JPS6058902B2 - liquid crystalline ester compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel organic compound and a method for producing the same.
More specifically, the present invention relates to a novel organic compound having a wide liquid crystal temperature range and a high clearing point, and a method for producing the same.

Various principles have been applied to electro-optical display elements using liquid crystals and have been put into practical use.

Electro-optical display elements using nematic liquid crystal materials are classified according to the dielectric anisotropy of the nematic liquid crystal material. For example, when an electric field is applied to a nematic liquid crystal material whose permittivity in the direction perpendicular to the long axis of the molecules is larger than that in the long axis direction, that is, a nematic liquid crystal material with negative dielectric anisotropy, A display element that utilizes the so-called dynamic scattering mode, a light scattering phenomenon caused by the collision between ions and a group of liquid crystal molecules, and the orientation of dichroic dyes by applying an electric field. A liquid crystal material with negative dielectric anisotropy is required for positive type guest-host display in pre-occurrence display that controls color display.

Also, when an electric field is applied to a nematic liquid crystal material whose permittivity in the long axis direction of the molecules is larger than the permittivity in the direction perpendicular to the long axis, that is, a nematic liquid crystal material with positive dielectric anisotropy, the twisting or tilting of the molecules occurs. There is a display element that utilizes a so-called field effect mode that utilizes changes in . Further, as a development of the field effect mode, there is a two-frequency display element that utilizes the low-frequency dielectric dispersion effect of liquid crystal. This is based on the following principle. FIG. 1 shows the frequency dependence of a typical liquid crystal composition with positive dielectric anisotropy. (Reference Appl, Phyo Letters 0141974P1
86~) Fc is the frequency at which dielectric anisotropy disappears, and is called the crossover frequency.

The two-frequency display method refers to the lower frequency region (
For example, in a liquid crystal composition that has positive dielectric anisotropy in the FL) and negative dielectric anisotropy in a higher frequency region than the FO (FH, for example), the liquid crystal molecules are twisted by changing the frequency under a constant applied voltage. Alternatively, the display is performed by limiting the tilt.

Here, by adding it to the liquid crystal substance or liquid crystal mixture, if the absolute value of negative dielectric anisotropy becomes larger in a frequency range higher than Fc, it is effective to lower the driving voltage and, in turn, to reduce power consumption. Generally, the following relationship exists between the FO value and the response time τ.

(τ is the average value of the rise time and fall time) In other words, when the response is improved, the FO value increases, and the absolute value of negative dielectric anisotropy in the high frequency region decreases.

On the other hand, if the Fc value is made small, the response becomes poor, but the absolute value of the negative dielectric anisotropy in the high frequency region becomes large, which is effective in reducing power consumption. However, although it is desired to have good responsiveness and to lower the FO value by adding it to a liquid crystal substance or liquid crystal mixture, there are not many liquid crystal ester compounds that can satisfy both of these requirements in a well-balanced manner. The object of the present invention is to be stable against chemical, thermal, light, humidity, etc., to reduce the FO value by adding it to liquid crystal substances or liquid crystal mixtures, and to have a good balance with response speed. The object of the present invention is to provide a new ester compound that exhibits small temperature changes and widens the liquid crystal temperature range.

The outline of the synthesis procedure of the liquid crystalline ester compound provided by the present invention is shown.

Step I A commercially available PCH liquid crystal (manufactured by Merck & Co., Ltd.) is heated and dissolved in ethylene glycol, an equimolar or more strong basic aqueous solution such as a potassium hydroxide aqueous solution is added, and the mixture is heated under reflux for 8 hours or more.

The reaction formula is as follows. Step ■ Add an equimolar amount or more of an acidic aqueous solution (e.g., hydrochloric acid, etc.) to the compound of the general formula obtained in Step I, stir for several hours, convert the salt to carboxylic acid, and add it with an appropriate solvent (e.g., (methanol, ethanol, etc.) Perform recrystallization.

The reaction formula is as follows. Step 2: Add thionyl chloride in a molar amount or more of the general formula obtained in Step 2, heat to reflux, and determine the point at which no gas is generated as the end of the reaction.

After the reaction is completed, excess thionyl chloride is removed by heating and reducing pressure. The reaction formula is as follows. The product obtained here is purified by distillation under reduced pressure by a predetermined method.

Step ■ Next, use toluene as a solvent and write the general formula Heat and dissolve the compound and cool it. Then, an equimolar amount of the compound and small amounts of sulfuric acid and boric acid as catalysts.

This was heated under reflux for 3 hours, and after refluxing, toluene was distilled off under reduced pressure. The residue is recrystallized (for example, using acetonitrile, methanol, etc. as a solvent) to obtain: The reaction formula is as follows.

Step ■ Obtained by Step■ and obtained in Step■ Ta Take equimolar amounts of Dissolve each in the solution.

Examples of the solvent include chloroform, ethyl ether, and toluene. The solution (SOll) in which is dissolved contains basic substances such as pyridine and triethylamine as catalysts for the reaction.

Under cooling, a solution of SOll (SOl Add 2) while stirring and allow to react.

The reaction formula is as follows. After adding SOl2,
In order to complete the reaction, the mixture is heated under reflux for several tens of minutes.

The ester compound obtained here is extracted with ether, chloroform, etc. after adding water.

Thereafter, the ether layer or chloroform layer is taken out and washed with an acidic aqueous solution (e.g. hydrochloric acid) and a basic aqueous solution (e.g. sodium hydroxide aqueous solution), and then washed with water repeatedly to remove impurities, and then heated or depressurized to remove impurities. , ether or chloroform, etc.

The obtained ester compound is recrystallized from an organic solvent such as ethanol or hexane. According to the following example,
The synthesis method of a specific liquid crystal ester compound and its properties are shown below.

Example 1 Step I Commercially available PCH-3 (structural formula (A).1m0I) was heated in 450ml of ethylene glycol.

To this boiling solution, an aqueous potassium hydroxide solution (KOH35y..H2O2Oy) was added little by little over a short period of time, and the mixture was heated under reflux for 8 hours or more. Step 2 After cooling, 500 ml or more of water was poured into the solution to dissolve the precipitated crystals.

Incidentally, the undissolved portion was removed by filtration. Add an excess amount (200ml or more) of concentrated hydrochloric acid little by little to this solution,
A white precipitate was formed and stirring was continued for 3 hours or more. After the stirring was completed, it was filtered, the crystals were thoroughly washed with water, dried, and recrystallized once with ethanol.

Obtained crystal 4-(41-propylcyclohexyl)-
The amount of benzoic acid was 20.1y. St
Crystal 19.1y (0.08
2 ml of thionyl chloride and 50 fI of thionyl chloride (0.42 ml) were added, and the mixture was heated under reflux for 1.5 hours.

The reaction was completed when gas generation ceased, and then excess thionyl chloride was distilled off under reduced pressure. Vacuum distillation of the residue (171
77! 19. Purified crystals of 4-(4″-propylcyclohexyl)benzoyl chloride were obtained using Hgl (51°C).
2y (0.073rn0) was obtained. Step (2) Next, pentylpheneol 32y (0.2rn01) was dissolved by heating using toluene 1' as a solvent.

After cooling, an equimolar amount of 2-chloro4-
Hydroxybenzoic acid 34.2q (0.2m
01), 0.5y of sulfuric acid, and 0.3y of boric acid as catalysts, heated under reflux for over 30 hours, then toluene was depressurized! Distilled away. Then, the residue was recrystallized with methanol, and as a result, a crystal with a structural formula of 52f (0.17m0) was obtained.

Step ■ The crystal obtained in Step ■ is 2.64y (0.01m0
The solution was dissolved in an appropriate amount (approximately 30 ml) of toluene.

(SOll) Also, the crystal 3.06 obtained in Step ■
y(4). Appropriate amount (about 30m1) for 01m01)
of toluene and 2 ml of pyridine.

(SOl2) While cooling SOl2 and stirring, SOll was added little by little to react, producing a white precipitate.

Thereafter, this was heated and refluxed for three or more times. After reflux,
Water was added to dissolve the white precipitate and extraction with toluene was performed. This toluene layer was taken out and washed three times with 10% hydrochloric acid, three times with pure water, three times with 10% sodium hydroxide solution, and again three times with pure water.

From this toluene layer, toluene was distilled off under reduced pressure to obtain crystals. The crystals were recrystallized three times using a mixed solvent of hexane and ethanol in a ratio of 1:1. Purified P-pentylphenyl 2-chloroP″-[p(4-propylcyclohexyl)benzoyloxy]benzoate 4.8
I got y. Example 2 Using the same method as in Example 1, P-
Pentylphenyl 2-chloroP′-[P″″-(4-
Pentylcyclohexyl)benzoyloxy]benzoate was obtained.

Example 3 Using the same method as in Example 1, P-pentylphenyl 2-chloroP'-[bi(4-pentylcyclohexyl)benzoyloxy]benzoate was obtained.

Table 1 below shows the structure and C.I. of the liquid crystalline ester compound of the present invention.
p. , M. p. shows.

However, M. p. is the transition point (melting point) from solid phase to nematic liquid crystal phase, C. p. indicates the transition point (clearing point) from a nematic liquid crystal phase to an isotropic liquid.

From Figure 2 to Figure 4, each infrared absorption spectrum 2
showed the tor. Example 4 Using commercially available P-pentylphenyl 2-chloro-4-(P-pentylbenzoylroxy)-benzoate as a mother liquid crystal, the liquid crystalline ester compound obtained by the present invention was added in the following component ratio, and its dielectric The dispersion is shown in FIG.

As can be seen from FIG. 5, as the amount of the liquid crystalline ester compound of the present invention added increases, the Fc value decreases.

Furthermore, the response is better than the decrease in the Fc value, and the balance between the two is satisfied. As described above, the liquid crystalline ester compound of the present invention reduces the Fc value by adding it to a liquid crystal substance or liquid crystal composition, but also has good responsiveness in comparison, and the balance between the two is satisfied. Their liquid crystal temperature range can be widened.

Further, the compound of the present invention is an ester compound, and it goes without saying that it is chemically, thermally, light- and temperature-stable. Furthermore, the liquid crystal ester compound of the present invention has a high clearing point, and by adding such a high clearing point compound to a known liquid crystal composition, the clearing point of the liquid crystal composition can be increased. This is a well-known fact.

In this way, it can be effectively used as a field-effect liquid crystal, and as mentioned above, it goes without saying that it can also be effectively used as a two-frequency display liquid crystal.

[Brief explanation of drawings]

Figure 1: Frequency dependence of dielectric anisotropy of typical liquid crystal compositions; Figure 2: Infrared absorption spectrum; Figure 3: Infrared absorption spectrum; Figure 4: Infrared absorption spectrum. Figure 5, Frequency dependence of dielectric anisotropy when the liquid crystalline ester compound of the present invention is added to the base liquid crystal, NO. 19%, NO. 2l8%, N
O. Measured at room temperature at 327%.

Claims (1)

[Claims] 1 The general formula is ▲ Numerical formula, chemical formula, table, etc. A liquid crystalline ester compound represented by: