CN108203584B - Compound, liquid crystal composition and application thereof - Google Patents

Abstract

The invention discloses a compound, which comprises at least one cyclic structure and a group bond shown in a general formula I. The invention also discloses a liquid crystal composition comprising the compound of the invention and an optoelectronic display device comprising the liquid crystal composition. The compound provided by the invention is stable in chemical property and physical property, has better low-temperature storage property, and simultaneously has dielectric anisotropy and refractive index anisotropy with proper sizes. When the liquid crystal material is applied to liquid crystal products, the transmittance of the products can be obviously improved, and the response speed is also obviously improved on the basis. In addition, the compound provided by the invention has good compatibility with other liquid crystal compounds and has wide applicability.

Description

Compound, liquid crystal composition and application thereof

Technical Field

The invention belongs to the field of liquid crystal materials, and particularly relates to a compound, a liquid crystal composition and application thereof.

Background

Liquid crystal display elements using the liquid crystal composition are widely used in displays of watches, calculators, word processors, and the like. These liquid crystal display elements utilize refractive index anisotropy, dielectric anisotropy, and the like of liquid crystal compounds. The operation modes of the liquid crystal display device are mainly classified into 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. In recent years, a mode in which an electric field is applied to an optically isotropic liquid crystal phase to exhibit electro birefringence has been actively studied.

The classification based on the driving method of the element is mainly classified into a Passive Matrix (PM) and an Active Matrix (AM). Passive matrices are further classified into static (static) and multiplexing (multiplex), and active matrices are classified into Thin Film Transistors (TFTs), Metal Insulator Metal (MIM), and the like.

These liquid crystal display elements include a liquid crystal composition having appropriate physical properties. General physical properties required for a liquid crystal compound as a component of a liquid crystal composition are as follows.

(1) Chemically stable and physically stable;

(2) has a high clearing point (liquid crystal phase-phase transition temperature of isotropic phase);

(3) a low lower limit temperature of a liquid crystal phase (optically isotropic liquid crystal phase such as a nematic phase, a cholesteric phase, a smectic phase, and a blue phase, etc.);

(4) excellent compatibility with other liquid crystal compounds;

(5) dielectric anisotropy with appropriate magnitude;

(6) with a suitably sized refractive index anisotropy.

When a liquid crystal composition containing the chemically and physically stable liquid crystal compound according to (1) is used for a liquid crystal display device, the voltage holding ratio can be improved. In addition, in the case of a liquid crystal composition containing a liquid crystal compound having a high clearing point or a low lower limit temperature of a liquid crystal phase as described in (2) and (3), the temperature range of a nematic phase or an optically isotropic liquid crystal phase can be expanded, and the liquid crystal composition can be used as a display element in a wide temperature range. Liquid crystal compounds are generally used as liquid crystal compositions prepared by mixing with many other liquid crystal compounds in order to exhibit properties that are difficult to be exhibited by a single compound. Therefore, the liquid crystal compound used in the liquid crystal display element is preferably excellent in compatibility with other liquid crystal compounds and the like as described in (4). In recent years, liquid crystal display elements having higher display performance, such as contrast, display capacity, response time characteristics, and the like, have been particularly demanded. Further, a liquid crystal composition having a low driving voltage is required for the liquid crystal material to be used. In addition, in order to drive an optical element driven in an optically isotropic liquid crystal phase at a low voltage, a liquid crystal compound having large dielectric anisotropy and refractive index anisotropy is preferably used.

When the image is displayed on the liquid crystal product, the rotating angle of the liquid crystal molecules can be controlled by applying different voltages, and then the penetration amount of light is changed to obtain different gray scales. For example, in a normally white mode liquid crystal panel, when no voltage is applied to the liquid crystal, the rod-like liquid crystal molecules are aligned in a posture similar to a lying posture, and at this time, light passes through the upper and lower polarizing plates most, and the liquid crystal panel exhibits a bright state; when a voltage is applied to the liquid crystal so that the liquid crystal stands vertically, light hardly passes through the liquid crystal panel, and the liquid crystal panel assumes a dark state. When each intermediate gray scale is required to be displayed, only the corresponding voltage is applied to the liquid crystal.

In the above-mentioned process of applying voltage to the liquid crystal, if the applied voltage is constant, the characteristics of the liquid crystal molecules are destroyed, and even if the voltage is removed, the liquid crystal cannot rotate any more with the change of the electric field, and thus different gray scales cannot be presented. Thus, the display voltage of the liquid crystal panel has positive and negative polarities, thereby changing the voltage applied to the liquid crystal. For example, when the display voltage of the liquid crystal panel is higher than the common electrode voltage, the display voltage is positive; on the contrary, when the display voltage of the liquid crystal panel is lower than the common electrode voltage, the display voltage is negative. Regardless of whether the display voltage is positive or negative, when the display voltage is the same as the absolute value of the voltage difference between the common electrode voltage, the same gray scale is exhibited.

As can be seen from the display process of the liquid crystal panel, the display gray scale is related to the transmittance of light. Therefore, the voltage setting of the liquid crystal panel can be carried out by measuring the transmittance curve of the liquid crystal panel, so that the display of each gray scale is controlled, and an image graph which accords with the sense of human is obtained.

The conventional liquid crystal display often has the problems of low transmittance, large threshold voltage (2.92V), slow response time, and the like due to the differences of the driving method and the liquid crystal molecular characteristics, and further causes the phenomena of difficult driving, image smear, and the like, so that the liquid crystal material with high transmittance and fast response is urgently needed to be provided.

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 compound having a high transmittance and a rapid response, a liquid crystal composition thereof, and a liquid crystal display element including the liquid crystal composition.

The technical scheme of the invention is as follows:

in one aspect, the invention provides a compound comprising at least one cyclic structure and a group of formula I,

wherein,

r represents an alkyl or haloalkyl group having 1 to 12 carbon atoms, wherein one or more-CH's in the alkyl or haloalkyl group₂-may each be independently replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-, or-O-CO-, in such a way that the oxygen atoms are not directly linked;

n represents an integer of 1 to 12.

Preferably, the at least one cyclic structure is linked to the group of formula I in the form of a "C-O" single bond,

wherein R represents a straight-chain alkyl or halogenated straight-chain alkyl group having 1 to 12 carbon atoms, wherein one or more of the straight-chain alkyl or halogenated straight-chain alkyl groups are non-adjacent to each other in-CH₂-may be replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-, or-O-CO-in such a way that the oxygen atoms are not directly linked.

Still preferably, the number of atoms in the ring skeleton of the cyclic structure is 3 to 12.

Further preferably, the compounds of the present invention have the structure of formula II,

wherein,

A₁，A₂，A₃and A₄Each independently represents a cyclic structure having an atomic number of 3 to 12 in a ring skeleton, and one or more H's on the cyclic structure may be substituted with a halogen or an alkyl group;

r' represents H, halogen, cyano, halogenated or non-halogenated alkyl with the number of carbon atoms of 1-15, and one or more non-adjacent-CH in the halogenated or non-halogenated alkyl with the number of carbon atoms of 1-15₂-may each be independently replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-, or-O-CO-;

Z₁、Z₂and Z₃Each independently represents a single bond, -CH₂CH₂-、-CH₂O-、-OCH₂-、-CF＝CF-、-CF₂O-、-OCF₂-、-COO-、-OCO-、-CH＝CH-、-C≡C-、-CF₂CH₂-、-CH₂CF₂-、-(CH₂)₄-、-CF₂CF₂-、-OCH₂CH₂CH₂-、-CH₂OCH₂CH₂-、-CH₂CH₂OCH₂-、-CH₂CH₂CH₂O-、-OCH₂CH₂O-、-CH₂OCH₂O-or-OCH₂OCH₂-；

a, b and c each independently represent 0, 1, 2,3 or 4.

Further preferably, n represents an integer of 4 to 10.

Further preferably, A is₁，A₂，A₃And A₄Each independently selected from the group consisting of benzene ring, cyclohexane, naphthalene ring, indene ring, tetralin, decahydronaphthalene, oxacyclohexane, cyclopropane, cyclobutane, cyclopentane, cycloheptane, bicyclo [2,2 ]]Octane;

wherein,

the above-mentioned cyclic structure may also satisfy at least one of the following conditions a and b:

a. one or more H in the cyclic structure may be substituted with halogen or alkyl;

b. one of the ring structuresOne or more-CH₂-may be replaced by-O-, -CO-, -CH ═ CH-, -C ≡ C-, -CO-O-or-O-CO-in such a way that the oxygen atoms are not directly linked.

Further preferably, A is₁，A₂，A₃And A₄Each independently selected from the group consisting of benzene ring, cyclohexane, naphthalene ring, tetralin, oxacyclohexane, and the above cyclic structure may also satisfy at least one of the conditions a and b.

Further preferably, the compounds of the present invention are selected from the group consisting of:

and

wherein,

R₁represents H, halogen, cyano, halogenated or unhalogenated alkyl with 1 to 15 carbon atoms, one or more non-adjacent-CH in the halogenated or unhalogenated alkyl with 1 to 15 carbon atoms₂-may each be independently replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-, or-O-CO-;

ring B₁、B₂、B₃And B₄Each independently represent

Or

And is

One or more CH in₂Can be replaced by the oxygen (O) instead of the oxygen (O),

may be replaced by F or CH₃Substitution;

Z_a1、Z_a2and Z_a3Each independently represents a single bond, -CH₂CH₂-、-CH₂O-、-OCH₂-、-CF₂CF₂-、-CF₂O-、-OCF₂-, -COO-, -OCO-or-CH ═ CH-;

in the general formulae IIa and IIb, n represents an integer of 2 to 10;

in the general formula IIc, n represents an integer of 4 to 10.

Further preferably, the ring B₁To represent

Wherein L is₁、L₂、L₃And L₄Each independently represents H, F or CH₃。

Further preferably, the compounds of the present invention are selected from the group consisting of:

and

wherein,

ring C₁、C₂And C₃Each independently represent

Or

And is

One or more CH in₂Can be replaced by the oxygen (O) instead of the oxygen (O),

may be replaced by F or CH₃Substitution;

Z_b1、Z_b2and Z_b3Each independently represents a single bond, -CH₂CH₂-、-CH₂O-、-OCH₂-、-CF₂O-、-OCF₂-；

L₁And L₂Each independently represents H or F.

Further preferably, said compound of formula ilaa is selected from the group consisting of:

and

the compound of formula iibb is selected from the group consisting of:

and

the compound of formula iicc is selected from the group consisting of:

and

further preferably, n is 4, 6, 8 or 10.

Further preferably, said R₁And R independently represents a halogenated or unhalogenated alkyl or alkoxy group having 1 to 12 carbon atoms.

It should be noted that only simple changes in the length of the chain of the above-mentioned compounds are also within the scope of the present invention.

In another aspect of the present invention, there is also provided a liquid crystal composition comprising at least one of the above-mentioned compounds.

In still another aspect, the present invention provides an electro-optical display device comprising the above liquid crystal composition.

Has the advantages that:

the compound provided by the invention is stable in chemical property and physical property, has better low-temperature storage property, and simultaneously has dielectric anisotropy and refractive index anisotropy with proper sizes. When the liquid crystal material is applied to liquid crystal products, the transmittance of the products can be obviously improved, and the response speed is also obviously improved on the basis. In addition, the compound provided by the invention has good compatibility with other liquid crystal compounds and has wide applicability.

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 structure of the liquid crystal composition is represented by the code listed in Table 1:

TABLE 1 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 cyclohexane, 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 (. degree. C.) clearing Point (nematic-isotropic phase transition temperature)

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

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

T (%) transmittance (DMS-505, cell thickness 5.2 μm)

t (ms) response time (DMS-505, 25 + -0.5 deg.C)

Wherein, the refractive index anisotropy is obtained by testing an Abbe refractometer under a sodium lamp (589nm) light source at 25 ℃;

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: the test box is TN90 type at 25 deg.C and 1KHz, and has a thickness of 7 μm.

Conditions for measuring transmittance: the DMS 505 is used to test the transmittance of a dimmer cell 5.2 μm thick.

Response time, test conditions were: 25 +/-0.5 ℃, 5.2 mu m IPS test box and DMS-505 as a test instrument.

In the following examples, the compound monomers and the reagents used are commercially available.

Example 1

The compound 1- (4-methoxy-butoxy) -4- (4-propyl-cyclohexyl) phenyl (No.2 (R)₁＝-C₃H₇，R＝-CH₃) Note that: numbering see table 2 below, the same below) as follows:

the preparation process comprises the following steps:

2.18g of propylcyclohexylphenol, 100ml of anhydrous Dimethylformamide (DMF), 2.76g of anhydrous potassium carbonate, 0.15g of potassium iodide and 1.4g of 4-chlorobutyl methyl ether were added to a 500ml three-necked flask, and stirred at 90 ℃ for 6 hours, after the completion of the reaction, the mixture was subjected to post-treatment and purification by column chromatography to obtain 2.5g of a white solid, Compound No.2 (R2)₁＝-C₃H₇，R＝-CH₃)，GC>99%, yield: 91 percent.

MS:55(11％)87(100％)107(8.9％)120(10％)133(7.8％)。

Example 2

The compound 2, 3-difluoro-4- (4-methoxy-butoxy) -4 '- (4-propyl-cyclohexyl) -1, 1' -biphenyl (No.66 (R)₁＝-C₃H₇，R＝-CH₃) The synthetic route of (c) is as follows:

the preparation process comprises the following steps:

1. synthesis of Compound M4

In a 500ml three-necked flask, 5.1g of 4-iodo-2, 3-difluorophenol, 150ml of anhydrous Dimethylformamide (DMF), 5.5g of anhydrous potassium carbonate, 0.3g of potassium iodide, 2.8g of 4-chlorobutyl methyl ether were added, stirred at 90 ℃ for 6 hours, and after the reaction was completed, post-treatment and purification by column chromatography gave 6.6g of a white solid, compound M4, GC > 97%, yield: 97 percent.

2. Compound No.66 (R)₁＝-C₃H₇，R＝-CH₃) Synthesis of (2)

3.4g of the compound M4, 2.5g of propylcyclohexylphenylboronic acid, 80ml of toluene, 40ml of ethanol, 40ml of water and 4.2g of anhydrous sodium carbonate are added into a 500ml three-necked flask, 0.1g of tetrakis (triphenylphosphine) palladium is added under the protection of nitrogen, the mixture is heated, stirred and refluxed for 6 hours, and after the reaction is finished, the mixture is subjected to post-treatment and column chromatography purification to obtain 3.1g of a white solid, namely the compound No.66 (R)₁＝-C₃H₇，R＝-CH₃)，GC>99%, yield: 75 percent.

MS：55(11％)87(100％)219(4.4％)232(5.6％)245(3.3％)416(1.7％)。

Example 3

The compound 2 ', 3' -difluoro-4- (4-methoxy-butoxy) -4 "-propyl-1, 1 ', 4', 1" -terphenyl (No.76 (R)₁＝-C₃H₇，R＝-CH₃) The synthetic route of (c) is as follows:

the preparation process comprises the following steps:

1. synthesis of Compound M7

In a 500ml three-necked flask, 4.4g of 4-iodophenol, 150ml of anhydrous Dimethylformamide (DMF), 5.5g of anhydrous potassium carbonate, 0.3g of potassium iodide, 2.8g of 4-chlorobutyl methyl ether were added, and the mixture was stirred at 90 ℃ for 6 hours, and after the reaction was completed, post-treatment and purification by column chromatography gave 5.7g of a white solid, compound M7, GC > 97%, yield: 93 percent.

2. Compound No.76 (R)₁＝-C₃H₇，R＝-CH₃) Synthesis of (2)

Adding 3.1g of compound M7, 2.8g of propyl difluorobiphenyl boric acid, 80ml of toluene, 40ml of ethanol, 40ml of water and 4.2g of anhydrous sodium carbonate into a 500ml three-neck flask, adding 0.1g of tetrakis (triphenylphosphine) palladium under the protection of nitrogen, heating, stirring and refluxing for 6 hours, after the reaction is finished, carrying out post-treatment and column chromatography purification to obtain 3.4g of white solid, namely compound No.76 (R)₁＝-C₃H₇，R＝-CH₃)，GC>99%, yield: 83 percent.

MS：55(7.8％)87(100％)302(7.8％)331(23.4％)359(4.7％)446(3.1％)。

Example 4

The compound 4' - [ (hexyloxy) butoxy]- (1, 1-biphenylyl) -4-yl-4-methyl- [1, 1-bis (cyclohexyl)]-4-carboxylic acid (No.116 (R)₁＝-CH₃，R＝-C₆H₁₃) The synthetic route of (c) is as follows:

the preparation process comprises the following steps:

1. synthesis of Compound M11

In a 500ml three-necked flask, 3.7g hydroquinone, 150ml anhydrous Dimethylformamide (DMF), 5.5g anhydrous potassium carbonate, 0.3g potassium iodide, 3.8g 4-chlorobutyl hexyl ether were added, stirred at 90 ℃ for 6 hours, after the reaction was completed, post-treated, and purified by column chromatography to obtain 1.3g white solid, compound M11, GC > 97%, yield: 19 percent.

2. Compound No.116 (R)₁＝-CH₃，R＝-C₆H₁₃) Synthesis of (2)

Adding 1.3g of compound M11, 0.85g of methyl dicyclohexyl formic acid, 5mg of 4-dimethylamino pyridine and 100ml of dichloromethane into a 250ml three-neck flask, cooling to 0 ℃, dropwise adding a solution consisting of 1.5g N, N' -dicyclohexyl carbodiimide (DCC) and 10ml of dichloromethane, stirring at room temperature for 12 hours after dropwise adding, post-treating, and purifying by column chromatography to obtain 1.7g of compound M11, 0.85g of methyl dicyclohexyl formic acid, 5mg of 4-dimethylamino pyridine and 100ml of dichloromethaneWhite solid, Compound No.116 (R)₁＝-CH₃，R＝-C₆H₁₃)，GC>99%, yield: 82 percent.

MS：55(11％)87(100％)186(31.6％)307(16.3％)。

Example 5

Referring to the synthesis methods of the compounds of examples 1 to 4, compounds Nos. 1 to 119 shown in Table 2 below can be prepared, respectively, by simply replacing compounds M1 to M12 in the above reaction.

For example:

the compound No.6 (R) can be prepared by replacing propylcyclohexylphenol M1 with ethyl-linked phenol and replacing 4-chlorobutyl methyl ether M2 with 2-chloroethyl hexyl ether₁＝-C₂H₅，R＝-C₆H₁₃)；

The compound No.7 (R) was obtained by substituting propylcyclohexylphenol M1 for propylcouplet phenol₁＝-C₃H₇，R＝-CH₃)；

The compound No.8 (R) can be prepared by replacing propyl cyclohexyl phenol M1 with ethoxy diphenol and replacing 4-chlorobutyl methyl ether M2 with 6-chlorohexyl methyl ether₁＝-OC₂H₅，R＝-CH₃)；

The compound No.12 (R) can be prepared by replacing propylcyclohexylphenol M1 with butylcyclohexyldifluorophenol₁＝-C₄H₉，R＝-CH₃)；

The compound No.17 (R) was obtained by substituting propylcyclohexylphenol M1 for hexyloxydifluorobiphenol₁＝-OC₆H₁₃，R＝-CH₃)；

The compound No.27 (R) was obtained by substituting propylcyclohexylphenol M1 for propylcyclohexylmethyleneoxydiphenol₁＝-C₃H₇，R＝-CH₃)；

The compound No.36 (R) can be prepared by replacing propylcyclohexylphenol M1 with ethylbicyclohexylphenol and 4-chlorobutyl methyl ether M2 with 2-chloroethylether₁＝-C₂H₅，R＝-C₂H₅)；

The compound No.43 (R) was prepared by replacing propylcyclohexylphenol M1 with pentylcyclohexylbiphenol and 4-chlorobutyl methyl ether M2 with 3-chloropropylether₁＝-C₅H₁₁，R＝-C₂H₅)；

The compound No.81 (R) was obtained by replacing propylcyclohexylphenol M1 with methylbicyclohexylmethyleneoxydiphenol₁＝-CH₃，R＝-CH₃)。

TABLE 2 structural formulas of Compound Nos. 1 to 119

Application comparative example 1

Compound M 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, the test data are shown in table 3 below:

TABLE 3 liquid crystal composition formulation and its test Properties

Application example 1

With the compound No.2 (R)₁＝-C₃H₇，R＝-CH₃) The 3CPO2 in the mixture M was replaced by the same amount of each component to obtain a mixture M1, which was filled between two substrates of a liquid crystal display for performance testing, and the test data are shown in table 4 below:

TABLE 4 liquid crystal composition formula and its test performance

Application example 2

With the compound No.12 (R)₁＝-C₄H₉，R＝-CH₃) Replacing 3CWO4 in the mixture M, and keeping the content of each component unchanged to obtain a mixture M2 which is filled between two substrates of a liquid crystal display for performance test, wherein the test data are shown in the following table 5:

TABLE 5 liquid crystal composition formulation and its test Properties

Application example 3

With the compound No.66 (R)₁＝-C₃H₇，R＝-CH₃) Instead of 3CPWO2 in mixture M, the content of each component was unchanged to obtain mixture M3, which was filled between two substrates of a liquid crystal display for performance testing, and the test data are shown in table 6 below:

TABLE 6 liquid crystal composition formula and its test performance

Application example 4

With the mixture M as a mother liquid crystal (host), Compound No.7 (R) was added₁＝-C₃H₇，R＝-CH₃)、No.8(R₁＝-OC₂H₅，R＝-CH₃)、No.17(R₁＝-OC₆H₁₃，R＝-CH₃)、No.76(R₁＝-C₃H₇，R＝-CH₃) 10% by weight of host: mixing at a ratio of 90% to obtain mixtures M4, M5, M6 and M7, respectively filling the mixtures between two substrates of a liquid crystal display for performance test, wherein the test data are shown in the following table 7:

TABLE 7 liquid crystal composition formulations and their test properties

Mixture of	T(％)	t(ms)
			M4	13.7	44
M5	14.3	45.2
			M6	13.7	45.7
M7	14.1	48.6

Comparing the application comparative example 1 with the application examples 1-4, the compound provided by the invention can obviously improve the transmittance of the product when being applied to the liquid crystal composition, and the response speed is obviously improved on the basis. In addition, the compound provided by the invention has good compatibility with other liquid crystal compounds and has wide applicability.

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 (6)

1. A compound comprising at least one cyclic structure and a group of formula I,

the compound is selected from the group consisting of:

and

wherein R and R₁Each independently represents a halogenated or non-halogenated alkyl or alkoxy group having 1 to 12 carbon atoms;

ring B₁To represent

Wherein L is₁And L₂Denotes F, L₃And L₄Represents H;

ring B₂And B₃Each independently represent

And is

One or more CH in₂Can be replaced by the oxygen (O) instead of the oxygen (O),

may be replaced by F or CH₃Substitution;

Z_a1and Z_a2Represents a single bond; and is

n represents an integer of 4 to 10.

2. The compound according to claim 1, characterized in that it is selected from the group consisting of:

and

wherein,

ring C₁And ring C₂Each independently represent

And is

One or more CH in₂Can be replaced by the oxygen (O) instead of the oxygen (O),

may be replaced by F or CH₃Substitution;

Z_b1and Z_b2Each independently represents a single bond.

3. The compound of claim 2, wherein the compound of formula iiaa is selected from the group consisting of:

and

the compound of formula iibb is selected from the group consisting of:

and

4. a compound according to claim 3, wherein n is 4, 6, 8 or 10.

5. A liquid crystal composition comprising a compound according to any one of claims 1 to 4.

6. An electro-optical display device comprising the liquid crystal composition of claim 5.