquid crystal composition can improve the birefringence and dielectric anisotropy of the liquid crystal composition, and make the liquid crystal composition have a wider nematic phase temperature range and stronger ultraviolet resistance, thereby facilitating the application of the liquid crystal composition in a liquid crystal device. For convenience of representation, the liquid crystal compound shown in the above formula (I) is referred to as a first liquid crystal compound hereinafter.

[0085] In the application, the total mass percentage content of the first liquid crystal compound in the liquid crystal composition is in the range of 0.5% to 80%, for example, specifically 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, etc. In some embodiments, the total mass percentage content of the first liquid crystal compound in the liquid crystal composition is 5% to 70%, and further can be 10% to 40%, etc. In the liquid crystal composition, the appropriate addition of the first liquid crystal compound helps to fully play its role and make the room temperature viscosity of the liquid crystal composition suitable and the comprehensive performance better. In some embodiments, specifically, the total mass percentage content of the first liquid crystal compound in the liquid crystal monomer is in the range of 0.5% to 80%, and further can be 5% to 70%, 10% to 40%, etc.

[0086] In some embodiments of the application, the liquid crystal monomer in the liquid crystal composition further comprises other liquid crystal compounds different from the aforementioned formula (I). For example, the liquid crystal monomer in the liquid crystal composition further comprises one or more second liquid crystal compounds shown in the following formula (II-1) to formula (II-7):

[0087] wherein, R2, R4, R6, R8, R 10 , R 14 are independently selected from one of halogenated or unsubstituted straight-chain alkyl, halogenated or unsubstituted straight-chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy, halogenated or unsubstituted chain alkenyloxy, substituted or unsubstituted cycloalkyl; R3, R5, R7, R9, R 11 , R13 R 15 is independently selected from one of a fluorine atom, a cyano group (-CN), an isothiocyanato group (-NCS), a halogenated or unsubstituted linear alkyl group, a halogenated or unsubstituted linear alkoxy group, a halogenated or unsubstituted chain alkenyl group, a halogenated or unsubstituted chain alkenyloxy group, a substituted or unsubstituted cycloalkyl group; X 10 ~X 40 is independently selected from one of a hydrogen atom, a halogen atom, a halogenated or unsubstituted linear alkyl group, a halogenated or unsubstituted linear alkoxy group, a halogenated or unsubstituted chain alkenyl group, a halogenated or unsubstituted chain alkenyloxy group, an unsubstituted cycloalkyl group.

[0088] In this case, the liquid crystal composition simultaneously uses the first liquid crystal compound and the second liquid crystal compound as liquid crystal monomers, which can ensure that the liquid crystal composition has low viscosity at room temperature, a wide nematic phase temperature range, high birefringence, and high dielectric anisotropy, making the liquid crystal composition more promising for application.

[0089] In the structural formula of the second liquid crystal compound, the halogenated or unsubstituted linear alkyl group, the halogenated or unsubstituted linear alkoxy group, the halogenated or unsubstituted chain alkenyl group, and the halogenated or unsubstituted chain alkenyloxy group are described and specifically exemplified in the foregoing of the present application, which will not be repeated here.

[0090] In the present application, the substituted or unsubstituted cycloalkyl group mentioned above can be a substituted or unsubstituted C3-C 20 cycloalkyl group. In some embodiments, the substituted or unsubstituted cycloalkyl group is a substituted or unsubstituted C3-C 15 cycloalkyl group, a substituted or unsubstituted C3-C 10 cycloalkyl group, a substituted or unsubstituted C3-C6cycloalkyl group, etc., such as a substituted or unsubstituted cyclopropyl group, a substituted or unsubstituted cyclobutyl group, a substituted or unsubstituted cyclopentyl group, a substituted or unsubstituted cyclohexyl group, etc.

[0091] The substituents in the substituted cycloalkyl group can include, but are not limited to, a halogen atom, a halogenated or unsubstituted straight-chain alkyl group, a halogenated or unsubstituted straight-chain alkoxy group, a halogenated or unsubstituted chain alkenyl group, a halogenated or unsubstituted chain alkenyloxy group, and one or more of the unsubstituted cycloalkyl group substituted or unsubstituted by at least one of the straight-chain alkyl group, the straight-chain alkoxy group, the chain alkenyl group, and the chain alkenyloxy group. The introduction of various different substituents can make the above-mentioned second liquid crystal compound more diverse, obtain compound products with slightly different performance, and better achieve the application. Exemplarily, the substituted cycloalkyl group can be a methyl-substituted cyclopentyl group, a methyl-substituted cyclohexyl group, a trifluoromethyl-substituted cyclohexyl group, a difluorovinyl-substituted cyclohexyl group, a cyclohexyl group substituted by a n-propyl-substituted cyclohexyl group, and the like.

[0092] In some embodiments of the present application, R6 to R 13 may not involve the substituted or unsubstituted cycloalkyl group. That is, R6, R8, R 10 are independently selected from one of a halogenated or unsubstituted straight-chain alkyl group, a halogenated or unsubstituted straight-chain alkoxy group, a halogenated or unsubstituted chain alkenyl group, a halogenated or unsubstituted chain alkenyloxy group, and a halogenated or unsubstituted chain alkenyloxy group; R7, R9, R 11 , and R 13 are independently selected from one of a fluorine atom, a halogenated or unsubstituted straight-chain alkyl group, a halogenated or unsubstituted straight-chain alkoxy group, a halogenated or unsubstituted chain alkenyl group, and a halogenated or unsubstituted chain alkenyloxy group. In this case, the synthesis of the above-mentioned formula (II-3), formula (II-4), formula (II-5), and formula (II-6) is relatively low.

[0093] In the present application, R2, R3, R4, R5, R 14 , and R 15 may involve the substituted or unsubstituted cycloalkyl group. In some cases, the selection range of R3, R 14 , and R 15 may not involve the substituted or unsubstituted cycloalkyl group.

[0094] In some embodiments of the present application, X 10 to X 40 are independently selected from one of a hydrogen atom (H), a fluorine atom (F), a fluorinated or unsubstituted C1-C6 straight-chain alkyl group, a fluorinated or unsubstituted C1-C6 straight-chain alkoxy group, a fluorinated or unsubstituted C1-C6 straight-chain alkylthio group, a fluorinated or unsubstituted C2-C6 chain alkenyl group, a fluorinated or unsubstituted C2-C6 chain alkenyloxy group, an unsubstituted C3-C 10 cycloalkyl group.

[0095] In some embodiments of the present application, in the above-mentioned formula (II-4), X 21 and X 23at least one of X 32 and X 34 is a hydrogen atom. As described above, this helps to ensure that the material represented by formula (II-4) and the material represented by formula (II-6) maintain a rod-like structure, and that the mixture of the first liquid crystal compound and the material represented by formula (II-4) or formula (II-6) exhibits good liquid crystal properties.

[0096] In some embodiments, in formula (II-4), X 21 is a hydrogen atom. In this case, formula (II-4) is specifically:

[0097] wherein X 19 , X 20 , X 22 , X 23 , X 24 , X 25 are selected from the range described above. Further, X 19 , X 20 are both hydrogen atoms; or X 19 , X 20 are independently selected from the aforementioned non-hydrogen groups; or X 19 and X 20 are both hydrogen atoms.

[0098] In other embodiments, in formula (II-4), X 20 , X 21 are not hydrogen atoms, and are independently selected from the aforementioned non-hydrogen groups, and X 19 , X 22 , and X 25 are hydrogen atoms. In this case, formula (II-4) is specifically:

[0099] wherein, in formula (II-5), X 28 is selected from the aforementioned non-hydrogen groups, so as to avoid the case where formula (II-5) and formula (II-4) are equivalent structures.

[0100] In some embodiments, in formula (II-6), X 34 is a hydrogen atom, and X 32 and X 33 are independently selected from a hydrogen atom or the aforementioned non-hydrogen groups, such as both being non-hydrogen groups, or both being hydrogen atoms, or X 32 is a non-hydrogen group, and X 33 is a hydrogen atom, and so on. In other embodiments, X 34 is not a hydrogen atom, and X 32 is a hydrogen atom, and X 33 is a hydrogen atom or the aforementioned non-hydrogen groups.

[0101] In some embodiments, the above-mentioned formula (II-6) can specifically include one or more of the following general structures:

[0102] As an example, the above-mentioned formula (II-1) can specifically include one or more of the following compounds:

[0103] As an example, the above-mentioned formula (II-2) can specifically include one or more of the following compounds:

[0104] As an example, the above-mentioned formula (II-3) can specifically include one or more of the following compounds:

[0105] As an example, the above-mentioned formula (II-4) can specifically include one or more of the following compounds:

[0106] As an example, the above-mentioned formula (II-5) can specifically include one or more of the following compounds:

[0107] As an example, the above-mentioned formula (II-6) can specifically include one or more of the following compounds:

[0108] As an example, the above-mentioned formula (II-7) can specifically include one or more of the following compounds:

[0109] In some embodiments of the present application, the above-mentioned liquid crystal composition includes the above-mentioned formula (II-3), formula (II-4), formula (II-6) and formula (II-7) simultaneously. The use of such a plurality of second liquid crystal compounds in combination with the above-mentioned formula (I) can improve the liquid crystal properties of the liquid crystal composition, such as good room temperature fluidity, and can also control the wide range of nematic phase temperature of the above-mentioned liquid crystal composition.

[0110] In some embodiments, the total mass percentage of the second liquid crystal compound in the liquid crystal composition is in the range of 0.5% to 90%, for example, specifically 0.8%, 1%, 2%, 5%, 10%, 15%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, or 88%, etc. In some embodiments, the total mass percentage of the second liquid crystal compound in the liquid crystal composition is in the range of 1% to 80%, further can be in the range of 5% to 70%, 5% to 65%, 10% to 65%, or 10% to 50%, etc. The appropriate amount of the second liquid crystal compound is added, and in combination with the first liquid crystal compound, the liquid crystal composition containing them can have a low viscosity at room temperature, is not easy to crystallize at low temperature, has a wide nematic phase temperature range, and has a large dielectric anisotropy value, a high birefringence, etc. The above-mentioned properties can be slightly different to meet the application requirements in different scenarios. In some embodiments, specifically, the total mass percentage of the second liquid crystal compound in the liquid crystal monomer is in the range of 0.5% to 90%, further can be in the range of 5% to 70%, or 5% to 65%, etc.

[0111] In some embodiments, the mass percentage of the second liquid crystal compound in the liquid crystal composition is greater than the mass percentage of the first liquid crystal compound. This is conducive to the liquid crystal composition having good low-temperature resistance, a wide nematic phase temperature range, a large dielectric anisotropy value, a high birefringence, etc. Further, the mass ratio of the second liquid crystal compound to the liquid crystal compound represented by formula (I) in the liquid crystal composition can be (1.1-5):1, for example, specifically 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.2:1, 2.5:1, 2.8:1, 3.0:1, 3.2:1, 3.5:1, 3.8:1, 4.0:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0112] In some embodiments, the liquid crystal composition can further include an additive, which includes but is not limited to one or more of ultraviolet absorbers, ultraviolet stabilizers, antioxidants, voltage stabilizers, etc. The presence of the additive can help improve one or more of the ultraviolet resistance, high-temperature stability, chemical oxidation resistance, etc. of the liquid crystal composition. The additive can be added as needed.

[0113] In some embodiments, the additive is present in the liquid crystal composition in an amount of 0.01% to 10%, for example, 0.02%, 0.05%, 0.1%, 0.5%, 0.6%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%, etc. In some embodiments, the additive is present in the liquid crystal composition in an amount of 0.05% to 5%, or 0.1% to 3%, etc. The additive is present in the liquid crystal composition in an appropriate amount, which can effectively improve the light / heat / chemical oxidation resistance of the liquid crystal composition, while not significantly affecting the birefringence and viscosity of the composition.

[0114] In some embodiments, the liquid crystal composition has a birefringence Δn of 0.30 or more, further 0.35 or more, for example, in the range of 0.35 to 0.50. Higher birefringence is particularly advantageous for the application of the liquid crystal composition in the field of optical communication, wireless communication, etc. For example, the Δn can be 0.34, 0.350, 0.355, 0.360, 0.370, 0.375, 0.380, 0.390, 0.40, 0.41, 0.42, 0.43, 0.45, 0.48, or 0.50, etc.

[0115] In some embodiments, the liquid crystal composition has a dielectric anisotropy value Δε of 5 or more, further 6 or more, or 8 or more, etc. In some embodiments, the Δε is in the range of 5 to 12, for example, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, or 11.5, etc.

[0116] In some embodiments, the liquid crystal composition has a temperature range of the nematic phase with a temperature width of 80℃ or more. In some embodiments, the temperature range of the nematic phase has a temperature width of 110℃ or more, or 110℃ or more, or 130℃ or more, etc.

[0117] In some embodiments, the liquid crystal composition has a crystallization point of 0℃ or less, which can reflect that the liquid crystal composition has good low-temperature stability and is not easy to solidify or crystallize at low temperature. The liquid crystal device made of the liquid crystal composition can be used in a low-temperature environment. In some embodiments, the liquid crystal composition has a crystallization point of -20℃ or less, or -30℃ or less, etc. In an example, the liquid crystal composition does not crystallize after being stored at -30℃ for 20 days. The liquid crystal composition with a desired crystallization point can be obtained according to the actual use scenario.

[0118] In the embodiments of the present application, the clearing point of the liquid crystal composition described above is in the range of 110-165°C. The term "clearing point" refers to the critical temperature at which a liquid crystalline substance turns into a liquid, i.e. the highest temperature at which a liquid crystalline state can exist. A suitable range of the clearing point of the liquid crystal composition can ensure that the liquid crystal composition can stably maintain a liquid crystalline state at a relatively high temperature, so that the liquid crystal device does not fail, and can also ensure that the temperature of the subsequent heating process of the liquid crystal composition is not too high. For example, the clearing point of the liquid crystal composition can be 115°C, 120°C, 125°C, 130°C, 135°C, 138°C, 140°C, 145°C, 150°C, 152°C, 155°C, 160°C, etc. In some embodiments, the clearing point is in the range of 120-155°C.

[0119] The embodiments of the present application also provide the use of the liquid crystal composition described above in a liquid crystal device. The liquid crystal composition is mainly used in the liquid crystal layer of the liquid crystal device. It can be understood that the liquid crystal device includes a liquid crystal layer. Generally, the liquid crystal device includes a first substrate with a first electrode layer, a second substrate with a second electrode layer, and a liquid crystal layer disposed between the first substrate and the second substrate. The liquid crystal layer can be made of the liquid crystal composition of the embodiments of the present application. The liquid crystal molecules in the liquid crystal layer can rotate under the action of an electric field of a certain intensity, and the refractive index changes, so that the light signal can be phase modulated. Generally, the liquid crystal device can be referred to as a "liquid crystal-based electro-optical adjustment device".

[0120] In the present application, the liquid crystal device can be applied in the fields of display, communication, etc., for example, in the fields of display imaging (such as holographic display, flat panel display, vehicle head-up display, intelligent vehicle lamp, laser projection, etc.), optical communication, wireless communication, etc. In the embodiments of the present application, the liquid crystal device can be used in wavelength selective switches, microwave antennas, liquid crystal optical waveguides, liquid crystal optical waveguides, liquid crystal optical gratings, dynamic focusing lenses, laser radars, laser projections, optical projection systems, flat panel displays, holographic displays, intelligent vehicle lamps, optical communication devices, or wireless communication devices, etc., as one or more components thereof.

[0121] The dynamic focusing lens can be an AR (Augmented Reality) glasses, a VR (Virtual Reality) glasses, etc. The optical projection system can be an AR HUD (Augmented Reality-head up display) system, which can be used in a vehicle head-up display. The flat panel display can be a TFT-LCD (Thin Film Transistor-Liquid Crystal Display) display, which can be used in a smart phone, a tablet computer, or a television. Exemplarily, a TFT-LCD display generally includes a TFT array substrate, a CF (Color Filter) substrate, and a liquid crystal layer sandwiched between the two. The TFT substrate is mainly responsible for the transmission of electrical signals. The CF substrate mainly provides the color required for display. The holographic display can include a holographic display screen (such as used in holographic movies, holographic performances, etc.), a holographic display helmet, etc. The wavelength selective switch can be used in optical communication equipment and laser radar. The phased array antenna can also be used in laser radar, which is an array antenna composed of multiple independent microwave antennas.

[0122] In some embodiments of the present application, the liquid crystal device is particularly used in a wavelength selective switch (WSS). The liquid crystal device in this case can be the LCoS device shown in FIG. 1, which is described above with reference to FIG. 1. The WSS changes the transmission direction of the optical signal by modulating the phase of the optical signal through the LCoS device.

[0123] Referring to FIG. 2, FIG. 2 is a schematic diagram of a structure of a wavelength selective switch (WSS). The WSS 200 can include at least one input port 201, at least one output port 202, and the liquid crystal device 100 described above. The optical signal can be input from at least one of the multiple input ports 201, modulated by the liquid crystal device 100, and then output from at least one of the multiple output ports 202, thereby changing the transmission direction of the optical signal, such as completing the switching, uploading, or downloading of the optical signal. The number of the input ports 201 and the output ports 202 can be equal or unequal, which is not limited in the present application. The input ports 201 and the output ports 202 can be composed of optical fibers, and the input / output ports can form an input / output fiber array.

[0124] It should be understood that the structure of the WSS shown in FIG. 2 is only illustrative. The WSS can also include gratings, lenses, mirrors, collimators and other optical path changing devices known in the art, which are not limited in the present application. For example, in some embodiments, a grating can be provided between the input port 201 and the liquid crystal device 100. The grating can be used to spatially demultiplex light signals of different wavelengths. The lens can be used to focus or collimate light. The mirror is used to reflect light.

[0125] The liquid crystal device 100 can have a larger phase modulation amount, higher resolution, faster response time, lower power consumption, and can be used in a wider temperature range due to the use of the liquid crystal composition with high birefringence, good dielectric properties, wide nematic phase temperature range, and strong ultraviolet resistance in the above embodiments of the present application. Accordingly, the comprehensive performance of the WSS including the liquid crystal device 100 is also excellent, and the market competitiveness is outstanding.

[0126] The present application also provides a device including the above-mentioned liquid crystal device of the present application. The device can be one or more of a wavelength selective switch, a microwave antenna, a liquid crystal optical waveguide, a liquid crystal grating, a dynamic focusing lens, a laser radar, a laser projector, an optical projection system, a flat panel display, a holographic display, a smart car light, an optical communication device, a wireless communication device, etc. The comprehensive performance of the above-mentioned device using the liquid crystal device of the present application is excellent and can operate stably.

[0127] The technical solutions of the present application are further described in the following embodiments.

[0128] Before introducing the specific embodiments of the present application, the structures of the groups involved in the present application and the corresponding codes are introduced, which are shown in Table 1 below.

[0129] Table 1

[0130] The test methods of each physical and chemical parameter mentioned in the present application are as follows.

[0131] The phase transition temperatures such as the crystallization point and clearing point of the liquid crystal compound / liquid crystal composition can be obtained from the DSC curve measured by a differential scanning calorimetry (DSC) instrument. When performing DSC test, the heating rate is 5℃ / min.

[0132] The Δn of the liquid crystal compound can be obtained by testing the birefringence value of the mixture of the liquid crystal compound and a standard liquid crystal (or called "mother crystal") with known birefringence at room temperature, and then calculating the Δn of the added liquid crystal compound at 25℃ and 589nm.

[0133] The test of Δn of the liquid crystal composition is similar to the test of Δn of the liquid crystal compound, and is also measured by the Abbe refractometer at 25°C under the condition of 589 nm.

[0134] The dielectric anisotropy of the liquid crystal composition can be measured by the dielectric constant Δε, which is measured at 25°C under the condition of 1 kHz. Δε = ε || -ε ⊥ .

[0135] The Δε of the liquid crystal compound is calculated from the Δε of the mixture of the liquid crystal compound and the standard liquid crystal with known birefringence at a certain mass ratio.

[0136] In the application, the specific formula of the standard liquid crystal is as follows:

[0137] In the above, the Δn of the standard liquid crystal is 0.2053, and the Δε is 1.080.

[0138] In addition, the test of the anti-ultraviolet ability of the liquid crystal composition includes: injecting the liquid crystal composition into the liquid crystal cell by the capillary tank method, and irradiating the liquid crystal cell with a 365 nm ultraviolet lamp at an irradiation intensity of 50 mW / cm 2 After 10 J of irradiation, the color of the liquid crystal cell is observed by the naked eye as an evaluation index of the anti-ultraviolet ability, and the evaluation standard is shown in Table 2.

[0139] Table 2

[0140] Preparation Example 1

[0141] The synthesis route of the above-mentioned first liquid crystal compound 3STGUF is as follows:

[0142] The preparation process of the above-mentioned 3STGUF includes:

[0143] (1) Preparation of 2-((4-bromo-3-fluorophenyl)ethynyl)-5-propyl-thieno[2,3-b]thiophene (compound S7):

[0144] Under nitrogen protection, 10.9 g of compound S5 (ethynyl-5-propyl-thieno[2,3-b]thiophene), 9.5 g of compound S6 (2-bromo-5-iodotoluene), 95.3 mg of cuprous iodide, 577.8 mg of bis(triphenylphosphine)palladium dichloride and 200 mL of triethylamine were added into a 500 mL round-bottom flask, and heated and stirred at 60°C overnight. After the system was cooled to room temperature, ethyl acetate was added for extraction twice, the organic phases were combined and dried with magnesium sulfate, and the organic phase was rotary evaporated under reduced pressure, and column chromatography was used for separation to obtain compound S-7.

[0145] (2) Preparation of 3STGUF:

[0146] In a 500 mL round bottom flask, 6.7 g of the above compound S7, 6.24 g of compound S8 (3,4,5-trifluorophenylboronic acid), 7.3 g of potassium carbonate, 205.0 mg of tetrakis(triphenylphosphine)palladium, and 150 mL of a 3:1 mixture of 1,4-dioxane and water (by volume) were added under nitrogen protection, and stirred at 100°C overnight. After the system was cooled to room temperature, ethyl acetate was added for extraction three times, the organic phase was combined and dried with magnesium sulfate, and rotary evaporation was performed under reduced pressure. Column chromatography was used to separate and obtain compound 3STGUF.

[0147] Compound 3STGUF was tested by nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, and nuclear magnetic resonance fluorine spectrum, and the test results were as follows:

[0148] 1 H NMR (400M, CDCl3) δ: 7.37 (s, 1H), 7.16-7.08 (m, 2H), 6.91 (s, 1H), 2.89-2.85 (t, 2H), 1.80-1.70 (m, 2H), 1.03-0.99 (t, 3H) ppm;

[0149] 13 C NMR (100M, CDCl3) δ: 152.40, 152.35, 152.29, 152.24, 151.43, 149.86, 149.80, 149.76, 141.56, 140.42, 139.02, 136.68, 125.12, 121.30, 118.90, 116.43, 115.71, 115.64, 115.55, 115.48, 90.49, 90.45, 85.25, 85.22, 33.33, 24.70, 13.65 ppm;

[0150] 19 F NMR (376M, CDCl3) δ: -133.87, -133.93, -158, 52, -158.58, -158.63 ppm.

[0151] The above structure test results show that the prepared compound 3STGUF is consistent with the above structural formula.

[0152] Preparation Example 2

[0153] The synthesis route of the above first liquid crystal compound 3STGGF is as follows:

[0154] The preparation process of the above 3STGGF includes:

[0155] (1) Preparation of compound S7: the same as preparation of example 1;

[0156] (2) Preparation of 3STGGF: under nitrogen protection, in a 500 mL round bottom flask, 6.7 g of the above compound S7, 5.61 g of compound S9 (3,4-difluorobenzenboronic acid), 7.3 g of potassium carbonate, 205.0 mg of tetrakis(triphenylphosphine)palladium, and 150 mL of a mixed solvent of 1,4-dioxane and water in a volume ratio of 3:1 were added, and heated and stirred at 100°C overnight. After the system was cooled to room temperature, ethyl acetate was added for extraction three times, the organic phase was combined and dried with magnesium sulfate, rotary evaporation was performed under reduced pressure, and column chromatography was used to separate to obtain compound 3STGGF.

[0157] The compound 3STGGF was tested by nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, and nuclear magnetic resonance fluorine spectrum, and the test results were as follows:

[0158] 1 H NMR (400M, CDCl3) δ: 7.46-7.36 (m, 4H), 7.33-7.24 (m, 3H), 6.96 (s, 1H), 2.94-2.90 (t, 2H), 1.85-1.76 (m, 2H), 1.08-1.04 (t, 3H) ppm;

[0159] 13 C NMR (100M, CDCl3) δ: 160.40, 157.92, 151.59, 151.46, 151.43, 151.21, 149.12, 149.07, 140.29, 136.76, 132.00, 130.39, 130.36, 127.68, 127.65, 127.20, 127.07, 125.21, 125.17, 125.14, 125.11, 125.07, 124.91, 124.45, 124.35, 121.09, 119.06, 118.81, 118.17, 118.14, 117.99, 117.95, 117.57, 117.40, 116.51, 92.16, 92.13, 85.51, 33.38, 24.78, 13.74 ppm;

[0160] 19 F NMR (376M, CDCl3) δ: -117.47, -137.26 -138.24 ppm.

[0161] The above structure test results show that the prepared compound 3STGGF is consistent with the above structural formula.

[0162] The birefringence △n, dielectric anisotropy △ε, phase transition temperature of the liquid crystal compounds 3STGUF and 3STGGF provided in the embodiments of the present application are tested, and the results are summarized in Table 3 below. In addition, the properties of several existing liquid crystal monomers are also summarized in Table 3.

[0163] Table 3

[0164] In Table 3, "Cr" represents the crystallizing point, "N" represents the nematic transition temperature, and "I" represents the isotropic transition temperature. Generally, I is the same as the clear point (Cp) of the liquid crystal compound.

[0165] From Table 3, it can be known that the nematic phase temperature range of the compound 3STGUF provided in the embodiments of the present application is 88.3-169.8℃, the temperature width of the nematic phase temperature range reaches 81.5℃, the birefringence △n is as high as 0.385, and the dielectric anisotropy △ε is as high as 18.05. The temperature width of the nematic phase temperature range of the compound 3STGGF provided in the embodiments of the present application reaches 137.1℃, the birefringence △n is as high as 0.425, and the dielectric anisotropy △ε is as high as 12.64. It can be seen that both of the two liquid crystal compounds can have a relatively wide nematic phase temperature range, a relatively high birefringence, and a relatively large dielectric anisotropy.

[0166] In addition, from the comparison between the liquid crystal compound 3STGUF provided in the present application and the existing liquid crystal monomers 3PTGUF and 3CSTUF, and the comparison between the liquid crystal compound 3STGGF provided in the present application and the existing liquid crystal monomer 3PTGGF, it can be known that, in the case that the dielectric anisotropy is close, the liquid crystal compounds provided in the present application have a higher birefringence and a wider nematic phase temperature. It is worth noting that the existing liquid crystal monomer 3CSTUF directly changes into a clear liquid when the ambient temperature is higher than the crystallizing point temperature 73.8℃, and there is no nematic transition temperature N, and there is also no nematic phase temperature range.

[0167] Application Example 1

[0168] A liquid crystal composition includes 100 parts by weight of a liquid crystal monomer, and the composition of the liquid crystal monomer is shown in Table 4 below.

[0169] The preparation method of the liquid crystal composition is as follows: according to the formula composition shown in Table 4, accurately weigh each component, and place it in a sample bottle provided with a magnet, heat and stir until clear, and cool to room temperature to obtain the corresponding liquid crystal composition.

[0170] The performance test results of the liquid crystal composition are also summarized in Table 4.

[0171] Table 4

[0172] As can be known from Table 4, the nematic phase temperature range of the liquid crystal composition provided by the application embodiment 1 reaches 207℃, the birefringence Δn reaches 0.375, and the dielectric anisotropy Δε reaches 8.48, which can well balance various performances.

[0173] Application Example 2

[0174] A liquid crystal composition comprises 100 parts by weight of a liquid crystal monomer, the composition of the liquid crystal monomer and the performance test results of the liquid crystal composition are shown in Table 5 below.

[0175] Table 5

[0176] Application Example 3

[0177] A liquid crystal composition comprises 100 parts by weight of a liquid crystal monomer, the composition of the liquid crystal monomer and the performance test results of the liquid crystal composition are shown in Table 6 below.

[0178] Table 6

[0179] In order to further highlight the beneficial effects of the application, the following Comparative Example 1 is also provided.

[0180] Comparative Example 1

[0181] A liquid crystal composition, the composition and performance test results of which are shown in Table 7 below.

[0182] Table 7

[0183] As can be known from the comparison of the performance test results of the liquid crystal composition of Comparative Example 1 in Table 7 and the performance test results of the liquid crystal compositions of the preceding application examples 1-3, the liquid crystal composition of Comparative Example 1 does not contain the first liquid crystal compound provided by the application embodiment with a unique bithiophene ring, and the birefringence and dielectric constant of the liquid crystal composition of Comparative Example 1 are lower than those of the application examples 1-3 under the condition of similar crystallization point. These results can indicate that the addition of the first liquid crystal compound provided by the application embodiment in the liquid crystal composition helps to improve the birefringence and dielectric anisotropy of the liquid crystal composition.

[0184] In addition, the liquid crystal compositions provided by the above application examples 1-3 and Comparative Example 1 are respectively subjected to UV resistance tests, and the test results are shown in Table 8 below.

[0185] Table 8

[0186] From the test results of Comparative Example 1 and Application Examples 1-3 in Table 8, it can be known that the liquid crystal compositions of Application Examples 1-3 containing the first liquid crystal compound with unique multi- polythiophene ring provided by the present application have very slight yellowing degree under the same UV irradiation dose. These results can indicate that adding the first liquid crystal compound provided by the present application in the liquid crystal composition can help to improve the UV resistance of the liquid crystal composition.

[0187] The above description is merely exemplary of the present application, and the description is relatively specific and detailed, but it should not be understood as limiting the scope of the present application. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

[0188] It should be noted that the words "first", "second", etc. used in the present application are used to distinguish different objects, and are not used to describe a specific order. The words "set", "connect", "mount" in the present application should be understood broadly, for example, it can be directly set, connected or mounted, or indirectly set, connected or mounted through an intermediate medium. The direction words mentioned in the present application, such as "up", "down", "front", "back", "left", "right", "inside", "outside", "positive", "back", "bottom", "top", etc. are only for better, clearer explanation and understanding of the present application, and are not indicative or implied that the components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application.

[0189] In the description of the present application, unless otherwise specified, "a plurality of" means greater than or equal to two. "At least one" means one or more. "At least one of the following" or the like means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0190] Further, the numerical range represented by "-" in the present application means a range including the numerical values written before and after "-" as minimum and maximum values, respectively. In the present application, the expression regarding the range of parameters, such as "greater than or equal to (≥)", "less than or equal to (≤)", "above", "below" includes the number.

Claims

1. A liquid crystal compound, characterized by, The liquid crystal compound has a general structural formula shown in the following formula (I): wherein ring A is selected from any one of the following structures: wherein R1 is selected from one of halogen or unsubstituted straight chain alkyl, halogen or unsubstituted straight chain alkoxy, halogen or unsubstituted chain alkenyl, halogen or unsubstituted chain alkenyloxy; X1 to X8 are independently selected from one of hydrogen atom, halogen atom, halogen or unsubstituted straight chain alkyl, halogen or unsubstituted straight chain alkoxy, halogen or unsubstituted chain alkenyl, halogen or unsubstituted chain alkenyloxy; X9 is selected from one of halogen atom, cyano group, isothiocyanato group, halogen or unsubstituted straight chain alkyl, halogen or unsubstituted straight chain alkoxy, halogen or unsubstituted chain alkenyl, halogen or unsubstituted chain alkenyloxy.

2. The liquid crystal compound according to claim 1, wherein said halogenated or unsubstituted straight-chain alkyl is a fluorinated or unsubstituted C1-C 10 straight-chain alkyl; said halogenated or unsubstituted straight-chain alkoxy is a fluorinated or unsubstituted C1-C 10 straight-chain alkoxy; said halogenated or unsubstituted chain alkenyl is a fluorinated or unsubstituted C2-C 10 chain alkenyl; said halogenated or unsubstituted chain alkenyloxy is a fluorinated or unsubstituted C2-C 10 chain alkenyloxy.

3. The liquid crystal compound according to claim 1 or 2, characterized by At least one of X1 and X4 is hydrogen atom, and at least one of X2 and X3 is hydrogen atom; at least one of X5 and X8 is hydrogen atom, and at least one of X6 and X7 is hydrogen atom.

4. The liquid crystal compound according to any one of claims 1 to 3, wherein X1, X2, X5, and X6 are hydrogen atom.

5. The liquid crystal compound according to any one of claims 1 to 4, wherein the birefringence of the liquid crystal compound represented by formula (I) is 0.30 or more, the dielectric anisotropy value is 9 or more, and the temperature range of the nematic phase is greater than or equal to 60°C.

6. A method for producing a liquid crystal compound, characterized by, comprising the steps of: (1) reacting an acetylenic species of the following formula (i) with an aryl halide of the following formula (ii) to give a species of the following formula (iii); (2) reacting the substance represented by formula (iii) with an aryl boronic acid represented by formula (iv) to obtain a liquid crystal composition represented by formula (I): wherein ring A is selected from any one of the following structures: wherein R1 is selected from one of halogen or unsubstituted straight chain alkyl, halogen or unsubstituted straight chain alkoxy, halogen or unsubstituted chain alkenyl, halogen or unsubstituted chain alkenyloxy; X1 to X8 are independently selected from one of hydrogen atom, halogen atom, halogen or unsubstituted straight chain alkyl, halogen or unsubstituted straight chain alkoxy, halogen or unsubstituted chain alkenyl, halogen or unsubstituted chain alkenyloxy; X9 is selected from one of halogen atom, cyano group, isothiocyanato group, halogen or unsubstituted straight chain alkyl, halogen or unsubstituted straight chain alkoxy, halogen or unsubstituted chain alkenyl, halogen or unsubstituted chain alkenyloxy.

7. A liquid crystal composition, characterized by comprising The liquid crystal composition comprises a liquid crystal monomer, and the liquid crystal monomer comprises at least one liquid crystal compound according to any one of claims 1 to 5, or comprises at least one liquid crystal compound prepared by the preparation method according to claim 6.

8. The liquid crystal composition according to claim 7, wherein The total mass percentage content of the liquid crystal compound in the liquid crystal composition is in the range of 0.5% to 80%.

9. The liquid crystal composition according to claim 7, wherein The total mass percentage content of the liquid crystal compound in the liquid crystal composition is in the range of 5% to 70%.

10. The liquid crystal composition according to any one of claims 7 to 9, wherein The liquid crystal composition further includes at least one second liquid crystal compound, wherein the at least one second liquid crystal compound includes one or more of the following Formula (II-1) to Formula (II-7): wherein R2, R4, R6, R8, R 10 , R 14 are independently selected from one of halogenated or unsubstituted straight chain alkyl, halogenated or unsubstituted straight chain alkoxy, halogenated or unsubstituted chain alkenyl, halogenated or unsubstituted chain alkenyloxy, halogenated or unsubstituted chain alkenyloxy, substituted or unsubstituted cycloalkyl; R3, R5, R7, R9, R 11 , R 13 are independently selected from one of a fluorine atom, a cyano group, an isothiocyanato group, a halogenated or unsubstituted straight-chain alkyl group, a halogenated or unsubstituted straight-chain alkoxy group, a halogenated or unsubstituted chain alkenyl group, a halogenated or unsubstituted chain alkenyloxy group, a substituted or unsubstituted cycloalkyl group; X 10 ~ X 40 one of a hydrogen atom, a halogen atom, a halogenated or unsubstituted straight-chain alkyl group, a halogenated or unsubstituted straight-chain alkoxy group, a halogenated or unsubstituted chain alkenyl group, a halogenated or unsubstituted chain alkenyloxy group, an unsubstituted cycloalkyl group.

11. The liquid crystal composition according to claim 10, wherein The substituent in the substituted cycloalkyl group comprises one or more of halogen atom, halogen or unsubstituted straight chain alkyl, halogen or unsubstituted straight chain alkoxy, halogen or unsubstituted chain alkenyl, halogen or unsubstituted chain alkenyloxy, and unsubstituted cycloalkyl group substituted with at least one of halogen or unsubstituted straight chain alkyl, straight chain alkoxy, chain alkenyl, chain alkenyloxy.

12. The liquid crystal composition according to claim 10 or 11, wherein In the formula (II-4), X 21 and at least one of X 23 In the formula (II-6), X 32 and at least one of X 34 is a hydrogen atom.

13. The liquid crystal composition according to any one of claims 10 to 12, wherein The total mass percentage content of the second liquid crystal compound in the liquid crystal composition is in the range of 0.5% to 90%.

14. The liquid crystal composition of claim 13, wherein The total mass percentage content of the second liquid crystal compound in the liquid crystal composition is in the range of 5% to 70%.

15. The liquid crystal composition according to any one of claims 10 to 14, wherein The total mass percentage content of the second liquid crystal compound in the liquid crystal composition is greater than the mass percentage content of the liquid crystal compound represented by formula (I).

16. The liquid crystal composition of claim 15, wherein The mass ratio of the second liquid crystal compound to the liquid crystal compound represented by formula (I) is (1.1-5.0):

1.

17. The liquid crystal composition of any one of claims 1 to 16, wherein The liquid crystal composition further comprises an additive, the additive comprising one or more of an ultraviolet absorber, an ultraviolet stabilizer, a voltage stabilizer, and an antioxidant.

18. The liquid crystal composition of any one of claims 1 to 17, wherein The birefringence of the liquid crystal composition is 0.30 or more, the dielectric anisotropy is 5 or more, and the temperature range of the nematic phase is greater than or equal to 80°C.

19. Use of the liquid crystal compound according to any one of claims 1-5, or the liquid crystal composition according to any one of claims 7-18, in a liquid crystal device.

20. The use of claim 19, wherein, The liquid crystal device is used in a wavelength selective switch, a microwave antenna, a liquid crystal optical waveguide, a liquid crystal grating, a dynamic focusing lens, a laser radar, a laser projection, an optical projection system, an intelligent vehicle lamp, a flat panel display, a holographic display, optical communication, or wireless communication.

21. A liquid crystal device, characterised in that The liquid crystal device comprises a liquid crystal layer, the liquid crystal layer comprising the liquid crystal compound according to any one of claims 1-5, or the liquid crystal composition according to any one of claims 7-18.

22. A liquid crystal device according to claim 21, wherein The liquid crystal device comprises a silicon-based backplane, a cover plate with a transparent electrode layer, and the liquid crystal layer disposed between the silicon-based backplane and the cover plate with the transparent electrode layer.

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