JP2534486B2 - Biphenyl pyridine derivative - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel liquid crystal compound, and more particularly to a biphenylpyridine derivative used in an electro-optical liquid crystal cell.

[Conventional technology]

In recent years, the electro-optical liquid crystal cell has been expected as a display device to replace the CRT, and studies for making it high-multiplexed have been actively made.

As a technology of particular note, TJ Scheffer et al. Control the molecular alignment of liquid crystals by optically active substances (they
270 ° twisted. ), The so-called super twist type liquid crystal cell (hereinafter STN) with improved display characteristics.
Called Cell) [Appl, Phyt Lett, 45, No.10, P1
021, '84]. According to this method, the molecular arrangement in the absence of electric field,
The molecular arrangement generated by the electric field is extremely stabilized in terms of energy, and the switching operation performed between the two provides a much higher contrast and steep threshold characteristics than a normal TN cell, and a wider viewing angle can be obtained. Therefore, it is in agreement with the general public that it will become the mainstream of liquid crystal multiplex display in the future.

The display characteristics of the STN cell are mainly governed by the helical pitch of the optically active substance or the alignment technology of the panel, etc., and the liquid crystal used there is stable against the influence of chemical and photochemical and electric fields. A compound having a low viscosity and a wide temperature range of nematic liquid crystal is preferable.

[Problems to be solved by the invention]

In order to secure the practical temperature range of the liquid crystal composition used in the electro-optical liquid crystal cell, the liquid crystal temperature range is in the low temperature to room temperature region (base liquid crystal) and in the high temperature region (high clearing point liquid crystal). Is adjusted by appropriately blending. Here, in general, the high clearing point liquid crystal increases in viscosity with an increase in its mass, and particularly when the liquid crystal composition for the STN cell is constituted, in the liquid crystal compounding operation, the high clearing point component is suppressed to a minimum amount. There is a need. For that purpose, a liquid crystal compound having an extremely wide nematic liquid crystal temperature range and having a higher and higher clearing point is desired.

[Means for solving problems]

The biphenylpyridine derivative of the present invention has the general formula (1) (Wherein R represents an alkyl group having 1 to 8 carbon atoms).

The compound represented by the general formula (1) is, for example, Shows a nematic phase at 145-255 ℃. This is a conventional similar 2-phenylpyridine derivative, such as Shows a nematic phase at 45.5 ℃ -68 ℃, Has a very high clearing point and a wide nematic phase compared to the nematic phase at 31 ° C to 41 ° C.

Further, the compound represented by the general formula (1) is an extremely stable and low-viscosity compound without any unstable element due to various stability or any element contributing to high viscosity in terms of its molecular structure. is there.

The compound of general formula (1) can be synthesized, for example, according to the following scheme.

(In the formula, R ₃ and R ₄ are alkyl having 1 to 8 carbon atoms) The outline of the reaction process will be described below.

Step 1. (II) is lithiated with n-butyllithium in dry benzene to obtain (III).

Step 2. React (III) with pyridine in dry diethyl ether.

Step3. This is reacted with R ₄ Br in dry tetrahydrofuran and hydrolyzed to obtain (I-1).

Step 4. React with Br _{3 in} dry tetrahydrofuran and hydrolyze to obtain (IV).

Step 5. (IV) is cyanated with cuprous cyanide in N-methyl-2-pyrrolidone to give (1-2).

 Step 6 (V) is obtained in the same manner as Step 1 to obtain (VI).

 React in the same manner as in Step 7 (VI).

 Step8. Obtain (VII) as in Step3.

 Step9. Obtain (VIII) from silver sulfate and iodine in sulfuric acid.

Step (10) (VIII) is performed in the same manner as Step 5 to obtain (1-3).

〔Example〕

 Hereinafter, the embodiments of the present invention will be described in detail with reference to Examples.

Example 1 Dissolve 38 g in 140 ml of dry benzene, place under a nitrogen stream,
Under this stirring, 100 ml of a hexane solution containing 15% n-butyllithium was added, and stirring was continued at room temperature overnight. The produced crystals were collected by filtration under a nitrogen stream, washed with hexane, and then dissolved in 400 ml of dry diethyl ether. This ether solution was cooled to −5 ° C., 12.6 g of dry pyridine was slowly added dropwise while stirring, and then the temperature was returned to room temperature and 3
Stirring was continued for hours. It was cooled to -5 ° C again, 800 ml of dry tetrahydrofuran was added thereto, and then C ₅ H ₁₁ Br22.7.
g was added dropwise over 15 minutes, and then the mixture was stirred at room temperature for 1 hour. After the reaction, water 1 was added, the mixture was stirred well, the ether layer was separated, washed with water three times, and then the ether was distilled off.

The residue is distilled under reduced pressure and the fraction at 220 ° C / 2 mmHz is collected.
This was passed through silica gel column chromatography using benzene as a solvent, and the obtained product was recrystallized from ethanol, I got 9.0g.

Phase transition temperature After mixing 2.2 g of silver sulfate, 34 ml of concentrated sulfuric acid and 4 ml of water, stirring and dissolving at 40 ° C. and returning to room temperature, 3.7 g of powdered iodine was added.

3.0 g was added while keeping room temperature, and the mixture was stirred for 2 hours.
The reaction mixture was gradually added to 200 m of water, and sodium sulfite 25
A 200 ml solution of g in water was added and stirred. The precipitate was collected by filtration, added to 500 ml of a 5% aqueous potassium oxide solution, stirred, extracted with chloroform, and washed with water.

Chloroform was distilled off, and the residue was repeatedly recrystallized using a chloroform-acetone mixed solvent, Obtained 1.5 g.

Phase transition temperature Next, 0.5 g of cuprous cyanide was dissolved by heating in 20 ml of dry N-methyl-2-pyrrolidone, and 1.2 g was added and the mixture was heated and refluxed for 2 hours. After reaction, the reaction mixture was cooled, and the reaction mixture was added to 50 ml of water, to which 5 g of ferric chloride and 5 ml of hydrochloric acid, water were added.
After adding 20 ml of the solution and stirring, the precipitate was collected by filtration. This precipitate is dissolved in chloroform and a 10% aqueous potassium hydroxide solution is added.
After washing twice with 50 ml, chloroform was distilled off. The residue was run through silica gel column chromatography using benzene as a solvent, and the obtained product was recrystallized from ethanol. Got 0.7g (Note that C, Sm, N, and I respectively represent a crystal phase, a smectic phase, a nematic phase, and an isotropic liquid phase.) The following compounds can be produced in the same manner as in the above examples.

[Effects of the Invention] As described above, the feature of the present invention resides in that it has an extremely wide nematic liquid crystal temperature range, and particularly has a high clearing point. It is obvious that these are compounded in a very small amount and are useful for expanding the liquid crystal temperature range of other liquid crystal mixed systems.

In addition, the pyridine ring intervening in the present invention is referred to as “heterocyclic intermolecular interaction” by BS Scheuble et al. (Japan Display '8
3., SID P224) can be expected to improve the electro-optical characteristics by inducing the same effect.

Claims (1)

(57) [Claims] 1. A general formula (1) (In the formula, R represents an alkyl group having 1 to 8 carbon atoms.) A biphenyl pyridine derivative.