JPS6364421B2 - - 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: (However, R is a straight-chain alkyl group having 4 carbon atoms, and R' is a straight-chain alkyl group having 5 carbon atoms.) 3-(trans-4'-n-alkylcyclohexane-1'-carbonyloxy -6-Relating to n-alkoxycarbonyloxy-phthalonitrile.In recent years, watches, calculators, etc. that use liquid crystal displays have come on sale in large quantities.This is because the liquid crystal display has low voltage drive, low power consumption, etc. This is because it has excellent features.The liquid crystal display with this excellent feature uses a method called the twisted nematic method.However, even with this excellent method, the number of digits that can be driven by multiplex drive is limited. There was a drawback that it was not suitable for large-capacity displays.A method proposed to improve the drawbacks of this method is the dual-frequency drive method.(References, Appl.
Phys.Left.Vol.25No.4 15 August 1974) This method is characterized by the use of low-frequency and high-frequency two-ac power supplies, and theoretically the number of digits that can be driven 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

The absolute value of dielectric anisotropy on the high frequency side (| △
εH| was increased. However, with the conventional method, |△εH| could only be raised to 4th place at most. For this reason, the number of driving digits of a dual-frequency drive display is generally limited to about 64 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 dielectric anisotropy negative on the high frequency side 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 liquid crystal composition for a guest-host liquid crystal display. The novel ester compound of the present invention has the general formula This compound can be synthesized by the following synthetic route. (However, R is a straight chain alkyl group having 4 carbon atoms,
R' represents a straight chain alkyl group having 5 carbon atoms. ) That is, first, commercially available trans-4-n-alkylcyclohexane-1-carboxylic acid was converted into an acid chloride using thionyl chloride, and then this acid chloride and 3, 6-Dioxyphthalonitrile is monoesterified to produce 3-(trans-4'-n-alkylcyclohexane-1'-carbonyloxy)-6-oxyphthalonitrile. Next, the desired compound can be obtained by esterifying this compound with commercially available n-alkoxycarbonyl 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 liquid crystal compositions containing this compound can be extremely lowered. ,
It does not narrow the liquid crystal temperature range. Furthermore, the two cyano groups are located in a direction substantially perpendicular to the long axis of the molecule, and can be expected to have a fairly large dipole moment, which can be inferred to contribute considerably to making the dielectric anisotropy negative. Next, compound 3-(trans-4'-n-
Alkylcyclohexane-1-carboxy)-6
-The method for producing n-alkoxygalbonyloxyphthalonitrile 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- is distilled under reduced pressure. A carboxylic acid chloride is obtained. Next, 3,6-dihydroxy-phthalonitrile (Reference:
Thiele and Meisehelwer Berichte 33, 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 with methanol to form 3,6-dihydroxy-
A monoester compound of phthalonitrile is obtained. 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 alkoxygalbonyl chloride is dissolved, and add to the ether solution while cooling and stirring. After the reaction is complete, wash with water,
After repeating dilute hydrochloric acid washing, water washing, alkaline washing, and water washing, the ether solution is dehydrated with anhydrous sodium sulfate. After dehydration, the ether is distilled off and recrystallization is repeated until the melting point of the residue becomes constant to obtain the desired product. The yield is about 25% based on trans-4-n-alkylcyclohexane-1-carboxylic acid. EXAMPLES In order to demonstrate the embodiments of the present invention in more detail, production examples thereof and application examples demonstrating their usefulness will be described below. Example 1 Commercially available trans-4-n-butylcyclohexane-1-carboxylic acid (melting point, 41.0°C, clearing point,
94.0°C) 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. By distilling the residue under reduced pressure, trans-4
-n-butylcyclohexane-1-carboxylic acid chloride was obtained. 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 mixture was allowed to stand for a while, and then the pyridine solution was poured into water-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-carbonylfoxy)-6-hydroxyphthalonitrile and 0.2g of triethylamine.
ml was dissolved in 30 ml of ether solution. This solution contains n
-amyloxycarbonyl chloride

10 ml of an ether solution containing 0.15 g of [Formula] 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, wash it twice with water, wash it with diluted hydrochloric acid three times, wash it with water twice, and add 5%
Washing with caustic soda was repeated three times and washing with water was repeated three times. After washing and dehydration with anhydrous sodium sulfate, the ether was distilled off. The residue was repeatedly recrystallized from ethanol until the melting point became constant. yield
0.2 g, melting point 58°C. Infrared absorption spectra of the intermediate compound and the target compound are shown in Figures 1 and 2. Figure 1 is an infrared absorption spectrum diagram of 3-(trans-4'-n-butylcyclohexane-1'-carbonyloxy)-6-hydroxyphthalonitrile.
Figure 2 shows the compound 3-(trans-4'-n) of the present invention.
FIG. 2 is an infrared absorption spectrum diagram of ``butylcyclohexane-1'-carbonyloxy)-6-n-amyloxycarbonyloxyphthalonitrile. Example 2 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 type guest-host liquid crystal display. Dichroic dye D is added to this liquid crystal composition.
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. This measurement result is
Indicated by the solid line in the figure. In the figure, the horizontal axis shows the driving voltage, and the vertical axis shows the transmittance (arbitrary unit). The numbers shown in the figure indicate the voltages at 90% and 10% when the initial value and saturation value of the contrast curve are divided into 100 equal parts. In addition to the liquid crystal composition shown in Table 1, a compound of the present invention is added. A liquid crystal composition prepared by adding 5% by weight of dichroic dye D-35 (manufactured by BDH Co., Ltd.) and 1% by weight of dichroic dye D-35 (manufactured by BDH) was filled into a vertical alignment cell, and 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 3 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 25.2°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 position 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 drawings]

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 changes in dielectric anisotropy with respect to frequency of a liquid crystal composition containing the compound of the present invention.

Claims (1)

[Claims] 1. The structural formula is An ester compound characterized by: