JPH04217638A - Tolan-based liquid crystalline compound - Google Patents

Abstract

PURPOSE:To provide the subject new tolan-based compounds having a large DELTAn and a high N-I point and excellent in compatibility with a nematic mixture liquid crystal mixture used for various practical purposes. CONSTITUTION:Compounds of formula I (R1 and R2 are 1-5C straight chain alkyl; n is 2-7; X is H or F; Cyclohexane ring is trans-form). The above- mentioned compounds can be obtained by reacting a compound of formula II with an acetylene compound of formula III in the presence of a base such as diethylamine and a catalyst composed of dichloro-bis(triphenylphosphine) palladium (II) and cuprous iodide in a solvent such as N,N-dimethylformamide. The resultant compounds is drivable in a wide temperature range, especially in a high temperature range, excellent in its response speed and useful as a material for formation of a liquid crystal cell free from Moire fringe.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel tolan-based liquid crystal compound useful as an electro-optical display material.

0002

2. Description of the Related Art The currently mainstream liquid crystal display cell is a TN cell, which is a type of field effect cell. This T
In an N-type cell, G. Mol by Bauer
．． Cryst. Liq. Cryst. 63 45 (19
As reported in 81), in order to prevent the occurrence of interference fringes on the cell surface that would impair the appearance of the cell, the refractive index anisotropy Δn of the liquid crystal material filled in the cell and the cell It is necessary to set the product of the thickness d (μm) to a certain value. In practically used liquid crystal cells, the value of △n・d is 0.
．． 5, 1.0, 1.6, or 2.2. Since the value of Δn·d is set to a constant value in this way, the value of d can be made small by using a liquid crystal material with a large value of Δn. When the value of d becomes small, the response time (τ) becomes

0003

[Math 1]

It becomes small according to the relational expression: Therefore, △n
A liquid crystal material with a large value of is an extremely important material for producing a liquid crystal cell with a fast response speed and no interference fringes. On the other hand, most practical liquid crystal materials are prepared by mixing several or more components, usually consisting of a compound that has a nematic phase near room temperature and a compound that has a nematic phase above room temperature. . Many of the above-mentioned mixed liquid crystals currently in practical use are required to have a nematic phase over the entire temperature range of -30°C to +65°C, but the variety of applied products for liquid crystal display cells is There is a demand for liquid crystal materials that extend the nematic liquid crystal temperature range to higher temperatures. ) is needed.

The present inventors developed a nematic liquid crystal compound having the general formula

0
006]

[Case 2]

A compound represented by the formula (wherein R and R' each independently represent an alkyl group) was provided.

[0008]

[Problems to be Solved by the Invention] However, this compound has the drawback of poor compatibility with nematic mixed liquid crystals, which are currently in practical use as host liquid crystals.

The problem to be solved by the present invention is to provide a liquid crystal compound that has a large Δn, a high N-I point, and has excellent compatibility with nematic mixed liquid crystals, which are currently widely used as host liquid crystals. It's about doing.

0010

[Means for Solving the Problems] In order to solve the above problems, the present invention provides formula (I)

[0011]

[Chemical formula 3]

(In the formula, R1 and R2 have 1 to 5 carbon atoms.
represents a straight-chain alkyl group, n represents an integer of 2 to 7, X represents H or F, and the cyclohexane ring has a trans configuration. ) is provided.

The compound represented by the general formula (I) according to the present invention can be produced according to the following production method.

[0014]

[C4]

(R1, R2, n and X in the general formulas (II) and (III) have the same meanings as R1, R2, n and X in the general formula (I), respectively). Formula (II
) in the presence of a base such as diethylamine, N
, N-dimethylformamide, dichloro-bis(triphenylphosphine)palladium(II).
The compound of formula (I) according to the present invention is produced by reacting with the compound of formula (III) using cuprous iodide as a catalyst.

Table 1 lists the transition temperatures of typical compounds represented by the general formula (I) thus produced.

[0017]

[Table 1]

(In the table, C is a crystalline phase, N is a nematic phase,
I each represent an isotropic liquid phase. ) The compound of general formula (I) according to the present invention is a nematic liquid crystal compound having weak positive dielectric constant anisotropy, and therefore, for example, it can be combined with other nematic liquid crystal compounds having negative dielectric constant anisotropy. It can be used as a material for dynamic light scattering type display cells in a mixture state, and it can also be used for field effect display cells in a mixture state with other nematic liquid crystal compounds having positive or negative dielectric constant anisotropy. Can be used as a material.

Preferred representative examples of liquid crystal compounds that can be used in combination with the compound represented by the general formula (I) include 4-substituted benzoic acid 4'-substituted phenyl ester, 4-substituted cyclohexane carbon Acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted biphenyl ester, 4-(4-substituted cyclohexanecarbonyloxy)benzoic acid 4'-substituted phenyl ester, 4-(4-substituted cyclohexyl)benzoic acid 4'-substituted phenyl ester, 4-(4-substituted cyclohexyl)benzoic acid 4'-substituted cyclohexyl ester,
4-substituted 4'-substituted biphenyl, 4-substituted phenyl 4'
-substituted cyclohexane, 4-substituted 4''-substituted terphenyl, 4-substituted biphenyl, 4'-substituted cyclohexane,
Examples include 2-(4-substituted phenyl)5-substituted pyrimidine.

Table 2 shows 85% by weight of mixed liquid crystal (A), which is currently widely used as a base liquid crystal as a nematic liquid crystal material, and compound No. 1 of formula (I) shown in Table 1. 1 or No
．． The N-I point and the anisotropy of refractive index △n measured for the mixed liquid crystal consisting of 15% by weight of 2 are posted, and for comparison, the N-I point and the measured N-I point for the mixed liquid crystal (A) itself are shown. △
n is posted.

[0021] The mixed liquid crystal (A) is

[0022]

[C5]

It consists of the following.

[0024]

[Table 2]

From the data listed in Table 2, the general formula (I
It can be understood that the compound represented by ) raises the NI point of the mixed liquid crystal (A) to a practically sufficient level and significantly increases Δn.

The effects of the present invention are also clarified by the following comparative experiments. The chemical structure is similar to the compound represented by the general formula (I) according to the present invention, and the compound represented by the formula (a
)

[0027]

[C6]

When the known compound [0028] was added to the above mixed liquid crystal (A), the solubility in the mixed liquid crystal (A) at -30°C was 6%. The N-I point of the mixed liquid crystal at this time was 62.1°C, and Δn was 0.101.

In contrast, one of the compounds according to the invention, namely the formula

[0030]

[C7]

Mixed liquid crystal (A
) was 13%. The NI point of the mixed liquid crystal at this time was 71.8°C, and Δn was 0.115.

From these facts, the general formula (
Compound I) has the following characteristics compared to typical known similar compounds:
It will be understood that since it can be added in large amounts to the nematic mixed liquid crystal that is currently in practical use as a base liquid crystal, the N-I point and Δn are significantly increased as a result.

[0033]

[Examples] Examples of the present invention will be shown below to further explain the present invention. However, the present invention is not limited to these examples. (Example 1) Formula

[0034]

[Chemical formula 8]

3.58g (0.0100mol) of the compound
was dissolved in 4.1 ml of diethylamine, and dichloro-bis(triphenylphosphine)palladium (I) was added to this solution.
I) 7 mg (0.010 mmol) and cuprous iodide 19
mg (0.10 mmol) and while stirring these at room temperature, 1.16 g of 4-methylphenylacetylene (
0.0100 mol) of N,N-dimethylformamide 5
ml solution was added dropwise, and then left at room temperature for 24 hours. This reaction solution was added to a cold dilute aqueous hydrochloric acid solution with stirring to make it acidic, and then the reaction product was extracted with toluene. After washing the extract with water and drying, toluene was distilled off from this liquid to obtain a reaction product.

The obtained reaction product was separated and purified using silica gel column chromatography, and then purified by recrystallization from ethanol.
．． 0075 mol) was obtained.

[0037]

[Chemical formula 9]

(Example 2) In Example 1, 3-fluoro4-methylphenylacetylene 1. was used instead of 4-methylphenylacetylene.
2.4 g (0.0066 mol) of the following compound was obtained in the same manner as in Example 1, except that 34 g (0.0100 mol) was used.

[0039]

[Chemical formula 10]

[0040]

Effects of the Invention The compound represented by the general formula (I) of the present invention has a high N-I transition temperature and a large Δn, and is a nematic mixed liquid crystal that is currently widely used as a base liquid crystal. By mixing the N-I point and △
n can be raised. Furthermore, compared to known structurally similar compounds, it has a higher solubility at low temperatures in nematic mixed liquid crystals, which are currently widely used as host liquid crystals, making it possible to create mixed liquid crystals with a higher N-I point and Δn. can.

Therefore, the compound represented by the general formula (I) of the present invention can be operated in a wide temperature range, particularly in a high temperature range,
It is useful as a material for producing a liquid crystal cell with a fast response speed and no interference fringes.

Claims (1)

[Claims] Claim 1: General formula [Formula 1] (wherein R1 and R2 represent a linear alkyl group having 1 to 5 carbon atoms, n represents an integer of 2 to 7, and X represents H or F. (wherein the cyclohexane ring is in the trans configuration).