CN106635051B - Liquid-crystal compounds with negative dielectric anisotropic and its application - Google Patents

Abstract

The present invention provides a kind of liquid-crystal compounds of the general formula I with negative dielectric anisotropic; the liquid-crystal compounds has big dielectric anisotropy absolute value, low viscosity, good intersolubility and good photostability and low-temperature stability; and the preparation process of the liquid-crystal compounds of general formula I of the present invention; raw material is easy to get; synthetic route is simple and practicable; it is suitble to scale industrial production; the present invention also provides a kind of liquid-crystal composition including the liquid-crystal compounds, the liquid-crystal composition has good liquid crystal property.

Description

Liquid crystal compound with negative dielectric anisotropy and application thereof

Technical Field

The invention relates to a liquid crystal compound, in particular to a liquid crystal compound with negative dielectric anisotropy and a synthesis method and application thereof.

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. Typical examples of the night view display mode include 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), CSH (color super homeotropic), and the like. The device is classified into a PM (passive matrix) type and an AM (active matrix) type according to a 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. The types of TFTs are 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 are classified into a reflection type using natural light, a transmission type using backlight, and a semi-transmission type using both light sources of natural light and backlight, depending on the type of light source.

Among these display modes, IPS mode, ECB mode, VA mode, CSH mode, and the like are different from TN mode or STN mode which are currently used in general in that the former uses a liquid crystal material having negative dielectric anisotropy. Among these display systems, VA display by AM driving is particularly applied to display elements requiring high speed and wide viewing angle, and among them, liquid crystal elements such as televisions are most expected.

The liquid crystal material used in any display mode is required to have a low driving voltage, a high response speed, a wide operating temperature range, a large absolute value of negative dielectric anisotropy, a high phase transition temperature, and good miscibility. However, the conventional liquid crystal composition has a highly conjugated molecular structure and tends to have poor compatibility with other liquid crystal materials, and thus it is difficult to use the liquid crystal composition as a component of a liquid crystal composition having good electrical characteristics. In addition, a liquid crystalline compound used as a component of a liquid crystal composition which requires light stability, such as a thin film transistor liquid crystal display device, is required to have high stability. In contrast, 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.

For a long time, a large number of liquid crystal compounds in which hydrogen on the benzene ring is substituted have been studied as a component of a liquid crystal composition having negative dielectric anisotropy which can be used for a liquid crystal display element.

Osman, m.a. at molec. crystals liq. crystals,82,295. negative dielectric anisotropy compounds of ref.1 structure are disclosed:

the compound Ref.1 has a large negative dielectric anisotropy due to the two cyano groups on the side of the molecule (literature value-20). This document also indicates that such lateral dicyano-based negative dielectric anisotropy compounds have the following disadvantages: 1) the viscosity is high; 2) the miscibility with the liquid crystal monomer is poor; 3) the light stability is poor. Due to the above disadvantages, the use of such negative compounds is limited.

The fluorine-containing negative compounds of Ref.2, Ref.3 were proposed by Reiffenrath et al in liquid crystals, 1989, Vol.5, No.1,159-170 to avoid the disadvantages of dicyano negative compounds:

although side fluorine-containing negative compounds such as Ref.2 and Ref.3 avoid the disadvantages of dicyano negative compounds, they cause the problem that the negative dielectric anisotropy value is too small (Ref.2 dielectric anisotropy value is-4.1, Ref.3 dielectric anisotropy value is-6.0). Therefore, lateral fluorine-containing compounds with large negative dielectrics are still sought.

Therefore, in order to meet the increasing application demands, there is a continuing need in the art for improved liquid crystal compounds of negative dielectric anisotropy.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a liquid crystal compound which has a large absolute value of dielectric anisotropy, low viscosity, higher voltage holding ratio, good intersolubility and good light stability and low-temperature stability, so that a composition containing the liquid crystal compound has the advantages of large dielectric anisotropy, low threshold voltage, high response speed, high contrast, good intersolubility and good light stability and low-temperature stability.

Another object of the present invention is to provide a method for synthesizing the above liquid crystal composition.

The invention also aims to provide the liquid crystal composition prepared from the liquid crystal compound and an application of the liquid crystal composition in a display.

The technical scheme is as follows: in order to accomplish the above object of the present invention, the present invention provides a compound having negative dielectric anisotropy, the compound having a structure of general formula i:

wherein,

R₁independently represent a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 10 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 10 carbon atoms, wherein one or more-CH₂-may be substituted by-O-, with the proviso that the oxygen atoms are not directly attached;

X₁and X₂Each independently represents-O-or-CH₂-；

Z represents a single bond, -CH₂O-、-CH₂CH₂-, -COO-or-CH ═ CH-.

In some embodiments of the invention, R is₁Independently represent a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 6 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 6 carbon atoms, wherein one or more-CH₂-may be substituted by-O-, with the proviso that the oxygen atoms are not directly attached.

In some embodiments of the invention, Z represents a single bond, -CH₂O-or-CH₂CH₂-。

In some embodiments of the invention, the compound of formula I is selected from the group consisting of one or more of the following formulae I-A to I-F:

and

wherein,

the R is₁Independently represent a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 6 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 6 carbon atoms.

In some embodiments of the invention, the compounds of formula I-A are preferably selected from the group consisting of one or more of the following structures:

and

in some embodiments of the invention, the compounds of formula I-B are preferably selected from the group consisting of one or more of the following structures:

and

in some embodiments of the invention, the compounds of formulae I-C are preferably selected from the group consisting of one or more of the following structures:

and

in some embodiments of the invention, the compounds of formulae I-D are preferably selected from the group consisting of one or more of the following structures:

and

in some embodiments of the invention, the compounds of formulae I-E are preferably selected from the group consisting of one or more of the following structures:

and

in some embodiments of the invention, the compounds of formulae I-F are preferably selected from the group consisting of one or more of the following structures:

and

in another aspect of the present invention, there is provided a liquid crystal composition comprising the liquid crystal compound of formula I of the present invention.

In some embodiments of the present invention, the liquid crystal composition further comprises one or more of the group consisting of formulas II, III, and/or IV:

and

wherein,

the R is₂、R₃、R₄、R₅、R₆And R₇The same or different, each independently represents a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 10 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 10 carbon atoms, wherein one or more-CH₂-may be substituted by-O-, with the proviso that the oxygen atoms are not directly attached;

m and n are the same or different and each independently represents 0 or 1.

Another aspect of the present invention provides a display device comprising the liquid crystal composition of the present invention.

The invention also provides application of the liquid crystal composition in VA, FFS, IPS and PSVA display modes.

Has the advantages that: compared with other negative liquid crystal compounds in the prior art, the liquid crystal compound with the general formula I has larger absolute value of dielectric anisotropy, low viscosity and high voltage holding ratio, and the composition containing the liquid crystal compound has large dielectric anisotropy, low threshold voltage, high response speed, high contrast, good intersolubility, good light stability and low-temperature stability; in addition, the preparation process of the liquid crystal compound with the general formula I has the advantages of easily obtained raw materials, simple and feasible synthetic route and suitability for large-scale industrial production.

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 1:

TABLE 1 radical structural code of liquid crystal compounds

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

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

Δ n: refractive index anisotropy (589nm, 20 ℃ C.)

Δ ε: dielectric anisotropy (1KHz, 25 ℃ C.)

γ 1: rotational viscosity (mpa.s, 25 ℃ C. unless otherwise stated)

Wherein, the refractive index anisotropy is obtained by testing an Abbe refractometer under a sodium lamp (589nm) light source at 25 ℃; the dielectric test cell was of the type TN90, the cell thickness being 7 μm.

and the delta epsilon ⊥ -epsilon ⊥, wherein epsilon ⊥ is the dielectric constant parallel to the molecular axis, epsilon ⊥ is the dielectric constant vertical to the molecular axis, and the test conditions are that the temperature is 25 ℃, the temperature is 1KHz, the test box is TN90 type, and the box thickness is 7 mu m.

The liquid-crystalline compounds of the formula I prepared in the examples below were tested for optical anisotropy and clearing point and for extrapolation parameters as follows:

a commercial liquid crystal with a serial number of TS023, produced by Jiangsu Hecheng display science and technology Limited is selected as a matrix, a liquid crystal compound shown as a general formula I is dissolved in the matrix liquid crystal (host) according to the weight proportion of 10 percent, the optical anisotropy, clearing point and dielectric anisotropy of the mixture are tested, and liquid crystal performance data of the liquid crystal compound shown as the general formula I are externally obtained according to the linear relation according to the adding proportion of the matrix.

The parent liquid crystal (host) is 20% of the following compound: 40%: mixing the following components in a ratio of 40%:

and

the test results of the performance parameters of the mother liquid crystal are as follows:

Cp：112 Δn：0.08 Δε：5.0 VHR：98.1％。

example 1

The synthetic route of compound I-A-7 is shown below:

1) synthesis of Compound B

Adding 10g of compound A (2, 3-difluoro-4-ethoxyphenylboronic acid), 9.7g of 2, 3-difluorobromobenzene, 100ml of toluene, 50ml of ethanol, 50ml of water, 21.2g of sodium carbonate into a 500ml three-necked bottle, adding 0.3g of Pd (PPh3)4 under the protection of nitrogen, heating and refluxing for 6h, separating liquid, washing with water, and carrying out column chromatography to obtain a white solid compound B11.5 g, wherein GC content is more than 97%, yield: 85.3 percent

2) Synthesis of Compound C

Adding 6.7g of compound B and 100ml of anhydrous tetrahydrofuran into a 250ml three-necked bottle, cooling to-78 ℃ under the protection of nitrogen, dropwise adding 10.5ml of n-butyl lithium n-hexane solution (2.4mol/L), stirring for 2h under heat preservation, dropwise adding a mixed solution of 1.8g of tetrahydropyran-2-one (CAS #542-28-9) and 10ml of anhydrous tetrahydrofuran, controlling the temperature to-65-70 ℃, stirring for 1h under heat preservation after dropwise adding is finished, then pouring a reaction solution into an ice water mixture, extracting by using methyl tert-butyl ether, separating, washing with water, evaporating the solvent to obtain 8g of compound C (0.02mol), and directly using the compound C for the next reaction without purification.

3) Synthesis of Compound I-A-7

Adding 8g (0.02mol) of the compound C obtained in the previous step and 100ml of dichloromethane into a 250ml three-necked flask, cooling to-75 ℃, adding a mixed solution of 5.8g of triethylsilane and 10ml of dichloromethane, then dropwise adding 0.05mol of boron trifluoride diethyl etherate, keeping the temperature and stirring for 3 hours, naturally heating to-10 ℃, carefully pouring the reaction liquid into a mixture of sodium bicarbonate and ice water, separating liquid, washing with water, and purifying by column chromatography to obtain 3g of a white solid, namely the compound I-A-7, wherein the GC content is more than 99%, and the yield is as follows: 42 percent.

Characterization data for compounds I-A-7:

MS:M⁺354(42％)297(100％)269(63％)241(16％)。

according to the above synthesis method, the compounds shown in the following table 1 can be used to obtain the target compound by transforming the compound C and the compound a:

TABLE 1

The liquid crystal properties of the above target compounds are as follows:

Ⅰ-A-7 Δn：0.155 Δε：-9.8；

Ⅰ-A-6 Δn：0.16 Δε：-10.5；

Ⅰ-A-8 Δn：0.155 Δε：-9.5；

Ⅰ-A-9 Δn：0.152 Δε：-9.2；

Ⅰ-A-1 Δn：0.128 Δε：-8.2；

Ⅰ-A-3 Δn：0.124 Δε：-8.0。

data of representative compounds of the formula I-A are provided in example 1, and it can be seen from the data of the liquid crystal compounds I-A-9, I-A-11, I-B-9, I-B-10, I-C-19 and I-D-19 in example 1 that the liquid crystal compounds contained in the formula I-A have large absolute values of dielectric anisotropy.

Example 2

The synthetic route of compounds I-E-7 is shown below:

1) synthesis of Compound D

Adding 13.5g of compound B and 150ml of anhydrous tetrahydrofuran into a 500ml three-neck flask, cooling to-78 ℃ under the protection of nitrogen, dropwise adding 20.8ml of n-butyl lithium n-hexane solution (2.4mol/L), continuously keeping the temperature of-78 ℃ after dropwise adding, stirring for 1.5h, then dropwise adding a mixture of 13g of triisobutyl borate and 25ml of anhydrous tetrahydrofuran, keeping the temperature of-78 ℃ after dropwise adding, stirring for 0.5h, naturally heating to room temperature, and carrying out aftertreatment to obtain a white-like solid, wherein the yield of the compound D11 g is more than 95 percent, and the HPLC (high performance liquid chromatography) is as follows: 70 percent.

2) Synthesis of Compound E

Adding 11g of compound D, 150ml of dichloromethane and 50ml of dioxane into a 500ml three-neck flask, cooling to 0 ℃, dropwise adding 30% hydrogen peroxide solution 12ml, controlling the temperature within 10 ℃, stirring at room temperature for 3h after dropwise adding is finished, performing post-treatment to obtain a slightly pink solid, wherein the compound E10 g is obtained, GC is more than 97%, and the yield is as follows: 100 percent.

3) Synthesis of Compound I-E-7

Adding 10g of compound E, 100ml of anhydrous tetrahydrofuran, 11g of triphenylphosphine and 4.1g of tetrahydropyran-2-methanol into a 500ml three-necked bottle, cooling to 0 ℃ under the protection of nitrogen, dropwise adding a mixture of 7.3g of diethyl azodicarboxylate and 30ml of anhydrous tetrahydrofuran, controlling the temperature to be within 10 ℃, stirring at room temperature for 3 hours after dropwise adding is finished, performing post-treatment, and purifying by column chromatography to obtain 7.3g of white solid, namely compound I-E-7, wherein GC is more than 99%, and the yield is as follows: 54.3 percent.

Characterization data for compounds I-E-7:

MS:M⁺384(45％)286(13％)258(21％)99(52％)85(100％)。

example 3

Compounds I-A-7, I-A-1, I-E-7, and V were mixed with the parent liquid crystal (host) at a ratio of 10:90, and the liquid crystal parameters of each compound were measured by extrapolation as shown in Table 2 below:

TABLE 2

	Δn	Δε	γ1
				Ⅰ-A-7	0.155	-9.8	291
Ⅰ-A-1	0.128	-8.2	208
				Ⅰ-E-7	0.156	-12.2	454
Ⅴ	0.152	-9.6	439
				host	0.08	5.0	116

Compared with the compound V, the compound has a low gamma 1 value when the dielectric anisotropy is similar; and when the gamma value is close, the absolute value of the dielectric anisotropy is larger; the detection data results of the above embodiments show that the liquid crystal compound provided by the invention can achieve the invention purposes of large dielectric anisotropy and low viscosity, so that the liquid crystal composition comprising the liquid crystal compound provided by the invention has higher response speed and lower threshold voltage, and a very good technical effect is obtained.

Example 4

The liquid crystal composition of example 4 was prepared according to the compounds and weight percentages listed in table 3, and filled between two substrates of a liquid crystal display for performance testing, and the test data are shown in the following table:

TABLE 3 liquid crystal composition formula and its test performance

The data of example 4 show that when the compound of the present invention is applied to a liquid crystal composition, the liquid crystal composition has good liquid crystal performance, and the compound of the present invention achieves very good technical effects.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A compound having negative dielectric anisotropy, the compound having the general structure i:

wherein,

R₁independently represent a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 10 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 10 carbon atoms, whereinOne or more-CH₂-may be substituted by-O-, with the proviso that the oxygen atoms are not directly attached;

X₁and X₂Each independently represents-O-or-CH₂-；

Z represents a single bond, -CH₂O-、-CH₂CH₂-, -COO-or-CH ═ CH-.

2. The compound having negative dielectric anisotropy according to claim 1, wherein R is₁Independently represent a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 6 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 6 carbon atoms, wherein one or more-CH₂-may be substituted by-O-, with the proviso that the oxygen atoms are not directly attached.

3. The compound having negative dielectric anisotropy according to claim 1, wherein Z represents a single bond, -CH₂O-or-CH₂CH₂-。

4. A compound having negative dielectric anisotropy according to any one of claims 1 to 3, characterized in that the compound of formula i is selected from the group consisting of one or more of the following formulae i-a to i-F:

wherein,

the R is₁Independently represent a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 6 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 6 carbon atoms.

5. A liquid crystal composition comprising the compound having negative dielectric anisotropy according to any one of claims 1 to 4.

6. The liquid crystal composition of claim 5, further comprising one or more of the group consisting of formulae II, III, and/or IV:

wherein,

the R is₂、R₃、R₄、R₅、R₆And R₇The same or different, each independently represents a substituted or unsubstituted, linear or branched alkyl or alkoxy group of 1 to 10 carbon atoms, a substituted or unsubstituted, linear or branched alkenyl or alkenyloxy group of 2 to 10 carbon atoms, wherein one or more-CH₂-may be substituted by-O-, with the proviso that the oxygen atoms are not directly attached;

m and n are the same or different and each independently represents 0 or 1.

7. A display device comprising the liquid crystal composition of claim 5.

8. A display device comprising the liquid crystal composition of claim 6.

9. Use of the liquid crystal composition of claim 5 in VA, FFS, IPS, PSVA display modes.

10. Use of the liquid crystal composition of claim 6 in VA, FFS, IPS, PSVA display modes.