JPH0432067B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel liquid crystal material exhibiting positive dielectric anisotropy and a liquid crystal composition containing the same.

Display methods of liquid crystal display elements that utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials include TN type,
DS type, guest-host type, dual frequency method type, DAP
There are various methods such as type, White-Taylor type, etc., and each method requires different properties of the liquid crystal material used. For example, depending on the type of display element, a liquid crystal material with positive or negative dielectric anisotropy may be required, or a material with 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 be 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 and put into 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 novel liquid crystal compound that can increase the clearing point of a liquid crystal composition and reduce the driving voltage of a liquid crystal display element using the liquid crystal composition.

The first aspect of the present invention is the general formula (In the formula, either X or Y has 1 to 1 carbon atoms.
15 represents an alkyl group or an alkoxy group, and the other represents fluorine. ) is 3-(p-substituted phenyl)-5-(p'-substituted phenyl)isoxazole.

The second aspect of the present invention contains 3-(p-substituted phenyl)-5-(p'-substituted phenyl)isoxazole represented by the general formula (wherein X and Y have the above-mentioned meanings). This is a liquid crystal composition characterized by the following.

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 increase the upper limit temperature for use of a liquid crystal display element using the present invention, and to lower the driving voltage thereof.

In addition to these effects, refractive index anisotropy (hereinafter △n
) is large, which also has the advantage that color unevenness due to non-uniform substrate spacing of the liquid crystal cell is less likely to occur.

Next, a method for producing the compound of the present invention will be described.
A p-substituted benzal-p'-substituted acetophenone is prepared by heating a p-substituted benzaldehyde and a p-substituted acetophenone in an aqueous ethanol solution in the presence of sodium hydroxide. Then,
By heating this compound with hydroxylamine hydrochloride in the presence of potassium hydroxide in an aqueous ethanol solution, 3-(p-substituted phenyl)-5-
A (p′-substituted phenyl)isoxazoline is obtained. Furthermore, by heating this isoxazoline with chromium oxide in an acetic acid solution, the desired 3-
(p-substituted phenyl)-5-(p'-substituted phenyl)
Isoxazole is obtained.

This can be expressed as a chemical formula as follows.

The present invention will be explained in more detail below using Examples.

Example 1 3-(p-fluorophenyl)-5-(p'-hexyloxyphenyl)isoxazole 3-(p-fluorophenyl)-5-(p'-hexyloxyphenyl)isoxazoline 5.0 Dissolve g in 200 ml of acetic acid, add 3.0 g of chromium oxide,
Stirring was performed at 80°C for 1 hour. After stirring,
The reaction solution was poured into 600 ml of ice water, and the precipitate obtained by filtration was dissolved in 100 ml of toluene and washed until the washing water became neutral. Next, toluene was distilled off under reduced pressure, and the remaining solid was recrystallized three times from ethyl acetate to obtain 1.6 g of the desired 3-(p-fluorophenyl)-5-(p'-hexyloxyphenyl)isoxazole.
(32%). The phase transition point is crystal-smectic point: 88.0℃, smectic-clearing point: 154.6℃
It was hot.

3-(p-fluorophenyl)-5-(p'-hexyloxyphenyl)isoxazoline used as a starting material was prepared as follows.

(a) 30.9g p-hexyloxybenzaldehyde
and 150 ml of an ethanol solution of 20.7 g of p-fluorophenone and 100 ml of an aqueous solution of 16 g of sodium hydroxide.
was added and refluxed for 3 hours. 200ml of toluene after cooling
was added and washed until the washing water became neutral. After the toluene was distilled off under reduced pressure, the residue was crystallized twice from methanol to obtain 33 g (67%) of p-hexyloxybenzal-p'-fluoroacetophenone.
Obtained: melting point 74°C.

(b) Add 11 g of hydroxylamide hydrochloride and 20 g of potassium hydroxide to 300 ml of an ethanol solution of 33 g of p-hersyloxybenzal-p'-fluoroacetophenone.
100 ml of an aqueous solution of 10 g was added thereto, and the mixture was refluxed for 3 hours. After cooling, dissolve the filtered precipitate in 100ml of toluene,
Washing was performed until the washing water became neutral. Next, after distilling off toluene under reduced pressure, the residue was diluted with ethanol.
After recrystallization, 3-(p-fluorophenyl)-5
8 g (23%) of -(p'-hexyloxyphenyl)isoxazoline were obtained: melting point 104°C.

Example 2 3-(p-octyloxyphenyl)-5-
(p'-fluorophenyl)isoxazole 3-(p-octyloxyphenyl)-5-
(p′-fluorophenyl)isoxazoline 2.8g
By the same procedure as in Example 1 using
-(p-octyloxyphenyl)-5-(p'-fluorophenyl)isoxazole 0.5g (18%)
I got it. The phase transition point is crystal-smectic point: 97.7
°C, smectic - clearing point: 148.5 °C.

Example 3 (Application example) Trans-4-propyl-(4'-cyanophenyl)cyclohexane 30% by weight Trans-4-pentyl-(4'-cyanophenyl)cyclohexane 40% by weight Trans-4-heptyl-(4'-cyanophenyl) ) The nematic clearing point of a liquid crystal mixture (hereinafter abbreviated as A) consisting of 30% cyclohexane by weight is 52°C, and the dielectric anisotropy value (hereinafter △
ε) is +11.2, and the optical anisotropy value (hereinafter abbreviated as Δn) is 0.119. A liquid crystal cell was prepared in which substrates having tin oxide transparent electrodes coated with silicon oxide and wrapped were assembled with an electrode spacing of 10 μm, and the liquid crystal composition (A)
When the characteristics were measured at 20℃, the threshold voltage was 1.54V, and the saturation voltage was 1.54V.
It was 2.13V.

90 parts by weight of this liquid crystal composition (A) and Example 1 of the present invention
The nematic clearing point of a composition comprising 10 parts by weight of 3-(p-fluorophenyl)-5-(p'-hexyloxyphenyl)isoxazole was 56°C;
△ε is +10.7, △n is 0.128, the threshold voltage of the liquid crystal cell using this composition is 1.44V, and the saturation voltage is
It was 2.03V.

Example 4 (Application example) 90 parts by weight of the liquid crystal composition (A) of Example 3 and 3-(p-octyloxyphenyl)-5 of Example 2 of the present invention
-(p′-fluorophenyl)isoxazole 10
The nematic clearing point of a composition consisting of parts by weight is
At 56°C, Δε was +10.3, Δn was 0.122, the threshold voltage of the liquid crystal cell using this composition was 1.51V, and the saturation voltage was 2.04V.

In this manner, the threshold voltage and saturation voltage of a liquid crystal display element could be lowered by applying the present invention.

Claims (1)

[Claims] 1. General formula (In the formula, either X or Y has 1 to 15 carbon atoms.
3-(p-substituted phenyl) represented by
-5-(p'-substituted phenyl)isoxazole. 2 General formula (In the formula, either X or Y has 1 to 15 carbon atoms.
3-(p-substituted phenyl) represented by
A liquid crystal composition containing -5-(p'-substituted phenyl)isoxazole.