JPH0133091B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to liquid crystal compounds that exhibit excellent behavior in liquid crystal mixed systems, particularly low viscosity and solubility. Nematic liquid crystals have optical properties such as light scattering and birefringence that change significantly under the influence of an electric field, and are widely used in electro-optical display devices that apply various display principles. Twisted nematic display elements are typical electro-optical display elements that utilize twisted nematic liquid crystals. A display element that has a guest-host effect by adding dichroic dyes or pleochroic dyes. Furthermore, a phase change type guest-host display element in which the orientation of a cholesteric liquid crystal or a nematic liquid crystal added with an optically active substance is controlled by an electric field is attracting attention. Common requirements for liquid crystal materials used in these applications include: (1) Covering room temperature and having a wide liquid crystal temperature range. (2) Low viscosity to ensure responsiveness. (3) To increase display contrast, the refractive index anisotropy (Δn) must be small. (4) Stable against moisture, light, heat, etc. (5) High solubility for forming a liquid crystal composition. and so on. However, there is currently no known single compound that satisfies all of these properties, and it is possible to achieve this goal by using a liquid crystal composition that is a combination of several types of compounds. This is the current situation. Further, by using such liquid crystal composition preparation techniques, among the above-mentioned requirements, especially (1) the liquid crystal temperature range can be easily improved. Therefore, the compounds particularly required here are those with low viscosity and excellent solubility;
It is a stable compound with a small Δn. An object of the present invention is to provide a liquid crystal compound that can be advantageously used as a material for liquid crystal compositions used in the various electro-optic display elements as described above. That is, the present invention provides the general formula

[Formula] (In the formula, when R ₁ is C ₃ H ₇ −, R ₂ represents C ₃ H ₇ −,
If R ₁ is C ₄ H ₉ −, R ₂ is C ₃ H ₇ −, C ₄ H ₉ −, C ₅ H ₁₁
-, _C6H13- , _C7H15- , _{C8H17- )} 4- _{n -} alkoxy-(trans-4'-
n-alkylcyclohexyl)-benzene. The compound is synthesized as follows. Commercially available 4-(trans-4'-n-alkylcyclohexyl)-benzonitrile [manufactured by Merck & Co.] was used in the literature (Mol.Cryst.Liq.Cryst, 1979.Vol56 Letters).
4-(trans-4'-n) according to the method of P51-56).
-alkylcyclohexyl)-aniline, 4-(trans-4'-n-alkylcyclohexyl)-phenol by a conventional method, and then condensed with an alkyl halide, 4-n-alkoxy-(trans-4'-n) -alkylcyclohexyl)-benzene is obtained. The reaction process will be shown below and its outline will be explained. Step 1: Commercially available 4-(trans-4'-n-alkylcyclohexyl)-benzonitrile is boiled and decomposed with caustic potassium in a mixed solvent of water and ethanol.
4-(trans-4'-n-alkylcyclohexyl)-benzamide is obtained. Steq 2: Dissolve this benzamide in dry methanol in which sodium metal has been dissolved, add bromine, mix, and heat to dissolve methyl-4-(trans-4'-n
-alkylcyclohexyl)-phenyl carbamate is obtained. Steq 3: This phenyl carbamate is boiled and decomposed with caustic potassium in 80% ethanol to obtain 4-(trans-4'-n-alkylcyclohexyl)-aniline. Steq 4: Mix this aniline with 70% sulfuric acid and create a diazo sulfate solution with sodium nitrite.
The diazosulfate solution is hydrolyzed to obtain 4-(trans-4'-n-alkylcyclohexyl)-phenol. Steq 5: This phenol and alkyl bromide are condensed in ethanol using caustic potassium, and the related -
4-n-alkoxy-(trans-4'-n-alkylcyclohexyl)-benzene is produced. The compound of the present invention has a nematic liquid crystal temperature range of around 20 to 40°C and is excellent in stability. Moreover, the viscosity η (20°C) of these compounds is 10 to 15 cp, and that of commonly known liquid crystal compounds is 25 cp.
Very low compared to ~60cp.
The advantage of lower viscosity is evident in twisted nematic display elements, where the response speed at low temperatures is faster. Further, the birefringence anisotropy Δn of these materials is relatively small at about 0.1. It is well known that a smaller Δn is advantageous in order to increase the display contrast of a phase change type guest-host display element or the like. In addition, their melting points are as low as 33.5-45℃, and their enthalpy of heat of fusion ΔH
Since it is as small as 7.9Kcal/Mol, it has high solubility when mixed with other liquid crystal compounds. As described above, the compound of the present invention can fully satisfy the conditions required for the various electro-optic display elements described above. Hereinafter, the manufacturing method and usefulness of the compound of the present invention will be explained in more detail with reference to Examples. Example 1 [Production of 4-n-butoxy-(trans-4'-n-butylcyclohexyl)-benzene] Step 1: 24.1 g of commercially available 4-(trans-4'-n-butylcyclohexyl)-benzonitrile and Dissolve 35g of caustic potash in 750ml of 70% ethanol,
Heated under reflux for 16 hours. After refluxing, the precipitated crystals were filtered, washed with water, and dried. This is 4-(trans-4'-n-butylcyclohexyl)-benzamide. Step 2: 96 g of sodium metal was dissolved in 4300 ml of dry methanol and cooled to room temperature. In this solution, 15.5 g of the above acid amide was dissolved, and 48.6 ml of bromine was added with vigorous stirring, followed by gentle heating for 4 hours. After the reaction, methanol was distilled off, 3000 ml of water was added to the residue, stirred, and the precipitate deposited was filtered, washed with water, and dried. This is methyl-4
-(trans-4'-n-butylcyclohexyl)-
It is a phenyl carbamate. Step 3: Add 8.7g of the above carbamate to caustic potash.
The mixture was added to 860 ml of 80% ethanol solution in which 228 g was dissolved, and a rubber balloon filled with nitrogen was installed at the top of the condenser, and the mixture was heated under reflux for 24 hours. After refluxing, ethanol was distilled off, the residue was poured into 300 ml of water, and this aqueous solution was extracted with ether. The ether layer was washed several times with water, dried over anhydrous sodium sulfate, and then the ether was distilled off. Further, the residue is distilled under reduced pressure to obtain a bp of 140 to 160
A fraction of ℃/2 mmHg was collected. This is 4-(trans-4'-n-pentylcyclohexyl)-aniline. Step 4: 5.4 g of the above aniline was mixed with 12 ml of concentrated sulfuric acid to form a homogeneous mixture. Furthermore, 12 ml of 40% sulfuric acid was added, thoroughly stirred, and cooled on ice. on the other hand,
A solution of 2.7 g of sodium nitrite and 6 ml of water was prepared and gradually added to the aniline-sulfuric acid mixture while cooling to prepare a diazo sulfate solution. Diazotization is in progress,
Heat the 50% sulfuric acid solution to about 90℃ on a water bath, and pour in the diazo sulfate solution that has completed the reaction little by little.
Hydrolyzed. Thereafter, the cooled and solidified crystals were filtered, washed with water, dried, and then sublimated under reduced pressure (2 mmHg). This is 4-(trans-4'-n-butylcyclohexyl)-phenol. Step 5: 1 g of the above phenol and 0.27 caustic potassium
Dissolve g in 10 ml of ethanol and add 0.7 g of butyl bromide.
was added and heated under reflux for 6 hours. After the reaction, ethanol was distilled off, 20 ml of water was added to dissolve the precipitated potassium bromide, and the product was extracted with ether. After washing the ether layer three times each with 10% NaOH and water, the ether was distilled off, and the residue was recrystallized from ethanol. This is related to the 4-n
-butoxy-(trans-4'-n-butylcyclohexyl)-benzene. Table 1 shows the transition point of the compound. Examples 2 to 6 4-(trans-4′-) obtained in Example 1 (Step 4)
n-Butylcyclohexyl)-phenol was reacted with the corresponding propyl bromide, pentyl bromide, hexyl bromide, heptyl bromide, and octyl bromide to prepare the following compounds. Fruit 2: 4-n-propoxy (trans-4'-n
-butylcyclohexyl)-benzene Real 3: 4-n-pentyloxy(trans-
4'-n-butylcyclohexyl)-benzene Real 4: 4-n-hexyloxy(trans-
4'-n-butylcyclohexyl)-benzene Real 5: 4-n-heptyloxy(trans-
4'-n-butylcyclohexyl)-benzene Real 6: 4-n-octyloxy(trans-
4'-n-butylcyclohexyl)-benzene These transition points are shown in Table 1. Example 7 In the same manner as in Example 1, commercially available 4-(trans-4'-n-propylcyclohexyl)-benzonitrile was converted into 4-(trans-4'-n-propylcyclohexyl)-phenol and bromated. It was reacted with propyl to produce 4-n-propoxy-(trans-4'-n-propylcyclohexyl)-benzene. Table 1 shows the transition points of the compounds.

[Table] The infrared absorption spectra of the compounds listed in Table 1 are shown in FIGS. 1 to 7. Example 8 Application example The compound of the present invention is added to a liquid crystal composition [referred to as composition A] consisting of

Liquid crystal compositions containing 20wt%, 40wt%, and 60wt% of [formula] [respectively,
Composition B, Composition C, and Composition D] were prepared;
The refractive index anisotropy Δn and dielectric constant anisotropy Δε of each were investigated. In addition, these were filled into an 8 μm thick liquid crystal display cell that had been vertically aligned using a treatment agent such as a chromium complex, and the operating voltages V _th , V _sat and response speeds τ _ON ,
τ _OFF was measured. These results are shown in Table 2.

【table】

【table】 [Brief explanation of drawings]

FIGS. 1 to 7 are diagrams showing infrared absorption spectra of the compounds shown below. Figure 1: 4-n-butoxy-(trans-4'-n
-butylcyclohexyl)-benzene, Figure 2:
4-n-propoxy-(trans-4'-n-butylcyclohexyl)-benzene, Figure 3: 4-n
-pentyloxy-(trans-4'-n-butylcyclohexyl)-benzene, Figure 4: 4-n-
Hexyloxy-(trans-4'-n-butylcyclohexyl)-benzene, Figure 5: 4-n-heptyloxy-(trans-4'-n-butylcyclohexyl)-benzene, Figure 6: 4-n- Octyloxy-(trans-4'-n-butylcyclohexyl)-benzene, Figure 7: 4-n-propoxy-(trans-4'-n-propylcyclohexyl)-benzene

Claims (1)

[Claims] 1 In the compound whose general formula is represented by [Formula], R ₁ is a straight-chain alkyl group having 3 or 4 carbon atoms, and R ₁ is an alkyl group having 3 carbon atoms. In the case, R ₂ is a straight chain alkyl group having 3 carbon atoms, and when R ₁ is a straight chain alkyl group having 4 carbon atoms, R ₂ is a straight chain alkyl group having 3 to 8 carbon atoms. Compound.