JPH0542437B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is directed to a novel compound, halogeno-1,3-
The present invention relates to a dioxane derivative and a liquid crystal composition containing this derivative. Conventional technology and its problems Display elements using liquid crystals utilize the optical anisotropy or induced anisotropy of liquid crystal materials, and are classified into TN type (twisted nematic type) and DS type ( There are various methods such as dynamic scattering type), guest-host type, and DAP type. The properties required of the liquid crystal materials used in these methods are different, but they are commonly required to exhibit a liquid crystal phase over as wide a temperature range as possible and to be stable against moisture, heat, light, air, etc. Ru. At present, there is no single compound that satisfies all such requirements, and liquid crystal compositions obtained by mixing several types of liquid crystal compounds or liquid crystal-like compounds are used. OBJECT OF THE INVENTION An object of the present invention is to provide a liquid crystal compound with large dielectric anisotropy. Another object of the present invention is to provide a compound that exhibits good compatibility and suppresses the increase in viscosity of a liquid crystal composition when mixed with other components when used as a liquid crystal composition. Structure of the invention The present invention is based on the general formula (In the formula, n is an integer from 1 to 10, Z represents a group selected from F, Br and Cl.) 1,
A liquid crystal composition containing a 3-dioxane derivative and the compound. The compound represented by the general formula () can be produced by a known method represented by the following reaction formula. In the formula, n and Z are as described above. That is, substituted benzyl chloride () and 4-
4-
(halogenobenzyloxy)benzaldehyde compound () is obtained. Next, this aldehyde compound () and the propanediol compound () are reacted in an inert organic solvent in the presence of a catalyst described below at normal pressure and reflux temperature. In the reaction between () and (), benzene, toluene, chloroform, carbon tetrachloride, methylene chloride, etc. are suitable as organic solvents, and as catalysts, Lewis acids such as aluminum chloride, tin tetrachloride, titanium tetrachloride, sulfuric acid, Mineral acids such as phosphoric acid, toluenesulfonic acid, etc. can be used. The desired compound of formula () can be isolated by subjecting the reaction product to a series of purification treatments such as solvent extraction, water washing, drying, and recrystallization. In addition, during the cyclization reaction, trans-isomer () and cis-isomer () are generated regarding the dioxane ring, but
(trans form: cis form = 3:1), the target compound is the trans form, and the cis form has a lower melting point and greater solubility in solvents, so by performing recrystallization one or more times, the cis form can be converted to the cis form. Only the separated trans isomer can be obtained. The 2-alkyl 1,3-propanediol () can be obtained by reducing alkyl malonic acid diethyl ester with lithium aluminum hydride. Examples of the above-mentioned substituted benzyl chloride () used in producing the compound of the present invention include the following compounds. Compounds in which halogen is represented by F, Br or Cl in o-halogenobenzyl chloride, m-halogenobenzyl chloride and p-halogenobenzyl chloride. The compound of the present invention represented by the general formula () can be mixed with other liquid crystal compounds or liquid crystal compositions and used as a new liquid crystal composition. As the other liquid crystal compound to be mixed with the compound represented by the general formula (), one or more compounds included in the group of compounds represented by the general formula shown below can be used. The content of the compound represented by the general formula () in the liquid crystal composition is preferably 1 to 1.
It is 30wt%, more preferably 5 to 20wt%. In addition, in each of the above formulas, R represents alkyl, and X represents

【formula】

【formula】

[expression] or

[Formula], Y represents -CN, halogen, R' or OR', R' represents an alkyl group, and m represents 1 or 2, respectively. Effects of the present invention Among the compounds of the present invention represented by the general formula (), especially those having a substituent at the p position in the above-mentioned formula () have a large dielectric constant anisotropy and a high clearing point, so the present invention By using the compound, the driving voltage of the obtained liquid crystal composition can be lowered and the clearing point thereof can be increased. EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. Example 1 5-Propyl-2-[4′-(4″-fluorobenzyloxy)phenyl]-1,3-dioxane Dissolve 6.1 g (0.05 mol) of 4-hydroxybenzaldehyde () in 200 ml of acetone and add anhydrous solution to the solution. 34.6 g (0.25 mol) of potassium carbonate was added and heated to reflux. 10.8 g (0.075 mol) of 4-fluorobenzyl chloride () was added to this. The reaction mixture was then heated to reflux for 10 hours, and then The reaction mixture was added to 500 ml of water and the precipitated crystals were separated. The crude crystals were recrystallized from ethyl alcohol to obtain 6.3 g (68%) of 4-(4'-fluorobenzyloxy)benzaldehyde (). The melting point was 97.7-98.8°C. 5 g (21.7 mmol) of 4-(4'-fluorobenzyloxy)benzaldehyde (), 2.6 g of 2-propyl-1,3-propanediol ()
(21.7 mmol) and 0.01 g of p-toluenesulfone were added to 100 ml of dry toluene and the mixture was refluxed.
Water produced by the reactants was separated using a Dean-Stark trap, and reflux was continued until no more water was distilled out. After the reaction was completed, the mixture was cooled to room temperature. Add toluene layer to 5% sodium hydrogen carbonate aqueous solution
Washed twice with 100 ml followed by water until neutral. The toluene solution was dried over anhydrous sodium sulfate, and then the toluene was distilled off. The resulting oil was recrystallized twice from ethyl alcohol to obtain the target product, 5-propyl-2-[4'-(4" 3.7 g (yield: 52%) of -fluorobenzyloxy)phenyl]-1,3-dioxane was obtained. This material exhibited a liquid crystal phase, with a C-S point (crystalline-smectic phase transition point) of 76.3°C and an S-N point. (Smektic-nematic phase transition point)
93.2℃ N-I point (nematic-isotropic liquid phase transition point)
It showed 111.8℃. Examples 2 to 4 The following compounds were obtained by a method similar to Example 1. 5-Propyl-2-[4'-(4''-chlorobenzyloxy)phenyl]1,3-dioxane C-N point (crystal-nematic phase transition point); 117.8
℃ N-I point; 128.8℃ 5-pentyl-2-[4'-(4''-chlorobenzyloxy)phenyl]-1,3-dioxane C-S point; 773℃ S-I point (smectic-
Isotropic liquid phase transition point); 138.1℃ 5-pentyl-2-[4'-(3''-fluorobenzyloxy)phenyl]-1,3-dioxane C-I point (crystal-isotropic liquid phase transition point); 57.5℃
SI point; 56.7°C Example 5 A trans-4-propyl-(4'-cyanophenyl)cyclohexane 30% by weight trans-4-bentyl-(4'-cyanophenyl)cyclohexane 40% by weight trans-4-heptyl-( The nematic clearing point of liquid crystal composition A having a composition of 30% by weight of 4'-cyanophenyl)cyclohexane is
At 52.1℃, the dielectric anisotropy value is +11.2, and the viscosity at 20℃ is
It is 23.4 cp. The liquid crystal composition A is placed in a 10 μm thick TN cell coated with silicon and rubbed,
When its characteristics were measured at 20℃, the threshold voltage was
The voltage was 1.54V, and the saturation voltage was 2.13V. 5% of the compound of the present invention is added to 85% by weight of this liquid crystal composition A.
-bentyl-2-[4′-(4″-fluorobenzyloxy)phenyl]-1,3-dioxane 15% by weight
The liquid crystal composition containing the above had an N-I point of 58°C, a dielectric anisotropy of 13.5, and a viscosity at 20°C of 25 c.p. When this liquid crystal composition was sealed in the aforementioned TN cell, the operating threshold voltage decreased to 1.47V and the saturation voltage decreased to 2.01V.

Claims (1)

[Claims] 1. General formula (In the formula, n is an integer from 1 to 10, and Z represents a group selected from F, Br, and Cl.) A 1,3-dioxane derivative represented by the following. 2 General formula (In the formula, n is an integer from 1 to 10, and Z represents a group selected from F, Br, and Cl.) A liquid crystal composition characterized by containing a 1,3-dioxane derivative represented by the following formula.