JPH055830B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel liquid crystal materials having positive dielectric anisotropy values, materials useful as components of liquid crystal compositions, and liquid crystal compositions containing them. The display methods of liquid crystal display elements that utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials include TN type, guest-tost type, dual frequency method type, DAP type, and white/white type.
There are various types such as the Taylor type, and each type requires different properties of the liquid crystal material used. For example, depending on the type of display element, a liquid crystal material with positive dielectric anisotropy may be required.
A negative value may be required, or an intermediate value may be suitable. The liquid crystal material used must exhibit a liquid crystal phase over as wide a temperature range as possible, and must also be electrochemically stable against moisture, heat, air, light, etc. At present, there is no single compound that satisfies all of these conditions, and several types of liquid crystal compounds and non-liquid crystal compounds are mixed for practical use. Recently, there has been an increasing demand for liquid crystal display elements that operate over a wide temperature range, that is, from low to high temperatures. Furthermore, there is a need for a liquid crystal composition that can lower the threshold voltage and saturation voltage required to drive a display element. An object of the present invention is to provide a compound useful as a component of a liquid crystal composition that satisfies such requirements. The present invention is based on the general formula (In the formula, () is an alkyl group or alkoxy group having 1 to 15 carbon atoms, and X is

【formula】

【formula】

【formula】

【formula】

[expression] or

[Formula] is shown, and Y represents fluorine, chlorine or cyano group. ), represented by 2
-Substituted ethyl-5-substituted pyridine and a liquid crystal composition containing the same. A compound of the present invention in which X is two rings in formula () has a liquid crystal phase. Furthermore, the compound of the present invention has excellent compatibility with other liquid crystal compounds, such as ester-based, Schiff base-based, biphenyl-based, phenylcyclohexane-based, and heterocyclic-based liquid crystal compounds, and can be used in compositions mixed with other liquid crystal compounds. It is possible to lower the driving voltage of a liquid crystal display element using Next, a method for producing the compound of the present invention will be described.
A compound in which Y in formula () is a halogen atom can be synthesized by the following method. Adding 3-substituted-6-methylpyridine () to a solution of lithium diisopropylamide in tetrahydrofuran produces 4-substituted benzaldehyde ().
or react with trans-4-substituted cyclohexylaldehyde () to produce 2-{β-(4-substituted phenyl)-β-hydroxyethyl}-5-substituted pyridine () or 2-{β-(trans-4-substituted cyclohexyl)-β-hydroxyethyl}-5
- Obtain substituted pyridine (). This compound was then dehydrated with potassium hydrogen sulfate and then treated with palladium-
The desired 2-substituted ethyl-5-substituted pyridine (2) is obtained by catalytic reduction using carbon. For compounds in which Y in the formula () is a cyano group, 3-substituted-6-methylpyridine () and 4
-substituted benzaldehyde () or trans-4-substituted cyclohexylaldehyde () in the presence of acetic anhydride, followed by catalytic reduction using palladium-carbon to obtain the desired 2-substituted ethyl-5-substituted Pyridine () is obtained. This is shown in the chemical formula as follows. If Y is halogen When Y is a cyano group ()+()-H ₂ O ―――――――→ (CH ₃ CO) ₂ O()H ₂ ―――→ Pd/C () The invention will now be described in more detail. Example 1 2-{β-(4-fluorophenyl)ethyl}
-5-pentyloxypyrine 3-pentyloxy-6-methylpyridine 9.0
g (0.05 mol) of lithium diisopropylamide
7.5g (0.07mol) of tetrahydrofuran solution
Then, 6.2 g (0.05 mol) of 4-fluorobenzaldehyde was added dropwise to 40 ml while maintaining the temperature at -70°C, and stirring was continued at this temperature for 1 hour. After further stirring at room temperature for 2 hours, 50 ml of water was added and the reaction product was extracted with 100 ml of Torton. This toluene solution was washed with 2N hydrochloric acid, then with an aqueous sodium carbonate solution, and then washed with water until the washing water became neutral. Then, after removing Torton under reduced pressure,
The remaining solid is crystallized from methanol to give 2-{β-(4
-fluorophenyl)-β-hydroxyethyl}-
3.6 g of 5-pentyloxypyridine was obtained. Next, add 0.3g of potassium hydrogen sulfate to this compound and heat the mixture at 180°C.
The mixture was stirred for 2 hours. After the reaction was completed, 50 ml of water and 50 ml of chloroform were added, followed by extraction with chloroform, and the extract was washed with washing water until it became neutral. Chloroform was distilled off under reduced pressure from this solution and 2-
2.5 g of {β-(4-fluorophenyl)vinyl}-5-pentyloxypyridine was obtained. Dissolve this compound in 50 ml of Torton, palladium-carbon
After adding 0.2 g, catalytic reduction was carried out at room temperature and pressure.
After the reaction was completed, the catalyst was removed, the solvent was distilled off under reduced pressure, and the desired product, 2-{β-(4-fluorophenyl)ethyl}, was obtained as a fraction at 179-180℃/1.5mmHg.
-5-pentyloxypyridine was obtained. Yield 1.2
g, and the melting point was 15.6-16.6°C. Example 2 2-{β-(4″-fluorobiphenyl-4′)
Ethyl}-5-pentyloxypyridine 2-{β-(4″-fluoropiphenyl -4') Ethyl}-5-pentyloxypyridine was synthesized. Crystalline smectic point: 55.8-56.3°C, smectic clearing point 115.4-
It was 116.4. Example 3 2-{β-(4-cyanophenyl)ethyl}-5
-Pentyloxypyridine 3-pentyloxy-6-methylpyridine 5.4
g (0.03 mol), 4-cyanobenzaldehyde 4.0
Add 2 ml of acetic anhydride to g (0.03 mol) and heat at 160℃.
After stirring for 16 hours, add 50ml of water and add 100ml of toluene.
Extract with This toluene solution was washed with an aqueous sodium carbonate solution, and then washed with water until the washing water became neutral. Next, toluene was distilled off from this solution under reduced pressure, and the remaining solid was recrystallized with methanol to obtain 2
1.5 g of -{β-(4-cyanophenyl)vinyl}-5-pentyloxypyridine was obtained. The following catalytic reduction was carried out in the same manner as in Example 1 to obtain the target product 2-{β-(4-cyanophenyl)ethyl}-5-
Pentyloxypyridine was obtained. The yield was 0.5 g, and the melting point was 66.4-67.2°C. Examples 4 to 8 The following compounds were obtained by a method similar to Examples 1 and 2. 2-{β-(4-fluorophenyl)ethyl}-5
-Ethylpyridine Melting point 28.0-28.5℃ 2-{β-(4″-fluoropifenyl-4′)ethyl}-5-ethylpyridine Melting point 99.0-100.0℃ 2-{β-(4″-fluoropifenylyl) -4') Ethyl}-5-pentylpyridine Crystal-smectic point: 59.9-60.5℃, Smectic-clearing point: 90.4-91.4℃ 2-{β-(4-cyanophenyl)ethyl}-5-
Ethylpyridine Melting point 72.0-72.7℃ 2-{β-(4-cyanophenyl)ethyl}-5-
Proxypyridine Melting point 52.6-53.5℃ Example 9 (Application example) Trans-4-propyl(4'-cyanophenyl)cyclohexane 24% Trans-4-pentyl-(4'-cyanophenyl)cyclohexane 36% Trans-4-heptyl- (4'-cyanophenyl)cyclohexane 25% 4-cyano-4'-(trans-4-pentylcyclohexyl)biphenyl 15% The nematic clearing point of the liquid crystal mixture with the following composition is
72.0℃, viscosity is 27.8cp at 20℃, dielectric anisotropy value (hereinafter abbreviated as Δε) is +11.6, optical anisotropy value (hereinafter Δn
) is 0.140. This is made into a cell with a thickness of 10 μm.
The threshold voltage of a liquid crystal cell sealed in a TN cell is
The voltage was 1.75V, and the saturation voltage was 2.40V. this mixture
A liquid crystal composition comprising 85 parts by weight of 2-{β-(4-fluorophenyl)ethyl}-5-pentyloxypyridine of Example 1 of the present invention had a nematic clearing point of 59.6°C and a viscosity of 59.6°C. is 24.7cp at 20℃, Δε
was +10.9Δn was -0.027, the threshold voltage was 1.35V, and the saturation voltage was 1.92V. As described above, by applying the present invention, it was possible to reduce the viscosity of a liquid crystal composition and also reduce the driving voltage of a liquid crystal display element. Example 10 (Application example) Trans-4-propyl-(4'-cyanophenyl)cyclohexane 30% Trans-4-pentyl-(4'-cyanophenyl)cyclohexane 40% Trans-4-heptyl-(4'-cyanophenyl)cyclohexane The nematic clearing point of a liquid crystal mixture with a composition of 30% is
52.1℃, viscosity is 23.4cp at 20℃, Δε is +11.2, Δn is
It is 0.119. A liquid crystal cell in which this was sealed in a TN cell with a cell thickness of 10 μm had a threshold voltage of 1.54V and a saturation voltage of 2.13V. 85 parts by weight of this mixture and 2-{β-(4″-fluorobiphenyl-4′)ethyl}-5-pentyloxypyridine of Example 2 of the present invention
The nematic clearing point of the liquid crystal composition consisting of 15 parts by weight is 55.4°C, the viscosity is 24.1 cp at 20°C, and Δε is +
11.2, Δn was 0.122, threshold voltage was 1.50V, and saturation voltage was 2.05V. In this way, by applying the present invention, it was possible to lower the driving voltage of the liquid crystal display element.

Claims (1)

[Claims] 1. General formula (In the formula, R represents an alkyl group or an alkoxy group having 1 to 15 carbon atoms, X represents [Formula] [Formula] [Formula] [Formula] [Formula] or [Formula], and Y represents fluorine or chlorine. 2-substituted ethyl-5-substituted pyridine represented by 2 General formula (In the formula, R represents an alkyl group or an alkoxy group having 1 to 15 carbon atoms, X represents [Formula] [Formula] [Formula] [Formula] [Formula] or [Formula], and Y represents fluorine or chlorine. A liquid crystal composition containing a 2-substituted ethyl-5-substituted pyridine represented by (or a cyano group)