JPS6346738B2 - - 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. 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. In order to meet these demands, there is a need for a liquid crystal compound that exhibits a liquid crystal phase over a wider temperature range and has low viscosity. The present invention satisfies these demands.
That is, the present invention has the general formula, (In the above formula, R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.)
4″-alkylcyclohexyl)cyclohexyl]
It is benzonitrile. The compounds of the present invention have low viscosity and a wide liquid crystal temperature range. For example, 4-[trans-4'-(trans-4''-propylcyclohexyl)cyclohexyl]benzonitrile has a crystal-smectic point (C-Sm point) of 73.1°C, a smectic-nematic point (Sm-N point) of 81.1°C, and a nematic point of 81.1°C. - It exhibits a liquid crystal phase in a wide temperature range with a clearing point (N-I point) of 242.5℃, a dielectric anisotropy value of +7, a viscosity of about 30cp at 20℃ (extrapolated value), and is resistant to moisture, heat, air, and light. It is a suitable compound for obtaining a liquid crystal composition that has low viscosity and exhibits a nematic liquid crystal phase over a wide temperature range.The method for producing the compound of the present invention will be described next. Phenylmagnesium bromide is produced from magnesium and reacted with 4-(trans-4′-alkylcyclohexyl)cyclohexanone to produce 4′-(trans-4″-alkylcyclohexyl)cyclohexane-1′-ol-benzene (). shall be. Next, this is dehydrated using potassium hydrogen sulfate as a catalyst to give 4′-
(trans-4″-alkylcyclohexyl)cyclohexene-1′-yl-benzene () was obtained, and then hydrogenated using a Raney nickel catalyst to obtain trans-4′-(trans-4″-alkylcyclohexyl)cyclohexylbenzene (). get.
It can also be obtained by directly hydrogenating () using Raney nickel. Next, the compound () is halogenated with iodic acid or periodic acid to give 4-[trans-4″-alkylcyclohexyl)cyclohexyl]halogenobenzene (), which is then cyanated with cuprous cyanide. The desired 4-[trans-4'-(trans-4''-alkylcyclohexyl)cyclohexyl]benzonitrile () 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 form 4-[trans-4′-(trans-4″-alkylcyclohexyl)cyclohexyl]acetylbenzene (), and then hypochlorite A haloform reaction is performed with sodium bromate 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 to an acid amide () with ammonia to produce thionyl chloride, etc. By dehydration, () is obtained.The chemical formula is: The compounds of the present invention will be explained in more detail with reference to Examples below. Example 1 4-[Trans-4'-(Trans-
4″-propylcyclohexyl) cyclohexyl [Manufacture of benzonitrile] Place 3.6 g (0.148 mol) of magnesium turnings in a three-necked flask, and add 23.2 g of bromobenzene.
(0.148 mol) dissolved in tetrahydrofuran, the reaction temperature was kept at 30-35℃ in a _N2 atmosphere.
If you slowly drop it while stirring, it will react and 3
Over time, the magnesium dissolves and becomes homogeneous, producing phenylmagnesium bromide. 4-
(Trans-4'-propylcyclohexyl) 26.2 g (0.118 mol) of cyclohexanone was dissolved in tetrahydrofuran to make 50 ml, and the reaction temperature was
Drop as quickly as possible while keeping the temperature below 10℃.
After dropping, raise the temperature to 35℃, stir for 30 minutes, and then
Add 100ml of 3N hydrochloric acid. The reaction solution was transferred to a separating funnel, extracted three times with 100 ml of n-heptane, and the combined n
- Wash the heptane layer with water until the washing liquid becomes neutral, and then distill off the n-heptane under reduced pressure. The remaining oil was [4'-(trans-4''-propylcyclohexyl)cyclohexane-1'-ol]benzene, and 19 g of potassium hydrogen sulfate was added to it.
Dehydrate for 2 hours at 170°C in a stream of _N2 . 200ml after cooling
After adding the n-heptane, remove the potassium hydrogen sulfate and wash the n-heptane layer with water using a separating funnel until the washing liquid becomes neutral. Next, n-heptane is distilled off under reduced pressure, and the remaining oil is recrystallized from n-heptane and acetone to obtain [4′-(trans-4″-
Propylcyclohexyl)cyclohexene-1'-
benzene. Add 7.5g of this to ethanol
Dissolve in 500ml and add 3.2g of Raney nickel catalyst.
Catalytic reduction is carried out through hydrogen at 50°C and normal pressure. Both raw materials and products are tracked by gas chromatography,
The reduction reaction was terminated when the raw materials disappeared, that is, after 8 hours. The amount of hydrogen absorbed at this time was 800 ml. After separating the catalyst, the solvent was distilled off under reduced pressure, and the remaining crystals were recrystallized from ethanol [trans-
4′-(trans-4″-propylcyclohexyl)
cyclohexyl]benzene was obtained. This 1.4g was dissolved in 50ml of acetic acid, and a mixture of 0.9ml of pure water, 1.0ml of concentrated sulfuric acid, 0.20g of iodic acid, 0.50g of iodine, and 0.4ml of carbon tetrachloride was refluxed at 80°C for 5 hours. The reaction solution was cooled, the precipitated crystals were filtered, and the crystals were recrystallized with n-heptane to obtain 4-[trans-
4′-(trans-4″-propylcyclohexyl)
cyclohexyl]iodobenzene. This item shows a liquid crystal state, and the C-Sm point is 119.0℃, Sm
- The N point was 139.2°C, and the N-I point was 189.2°C.
Add 1.2g of this to 50ml of N,N'-dimethylformamide.
0.63 g of cupric cyanide was added, and the mixture was reacted at 130°C for 4 hours. Add 100 ml of n-heptane, transfer to a separatory funnel, separate the liquid with 30% aqueous ammonia, then wash with water, wash with 6N hydrochloric acid, and then wash with water until the washing liquid becomes neutral. The solvent was distilled off under reduced pressure, and n
-The target 4 is obtained by recrystallizing with heptane.
-(trans-4′-(trans-4″-propylcyclohexyl)cyclohexyl)benzonitrile. Yield: 0.4g, yield is 45% for cyanation reaction, C-Sm point is 73.1℃, Sm-N point teeth
The temperature was 81.1°C, and the N-I point was 242.5°C. Examples 2 to 4 In place of 0.118 mol of 4-(trans-4'-propylcyclohexyl)cyclohexanone in Example 1, each corresponding cyclohexanone was used to produce 4-[trans-4'-(trans-cyclohexyl)cyclohexyl. ]Benzonitrile and 4-
[trans-4'-(trans-4''-pentylcyclohexyl)cyclohexyl]benzonitrile and 4-[trans-4'-(trans-4''-heptylcyclohexyl)cyclohexyl]benzonitrile were produced. The physical property values, etc. are shown in Table 1 together with the results of Example 1.

[Table] * Yield Example 5 at the cyanation stage (Usage example) Trans-4-propyl-(4'-cyanophenyl)cyclohexane 24% Trans-4-pentyl-(4'-cyanophenyl)cyclohexane 36% Trans The nematic temperature range of liquid crystal composition A having the following composition is -4-heptyl-(4'-cyanophenyl)cyclohexane 25% and trans-4-pentyl-(4'-cyanophenyl-4)cyclohexane 15%. The dielectric anisotropy value was +11, and the viscosity at 20°C was 29 cp. In place of trans-4-pentyl-(4'-cyanophenyl-4)cyclohexane in liquid crystal composition A, the same amount of 4-[trans-4'-(trans-4''-pentyl) of Example 3 of the present invention was used. The nematic temperature range of the liquid crystal composition containing cyclohexyl)cyclohexyl]benzonitrile is -15 to 75℃, the dielectric anisotropy value is +11, and the viscosity at 20℃ is 28cp.
It was hot. The compounds of the invention are thus ideal for extending the nematic temperature range without increasing the viscosity.

Claims (1)

[Claims] 1. General formula (In the above formula, R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.)
4″-alkylcyclohexyl)cyclohexyl]
Benzonitrile.