阅读说明：本技术 液晶化合物及其液晶组合物和液晶显示器件 (Liquid crystal compound, liquid crystal composition thereof and liquid crystal display device ) 是由 姜志炜 宋晓龙 徐爽 陈法兵 陈俊利 胡步洋 于 2020-04-21 设计创作，主要内容包括：本发明提供一种通式I的液晶化合物、包含该液晶化合物的液晶组合物和包含该液晶组合物的液晶显示器件。与现有技术相比,本发明提供的通式I的液晶化合物在维持适当的旋转粘度的情况下,还具有较大的清亮点、较大的光学各向异性和较大的介电各向异性绝对值,使得包含该液晶化合物的液晶组合物在维持适当的低温储存稳定性和适当的旋转粘度的情况下,还具有较大的清亮点、较大的光学各向异性、较大的介电各向异性绝对值、较大的弹性常数和较小的旋转粘度与展曲弹性常数的比值,进而使得包含该液晶组合物的液晶显示器件具有较宽的向列相温度范围、较好的对比度、较低的阈值电压和较短的响应时间。(The invention provides a liquid crystal compound shown in a general formula I, a liquid crystal composition containing the liquid crystal compound and a liquid crystal display device containing the liquid crystal composition. Compared with the prior art, the liquid crystal compound provided by the invention has larger clearing point, larger optical anisotropy and larger absolute value of dielectric anisotropy under the condition of maintaining proper rotational viscosity, so that the liquid crystal composition containing the liquid crystal compound also has larger clearing point, larger optical anisotropy, larger absolute value of dielectric anisotropy, larger elastic constant and smaller absolute values of rotational viscosity and splay elastic constant under the condition of maintaining proper low-temperature storage stability and proper rotational viscosityThe ratio, in turn, enables a liquid crystal display device comprising the liquid crystal composition to have a wider nematic phase temperature range, better contrast, lower threshold voltage and shorter response time.)

1. A liquid crystal compound of the general formula I:

wherein the content of the first and second substances,

R₁represents a linear or branched alkyl group having 1 to 12 carbon atoms,The straight chain or branched chain containing 1 to 12 carbon atomsOne or more-CH groups not adjacent to each other in the alkyl group of (A)₂-said linear or branched alkyl containing 1 to 12 carbon atoms, which may be independently replaced by-C ═ C-, -C ≡ C-, -O-, -CO-O-or-O-CO-, respectively,Each of one or more-H may be independently substituted with-F or-Cl;

ring (C)And ringEach independently represent WhereinOne or more-CH of₂-may be replaced by-O-and one or more single bonds in the ring may be replaced by a double bond, whereinMay be substituted by-CN, -F, -Cl, -CH₃or-OCH₃Substituted, and one or more of the rings-CH-may be replaced by-N;

x represents-O-, -S-, -CO-, -CF₂-, -NH-or-NF-;

y represents halogen, haloalkyl or haloalkoxy having 1 to 5 carbon atoms, or haloalkenyl or haloalkenyloxy having 2 to 5 carbon atoms;

Z₁、Z₂and Z₃Each independently represents a single bond, -CO-O-, -O-CO-, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-、-(CH₂)₄-、-CF₂O-or-OCF₂-；

n₁And n₂Each independently represents 0, 1, 2 or 3, wherein when n is₁When 2 or 3, ringMay be the same or different, Z₁May be the same or different; wherein when n is₂When 2 or 3, ringMay be the same or different, Z₂May be the same or different; and is

L₁、L₂、L₃And L₄Each independently represents-H, halogen, -OCH₃or-CH₃。

2. The liquid crystal compound according to claim 1, wherein the ring isAnd ringEach independently represent

3. The liquid crystal compound according to claim 1 or 2, wherein the liquid crystal compound of formula I is selected from the group consisting of:

and

4. the liquid-crystalline compound according to claim 3, wherein Y represents-F, -CF₃、-OCF₃or-CH₂CH₂CH＝CF₂；Z₁And Z₂Each independently represents a single bond, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-、-(CH₂)₄-、-CF₂O-or-OCF₂-；Z₃Represents a single bond, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-or- (CH)₂)₄-。

5. A liquid crystal composition comprising at least one liquid crystal compound of the general formula I as claimed in any of claims 1 to 4.

6. The liquid crystal composition of claim 5, wherein the liquid crystal compound of formula I is present in an amount of 0.1% to 40% by weight of the liquid crystal composition.

7. The liquid crystal composition of claim 5, further comprising at least one compound of formula M:

wherein the content of the first and second substances,

R_M1and R_M2Each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, One or more non-adjacent-CH in the linear or branched alkyl group containing 1 to 12 carbon atoms₂-may be independently replaced by-CH ═ CH-, -C ≡ C-, -O-, -CO-O-, or-O-CO-;

ring (C)Ring (C)And ringEach independently represent WhereinOne or more-CH of₂-can be replaced by-O-, andat most one-H in (a) may be substituted by halogen;

Z_M1and Z_M2Each independently represents a single bond, -CO-O-, -O-CO-, -CH₂O-、-OCH₂-、-C≡C-、-CH＝CH-、-CH₂CH₂-or- (CH)₂)₄-; and is

n_MRepresents 0, 1 or 2, wherein when n_MWhen 2, ringMay be the same or different, Z_M2May be the same or different.

8. The liquid crystal composition of claim 7, wherein the compound of formula M is selected from the group consisting of:

and

9. the liquid crystal composition of claim 5, further comprising at least one compound of formula N:

wherein the content of the first and second substances,

R_N1and R_N2Each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, One or more non-adjacent-CH in the linear or branched alkyl group containing 1 to 12 carbon atoms₂-may be independently replaced by-CH ═ CH-, -C ≡ C-, -O-, -CO-O-, or-O-CO-;

ring (C)And ringEach independently representWhereinOne or more-CH of₂-may be replaced by-O-and one or more single bonds in the ring may be replaced by a double bond, whereinMay be substituted by-F, -Cl or-CN, and one or more rings-CH-may be replaced by-N;

Z_N1and Z_N2Each independently represents a single bond, -CO-O-, -O-CO-, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-、-(CH₂)₄-、-CF₂O-or-OCF₂-；

L_N1And L_N2Each independently represents-H, an alkyl group containing 1 to 3 carbon atoms or halogen; and is

n_N1Represents 0, 1, 2 or 3, n_N2Represents 0 or 1, and 0. ltoreq. n_N1+n_N2Is less than or equal to 3, wherein when n is_N1When 2 or 3, ringMay be the same or different, Z_N1May be the same or different.

10. A liquid crystal display device comprising the liquid crystal composition of any one of claims 5 to 9.

Technical Field

The invention relates to the field of liquid crystal, in particular to a liquid crystal compound, a liquid crystal composition containing the liquid crystal compound and a liquid crystal display device containing the liquid crystal composition.

Background

Liquid crystal display elements are used in various household electric appliances such as watches and calculators, measuring instruments, automobile panels, word processors, computers, printers, televisions, and the like. Liquid crystal display elements are classified into types of PC (phase change), TN (twisted nematic), STN (super twisted nematic), ECB (electrically controlled birefringence), OCB (optically compensated bend), IPS (in-plane switching), VA (vertical alignment), and the like, according to the type of display mode. Liquid crystal display devices can be classified into a PM (passive matrix) type and an AM (active matrix) type according to the driving method of the device. PM is classified into static (static) and multiplex (multiplex) types. AM is classified into a TFT (thin film transistor), an MIM (metal insulator metal), and the like. Types of TFTs include amorphous silicon (amorphous silicon) and polycrystalline silicon (polysilicon). The latter is classified into a high temperature type and a low temperature type according to a manufacturing process. Liquid crystal display elements can be classified into a reflection type using natural light, a transmission type using a backlight, and a semi-transmission type using both light sources of natural light and backlight, depending on the type of light source.

In the case of low information content, passive driving is generally adopted. However, as the amount of information increases and the display size and the number of display paths increase, the phenomena of crosstalk and contrast reduction become serious, and thus, the Active Matrix (AM) driving is generally adopted, and at present, the Thin Film Transistor (TFT) is often adopted for driving. In an AM-TFT element, the TFT switching devices are addressed in a two-dimensional grid, charging the pixel electrodes for a finite time on, and then turning off until they are addressed again in the next cycle. Therefore, between two addressing periods, it is not desirable to change the voltage on the pixel, otherwise the transmittance of the pixel will change, resulting in instability of the display. The rate of discharge at a pixel depends on the electrode capacity and the resistivity of the dielectric material between the electrodes. Therefore, the liquid crystal material is required to have higher resistivity, good chemical stability and thermal stability, and stability to electric fields and electromagnetic radiation, and simultaneously, the liquid crystal material is required to have appropriate optical anisotropy Δ n and lower threshold voltage so as to achieve the purposes of reducing driving voltage and reducing power consumption; it is also required that the liquid crystal material has a low viscosity to meet the demand for a rapid response. Such liquid crystal compositions have been reported in many documents, for example, WO9202597, WO9116398, WO9302153, WO9116399, CN1157005A and the like.

The liquid crystal display element contains a liquid crystal composition having a nematic phase, and the liquid crystal composition has appropriate characteristics. By improving the characteristics of the liquid crystal composition, an AM element having good characteristics can be obtained. The relationship between the characteristics of the liquid crystal composition and the AM element is summarized in table 1 below. The characteristics of the liquid crystal composition are further described based on a commercially available AM element. The temperature range of the nematic phase is associated with the temperature range in which the element can be used. The upper limit temperature of the nematic phase is preferably about 70 ℃ or higher, and the lower limit temperature of the nematic phase is preferably about-10 ℃ or lower. The viscosity of the liquid crystal composition correlates to the response time of the cell. In order to display a dynamic image on the device, it is preferable that the response time of the device is short.

TABLE 1 Properties of liquid Crystal composition and AM element

The optical anisotropy of the liquid crystal composition correlates with the contrast of the cell. Depending on the display mode of the element, a large optical anisotropy or a small optical anisotropy (i.e., an appropriate optical anisotropy) is required. The product (Δ n × d) of the optical anisotropy (Δ n) of the liquid crystal composition and the cell thickness (d) of the element is designed to maximize the contrast. The appropriate product value depends on the type of operation mode, and a liquid crystal composition having a large optical anisotropy is preferable for an element having a small cell thickness.

A liquid crystal display element containing a liquid crystal composition having a large absolute value of dielectric anisotropy can reduce the base voltage value, reduce the driving voltage, and further reduce the power consumption.

The liquid crystal display element containing the liquid crystal composition with the lower threshold voltage can effectively reduce the display power consumption, and particularly has longer endurance time in consumables (such as mobile phones, tablet computers and other portable electronic products). However, for liquid crystal compositions having a lower threshold voltage (generally containing large dielectric polar groups), the degree of order of the liquid crystal molecules is low, reflecting the K of the degree of order of the liquid crystal molecules_aveThe value also decreases, affecting the light leakage and contrast of the liquid crystal material, which are often difficult to compromise.

The liquid crystal composition with low viscosity can improve the response speed of the liquid crystal display element. When the response speed of the liquid crystal display element is high, it can be applied to animation display. In addition, when the liquid crystal composition is injected into the cell of the liquid crystal display device, the injection time can be shortened, and the workability can be improved. Rotational viscosity gamma₁Directly influences the response time of the liquid crystal composition after power-up, wherein the rise time (tau)_on) And fall time (τ)_off) Both with the rotational viscosity gamma of the liquid crystal composition₁In direct proportion. Due to rise time (tau)_on) Depending on the cell and the driving voltage, the rise time (τ) can be adjusted by increasing the driving voltage and decreasing the cell thickness of the cell_on). Fall time (tau)_off) Independent of the driving voltage, it is mainly dependent on the elastic constant of the liquid crystal composition and the cell of the liquid crystal cellThickness dependent, thinning of the cell thickness reduces the fall time (τ)_off) The liquid crystal molecules in different display modes have different motion modes, and the falling time (tau) in TN mode, IPS mode and VA mode_off) Respectively, the average elastic constant, the torsional elastic constant and the bending elastic constant.

The response time is limited by the rotational viscosity (gamma)₁) Ratio to the elastic constant (K). In view of liquid crystal materials, it is necessary to reduce the rotational viscosity of the liquid crystal medium as much as possible and to increase the elastic constant to achieve the purpose of increasing the response time. However, the rotational viscosity and the elastic constant are a pair of contradictory parameters, and a decrease in the rotational viscosity causes a decrease in the elastic constant. Therefore, γ needs to be studied for different display modes₁/K₁₁The most preferred range of values is used.

U.S. patent application publication No. US20180030020a1 discloses the following compounds of general formula S having a difluorodibenzo ring structure:

further disclosed are specific compounds of the following general formula S-1, general formula S-2 and general formula S-3:

wherein the content of the first and second substances,

alkyl represents an alkyl group having 1 to 15 carbon atoms;

R²represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group or an alkynyl group having 2 to 15 carbon atoms.

Although these fluorodibenzo-based compounds have a large absolute value of dielectric anisotropy, they have problems of large viscosity and small use temperature range, and are disadvantageous in the construction of a liquid crystal display device having a high reaction rate and a wide use temperature range.

Therefore, it is a new development in the liquid crystal field to further improve the structure of these difluorodibenzo compounds in order to obtain liquid crystal compounds satisfying both a large absolute value of dielectric anisotropy, a short response time, and a wide nematic phase temperature range.

Disclosure of Invention

The purpose of the invention is as follows: in view of the drawbacks of the prior art, an object of the present invention is to provide a liquid crystal compound having a large clearing point, a large optical anisotropy, and a large absolute value of dielectric anisotropy while maintaining an appropriate rotational viscosity.

The invention also aims to provide a liquid crystal composition containing the liquid crystal compound.

It is a further object of the present invention to provide a liquid crystal display device comprising the above liquid crystal composition.

The technical scheme is as follows: in order to achieve the above object, the present invention provides a liquid crystal compound of the general formula I:

wherein the content of the first and second substances,

R₁represents a linear or branched alkyl group having 1 to 12 carbon atoms,One or more non-adjacent-CH in the linear or branched alkyl group containing 1 to 12 carbon atoms₂-said linear or branched alkyl containing 1 to 12 carbon atoms, which may be independently replaced by-C ═ C-, -C ≡ C-, -O-, -CO-O-or-O-CO-, respectively,OrEach of one or more-H may be independently substituted with-F or-Cl;

ring (C)And ringEach independently representOrWhereinAndone or more-CH of₂-may be replaced by-O-and one or more single bonds in the ring may be replaced by a double bond, whereinAndmay be substituted by-CN, -F, -Cl, -CH₃or-OCH₃Substituted, and one or more of the rings-CH-may be replaced by-N;

x represents-O-, -S-, -CO-, -CF₂-, -NH-or-NF-;

y represents halogen, haloalkyl or haloalkoxy having 1 to 5 carbon atoms, or haloalkenyl or haloalkenyloxy having 2 to 5 carbon atoms;

Z₁、Z₂and Z₃Each independently represents a single bond, -CO-O-, -O-CO-, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-、-(CH₂)₄-、-CF₂O-or-OCF₂-；

n₁And n₂Each independently represents 0, 1, 2 or 3, wherein when n is₁When 2 or 3, ringMay be the same or different, Z₁May be the same or different; wherein when n is₂When 2 or 3, ringMay be the same or different, Z₂May be the same or different; and is

L₁、L₂、L₃And L₄Each independently represents-H, halogen, -OCH₃or-CH₃。

In some embodiments of the invention, preferably, R₁Represents a linear or branched alkyl group having 1 to 10 carbon atoms, a linear or branched alkoxy group having 1 to 9 carbon atoms, or a linear or branched alkenyl group having 2 to 10 carbon atoms; further preferably, R₁Represents a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkoxy group having 1 to 7 carbon atoms, or a linear or branched alkenyl group having 2 to 8 carbon atoms; even further preferably, R₁Represents a linear or branched alkyl group having 1 to 5 carbon atoms, a linear or branched alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkenyl group having 2 to 5 carbon atoms.

In some embodiments of the invention, the ringAnd ringEach independently represent

Preferably, the ringAnd ringEach independently represent It is further preferred that the first and second liquid crystal compositions,and ringEach independently represent

In some embodiments of the invention, the liquid crystal compound of formula I is selected from the group consisting of:

and

in some embodiments of the invention, preferably, X represents-O-, -S-or-CO-.

In some embodiments of the invention, preferably, Y represents-F, -CF₃、-OCF₃or-CH₂CH₂CH＝CF₂。

In some embodiments of the invention, preferably, Z is₁And Z₂Each independently represents a single bond, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-、-(CH₂)₄-、-CF₂O-or-OCF₂-; further preferably, Z₁And Z₂Each independently represents a single bond, -CH₂O-、-OCH₂-、-CH₂CH₂-、-CF₂O-or-OCF₂-。

In some embodiments of the invention, preferably, Z is₃Represents a single bond, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-or- (CH)₂)₄-; further preferably, Z₃Represents a single bond, -CH₂O-、-OCH₂-、-CH₂CH₂-、-CF₂CF₂-or- (CH)₂)₄-。

In some embodiments of the invention, the compound of formula I-2 is selected from the group consisting of:

wherein the content of the first and second substances,

L₁、L₂、L₅、L₆and L₇Each independently represents-F or-Cl.

In some embodiments of the invention, the compound of formula I-3 is selected from the group consisting of:

wherein the content of the first and second substances,

H₁and H₂Each independently represents-CH₂-or-O-; and is

L₁、L₂、L₈、L₉And L₁₀Each independently represents-F or-Cl.

In some embodiments of the invention, the compound of formula I is selected from the group consisting of:

in another aspect, the present invention further provides a liquid crystal composition comprising at least one liquid crystal compound of formula I.

The liquid crystal compound of the general formula I accounts for the weight percentage of the liquid crystal composition of the invention: preferred lower limit values of the weight percentage of the liquid crystal compound of the general formula I with respect to the total weight of the liquid crystal composition of the present invention are 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, 14%, 15%, or 20%; preferred upper limit values of the weight percentage of the liquid crystal compound of the general formula I with respect to the total weight of the liquid crystal composition of the present invention are 40%, 38%, 36%, 30%, 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 12%, 10%, 8%, 6%, 5%, 4% or 3%.

In some embodiments of the present invention, the liquid crystal compound of formula I comprises 0.1% to 40% by weight of the liquid crystal composition; preferably, the liquid crystal compound of the general formula I accounts for 1-40% of the liquid crystal composition by weight; further preferably, the liquid crystal compound of the general formula I accounts for 1-30% of the liquid crystal composition by weight.

In some embodiments of the invention, the liquid crystal composition further comprises at least one compound of formula M:

wherein the content of the first and second substances,

R_M1and R_M2Each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, One or more non-adjacent-CH in the linear or branched alkyl group containing 1 to 12 carbon atoms₂-may be independently replaced by-CH ═ CH-, -C ≡ C-, -O-, -CO-O-, or-O-CO-;

ring (C)Ring (C)And ringEach independently representOrWhereinOne or more-CH of₂-can be replaced by-O-, andat most one-H in (a) may be substituted by halogen;

Z_M1and Z_M2Each independently represents a single bond, -CO-O-, -O-CO-, -CH₂O-、-OCH₂-、-C≡C-、-CH＝CH-、-CH₂CH₂-or- (CH)₂)₄-; and is

n_MRepresents 0, 1 or 2, wherein when n_MWhen 2, ringMay be the same or different, Z_M2May be the same or different.

In some embodiments of the invention, preferably, R_M1And R_M2Each independently represents a linear alkyl group having 1 to 10 carbon atoms, a linear alkoxy group having 1 to 9 carbon atoms, or a linear alkenyl group having 2 to 10 carbon atoms; further preferably, R_M1And R_M2Each independently represents a linear alkyl group having 1 to 8 carbon atoms, a linear alkoxy group having 1 to 7 carbon atoms, or a linear alkenyl group having 2 to 8 carbon atoms; even further preferably, R_M1And R_M2Each independently represents a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 carbon atoms, or a linear alkenyl group having 2 to 5 carbon atoms.

In some embodiments of the invention, preferably, R_M1And R_M2Each independently represents a straight-chain alkenyl group having 2 to 8 carbon atoms; further preferably, R_M1And R_M2Each independently represents a straight-chain alkenyl group having 2 to 5 carbon atoms.

In some embodiments of the invention, preferably, R_M1And R_M2One of the alkenyl groups is a linear alkenyl group having 2 to 5 carbon atoms, and the other is a linear alkyl group having 1 to 5 carbon atoms.

In some embodiments of the invention, preferably, R_M1And R_M2Each independently represents a linear alkyl group having 1 to 8 carbon atoms or a linear alkoxy group having 1 to 7 carbon atoms; further preferably, R_M1And R_M2Each independently representA linear alkyl group having 1 to 5 carbon atoms or a linear alkoxy group having 1 to 4 carbon atoms.

In some embodiments of the invention, preferably, R_M1And R_M2One of the alkyl groups is a linear alkyl group having 1 to 5 carbon atoms, and the other is a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxy group having 1 to 4 carbon atoms; further preferably, R_M1And R_M2Both independently are a linear alkyl group having 1 to 5 carbon atoms.

The alkenyl group in the present invention is preferably selected from groups represented by any one of formulae (V1) to (V9), and particularly preferably formula (V1), formula (V2), formula (V8), or (V9). The groups represented by formulae (V1) to (V9) are shown below:

wherein denotes the carbon atom in the ring structure to which it is bonded.

The alkenyloxy group in the present invention is preferably selected from groups represented by any one of formulae (OV1) to (OV9), and particularly preferably formula (OV1), formula (OV2), formula (OV8), or (OV 9). The groups represented by formulae (OV1) to (OV9) are shown below:

wherein denotes the carbon atom in the ring structure to which it is bonded.

In some embodiments of the invention, the compound of formula M is selected from the group consisting of:

in some embodiments of the present invention, the content of the compound of formula M must be appropriately adjusted according to the required properties of solubility at low temperature, transition temperature, electrical reliability, birefringence, process adaptability, drop trace, burn-in, dielectric anisotropy, and the like.

The weight percentage of the compound of formula M in the liquid crystal composition of the present invention: preferred lower limit values of the weight percentage of the compound of formula M with respect to the total weight of the liquid crystal composition of the present invention are 0.1%, 1%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 20%, 25%, 30%, 35%, 40%, 45% or 50%; preferred upper limits of the weight percentage of the compound of formula M relative to the total weight of the liquid crystal composition of the present invention are 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45.5%, 45%, 40%, 35%, 30%, 28%, 27%, 26%, 25.5%, 25%, 24%, 23%, 22%, 21% or 20%.

In some embodiments of the invention, the compound of formula M comprises 0.1% to 90% by weight of the liquid crystal composition; preferably, the compound of the general formula M accounts for 1 to 80 percent of the weight of the liquid crystal composition; further preferably, the compound of the general formula M accounts for 5 to 60 weight percent of the liquid crystal composition.

The content of the compound of the formula M is preferably higher in the lower limit value and higher in the upper limit value when the viscosity of the liquid crystal composition of the present invention needs to be kept low and the response time is short; further, when it is necessary to keep the clearing point of the liquid crystal composition of the present invention high and the temperature stability is good, it is preferable that the lower limit value is high and the upper limit value is high; in order to keep the driving voltage low and increase the absolute value of the dielectric anisotropy, it is preferable to lower the lower limit and lower the upper limit.

In some embodiments of the invention, R is preferred when reliability is a concern_M1And R_M2Are all alkyl; in the case where importance is attached to reduction in volatility of the compound, R is preferably_M1And R_M2Are both alkoxy groups;when importance is attached to the reduction in viscosity, R is preferably used_M1And R_M2At least one of which is alkenyl.

In some embodiments of the invention, the liquid crystal composition further comprises at least one compound of formula N:

wherein the content of the first and second substances,

R_N1and R_N2Each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, One or more non-adjacent-CH in the linear or branched alkyl group containing 1 to 12 carbon atoms₂-may be independently replaced by-CH ═ CH-, -C ≡ C-, -O-, -CO-O-, or-O-CO-;

ring (C)And ringEach independently representOrWhereinOne or more-CH of₂-may be replaced by-O-and one or more single bonds in the ring may be replaced by a double bond, whereinMay be substituted by-F, -Cl or-CN, and one or more rings may be substituted by-CH-may be substituted by-N;

Z_N1and Z_N2Each independently represents a single bond, -CO-O-, -O-CO-, -CH₂O-、-OCH₂-、-CH＝CH-、-C≡C-、-CH₂CH₂-、-CF₂CF₂-、-(CH₂)₄-、-CF₂O-or-OCF₂-；

L_N1And L_N2Each independently represents-H, an alkyl group containing 1 to 3 carbon atoms or halogen; and is

n_N1Represents 0, 1, 2 or 3, n_N2Represents 0 or 1, and 0. ltoreq. n_N1+n_N2Is less than or equal to 3, wherein when n is_N1When 2 or 3, ringMay be the same or different, Z_N1May be the same or different.

The weight percentage of the compound of the general formula N in the liquid crystal composition of the invention is as follows: the lower limit of the weight percentage of the compound of formula N with respect to the total weight of the liquid crystal composition of the present invention is 0%, 0.1%, 1%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 20%, 22%, 24%, 26%, 28%, 30% or 35%; the upper limit of the weight percentage of the compound of formula N with respect to the total weight of the liquid crystal composition of the present invention is 60%, 58%, 56%, 54%, 52%, 50%, 45%, 40%, 35%, 30%, 28%, 25.5%, 25%, 24%, 22%, 20%, 18%, 15%, or 10%.

In some embodiments of the invention, the compound of formula N comprises 0% to 60% by weight of the liquid crystal composition; preferably, the compound of the general formula N accounts for 0.1-55% of the liquid crystal composition by weight.

In some embodiments of the present invention, when it is desired to keep the viscosity of the liquid crystal composition of the present invention low and the response time short, it is preferable that the lower limit value and the upper limit value of the content of the compound of formula N are low; further, when it is necessary to keep the clearing point of the liquid crystal composition of the present invention high and the temperature stability good, the lower limit value and the upper limit value of the content of the compound of the general formula N are preferably low; in addition, when the absolute value of the dielectric anisotropy is increased in order to keep the driving voltage low, it is preferable that the lower limit value and the upper limit value of the content of the compound of the general formula N be increased.

In some embodiments of the invention, preferably, R_N1And R_N2Each independently represents a linear or branched alkyl group having 1 to 10 carbon atoms, a linear or branched alkoxy group having 1 to 9 carbon atoms, or a linear or branched alkenyl group having 2 to 10 carbon atoms; further preferably, R_N1And R_N2Each independently represents a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkoxy group having 1 to 7 carbon atoms, or a linear or branched alkenyl group having 2 to 8 carbon atoms; even further preferably, R_N1And R_N2Each independently represents a linear or branched alkyl group having 1 to 5 carbon atoms, a linear or branched alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkenyl group having 2 to 5 carbon atoms.

In some embodiments of the invention, R_N1Further preferred is a linear or branched alkyl group having 1 to 5 carbon atoms, or a linear or branched alkenyl group having 2 to 5 carbon atoms; r_N1Still more preferably a linear or branched alkyl group having 2 to 5 carbon atoms, or a linear or branched alkenyl group having 2 to 3 carbon atoms; r_N2Further preferred is a straight or branched alkoxy group having 1 to 5 carbon atoms.

In some embodiments of the invention, the ringAnd ringEach independently represent

In some embodiments of the invention, the compound of formula N is selected from the group consisting of:

in some embodiments of the present invention, the liquid crystal composition further comprises at least one compound selected from the group consisting of compounds of formula A-1 and formula A-2:

wherein the content of the first and second substances,

R_A1and R_A2Each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms,OrOne or more non-adjacent-CH in the linear or branched alkyl group containing 1 to 12 carbon atoms₂-said linear or branched alkyl radical containing from 1 to 12 carbon atoms which may be independently replaced by-CH ═ CH-, -C ≡ C-, -O-, -CO-O-or-O-CO-, respectively,Each of one or more-H may be independently substituted with-F or-Cl;

ring (C)Ring (C)Ring (C)And ringEach independently representWhereinAndone or more-CH of₂-may be replaced by-O-and one or more single bonds in the ring may be replaced by a double bond, whereinAndmay be substituted by-F, -Cl or-CN, and one or more rings-CH-may be replaced by-N;

Z_A11、Z_A21and Z_A22Each independently represents a single bond, -CH₂CH₂-、-CF₂CF₂-、-CO-O-、-O-CO-、-O-CO-O-、-CH＝CH-、-CF＝CF-、-CH₂O-or-OCH₂-；

L_A11、L_A12、L_A13、L_A21And L_A22Each independently represents-H, an alkyl group containing 1 to 3 carbon atoms or halogen;

X_A1and X_A2Each independently represents halogen, haloalkyl or haloalkoxy having 1 to 5 carbon atoms, or haloalkenyl or haloalkenyloxy having 2 to 5 carbon atoms;

n_A11represents 0, 1, 2 or3, wherein when n_A11When 2 or 3, ringMay be the same or different, Z_A11May be the same or different;

n_A12represents 1 or 2, wherein when n_A12When 2, ringMay be the same or different; and is

n_A2Represents 0, 1, 2 or 3, wherein when n is_A2When 2 or 3, ringMay be the same or different, Z_A21May be the same or different.

As to the weight percentage of the liquid crystal composition of the present invention with respect to the compounds of the group consisting of the compounds of the general formula A-1 and the general formula A-2: the lower limit of the weight percentage of the compound of the group consisting of the compounds of the general formula a-1 and the general formula a-2 is 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 20% with respect to the total weight of the liquid crystal composition of the present invention; the upper limit value of the weight percentage of the compound of the group consisting of the compounds of the general formula a-1 and the general formula a-2 is 60%, 55%, 50%, 45%, 40%, 38%, 35%, 30%, 28%, 27%, 26%, 25.5% or 25% with respect to the total weight of the liquid crystal composition of the present invention.

In some embodiments of the present invention, the compounds of the group consisting of compounds of formula A-1 and formula A-2 comprise 0% to 60% by weight of the liquid crystal composition.

In some embodiments of the invention, the compound of formula A-1 is selected from the group consisting of:

wherein the content of the first and second substances,

R_A1represents a straight-chain or branched alkyl group having 1 to 8 carbon atoms,One or more non-adjacent-CH groups in the linear or branched alkyl group having 1 to 8 carbon atoms₂-may be independently replaced by-CH ═ CH-, -C ≡ C-, -O-, -CO-O-, or-O-CO-, respectively, and one or more-H groups in said linear or branched alkyl group containing 1 to 8 carbon atoms may be independently substituted by-F or-Cl, respectively;

R_vand R_wEach independently represents-CH₂-or-O-;

L_A11、L_A12、L_A11’、L_A12’、L_A14、L_A15and L_A16Each independently represents-H or-F;

L_A13and L_A13' independently of each other represents-H or-CH₃；

X_A1represents-F, -CF₃or-OCF₃(ii) a And is

v and w each independently represent 0 or 1.

The weight percentage of the compound of formula A-1 to the liquid crystal composition of the present invention: the lower limit of the weight percentage of the compound of formula a-1 with respect to the total weight of the liquid crystal composition of the present invention is 0%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 20%; the upper limit value of the weight percentage of the compound of formula a-1 with respect to the total weight of the liquid crystal composition of the present invention is 50%, 45%, 40%, 38%, 35%, 30%, 28%, 27%, 26%, 25.5%, or 25%.

In some embodiments of the present invention, the compound of formula A-1 comprises 0% to 50% by weight of the liquid crystal composition.

With respect to the preferable content of the compound of the general formula A-1, in the case where the viscosity of the liquid crystal composition of the present invention is kept low and the response speed is high, it is preferable to make the lower limit value slightly lower and the upper limit value slightly lower; further, when the clearing point of the liquid crystal composition of the present invention is kept high and the temperature stability is good, it is preferable to make the lower limit value slightly lower and the upper limit value slightly lower; in order to increase the absolute value of the dielectric anisotropy while keeping the driving voltage low, it is preferable to increase the lower limit and the upper limit slightly.

In some embodiments of the invention, the compound of formula a-2 is selected from the group consisting of:

wherein the content of the first and second substances,

R_A2represents a linear or branched alkyl group having 1 to 8 carbon atoms, one or two or more-CH groups which are not adjacent to each other in the linear or branched alkyl group having 1 to 8 carbon atoms₂-may be independently replaced by-CH ═ CH-, -C ≡ C-, -O-, -CO-O-, or-O-CO-, respectively, and one or more-H present in these groups may be independently substituted by-F or-Cl, respectively;

L_A21、L_A22、L_A23、L_A24and L_A25Each independently represents-H or F; and is

X_A2represents-F, -CF₃、-OCF₃or-CH₂CH₂CH＝CF₂。

The weight percentage of the compound of formula A-2 to the liquid crystal composition of the present invention: the lower limit of the weight percentage of the compound of formula a-2 with respect to the total weight of the liquid crystal composition of the present invention is 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 20%; the upper limit of the weight percentage of the compound of formula a-2 with respect to the total weight of the liquid crystal composition of the present invention is 60%, 55%, 50%, 45.5%, 45%, 42.5%, 40%, 35%, 30%, 28%, 27%, 26%, or 25%.

In some embodiments of the invention, the compound of formula A-2 comprises 0% to 60% by weight of the liquid crystal composition.

The preferable content of the compound of the general formula a-2 is preferably such that the lower limit value is slightly lower and the upper limit value is slightly lower, when the viscosity of the liquid crystal composition of the present invention is kept low and the response speed is high; further, when the clearing point of the liquid crystal composition of the present invention is kept high and the temperature stability is good, it is preferable to make the lower limit value slightly lower and the upper limit value slightly lower; in order to increase the absolute value of the dielectric anisotropy while keeping the driving voltage low, it is preferable to increase the lower limit and the upper limit.

In addition to the above compounds, the liquid crystal composition of the present invention may contain a conventional nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, antioxidant, ultraviolet absorber, infrared absorber, polymerizable monomer, light stabilizer, and the like.

Possible dopants which are preferably added to the liquid crystal composition according to the invention are shown below.

In some embodiments of the invention, the dopant comprises 0% to 5% by weight of the liquid crystal composition; preferably, the dopant accounts for 0.01-1% of the liquid crystal composition by weight.

Further, additives such as an antioxidant and a light stabilizer used in the liquid crystal composition of the present invention are preferably as follows:

wherein n represents a positive integer of 1 to 12.

Preferably, the light stabilizer is selected from the group consisting of the light stabilizers shown below:

in some embodiments of the invention, the light stabilizer comprises from 0% to 5% by weight of the total liquid crystal composition; preferably, the light stabilizer accounts for 0.01 to 1 percent of the total weight of the liquid crystal composition; more preferably, the light stabilizer is 0.01 to 0.1 percent of the total weight of the liquid crystal composition.

In still another aspect, the present invention provides a liquid crystal display device comprising the liquid crystal composition according to the present invention.

Has the advantages that:

compared with the prior art, the liquid crystal compound of the general formula I provided by the invention has a larger clearing point, a larger optical anisotropy and a larger absolute value of dielectric anisotropy under the condition of maintaining a proper rotary viscosity, so that a liquid crystal composition containing the liquid crystal compound also has a larger clearing point, a larger optical anisotropy, a larger absolute value of dielectric anisotropy, a larger elastic constant and a smaller ratio of rotary viscosity to splay elastic constant under the condition of maintaining proper low-temperature storage stability and proper rotary viscosity, and a liquid crystal display device containing the liquid crystal composition further has a wider nematic phase temperature range, a better contrast, a lower threshold voltage and a shorter response time.

Detailed Description

The invention will be illustrated below with reference to specific embodiments. It should be noted that the following examples are illustrative of the present invention, and are not intended to limit the present invention. Other combinations and various modifications within the spirit or scope of the present invention may be made without departing from the spirit or scope of the present invention.

For convenience of expression, in the following examples, the group structures of the liquid crystal compounds are represented by the codes listed in Table 2:

TABLE 2 radical structural code of liquid crystal compounds

Compounds of the following formula are exemplified:

the structural formula is represented by the code listed in Table 1, and can be expressed as: nCCGF, wherein n in the code represents the number of C atoms of the left alkyl group, for example, n is 3, namely, the alkyl group is-C₃H₇(ii) a C in the code represents 1, 4-cyclohexylene, G represents 2-fluoro-1, 4-phenylene and F represents fluorine.

The abbreviated codes of the test items in the following examples are as follows:

cp clearing Point (nematic phase-transition temperature of isotropic phase,. degree.C.)

Δ n optical anisotropy (589nm, 25 ℃ C.)

Delta epsilon dielectric anisotropy (1KHz, 25 ℃ C.)

t_-30℃Low temperature storage time (h, -30 ℃ C.)

γ₁Rotational viscosity (mPa. multidot.s, 25 ℃ C.)

K₁₁Elasticity constant of splay

K₃₃Flexural elastic constant

γ₁/K₁₁Ratio of rotational viscosity to splay spring constant

Wherein the content of the first and second substances,

cp: obtained by melting point apparatus testing.

Δ n: the test result is obtained by using an Abbe refractometer under a sodium lamp (589nm) light source and at 25 ℃.

Δε：Δε＝ε_∥-ε_⊥Wherein, epsilon_∥Is a dielectric constant parallel to the molecular axis,. epsilon_⊥For the dielectric constant perpendicular to the molecular axis, test conditions: a VA type test box with the temperature of 25 ℃, the frequency of 1KHz and the box thickness of 6 mu m.

t_-30℃: the nematic liquid crystal medium was placed in a glass bottle, stored at-30 ℃ and the time recorded when crystal precipitation was observed.

γ₁: testing by using an LCM-2 type liquid crystal physical property evaluation system; and (3) testing conditions are as follows: at 25 ℃ and 240V, the thickness of the test box is 20 μm.

K₁₁And K₃₃: using an LCR instrument and a VA test box to test the C-V curve of the liquid crystal and calculating to obtain the C-V curve; and (3) testing conditions are as follows: the thickness of the box is 6 μm, and V is 0.1-20V.

The liquid crystal compounds of formula I of the present invention can be prepared by conventional organic synthesis methods, wherein the methods of introducing the target terminal groups, ring structures and linking groups into the starting materials are described in the following documents: organic Synthesis (Organic Synthesis, John Wiley & Sons Inc.), Organic reaction (Organic Reactions, John Wiley & Sons Inc.), and synthetic Organic Synthesis (Comprehensive Organic Synthesis, pegman Press), etc.

To form the linking group Z in the liquid-crystalline compound of the formula I₁、Z₂And Z₃The method of (1) can be referred to the following scheme, wherein MSG¹Or MSG²Is a 1-valent organic radical having at least one ring, a plurality of MSGs as used in the following schemes¹(or MSG)²) May be the same or different.

(1) Synthesis of single bonds

Arylboronic acid 1 is reacted with compound 2 synthesized by a known method in an aqueous solution of sodium carbonate in the presence of a catalyst such as tetrakis (triphenylphosphine) palladium (Pd (PPh)₃)₄) In the presence of) to obtain the single-bond compound IA. Or by reacting compound 3 synthesized by a known method with n-butyllithium (n-BuLi), followed by reaction with zinc chloride, and then in the presence of a catalyst such as dichlorobis (triphenylphosphine) palladium (PdCl)₂(PPh₃)₂) With compound 2) in the presence of a pharmaceutically acceptable salt thereof to prepare compound IA.

(2) Synthesis of-CO-O-and-O-CO-)

Compound 3 is reacted with n-butyllithium and then with carbon dioxide to obtain carboxylic acid 4. Compound IB having-CO-O-is synthesized by dehydrating compound 4 with phenol 5 synthesized by a known method in the presence of 1, 3-Dicyclohexylcarbodiimide (DCC) and 4-Dimethylaminopyridine (DMAP). Compounds having-O-CO-can also be synthesized by this method.

(3)-CF₂O-and-OCF₂Synthesis of (A)

With reference to m.kuroboshi et al, promo chemie (chem.lett.), 1992,827, compound 6 was obtained by treating compound IB with a sulfurizing agent such as lawson's reagent, and then compound 6 was fluorinated with hydrogen fluoride-pyridine (HF-Py) and N-bromosuccinimide (NBS) to synthesize a compound having-CF₂Compound IC of O-. Preparation of a compound having-CF by fluorination of compound 6 with (diethylamino) sulfur trifluoride (DAST) can also be carried out with reference to W.H.Bunnelle et al, proceedings of organic chemistry (J.org.chem), 1990, 55, 768₂Compound IC of O-. Can also be synthesized by these methods to have-OCF₂-a compound of (a).

(4) Synthesis of-CH

Compound 3 is reacted with N-butyllithium, followed by reaction with a formamide such as N, N-Dimethylformamide (DMF) to obtain aldehyde 7. Potassium tert-butoxide (t-BuOK) was reacted with phosphonium salt 8 synthesized by a known method to produce phosphonium salt and aldehyde 7 to obtain compound ID. The above method generates cis-isomer due to reaction conditions. It is to be understood that the cis isomer may be converted to the trans isomer by well-known methods as necessary.

(5)-CH₂CH₂Synthesis of (A)

Compound IE may be prepared by subjecting compound ID to a hydrogenation reaction using a catalyst such as palladium on carbon (Pd/C).

(6)-CH₂O-or-OCH₂Synthesis of (A)

Using sodium borohydride (NaBH)₄) Compound 7 is reduced to obtain compound 9. Then, compound 9 is halogenated with hydrobromic acid to obtain compound 10, or the hydroxyl group of compound 9 is protected with p-toluenesulfonic acid (TsOH) to obtain compound 11. Then, compound 10 or compound 11 is reacted with compound 5 in the presence of potassium carbonate to obtain compound IF. Can also be synthesized by these methods to have-OCH₂-a compound of (a).

As for rings such as 1, 4-cyclohexylene, 1, 3-dioxane-2, 5-diyl, 1, 4-phenylene, 2-fluoro-1, 4-phenylene, 2, 3-difluoro-1, 4-phenylene, 2, 5-difluoro-1, 4-phenylene, 2, 6-difluoro-1, 4-phenylene, 2,3,5, 6-tetrafluoro-1, 4-phenylene, starting materials are already commercially available or synthetic methods thereof are known in the art.

Preferred synthetic methods for representative compounds are set forth below.

Example 1

The synthetic route of compound I-1-1 is shown below:

step 1 preparation of Compounds of formula B-3

160g of the compound of the formula B-1 ((4-ethoxy-2, 3-difluorophenyl) boronic acid), 160.5g of the compound of the formula B-2 (2-bromo-6-fluorophenol) and 72g of sodium carbonate were charged in a 3L reaction flask and sufficiently dissolved with 1.2L of a mixed solvent composed of toluene, ethanol and water (the volume ratio of toluene, ethanol and water was 2:1: 1). 0.5g of dichloro-di-tert-butyl- (4-dimethylaminophenyl) phosphine palladium (II) is added under the protection of nitrogen, and the mixture is refluxed for 6 hours. After the reaction was completed, the reaction solution was cooled, 500mL of water was added for liquid separation, the aqueous phase was extracted with toluene, the organic phases were combined, the organic phase was washed with saturated brine to neutrality, dried, concentrated, and recrystallized from isopropanol to obtain 182.8g of a compound of formula B-3 (4 '-ethoxy-2', 3,3 '-trifluoro- [1, 1' -biphenyl ] -2-ol) as a white solid (purity: 99.35%, yield: 86%).

MS：164(20％)、191(13％)、240(100％)、268(70％)。

Step 2. preparation of Compound of formula B-4

A3L reaction flask was charged with 180g of the compound of formula B-3 and 180g of potassium carbonate, and was sufficiently dissolved with 800mL of N, N-dimethylformamide. The reaction was carried out at 130 ℃ for 12 h. After the reaction was completed, the reaction solution was cooled, 3L of water was added, stirred and suction-filtered to obtain a crude product, which was slurried with ethanol, suction-filtered and dried to obtain 142g of a compound of formula B-4 (3-ethoxy-4, 6-difluorodibenzo [ B, d ] furan) as a white solid (purity: 99.25%, yield: 85.4%).

MS：144(20％)、191(15％)、220(100％)、248(70％)。

Step 3. preparation of Compound of formula B-5

A2L reaction flask was charged with 120g of the compound of formula B-4 and dissolved well in 700mL of tetrahydrofuran under nitrogen. 168mL of n-butyllithium was added at-80 ℃ and the reaction was carried out for 3 hours while controlling the temperature at-80 ℃. 79.18g of triisopropyl borate are added and the reaction is carried out for 3h at the temperature of-80 ℃. The pH was adjusted to 2-3 by adding dilute hydrochloric acid, slurried once with 200mL of water, slurried once with 300mL of petroleum ether, suction-filtered, and the cake was dried to obtain 118.6g of a compound of formula B-5 ((7-ethoxy-4, 6-difluorodibenzo [ B, d ] furan-3-yl) boronic acid) as a white solid (purity: 99.04%, yield: 84%).

MS：43.9(100％)、206(33％)、236(100％)、263(25％)、292(35％)。

Step 4. preparation of Compounds of formula I-1-1

A1L reaction flask was charged with 60g of the compound of formula B-5, 45.5g of the compound of formula B-6 (3,4, 5-trifluorobromobenzene) and 15.5g of sodium carbonate, and sufficiently dissolved with 0.6L of a mixed solvent composed of toluene, ethanol and water (toluene, ethanol and water in a volume ratio of 2:1: 1). Under the protection of nitrogen, 0.2g of dichloro-di-tert-butyl- (4-dimethylaminophenyl) phosphine palladium (II) is added and reflux reaction is carried out for 4 hours. After completion of the reaction, the reaction solution was cooled, 300mL of water was added, liquid was separated, the aqueous phase was extracted with toluene, the organic phases were combined, the organic phase was washed with saturated brine to pH 7, dried, concentrated, and recrystallized from petroleum ether to obtain 65g of a compound of formula I-1-1 (3-ethoxy-4, 6-difluoro-7- (3,4, 5-trifluorophenyl) dibenzo [ b, d ] furan) (purity: 99.57%, yield: 84%) as a white solid.

MS：274(18％)、292(15％)、350(100％)、378(35％)。

According to the above synthesis method, the compound of formula B-6 can be replaced with a compound of formula B-12 shown in the following Table 3 to obtain the target compound I-1-2:

TABLE 3

Example 2

The synthetic route of compound I-3-5-1 is shown below:

step 1 preparation of Compounds of formula B-8

120g of the compound of the formula B-7 ((2, 3-difluoro-4 '-propyl- [1, 1' -biphenyl ] -4-yl) boronic acid), 160.5g of the compound of the formula B-2 (2-bromo-6-fluorophenol) and 83g of sodium carbonate were charged in a 3L reaction flask, and sufficiently dissolved with 1.2L of a mixed solvent composed of toluene, ethanol and water (the volume ratio of toluene, ethanol and water was 2:1: 1). 0.5g of dichloro-di-tert-butyl- (4-dimethylaminophenyl) phosphine palladium (II) is added under the protection of nitrogen, and the mixture is refluxed for 6 hours. After the reaction was completed, the reaction solution was cooled, 500mL of water was added for liquid separation, the aqueous phase was extracted 2 times with toluene, the organic phases were combined, the organic phase was washed with a saturated saline solution to neutrality, dried, concentrated, and recrystallized with a mixed solvent of toluene and ethanol (the volume ratio of toluene to ethanol was 1:1) to obtain 130g of a compound of formula B-8 (2 ', 3, 3' -trifluoro-4 "-propyl- [1,1 ': 4', 1" -terphenyl ] -2-ol) as a white solid (purity: 99.44%, yield: 87.3%).

MS：111(15％)、231(46％)、299(100％)、342(30％)。

Step 2 preparation of Compounds of formula B-9

A2L reaction flask was charged with 120g of the compound of formula B-8 and 120g of sodium carbonate, and was dissolved well with 800mL of N, N-dimethylformamide. The reaction was carried out at 130 ℃ for 12 h. After the reaction was completed, the reaction solution was cooled, 3L of water was added, stirred and suction-filtered to obtain a crude product, which was slurried with ethanol, suction-filtered and dried to obtain 101g of a compound of formula B-9 (4, 6-difluoro-3- (4-propylphenyl) dibenzo [ B, d ] furan) (purity: 99.15%, yield: 89.3%) as a white solid.

MS：119(26％)、203(36％)、279(100％)、322(33％)。

Step 3. preparation of Compound of formula B-10

A2L reaction flask was charged with 95g of the compound of formula B-9 and dissolved well with 600mL of tetrahydrofuran. 141mL of n-butyllithium were added at-80 ℃ under nitrogen protection, and the temperature was controlled at-80 ℃ for 3 h. 49.5g of triisopropyl borate is added, and the temperature is controlled to-80 ℃ for reaction for 3 hours. Diluted hydrochloric acid was added to adjust pH 2-3, followed by beating with water and petroleum ether in this order, suction filtration, and drying of the cake to obtain 90g of a compound of formula B-10 ((4, 6-difluoro-7- (4-propylphenyl) dibenzo [ B, d ] furan-3-yl) boronic acid) (purity: 99.26%, yield: 83.4%) as a white solid.

MS：247(85％)、321(100％)、323(60％)、366(30％)。

Step 4. preparation of Compound of formula I-3-5-1

Into a 2L reaction flask were charged 80g of the compound of formula B-10, 46.3g of the compound of formula B-11 (3, 4-difluorobromobenzene) and 18g of sodium carbonate, and sufficiently dissolved with 0.8L of a mixed solvent composed of toluene, ethanol and water (toluene, ethanol and water in a volume ratio of 2:1: 1). Under the protection of nitrogen, 0.1g of dichloro-di-tert-butyl- (4-dimethylaminophenyl) phosphine palladium (II) is added and reflux reaction is carried out for 4 hours. After completion of the reaction, the reaction solution was cooled, 300mL of water was added, liquid separation was performed, the aqueous phase was extracted with toluene, the organic phases were combined, the organic phase was washed with saturated brine to pH 7, dried, concentrated, and recrystallized from petroleum ether to obtain 70g of a compound of formula I-3-5-1 (3- (3, 4-difluorophenyl) -4, 6-difluoro-7- (4-propylphenyl) dibenzo [ b, d ] furan) (purity: 99.69%, yield: 73.7%) as a white solid.

MS：119(24％)、315(39％)、321(75％)、391(100％)、434(37％)。

The liquid crystal compound of the general formula I prepared in the above example and the compound DB-1 (structural formula:respectively mixing the mixture with mother liquid crystal according to the weight ratio of 10% to 90% to form a mixture. The values of the respective performance parameters of the test compounds were calculated by extrapolation method (extrapolated method), where extrapolated values of Cp, Δ n and Δ ∈ are ((measured value of mixture) -0.9 × (measured value of mother liquid crystal))/0.1, γ₁Extrapolated value of (2) < 10 >^{10(lgA-0.9lgB)}Wherein A is γ of the mixture₁B is gamma of a mother liquid crystal₁. The clearing points Cp, optical anisotropy Deltan, dielectric anisotropy Deltaepsilon and rotational viscosity gamma are carried out according to the method₁And (5) deducing the value of the equal performance parameter.

The parent liquid crystal is a liquid crystal composition as shown in table 4 below:

TABLE 4

The extrapolation of the liquid crystal performance parameters of the above compounds is shown in Table 5 below:

TABLE 5

Generic code	Component code	Cp	Δn	γ1	Δε
						DB-1	2OB(O)O2	55	0.189	126	-13.5
I-1-1	2OB(O)UF	80	0.210	130	-16
						I-1-2	2OB(O)POCF3	75.3	0.213	133	-17.5
I-3-5-1	3PB(O)GF	120.6	0.215	150	-17

As can be seen from table 5 above, the liquid crystal compound of formula I of the present invention has a larger clearing point, a larger optical anisotropy, and a larger absolute value of dielectric anisotropy while maintaining a suitable rotational viscosity, as compared to the liquid crystal compounds of the prior art.

Application comparative example 1

The liquid crystal composition of application comparative example 1 was prepared by using the compounds listed in table 6 and their weight percentages, and filled between two substrates of a liquid crystal display to perform a performance test.

TABLE 6 formulation of liquid crystal composition and results of performance parameter test

Application example 1

The liquid crystal composition of application example 1 was prepared by using the compounds listed in table 7 and their weight percentages, and filled between two substrates of a liquid crystal display to perform a performance test.

TABLE 7 formulation of liquid crystal composition and results of performance parameter test

Comparative application example 2

The liquid crystal composition of application comparative example 2 was prepared by using the compounds listed in table 8 and their weight percentages, and filled between two substrates of a liquid crystal display to perform a performance test.

TABLE 8 formulation of liquid crystal composition and results of performance parameter test

Application example 2

The liquid crystal composition of application example 2 was prepared by using the compounds listed in table 9 and their weight percentages, and filled between two substrates of a liquid crystal display to perform a performance test.

TABLE 9 formulation of liquid crystal composition and results of testing performance parameters

Application example 3

The liquid crystal composition of application example 3 was prepared by using the compounds listed in table 10 and their weight percentages, and filled between two substrates of a liquid crystal display to perform a performance test.

TABLE 10 formulation of liquid crystal composition and results of performance parameter test

Application example 4

The liquid crystal composition of application example 4 was prepared by using the compounds listed in Table 11 and their weight percentages, and filled between two substrates of a liquid crystal display to perform a performance test.

TABLE 11 formulation of liquid crystal composition and results of performance parameter test

Application example 5

The liquid crystal composition of application example 5 was prepared by using the compounds listed in table 12 and their weight percentages, and filled between two substrates of a liquid crystal display to perform a performance test.

TABLE 12 formulation of liquid crystal composition and results of testing performance parameters

By comparing the application comparative example 1 with the application example 1 and comparing the application comparative example 2 with the application example 2, the liquid crystal composition provided by the invention has larger clearing point, larger optical anisotropy, larger absolute value of dielectric anisotropy, larger elastic constant and smaller ratio of rotational viscosity to splay elastic constant under the condition of maintaining proper low-temperature storage stability and proper rotational viscosity, so that a liquid crystal display device comprising the liquid crystal composition has wider nematic phase temperature range, better contrast, lower threshold voltage and shorter response time.

The above embodiments are merely illustrative of the technical concept and features of the present invention, and the present invention is not limited thereto, and equivalent changes and modifications made according to the spirit of the present invention should be covered thereby.