JPS643183B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel ester compound, and more particularly to a novel ester compound having the general formula:

3-(trans-4'-n-alkylcyclohexane-1'- Carbonyloxy)-6-n-alkanoyloxy-phthalonitrile. In recent years, large quantities of wristwatches, calculators, etc. that use liquid crystal displays have become available on sale. This is because the liquid crystal display has excellent features such as low voltage driving and low power consumption. A liquid crystal display with this excellent feature employs a system called a twisted nematic system. However, even this excellent method had the disadvantage that the number of digits that could be driven by multiplex drive was small, making it unsuitable for large-capacity displays. A dual-frequency drive method has been proposed to improve the drawbacks of this method. (References, Appl,
Phys, Lett. Vol. 25 No. 4 15 August 1974) The feature of this system is that it uses two AC power supplies of low frequency and high frequency, and theoretically the number of digits that can be multiplexed is infinite. There are various properties required of liquid crystals, one of which is that dielectric anisotropy on the high frequency side be negative and its absolute value large. Conventionally, general formulas were used to meet these requirements. or

A liquid crystal represented by [Formula] (where R and R' represent an alkyl group),
Or by adding a non-liquid crystal compound etc. to the liquid crystal composition,
Absolute position of dielectric anisotropy on the high frequency side (｜△εH｜)
was increasing. However, with the conventional method, |△εH| could only be raised to the third place at most. For this reason, the number of driving digits of a dual-frequency drive display body has been limited to approximately 50 digits. On the other hand, apart from this direction of multiplexing, research is also being carried out on colorization that applies the guest-host effect using liquid crystals and dyes. The drawback of this method is that the driving voltage is high for positive types that produce color when voltage is applied. This is because, as is well known, there is no liquid crystal composition that has negative dielectric anisotropy at low frequencies and has a large absolute position. One of the objects of the present invention is to provide a compound that makes the dielectric anisotropy negative at high frequencies and increases its absolute position by just adding a small amount. This was done in order to increase the absolute value of dielectric anisotropy on the low frequency side by adding only a small amount, and to provide a compound suitable as a material for a guest-host liquid crystal composition. The novel ester compound of the present invention has the general formula

A compound represented by the formula (where R represents a straight-chain alkyl group having 4,5 carbon atoms and R' represents a straight-chain alkyl group having 6,7 carbon atoms),
This compound can be synthesized by the following synthetic route. First, commercially available trans-4-n-alkylcyclohexane-1-carboxylic acid is converted into an acid chloride using thionyl chloride, and then this acid chloride and 3,6-dioxyphthalate are converted into an acid chloride using a suitable base catalyst and solvent. Monoesterifying nitrile to form 3-(trans-4'-
Make n-alkylcyclohexane-1'-carbonyloxy)-6-oxyphthalonitrile. Next, the desired compound can be obtained by esterifying this compound with a commercially available alkanoyl chloride. Compounds synthesized by this method do not exhibit a liquid crystal phase, but they have a rod-like structure similar to compounds that exhibit a nematic liquid crystal phase, so the clearing point of a composition containing this compound is extremely lowered, It does not narrow the liquid crystal temperature range. In addition, the two cyano groups are located in a direction substantially perpendicular to the long axis of the molecule, and are expected to have a considerably large dipole moment, which can be inferred to contribute considerably to making the dielectric anisotropy negative. Next, compound 3-(trans-4'-n-
The method for producing alkylcyclohexane-1'-carbonyloxy)-6-n-alkanoyloxyphthalonitrile will be explained in detail. Commercially available trans-4-n-alkylcyclohexane-1-carboxylic acid (these compounds are
53-22882) and an excess amount of thionyl chloride are placed in a flask and heated to reflux. After reflux, excess thionyl chloride is distilled off and trans-4-n-alkylcyclohexane-1-carboxylic acid chloride is obtained by distillation under reduced pressure. get. Next 3,6
-dihydroxy-phthalonitrile (literature,
Thieleund Meiseheimer Berichte33 675
(1900)) is dissolved in pyridine and allowed to stand for a while at room temperature. After standing, the pyridine solution is poured into cold concentrated hydrochloric acid, and the precipitated crystals are recrystallized from methanol to obtain a monoester compound of 3,6-dihydroxy-phthalonitrile. Next, an ether solution is prepared by dissolving this monoester compound and about twice the molar amount of triethylamine. Separately, prepare an ether solution in which an equivalent amount of alkanoyl chloride is dissolved, and add to the ether solution while cooling and stirring. After the reaction is complete, wash with water, wash with dilute hydrochloric acid, wash with water, wash with alkali, wash with water, repeat the washing process, dehydrate with anhydrous sodium sulfate, distill off the ether, and repeat recrystallization of the residue until the melting point becomes constant to obtain the desired product. get. The yield is about 30% based on trans-4-n-alkylcyclohexane-1-carboxylic acid. EXAMPLES Below, in order to demonstrate the embodiments of the present invention in more detail, examples of its production and application examples showing its usefulness will be described. Example 1 Commercially available trans-4-n-butylcyclohexane-1-carboxylic acid (melting point 41.0°C, clearing point 94.0
℃) and 20 ml of thionyl chloride were placed in a 100 ml flask and heated under reflux until gas generation stopped.
After refluxing, excess thionyl chloride was distilled off under reduced pressure. Trans-4-n-butylcyclohexane-1-carboxylic acid chloride was obtained by distilling the residue under reduced pressure. Boiling point 86-89℃/1mmHg Yield 84% Followed by 3,6-dihydroxyphthalonitrile
1.6 g was dissolved in 10 ml of pyridine. To this, 2 g of trans-4-n-butylcyclohexane-1-
Carboxylic acid chloride was added dropwise. After dropping, the solution was allowed to stand for a while, and then the pyridine solution was poured into ice-cooled concentrated hydrochloric acid to precipitate crystals. The crystals were recrystallized three times from methanol. Yield: 1.5g Next, 0.33g of 3-(trans-4-n-butylcyclohexane-1-carbonyloxy)-6-hydroxyphthalonitrile and 0.2g of triethylamine.
ml was dissolved in 30 ml of ether. To this solution, 10 ml of an ether solution containing 0.14 g of hexanoyl chloride (C ₅ H ₁₁ COCl) was added dropwise. Cooling and stirring were performed during the dropwise addition. After the addition, the mixture was refluxed for 30 minutes to complete the reaction. After refluxing, take the ether solution into a separating funnel and wash with water 2 times, wash with diluted hydrochloric acid 3 times, wash with water 2 times, 5
% caustic soda washing three times and water washing three times. After washing and dehydrating with anhydrous sodium sulfate,
The ether was distilled off. The residue was repeatedly recrystallized from ethanol until the melting point became constant. Melting point: 80°C Yield: 0.3g The infrared absorption spectra of the intermediate compound and the target compound are shown in Figures 1 and 2. Figure 1 shows 3-(trans-4'-n-butylcyclohexane-1'-carbonyloxy)-6-hydroxy-
FIG. 2 is an infrared absorption spectrum diagram of phthalonitrile.
FIG. 2 is an infrared absorption spectrum diagram of phthalonitrile (-butylcyclohexane-1-carbonyloxy)-6-n-hexanoyloxy. Examples 2-3 Similarly, 3-(trans-4'-n-butylcyclohexane-1-carbonyloxy)-6-n
-Octanoyloxyphthalonitrile Melting point 93℃ 3-(trans-4'-n-amylcyclohexane-1-carbonyloxy)-6-n-octanoyloxyphthalonitrile A melting point of 85°C was obtained. Incidentally, other compounds can also be synthesized by a similar method. Example 4 Application Example The liquid crystal composition shown in Table 1 has negative dielectric anisotropy and is suitable as a liquid crystal composition for a positive guest-host liquid crystal display. Dichroic dye D-
A liquid crystal composition prepared by adding 1% by weight of 35 (manufactured by BDH) was filled into a vertical alignment cell, and the contrast characteristics were measured. The measurement results are shown by the solid line in FIG. In the figure, the horizontal axis represents the driving voltage,
The vertical axis indicates transmittance (arbitrary units). The numbers shown in the figure represent the initial and saturation values of the contrast curve.
Shows the voltage at 90% and 10% when divided into 100 equal parts. Table 1 shows liquid crystal compositions and further compounds of the present invention. A liquid crystal composition prepared by adding 5% by weight of dichroic dye D-35 (manufactured by BDH) and 1% by weight was filled into a vertical alignment cell, and the contrast characteristics were measured. The measurement results are shown by the dotted line in FIG. As can be seen from the figure, adding only 5 weight percent of the compound of the present invention reduces the voltage by nearly 0.8V. It is well known to those skilled in the art that if a further reduction is desired, the amount added can be increased.

[Table] Example 5 Application Example The liquid crystal compositions shown in Table 2 were prepared, and the dielectric anisotropy (Δε) with respect to frequency was measured. Figure 4 shows the measurement results at 25.5°C. For comparison, the results when the compound of the present invention is not contained are shown by the dotted line. As can be seen from the figure, by adding the compound of the present invention, the absolute value of dielectric anisotropy on the high frequency side increases. This property is an important property for driving a dual-frequency drive liquid crystal display in multiple digits.

【table】

[Table] As described above, the compound of the present invention exhibits great power as a component of a liquid crystal composition for a positive type guest-host liquid crystal display or a dual-frequency drive liquid crystal display.

[Brief explanation of the drawing]

Figures 1 and 2 are compounds, respectively. and compound It is a figure showing an infrared absorption spectrum of. FIG. 3 is a diagram comparing the contrast characteristics of a liquid crystal composition containing the compound of the present invention and a liquid crystal composition not containing the compound. The solid line shows the contrast characteristics of the liquid crystal composition that does not contain the liquid crystal composition, and the dotted line shows the contrast property of the liquid crystal composition that contains the liquid crystal composition. FIG. 4 is a diagram showing the change in dielectric anisotropy with respect to frequency of a liquid crystal composition containing the compound of the present invention.

Claims (1)

[Claims] 1. The general formula is (However, R has 4,5 carbon atoms and R' has 6,7 carbon atoms.
represents a straight-chain alkyl group. ) An ester compound characterized by being represented by: