JPS64385B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel liquid crystal materials exhibiting positive dielectric anisotropy. Liquid crystal display elements utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials, and their display methods include TN type, DS type, guest-host type,
There are various types such as DAP type and White-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 a positive dielectric anisotropy Δε may be required, a material with a negative dielectric anisotropy may be required, or a material with an intermediate value may be suitable.
However, in any case, the liquid crystal materials used exhibit a liquid crystal phase over a wide temperature range, and also contain moisture and
It must be stable against heat, air, light, etc. At present, there is no single compound that satisfies all of these conditions, and the current state of affairs is to mix several types of liquid crystal compounds and non-liquid crystal compounds to obtain compounds that can withstand practical use. In recent years, there has been a demand for liquid crystal display elements that operate over a wide temperature range, ie, from low temperatures to high temperatures. In order to meet this requirement, there is a need for a material that exhibits a liquid crystal phase over a wide temperature range and has low viscosity. The present invention satisfies these requirements. That is, the general formula (In the above formula, R represents hydrogen or an alkyl group having 1 to 6 carbon atoms) 4-cyano-4′-[trans-4″-
(trans-4-alkylcyclohexyl)cyclohexyl]biphenyl. The compound of the present invention is, for example, one of the 4-
Cyano-4′ [Trans-4″-(Trans-4-
Propylcyclohexyl) cyclohexyl]biphenyl has a crystal-smectic (C-Sm) point of 109.0
°C, smektik-nemachik (Sm-N) point
It exhibits a liquid crystal phase over a wide temperature range, such as 155.9℃ and a nematic transparent (N-I) point of 380℃ (extrapolated value).
A low-viscosity nematic liquid crystal composition with a dielectric anisotropy value of about +7 and a viscosity of about 80 cp (extrapolated value) at 20°C, stable against moisture, air, light, etc., and can be used in a wide temperature range with a small amount of addition. It is a substance useful for making. Next, a method for producing the compound of the present invention will be described. First, 4-biphenylmagnesium bromide is produced from 4-bromobiphenyl and metallic magnesium, and this is reacted with 4-(trans-4'-alkylcyclohexyl)cyclohexanone to produce 4-[4
(trans-4-alkylcyclohexyl)
Cyclohexane-1″-ol]biphenyl ()
shall be. Next, this was dehydrated using potassium hydrogen sulfate as a catalyst to obtain 4-[4″-(trans-4-alkylcyclohexyl)cyclohexene-1″-yl].
Biphenyl () was then hydrogenated using a Raney-nickel catalyst to obtain 4-[trans-4″-
(trans-4-alkylcyclohexyl)cyclohexyl]biphenyl () is obtained. It can also be obtained by directly hydrogenating () using Raney nickel. Next, by halogenating the compound () with iodic acid or periodic acid, 4-iodo-4'-[trans-
4″-(trans-4-alkylcyclohexyl)cyclohexyl]biphenyl (), and cyanating it with cuprous cyanide produces the desired 4
-Cyano-4′-[Trans-4″-(Trans-4
-alkylcyclohexyl)cyclohexyl]
Biphenyl () is obtained. If the above is expressed as a chemical formula, The compound of the formula () can also be produced from the compound of the above () by the following route, although the number of steps is increased. That is, the compound () is reacted with acetyl chloride or acetic anhydride in the presence of anhydrous aluminum chloride to obtain 4-acetyl-4'-[trans-4''-(trans-4-alkylcyclohexyl)cyclohexyl]biphenyl (),
Next, a haloform reaction is carried out with sodium hypobromite or sodium hypochlorite to convert the acetyl group into a carboxyl group to form a carboxylic acid (), which is then converted into an acid chloride () with thionyl chloride, and then converted into an acid amide () with ammonia. Dehydration with thionyl chloride etc. gives (). Shown as a chemical formula, Hereinafter, the compounds of the present invention will be explained in more detail with reference to Examples. Example 1 [Manufacture of 4-cyano-4′-[trans-4″-(trans-4-propylcyclohexyl)cyclohexyl]biphenyl (with the formula () where R=C ₃ H ₅ )] Magnesium shavings 3.6 g (0.148 mol) in a three-necked flask and 34.5 g of 4-bromobiphenyl
(0.148 mol) dissolved in 100 ml of tetrahydrofuran is slowly added dropwise while stirring while maintaining the reaction temperature at 30-35°C in a N ₂ stream. After 3 hours, the reaction ended and the magnesium dissolved and became homogeneous 4-
This produces biphenylmagnesium bromide. To this, a solution of 26.2 g (0.118 mol) of 4-(trans-4'-propylcyclohexyl)cyclohexane dissolved in 50 ml of tetrahydrofuran was added at a reaction temperature of 10
Drop quickly while keeping the temperature below ℃. After dropping, the temperature was raised to 35℃, stirred for 30 minutes, and then 100ml of 3N hydrochloric acid was added.
Add. The reaction solution was transferred to a separatory funnel, extracted with n-heptane (100 ml x 3), the combined n-heptane layers were washed with water until the washings became neutral, and the solvent was distilled off under reduced pressure. The residue was 4-[4″-(trans-4-propylcyclohexyl)cyclohexane-1″-ol]biphenyl, to which 15 g of potassium hydrogen sulfate was added and the mixture was heated at 170°C in a N ₂ stream.
time to dehydrate. After cooling, add 300ml of n-heptane, separate the potassium hydrogen sulfate, wash the n-heptane layer with water on a separating funnel until the washings become neutral, remove the solvent under reduced pressure, and separate the n-heptane and acetone. The product obtained by recrystallization is 4-[4″-(trans-
4-propylcyclohexyl)cyclohexene-1″-yl]biphenyl. 5.4
Dissolve g (0.0150 mol) in 300 ml of ethanol,
2.2 g of Raney nickel catalyst was added, and catalytic reduction was carried out in an autoclave at 50° C. by applying hydrogen pressure of 5 kg/cm ² . The reduction reaction was monitored by gas chromatography and was terminated when the raw material disappeared, that is, after 5 hours. The amount of hydrogen absorbed at this time was 410 ml.
After removing the catalyst, the solvent was distilled off under reduced pressure, and the residue was recrystallized from n-heptane to give 4-[trans-4″-
(trans-4-propylcyclohexyl)cyclohexyl]biphenyl is obtained. of this
Dissolve 2.5g (0.0069mol) in 200ml of acetic acid and add pure water.
1.3ml, concentrated sulfuric acid 1.4ml, iodic acid 0.28g, iodine
A mixture of 0.71 g and 0.6 ml of carbon tetrachloride was refluxed at 80°C for 10 hours. The reaction solution was cooled, the precipitated crystals were filtered, and the crystals were recrystallized with n-heptane to obtain 4-iodo-4'-[trans-4''-(trans-4-propylcyclohexyl)cyclohexyl]. Biphenyl. 2.1g of this stuff.
(0.0043 mol) in N,N-dimethylformamide
Dissolve in 100ml, add 0.77g of cuprous cyanide,
The mixture was refluxed at 130°C for 5 hours. After cooling, n-heptane
Add 100 ml of 30% ammonia water to 100 ml to separate the liquid, then wash with water, wash with 6N hydrochloric acid, and then wash with water until the washing liquid becomes neutral. Remove the solvent under reduced pressure,
Recrystallized with n-heptane, the obtained product is 4-cyano-4′-[trans-4″-(trans-4-
Propylcyclohexyl)cyclohexyl]biphenyl. Yield 0.7g, yield 42% for cyanation reaction, C-Sm point 109.0℃, Sm-N point 155.9
℃, and the N-I point was 380℃ (extrapolated value). Examples 2 and 3 Cyclohexylcyclohexanone and 4-(trans-4'-pentylcyclohexyl)cyclohexanone were used in place of 4-(trans-4'-propylcyclohexyl)cyclohexane in Example 1, and the first Compounds of formula () shown in the Examples 2 and 3 columns of the table were obtained. The yield properties and the like are shown in Table 1 together with the results of Example 1.

[Table] Example 4 Trans-4-propyl-(4'-cyanophenyl)cyclohexane 28% Trans-4-pentyl-(4'-cyanophenyl)cyclohexane 42% Trans-4-heptyl-(4'-cyanophenyl)cyclohexane 30 %, the nematic liquid crystal temperature range of the liquid crystal composition is -3 to 52°C. This liquid crystal composition has a cell thickness of
When sealed in a 10 μm TN cell (twisted nematic cell), the operating threshold voltage was 1.53V and the saturation voltage was 2.12V. The viscosity was 23 cp at 20°C. 4 of Example 1 of the present invention was added to 95 parts of the above liquid crystal composition.
-Cyano-4′-[Trans-4″-(Trans-4
-Propylcyclohexyl) cyclohexyl]
The nematic liquid crystal temperature range of the liquid crystal composition containing 5 parts of biphenyl expands from -15 to 64.0°C, and when this is sealed in a TN cell with the same cell thickness of 10 μm, the operating threshold voltage is 1.63V, and the saturation voltage is The voltage was 2.3V, and the viscosity at 20°C was 25.6cp.

Claims (1)

[Claims] 1. General formula (In the above formula, R represents hydrogen or an alkyl group having 1 to 6 carbon atoms) 4-cyano-4′-[trans-4″-
(trans-4-alkylcyclohexyl)cyclohexyl]biphenyl.