JPS642112B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel organic compound, and more particularly to a novel compound useful as a component of a liquid crystal composition. As is well known, liquid crystal materials with positive dielectric anisotropy utilize nematic liquid crystals with twisted liquid crystal alignment.
In addition to being used in TN display elements, it is also used in color liquid crystal display elements that apply the guest-host effect by adding appropriate pigment substances. Currently, there is no single compound of these liquid crystal materials that can withstand practical use due to its various properties, such as liquid crystal temperature range, operating voltage, and response characteristics. Currently, liquid crystal compounds are mixed to obtain materials that can withstand a certain level of use. The present invention provides a novel compound useful as a component of a liquid crystal composition that has excellent practical performance and good stability and is used for such purposes. The compounds of the present invention have the general formula (However, in the above formula, n is 1 or 2, R ₁ ,
_R2 represents H or an alkyl group having 1 to 10 carbon atoms). Most of the compounds of formula () are nematic liquid crystals. However, it is not used alone because its liquid crystal temperature range is impractical, and is used in combination with other liquid crystal compounds. In this case, the compounds of the present invention generally have extremely good compatibility and are stable;
Therefore, it can be mixed with other liquid crystal substances to fully exhibit its properties. 2-(4′-transistor-4″-alkylcyclohexyl phenyl)trans-5-alkyl metadioxane which is a compound where n=1 in the formula () (R ₁ and R ₂ are the same as above) is the most preferable one among this compound, and is a liquid crystal material with dielectric constant anisotropy Δε of a positive value close to almost 0, and the liquid crystal range is from medium to high temperature. It is very useful as a so-called medium- to high-temperature liquid crystal component because it has a large area and a wide area. Furthermore, since it has a low viscosity, adding this compound increases the response speed and reduces the temperature dependence of the threshold voltage, making it possible to obtain a liquid crystal composition suitable for dynamic driving. 2{4'- which is a compound where n=2 in the formula ()
(4″-trans-4-alkylcyclohexyl phenyl)-phenyl-trans-5-alkyl metadioxane (R ₁ and R ₂ are the same as above) has a higher liquid crystal temperature range than the compound with n=1 and is used as a high temperature liquid crystal component. Next, the method for producing the compound () of the present invention will be described. First, the outline of the process is shown using a chemical formula. Here, the initial carboxylic acid () can be obtained as follows depending on the number of n. That is, 4-alkyl-1-phenylcyclohexanol is synthesized from monoprombenzene and 4-alkylcyclohexanone through a Grignard reaction. Next, a hydrogenation reaction is carried out in ethanol using Raney nickel as a catalyst to obtain a mixture of cis and trans forms of 4-alkyl-1-phenylcyclohexane. This is distilled under reduced pressure, and then subjected to a Friedel-Crafts reaction with acetyl chloride using methylene chloride as a solvent and aluminum chloride to produce 4-(4'-alkylcyclohexyl)-acetophenone. By distilling this under reduced pressure, only the trans isomer from which the cis isomer has been separated can be obtained. Furthermore, by reacting with sodium bromite in a mixed solvent of water/dioxane at 20°C for several hours, oxidizing it, making it acidic and precipitating a liquid crystal, and recrystallizing it with acetic acid, a compound with n=1 in the formula () can be obtained. It will be done. In the formula (), the compound where n = 2 is used instead of monobromobenzene, which is the starting material when n = 1.
It can be obtained in exactly the same manner using bromobiphenyl. The carboxylic acid obtained as described above is first reacted with a halogenating agent such as thionyl chloride to form an acid chloride, then hydrogenated in an inert solvent in the presence of a reducing catalyst, and converted into an aldehyde by chlorine-hydrogen exchange. . Inert solvents include benzene, toluene,
Xylene or the like may be used, and a preferred reducing catalyst is a palladium catalyst using barium sulfate as a carrier and a catalyst poison such as quinoline sulfur added thereto to weaken the activity. The reaction proceeds at normal pressure and at room temperature to reflux temperature. The aldehyde of the formula () can be obtained by subjecting the reactant to a series of operations such as solvent extraction, washing, solvent distillation, and distillation. Next, this aldehyde and propanediol are reacted in an inert organic solvent in the presence of a catalyst at normal pressure and reflux temperature. Benzene, toluene, chloroform, carbon tetrachloride, methylene chloride, etc. are suitable as organic solvents, and Lewis acids such as aluminum chloride, tin tetrachloride, titanium tetrachloride, sulfuric acid, phosphoric acid, toluenesulfonic acid, etc. are suitable as catalysts. Hydrogen acid etc. can be used. The desired product is obtained by subjecting the reactant to a series of purification treatments such as solvent extraction, water washing, drying, and recrystallization.
A compound of formula can be isolated. Nao () →
During the reaction of (), trans-isomer () and cis-isomer () are generated due to dioxane reduction, but since the cis-isomer has a lower melting point and higher solubility, recrystallization is performed one or more times to form the cis-isomer (). It is possible to obtain only the trans-isomer () separated from the trans-isomer. Another raw material, 2-alkylbropanediol-1,3-, can be obtained by the following process. That is, diethyl malonate is alkylated by reacting with an alkyl bromide in anhydrous ethanol in the presence of sodium ethoxide, and then reduced with lithium aluminum hydride in anhydrous tetrahydrofuran as a solvent. The reaction product was obtained by dissolving inorganic substances with dilute sulfuric acid, extracting with ether, washing with water, distilling off the ether, and distilling under reduced pressure to obtain 2-alkylbropanediol.
Get 1,3. The method for producing the compound of the present invention, its properties, and the liquid crystal composition containing the same will be explained in more detail below using Examples. Example 1 [2-(4′-trans 4″-pentylcyclohexylphenyl)trans-5-n-butyl-
Production of 1,3-dioxane] 100 g (0.364 mol) of 4-(trans-4'-n-pentylcyclohexyl)-benzoic acid and 131.1 g (1.1 mol) of thionyl chloride were mixed in a flask,
The reaction was carried out under heating under reflux for 1 hour, and then excess thionyl chloride was distilled off under reduced pressure. This acid chloride was dissolved in 300 ml of dry xylene, and 5% palladium catalyst with barium sulfate as a carrier was added to the solution.
g and 1 ml of quinoline sulfur solution. The quinoline/sulfur solution was obtained by refluxing 1 g of sulfur and 6 g of quinoline for 6 hours, and then diluting the solution to 70 ml with xylene. After replacing the air in the flask with hydrogen, place the flask in an oil bath while passing hydrogen for 140~
Heat to 150°C, blow in hydrogen with stirring, and allow to react for about 3 hours. After the reaction, cool and add 100 ml of 10% aqueous sodium hydroxide solution to decompose and remove the acid chloride in the final reaction. The xylene layer was then washed with water, dehydrated and dried over anhydrous sodium sulfate, and then the xylene was distilled off under reduced pressure, and the residue was distilled under reduced pressure. 172-174℃/1mmHg fraction is 74.2g (0.287
mole), which is 4-(trans-4'-n-
pentylcyclohexyl phenyl)-benzaldehyde. 2.58g (0.01mol) of the above benzaldehyde2
-1.32g of n-butylpropanediol 1,3
(0.01 mol) and para-toluenesulfonic acid 0.05
Dissolve g in 100 ml of dry toluene in a flask,
The mixture was further reacted under heating under reflux for 30 minutes. After the reaction, the toluene layer was cooled and washed twice with a 5% aqueous sodium bicarbonate solution and once with water. The toluene layer was dried over anhydrous sodium sulfate, and then the toluene was distilled off. Recrystallization from ethyl alcohol gave 2.31 g of needle crystals. This is purpose 2
-(4′-trans-4″-n-pentylcyclohexylphenyl)trans-5-n-butyl-1,
The physical properties of 3-dioxane, such as its melting point, are shown in Table 1. Moreover, the elemental analysis values are in good agreement with the calculations as shown below. Analyzed value (%) Calculated value (%)
(As C ₂₅ H ₄₀ O ₂ ) C 80.62 80.59 H 10.80 10.82 Example 2-14 In the same manner as in Example 1, n, R ₁ , R ₂ in formula ()
The melting point, phase transition point, etc. of the compound obtained by manufacturing a compound with various changes in the type of raw material carboxylic acid and the type of alkyl group of 2-alkylpropanediol-1,3 are In the table,
The results are shown together with the results of Example 1.

【table】

[Table] Example 18 (Application example 1) When a liquid crystal composition having the following composition was prepared, its nematic liquid crystal temperature range was -20°C or less to 71°C, and the viscosity at 20°C was 50CP. In addition, this liquid crystal composition was encapsulated in two glass substrates equipped with transparent electrodes subjected to surface alignment treatment, and a 10 μm thick glass substrate was prepared.
When a TN type cell was made and the threshold voltage and saturation voltage at 25°C were measured, they were 1.65V and 2.25V, respectively, indicating that the cell was sufficiently practical. Example 19 (Application example 2) When we prepared a liquid crystal composition with the following composition and measured its nematic liquid crystal temperature range, it was -15°C to 79°C.
Adhesion at 20°C was 32CP. Using this, we made a TN cell in the same way as in Application Example 1, and measured its threshold voltage and saturation voltage, which were 1.95V, respectively.
It was 2.70V. Example 20 (Application example 3) The nematic liquid crystal temperature range of the liquid crystal composition with the composition is -20 or less to 63℃, and the viscosity at 20℃ is
It was 37CP. In addition, a TN cell was made using this liquid crystal composition in the same manner as in Application Example 1, and its threshold voltage and saturation voltage were measured and found to be 1.72V and 1.72V, respectively.
It was 2.35V.

Claims (1)

[Claims] 1. General formula (However, in the above formula, n is 1 or 2, and R ₁ and R ₂ represent H or an alkyl group having 1 to 10 carbon atoms.) A 2,5-substituted metadioxane derivative represented by: 2 General formula (R ₁ and R ₂ are the same as above) 2 and 5 of claim 1
-Substituted metadioxane derivative. 3 General formula (However, in the above formula, n is 1 or 2, and R ₁ and R ₂ represent H or an alkyl group having 1 to 10 carbon atoms.) Contains at least one 2,5-substituted metadioxane derivative represented by A liquid crystal composition characterized by: