JPS6310137B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel liquid crystal compounds useful as electro-optic display materials. Nematic liquid crystals are currently widely used as display elements. These display methods can be roughly divided into the TN type (twisted nematic type),
Typical examples include DS type (dynamic scattering type), DAP type (field-controlled birefringence type), PC type (cholesteric-nematic phase transition type), and GH type (guest-host type) using dichroic dyes. It is something. Until now, smectic liquid crystals have not been widely used in practice, but depending on their compatibility with nematic liquid crystals, they can be added to nematic liquid crystals to improve their properties. Capacity information can now be displayed, and there is an urgent need to put it into practical use, and there is also active development of display methods that have faster response performance than the TN type. At present, there are no single compounds of liquid crystal materials used in these display elements that can withstand practical use in terms of their properties, such as liquid crystal temperature range, operating voltage, response performance, etc.; Currently, liquid crystal compounds suitable for practical use are obtained by mixing about 20 types of liquid crystal compounds. Particularly recently, liquid crystal display elements have come to be used in automobiles and the like, and there is a demand for devices that can be used in a wider temperature range and that have a faster response speed at low temperatures. In order to constitute such a liquid crystal composition, a high temperature liquid crystal compound (one with a high upper limit of the liquid crystal temperature range) and a low viscosity liquid crystal compound are essential as its components. However, usually the former high-temperature liquid crystal compounds have an inherently high viscosity, and until now the latter low-viscosity liquid crystal compounds have been known to be used, e.g.

【Formula】Ya

[Production of trans, trans-4-propyl-4'-methylbicyclohexane]

1st stage Trans-(trans-
Add 68.2 g (0.270 mol) of 4'-propylcyclohexyl cyclohexanecarboxylic acid, 200 ml of methyl alcohol, and 14 ml of concentrated sulfuric acid, heat with a mantle heater, and reflux for 4 hours. Cool, add 200 ml of water and 100 ml of heptane, transfer to a separatory funnel, and wash the organic layer with water. Heptane is distilled off under reduced pressure, and the crude product is dissolved in 50 ml of ethyl alcohol and recrystallized. Separate this and dry it to produce trans-4-(trans-
65 g of 4'-propylcyclohexyl)cyclohexanecarboxylic acid methyl ester () are obtained. The melting point (C-N point) of this product is 34.2℃ and the clearing point (N-I point)
point) was 62.8℃. Second stage: 7.0 g (0.183 mol) of lithium aluminum hydride in 440 ml of dried tetrahydrofuran (THF)
ml and stir vigorously, then add the compound ()
A solution of 65 g (0.244 mol) dissolved in 65 ml of THF is added dropwise while keeping the reaction temperature below 20°C. After the dropwise addition is completed, the mixture is heated to 55°C, reacted for 2 hours, and cooled. Next, after adding 13 ml of ethyl acetate and 100 ml of water,
Adding 400 ml of 18% sulfuric acid water separates the organic layer and aqueous layer. Add 200 ml of heptane, transfer to a separatory funnel, wash with 500 ml of water, then wash with 500 ml of 2% aqueous sodium bicarbonate solution, and further wash with water until the aqueous layer becomes neutral. Heptane, THF, etc. were distilled off under reduced pressure, and the residue was recrystallized from 100 ml of ethyl alcohol.
Separately, 49.3 g of compound () is obtained by drying. The melting point of this product was 125.8-126.9°C. Third step: Put 57 ml of hydrobromic acid (47% bromine hydrogen content) into a 500 ml three-necked flask, cool in an ice bath, stir, and slowly add 6.3 ml of concentrated sulfuric acid. Furthermore, 26.2 g (0.11 mol) of compound () was added, heated with a mantle heater to reflux, and maintained at reflux for 7 hours. Cool, add 50 ml of toluene, transfer to a separatory funnel, and wash the organic layer with water to make it neutral. Toluene was distilled off under reduced pressure, and the residue was dissolved in 30 ml of ethyl acetate and recrystallized. Separate and dry this to obtain 23.5 g of compound (). The melting point of this product is 42.3-44.1°C. 4th stage: 3.1g of compound () in a 100ml three-necked flask
(0.01 mol), ethyl alcohol 15ml, ethyl acetate
Add 15 ml, 3 g of 5% Pd-carbon powder, and 3 g of magnesium oxide, and perform hydrogen displacement three times to absorb hydrogen. The reaction temperature was room temperature (25°C), and the amount of hydrogen absorbed reached a saturated state at 250 ml. After maintaining the saturated state for 1 hour, stop absorbing hydrogen gas and
After removing the %Pd-carbon powder and magnesium oxide, and distilling off the organic matter in the liquid under reduced pressure, distillation is performed under reduced pressure to collect the fraction with a boiling point of 102°C to 105°C/2 mmHg to obtain the desired trans, trans-4-propyl- 1.2 g of 4'-methylbicyclohexane was obtained.
The CS point of this product was 4°C, and the SI point was 24.5°C. Moreover, the elemental analysis values of this product are in good agreement with the calculated values as shown below. Actual value (%) Calculated value (%) (as C ₁₆ H ₃₀ ) C 86.37 86.40 H 13.58 13.60 Example 2 [Production of trans, trans-4-propyl-4'-pentylbicyclohexane] Third of Example 1 5 g (0.017 mol) of trans, trans-4-propyl-4'-bromomethylbicyclohexane obtained in step 1 was added under a dry nitrogen atmosphere.
Add 15 ml of anhydrous ether to a 100 ml three-necked flask.
Add and stir at 20℃ to dissolve. To this, 15.9 ml of a 1.67N hexane solution of n-butyllithium was added dropwise over about 5 minutes while maintaining the liquid temperature at 20 to 25°C. After dropping, reflux on a water bath and keep for 1 hour. chilled water 5
ml, add 10 ml of 6N-HCl water, transfer to a separatory funnel, and add 30 ml of toluene. Wash the organic layer with water until it becomes neutral. The solvent was distilled off under reduced pressure, the residue was dissolved in 2 ml of ethyl acetate, recrystallized in a freezer (-10°C), and filtered. When the crystals were dried, 0.2 g was obtained. The C-S point of this product was 15.6°C, and the SI point was 97.2°C. Moreover, the elemental analysis values of this product are in good agreement with the calculated values as shown below. Actual value (%) Calculated value (%) (as C ₂₀ H ₃₈ ) C 86.22 86.25 H 13.28 13.30 Example 3 Other compounds of formula () were obtained in the same manner as in Example 1 or 2. The phase transition point is shown in Table 1 together with the results of Examples 1 and 2.

【table】

[Table] Example 4 (Usage example) The nematic liquid crystal temperature range (MR) of the liquid crystal composition consisting of is -3 to 52.5℃, and the viscosity η ₂₀ at 20℃ is
23cp, dielectric anisotropy △ε is 11.3 (ε=16.2, ε
⊥=4.9), and when this is sealed in a TN cell with a cell thickness of 10 μm, the threshold voltage is 1.5V and the saturation voltage is 2.2V.
It was hot. Example 1, which is one of the compounds of the present invention, was added to this liquid crystal composition.

The MR of the liquid crystal composition containing 16.7 parts of [Formula] expands to the low temperature side from -20 to 42.5℃, η ₂₀ is low at 18 cp, and △ε is
8.2 (ε=12.8, ε⊥=4.6), and when this is sealed in the same TN cell as above, the threshold voltage is 1.45V,
The saturation voltage was 1.96V, which was lower in both cases.

Claims (1)

[Claims] 1. General formula (In the above formula, R ₁ represents an alkyl group having 2 to 8 carbon atoms, and R ₂ represents an alkyl group having 1 to 8 carbon atoms) trans, trans-4-alkyl-4'-alkyl Bicyclohexanes. 2 General formula (In the above formula, R ₁ represents an alkyl group having 2 to 8 carbon atoms, and R ₂ represents an alkyl group having 1 to 8 carbon atoms) trans, trans-4-alkyl-4'-alkyl A liquid crystal composition containing at least one type of bicyclohexane.