WO2017071575A1 - Liquid crystal compound having negative dielectric anisotropy and application thereof - Google Patents

Abstract

Provided is a liquid crystal compound of general formula I having a negative dielectric anisotropy. The liquid crystal compound has a large dielectric anisotropy absolute value, a high voltage holding ratio, a good intersolubility, and a good photostability and low temperature stability; moreover, the preparation process of the liquid crystal compound of general formula I of the present invention has readily available raw materials and a simple and practicable synthetic route, and is suitable for large-scale industrial production. Further provided is a liquid crystal composition comprising the liquid crystal compound. The liquid crystal composition has good liquid crystal properties.

Description

Liquid crystal compound with negative dielectric anisotropy and application thereof Technical field

The present invention relates to a liquid crystal compound, particularly a liquid crystal compound having negative dielectric anisotropy, a method for synthesizing the same, and an application thereof.

Background technique

The liquid crystal display element can be used in various household electric appliances, measurement equipment, automobile panels, word processors, computers, printers, televisions, and the like represented by watches and clocks and electronic calculators. As a night view display mode, in a representative manner, PC (phase change), TN (twist nematic), STN (super twisted nematic), ECB (electrically controlled) can be cited. Birefringence, electronically controlled birefringence, OCB (optically compensated bend), IPS (in-plane switching), VA (vertical alignment), CSH (color super homeotropic) ) and other class patterns. According to the driving method of components, it is divided into PM (passive matrix) type and AM (active matrix) type. PM is divided into static (static) and multiplex (multiplex) types. The AM is classified into a TFT (thin film transistor), a MIM (metal insulator metal), and the like. The types of TFTs are amorphous silicon and polycrystalline silicon. The latter is classified into a high temperature type and a low temperature type according to a manufacturing process. The liquid crystal display element is classified into a reflection type using natural light, a transmission type using a backlight, and a semi-transmissive type using both natural light and backlight depending on the type of the light source.

Among these display modes, the IPS mode, the ECB mode, the VA mode, or the CSH mode are different from the conventional TN mode or the STN mode in that the former uses a liquid crystal material having a negative dielectric anisotropy. Among these display modes, in particular, an AM-driven VA-type display is used in a display element requiring a high-speed and wide viewing angle, and among them, the most desirable one is application to a liquid crystal element such as a television.

Regardless of the display mode, the liquid crystal material used 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 mutual solubility. . However, in the prior art, a highly conjugated molecular structure has a tendency to be inferior in compatibility with other liquid crystal materials, and is difficult to be used as a constituent element of a liquid crystal composition having good electrical characteristics. In addition, a liquid crystal compound used as a constituent element of a liquid crystal composition requiring light stability such as a liquid crystal display device of a thin film transistor type is required to have high stability. On the other hand, a liquid crystal display element containing a liquid crystal composition having a large absolute value of dielectric anisotropy can lower the basic voltage value, lower the driving voltage, and further reduce the power consumption.

A large number of hydrogen-substituted liquid crystal compounds on a benzene ring have been studied for a long time 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., in Molec. crystals liq. Crystals, 82, 295. discloses a negative dielectric anisotropic compound of the Ref. 1 structure:

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

Reiffenrath et al., Liquid Crystals, 1989, Vol. 5, No. 1, 159-170, propose fluorine-containing negative compounds of Ref. 2, Ref. 3 to avoid the disadvantages of bis-cyano-negative compounds:

Although the side fluorine-containing negative compounds such as Ref.2 and Ref.3 avoid the disadvantages of the bis-cyano-negative compound, the negative dielectric anisotropy value is too small (Ref. 2 dielectric anisotropy literature). The value is -4.1, and the Ref. 3 dielectric anisotropy literature value is -6.0). Therefore, compounds with large negative dielectric side fluorine species still need to be explored.

Therefore, in order to meet the increasing demand for applications, there is a need in the art for liquid crystal compounds that continuously improve negative dielectric anisotropy.

Summary of the invention

OBJECT OF THE INVENTION: It is an object of the present invention to provide a liquid crystal compound having a large dielectric anisotropy absolute value, a low viscosity, a high voltage holding ratio, good mutual solubility, and good light stability. And low temperature stable liquid crystal compound, such that the composition containing the liquid crystal compound has large dielectric anisotropy, low threshold voltage, fast response speed, high contrast, good mutual solubility, and good light stability And low temperature stability.

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

Still another object of the present invention is to provide use of the above liquid crystal compound for preparing a liquid crystal composition and a display containing the same.

Technical Solution: In order to accomplish the above object, the present invention provides a compound having a negative dielectric anisotropy, the compound having the structure of Formula I:

among them,

R ₁ and R _{2 are the} same or different and each independently represents an alkyl group of 1 to 10 carbon atoms;

X ₁ and X _{2 are} each different and independently represent -O- or -CH ₂ -;

Z represents a single bond, -CH ₂ O-, -CH ₂ CH ₂ -, -COO- or -CH=CH-.

In some embodiments of the invention, R ₁ and R _{2 are the} same or different and each independently represents an alkyl group of 1 to 6 carbon atoms.

In some embodiments of the present invention, the Z represents a single bond, -CH ₂ O- or -CH ₂ CH ₂ -.

In some embodiments of the present invention, the Z represents a single bond or -CH ₂ CH ₂ -.

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 through I-F:

as well as

among them,

The R1 and R2 are the same or different and each independently represents an alkyl group of 1 to 6 carbon atoms.

In some embodiments of the invention, the compound of Formula I is preferably selected from the group consisting of one or more of the following formulae:

as well as

among them,

The R1 and R2 are the same or different and each independently represents an alkyl group of 1 to 6 carbon atoms.

In some embodiments of the invention, the compound of Formula I-A is preferably selected from the group consisting of one or more of the following structures:

as well as

In some embodiments of the invention, the compound of Formula I-B is preferably selected from the group consisting of one or more of the following structures:

as well as

In some embodiments of the invention, the compound of Formulas I-C is preferably selected from the group consisting of one or more of the following structures:

as well as

In some embodiments of the invention, the compound of Formulas I-D is preferably selected from the group consisting of one or more of the following structures:

as well as

In some embodiments of the invention, the compound of Formulas I-E is preferably selected from the group consisting of one or more of the following structures:

as well as

In some embodiments of the invention, the compound of Formulas I-F is preferably selected from the group consisting of one or more of the following structures:

as well as

Another aspect of the present invention provides a liquid crystal composition comprising the liquid crystal compound of the formula I of the present invention.

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

as well as

among them,

The R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R _{8 are the} same or different and 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 -CH ₂ - may be substituted by -O-, provided that the oxygen atom is not Directly connected;

The 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.

Another aspect of the present invention provides an application comprising the liquid crystal composition of the present invention in VA, FFS, IPS, PSVA display modes.

Advantageous Effects: The liquid crystal compound of the formula I provided by the present invention and other negative liquid crystal compounds of the prior art Compared with a larger absolute value of dielectric anisotropy, a low viscosity, and a high voltage holding ratio, the composition containing the liquid crystal compound has large dielectric anisotropy, low threshold voltage, and fast response speed. High contrast, good mutual solubility and good light stability and low temperature stability; and the preparation process of the liquid crystal compound of the formula I of the invention, the raw materials are easy to obtain, the synthesis route is simple and easy, and it is suitable for large-scale industrial production.

detailed description

The invention will now be described in connection with specific embodiments. It is to be understood that the following examples are illustrative of the invention and are not intended to limit the invention. Other combinations and various modifications within the inventive concept can be made without departing from the spirit or scope of the invention.

For ease of expression, in the following examples, the group structure of the liquid crystal compound is represented by the codes listed in Table 1:

Table 1 Group structure code of liquid crystal compound

The shorthand code for the test project in the following examples is as follows:

Clearing point (nematic-isotropic phase transition temperature)

Cp:

Degree, °C)

Δn refractive index anisotropy (589nm, 20°C)

Δε dielectric anisotropy (1KHz, 25°C)

VHR initial voltage retention rate (%)

Among them, the refractive index anisotropy was measured at 25 ° C under a sodium light (589 nm) light source using an Abbe refractometer; the dielectric test box was a TN90 type, and the cell thickness was 7 μm.

Δε=ε‖-ε⊥, where ε‖ is the dielectric constant parallel to the molecular axis, ε⊥ is the dielectric constant perpendicular to the molecular axis, test conditions: 25°C, 1KHz, test box is TN90 type, box thickness 7μm.

VHR (initial) is tested using TOY06254 liquid crystal physical property evaluation system; pulse voltage: 5V 6HZ, test temperature is 60 ° C, test unit period is 166.7 ms;

The liquid crystal compounds of the general formula I prepared by the following examples were tested for optical anisotropy and clearing points and the extrapolation parameters were determined as follows:

The commercial liquid crystal No. TS023 produced by Jiangsu Hecheng Display Technology Co., Ltd. was selected as the precursor, and the liquid crystal compound represented by Formula I was dissolved in the parent liquid crystal (10% by weight) to test the optical anisotropy of the mixture. Clearing point and dielectric anisotropy, and liquid crystal performance data of the liquid crystal compound represented by Formula I was extrapolated according to a linear relationship according to the ratio added in the matrix.

The parent liquid crystal (host) is obtained by mixing the following compounds in a ratio of 20%:40%:40%:

as well as

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

Cp: 112 Δn: 0.08 Δε: 5.0 VHR: 98.1%.

Example 1

The synthetic route of compound I-A-9 is as follows:

1) Synthesis of Compound B

In a 500 ml three-necked flask, 8.6 g of Compound A, 9.7 g of 2,3-difluorobromobenzene, 100 ml of toluene, 50 ml of ethanol, 50 ml of water, 21.2 g of sodium carbonate, and 0.3 g of Pd(PPh3)4 were added while heating under nitrogen. After refluxing for 6 h, the mixture was separated, washed with water, and then purified by column chromatography to yield white solid compound B 10.1 g, GC>97%, yield: 84.2%

2) Synthesis of Compound D

In a 250ml three-necked flask, add 6g of compound B, 100ml of anhydrous tetrahydrofuran, under nitrogen protection, cool to -78 ° C, add 10.5ml of n-hexane solution of n-butyllithium (2.4mol / L), stir for 2h, add dropwise a mixed solution of 2.6 g of compound C and 10 ml of anhydrous tetrahydrofuran, and controlled to between -65 and -70 ° C. After the completion of the dropwise addition, the mixture was stirred for 1 hour, and then the reaction solution was poured into an ice-water mixture, methyl tert-butyl The ethyl ether was extracted, separated, washed with water, and evaporated to give a compound D 8 g (0.02 mol), which was used in the next step without purification.

3) Synthesis of Compound I-A-9

In a 250 ml three-necked flask, 8 g (0.02 mol) of Compound D obtained in the above step, 100 ml of dichloromethane was added, and the temperature was lowered to -75 ° C, and a mixed solution of 5.8 g of triethylsilane and 10 ml of dichloromethane was added, and then 0.05 mol was added dropwise. The boron trifluoride etherate was stirred for 3 hours, and the temperature was naturally raised to -10 ° C. The reaction mixture was poured into a mixture of sodium hydrogencarbonate and ice water, and the mixture was separated, washed with water and purified by column chromatography to give white compound 3.2 g. I-A-9, GC>99%, yield: 43.7%.

Characterization data of compound I-A-9:

MS: M ⁺ 366 (41%) 267 (100%) 240 (55%).

According to the above synthesis method, the compound represented by the following Table 1 can be converted by the compound C and the compound A to obtain other target compounds:

Table 1

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

Representative compound data of the formulae I-A, I-B, I-C and I-D are provided in Example 1, by the liquid crystal compounds I-A-9, I-A-11 of Example 1, The data of I-B-9, I-B-10, I-C-19 and I-D-19 can be seen that the liquid crystals contained in the formulae I-A, I-B, I-C and I-D The compounds all have large absolute values of dielectric anisotropy.

Example 2

Compound I-A-9, compound I-A-11, compound I-B-9, compound V and parent liquid crystal (host) were mixed at a ratio of 10:90, and the liquid crystal parameters of each compound were tested by extrapolation as shown in Table 2 below. Show:

Table 2

	Cp(°C)	Δn	Δε	VHR (%)	T -10 ° C
I-A-9	75.2	0.126	-8.2	97.0	>144h
I-A-11	71.6	0.12	-8.0	97.1	>144h
I-B-9	62.6	0.124	-8.5	97.0	>144h
V	183	0.18	-5.7	94.0	<72h
Host	112	0.08	5.0	98.1	-

Note: T _{-10 ° C} indicates the storage stability of the mixture of the compounds I-A-9, I-A-11, I-B-9, V and the parent liquid crystal host in a ratio of 10:90 at -10 °C.

Compared with the prior art compound V, the compound of the invention has a larger absolute value of dielectric anisotropy and higher Voltage retention and stable low temperature stability.

Example 3

The liquid crystal composition of Example 3 was prepared according to each compound and weight percentage listed in Table 3, and was filled in the performance test between the two substrates of the liquid crystal display. The test data is shown in the following table:

Table 3 liquid crystal composition formula and its test performance

Example 4

The liquid crystal composition of Example 4 was prepared according to each compound and weight percentage listed in Table 4, and was filled in the performance test between the two substrates of the liquid crystal display. The test data is shown in the following table:

Table 4 liquid crystal composition formula and its test performance

Example 5

The liquid crystal composition of Example 5 was prepared according to each compound and weight percentage listed in Table 5, and was filled in the performance test between the two substrates of the liquid crystal display. The test data are shown in the following table:

Table 5 liquid crystal composition formula and its test performance

As can be seen from the data of Examples 3, 4 and 5, when the compound of the present invention is applied to a liquid crystal composition, the liquid crystal composition has good liquid crystal properties, and the compound of the present invention has achieved very good technical effects.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the present invention. A person skilled in the art can make some modifications or modifications to equivalent embodiments by using the above-disclosed technical contents without departing from the technical scope of the present invention. It is still within the scope of the technical solution of the present invention to make any simple modifications, equivalent changes and modifications to the above embodiments.

Claims (9)

1. A compound having a negative dielectric anisotropy, the compound having the structure of Formula I:

   

   among them,

   R ₁ and R _{2 are the} same or different and each independently represents an alkyl group of 1 to 10 carbon atoms;

   X ₁ and X _{2 are} each different and independently represent -O- or -CH ₂ -;

   Z represents a single bond, -CH ₂ O-, -CH ₂ CH ₂ -, -COO- or -CH=CH-.
2. The compound having negative dielectric anisotropy according to claim 1, wherein said Z represents a single bond, -CH ₂ O- or -CH ₂ CH ₂ -.
3. The compound having negative dielectric anisotropy according to claim 1, wherein said Z represents a single bond or -CH ₂ CH ₂ -.
4. The compound having negative dielectric anisotropy according to claim 1, wherein R ₁ and R _{2 are the} same or different and each independently represents an alkyl group of 1 to 6 carbon atoms.
5. The compound having negative dielectric anisotropy according to claim 1, wherein the compound of the formula I is selected from the group consisting of one or more of the following formulae I-A to I-F; :

   

   among them,

   The R ₁ and R _{2 are the} same or different and each independently represents an alkyl group of 1 to 6 carbon atoms.
6. A liquid crystal composition comprising the compound having negative dielectric anisotropy according to any one of claims 1 to 5.
7. A liquid crystal composition of a compound having negative dielectric anisotropy according to claim 6, wherein said liquid crystal composition further comprises a group consisting of one or more of the formulae II, III and \ or IV :

   

   among them,

   The R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R _{8 are the} same or different and 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 -CH ₂ - may be substituted by -O-, provided that the oxygen atom is not Directly connected;

   The m and n are the same or different and each independently represents 0 or 1.
8. A display device comprising the liquid crystal composition of the compound having negative dielectric anisotropy according to claim 6.
9. Use of a liquid crystal composition of a compound having negative dielectric anisotropy according to claim 6 in a display mode of VA, FFS, IPS, PSVA.