JP2830193B2 - Liquid crystal compound and liquid crystal composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel liquid crystal compound and a liquid crystal composition useful as a component of a nematic liquid crystal composition used for a liquid crystal display device.

[Summary of the Invention] The present invention has a general formula (In the above formula, R and R 'each represent a linear alkyl group having 1 to 10 carbon atoms, and the cyclohexane ring and the 1,3-dioxane ring are trans-forms.) It is a dioxane derivative and exhibits a nematic liquid crystal phase. Further, the compound of the present invention comprises (1) a nematic phase-isotropic liquid transition temperature (NI)
Point) is very high.

(2) The refractive index anisotropy (Δn) is small.

(3) Good compatibility with other liquid crystal compounds or liquid crystal compositions.

Etc.

Therefore, a liquid crystal composition having a wide nematic liquid crystal temperature range and a small Δn can be provided by mixing the compound of the present invention with another liquid crystal compound or a liquid crystal analog compound. Further, by using a liquid crystal composition in which the compound of the present invention is mixed, a liquid crystal display device having a wide operating temperature range and a wide viewing angle range can be provided.

[Conventional technology]

Compared to other display devices, liquid crystal display devices have features such as easy downsizing and thinning, low drive voltage, and very low power consumption.
It is widely applied as a display device for automobile dashboards and various measuring instruments. Furthermore, recently, it is being applied to a display device having a very large number of pixels, such as a pocket television, a word processor, and a display of a personal computer, and is attracting attention as a display device replacing the CRT in the future. Nematic liquid crystal is the most widely used liquid crystal material used in liquid crystal display devices, and its display method is a twisted nematic type (T
N) and super twisted nematic type (STN) are typical. The characteristics required for liquid crystal materials differ depending on the application field, but they are thermally, optically and chemically stable, and
A liquid crystal material having a very high -I point, a small Δn, and excellent compatibility is a characteristic required for many application fields.

[Problems to be solved by the invention]

Since various characteristics are required for a liquid crystal material used for a liquid crystal display device, a liquid crystal material that can be used as a single component has not been known at present. Therefore, in reality, a liquid crystal composition in which a plurality of liquid crystal compounds having different properties or a compound similar thereto is mixed is used. When it is desired to widen the nematic temperature range of the liquid crystal composition, it is conceivable to mix a large amount of a liquid crystal compound having a high NI point, but a liquid crystal compound conventionally used for this purpose, for example, However, since the NI point is relatively low at 250 ° C. or lower and the compatibility is not so good, several types of compounds must be used in combination, which is disadvantageous in cost. Further, compounds having a high NI point generally have a large Δn. One of the disadvantages of the TN type liquid crystal display is that the viewing angle is narrow,
This property depends on Δn, and it is known that the viewing angle becomes wider when Δn is reduced. Therefore, a liquid crystal compound having a small Δn can be used in a wide field.

Therefore, the object of the present invention is to have a very high NI point,
Is to provide a liquid crystal compound having a small nematic temperature range because of good compatibility when mixed with another nematic liquid crystal composition, and a wide nematic temperature range, a small Δn, and a small viewing angle dependence. To provide.

[Means for solving the problem]

The liquid crystal compound of the present invention has the general formula (In the above formula, R and R 'each represent a linear alkyl group having 1 to 10 carbon atoms, and the cyclohexane ring and the 1,3-dioxane ring are trans-forms.) .

The liquid crystal compound of the present invention can be produced, for example, by the following synthesis method. That is, 2- (4'-A Cis-trans mixture of (alkylcyclohexyl) propane-1,3-diol (2) and 4- (trans-4'-alkylcyclohexyl) benzaldehyde (3) in methylene chloride solvent using p-toluenesulfonic acid as catalyst A cis-trans mixture of 2- [4- (trans-4'-alkylcyclohexyl) phenyl] -5- (4-alkylcyclohexyl) -1,3-dioxane is synthesized by reacting, and recrystallized to be a trans form ( 1) is obtained by separation and purification. Here, compound (2) can be produced, for example, by the following synthesis method. That is, 4-alk The cis-trans mixture of rucyclohexanol (3) is brominated with phosphorus tribromide in ether to give the cis-trans mixture of 4-alkylcyclohexyl bromide (4). The compound (4) is reacted with diethyl malonate in ethanol using sodium ethylate to obtain a cis-trans mixture of diethyl 4-alkylcyclohexylmalonate (6). Compound (6) was converted to NaAlH ₂ (OC ₂ H ₄ OCH ₃ )
Reduction using ₂ gives compound (2). Compound (3) can be produced, for example, by the following synthesis method. That is, 4-
(Trance-4'- (Alkylcyclohexyl) benzonitrile is reacted in toluene with NaAlH ₂ (OC ₂ H ₄ OCH ₃ ) ₂ at 0 ° C. or lower to obtain a compound (3).

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples and application examples.

The method of Example 1 2- (4'-pentylcyclohexyl) propane-1,3-diol (Compound (2) with that of R = C ₅ H _11).

95 g (0.56 mol) of 4-alkylcyclohexanol is dissolved in 300 cm ³ of diethyl ether, cooled to 0 ° C. or less in an ice-NaCl bath, and 100 g (0.37 mol) of phosphorus tribromide with stirring.
Was added dropwise over 2 hours. Thereafter, the mixture was stirred at room temperature for 1 hour and further stirred under reflux for 5 hours. The reaction was poured into ice 500 g, washed with 10% HBr aqueous solution and water The ether layer was separated and dried over Na ₂ SO _4. Ether was distilled off, and the remaining oil was distilled under reduced pressure (120 ° C./9 mmHg) to obtain 72 g (0.31 mol) of 4-pentylcyclohexyl bromide. next,
8.5 g (0.37 mol) of sodium was dissolved in 270 cm ³ of ethanol, 74 g (0.46 mol) of diethyl malonate and 72 g (0.31 mol) of 4-pentylcyclohexyl bromide were added, and the mixture was refluxed for 10 hours with stirring. The produced NaBr was filtered off, the ethanol in the filtrate was distilled off, water was added to the residue, extracted with chloroform, and washed with 10% hydrochloric acid and water. Chloroform was distilled off and the remaining oil was distilled under reduced pressure (154 ° C / 1.1 mmHg) to give
-40 g of diethyl pentyl cyclohexylmalonate (0.13
Mol). Next, 215 cm ³ (0.77 mol) of a 70% toluene solution of NaAlH ₂ (OC ₂ H ₄ OCH ₃ ) ₂ was dissolved in 215 cm ³ of toluene, and 40 g (0.13 mol) of diethyl 4-pentylcyclohexylmalonate was added dropwise with stirring. And then 80-90 ° C
For 5 hours. 10% hydrochloric acid was added dropwise to the reaction product, and the toluene layer was separated and washed with 10% hydrochloric acid and water. The toluene was distilled off, and the residue was recrystallized from hexane to give 23 g of 2- (4'-pentylcyclohexyl) propane-1,3-diol (0.2 g).
10 mol).

The method of Example 2 4- (trans-4'-propylcyclohexyl) benzaldehyde (Compound (3) in one of the R = C ₃ H _7).

22.7 g (0.10 mol) of 4- (trans-4′-propylcyclohexyl) benzonitrile was dissolved in 100 cm ³ of toluene, cooled to 0 ° C. or less in an ice-NaCl bath, and stirred while stirring.
_{AlH 2 (OC 2 H 4 OCH} 3) 70% toluene solution 18cm ³ of ₂ was added dropwise over a solution dissolved in toluene 50 cm ³ 30 minutes, after completion of dropwise addition, the mixture was stirred for 1 hour at this temperature. While stirring the reaction mixture, 2.5 MH ₂ SO ₄ 150 cm ³ was added dropwise, and the toluene layer was separated and separated.
Washed with MH ₂ SO ₄ and water. The toluene was distilled off, and the remaining oil was distilled under reduced pressure (144 ° C./3 mmHg) to give 4- (trans-
4'-propylcyclohexyl) benzaldehyde 21 g
(0.091 mol).

Example 3 trans-2- [4 ′-(trans-4 ″-
The method of synthesizing propyl) phenyl] -5- (trans-4'-pentylcyclohexyl) -1,3-dioxane (Compound (1) in _{R = C 5 H 11, R} '= C 3 ones H _7).

2- (4'-pentylcyclohexyl) propane-1,
2.5 g (0.011 mol) of 3-diol and 4- (trans-4 '
-Propylcyclohexyl) benzaldehyde 2.5 g (0.
Was dissolved in 60 cm ³ of methylene chloride, and 0.1 g of p-toluenesulfonic acid was added. The mixture was refluxed for 3 hours while removing a generated water by attaching a water separator. Reactants with 5% NaCO
_{3 After} washing with an aqueous solution and water, methylene chloride was distilled off. The residue was recrystallized from a mixed solvent of chloroform and acetone to give trans-2- [4 '-(trans-4 "-propylcyclohexyl) phenyl] -5- (trans-4'-pentylcyclohexyl) -1,3-dioxane. 1.8 g (0.004 mol) of this compound had the following phase transition temperatures:

(Here, C represents a crystal, S ₁ and S ₂ represent a smectic phase, N represents a nematic phase, and I represents an isotropic liquid.) The following compounds were produced by the same synthesis method as in Example 3.

Trans-2- [4 '-(trans-4 "-pentylcyclohexyl) phenyl] -5- (trans-4'-
Pentylcyclohexyl) -1,3-dioxane Trans-2- [4 '-(trans-4 "-heptylcyclohexyl) phenyl] -5- (trans-4'-
Pentylcyclohexyl) -1,3-dioxane Trans-2- [4 '-(trans-4 "-propylcyclohexyl) phenyl] -5- (trans-4'-
Hexylcyclohexyl) -1,3-dioxane Trans-2- [4 '-(trans-4 "-pentylcyclohexyl) phenyl] -2- (trans-4'-
Hexylcyclohexyl) -1,3-dioxane Trans-2- [4 '-(trans-4 "-propylcyclohexyl) phenyl] -2- (trans-4'-
Propylcyclohexyl) -1,3-dioxane Trans-2- [4 '-(trans-4 "-pentylcyclohexyl) phenyl] -5- (trans-4'-
Propylcyclohexyl) -1,3-dioxane Application Example A liquid crystal composition [A] obtained by mixing the compound of Example 3 with a commercially available liquid crystal composition ZLI-1565 (manufactured by Merck) as a comparative example. Was mixed to prepare a liquid crystal composition [B].

Liquid crystal composition [A] The NI point and Δn of these liquid crystal compositions were measured. Further, the sample was sealed in a TN type cell having a thickness of 9 μm, and the viewing angle dependency α was measured. Here, α was defined by the following equation. Note that V
_th and V _sat respectively Voltage at a luminance of 10% and 90%, T represents temperature, and φ represents viewing angle.

 Table 1 shows the above measurement results.

[Effects of the Invention] As described above, the liquid crystal compound of the present invention has a very high NI point (> 280 ° C), a small Δn, and a low-temperature smectic phase (40-60 ° C) below the nematic phase. ) And good compatibility with other liquid crystal compounds.

In addition, it was confirmed that by mixing the compound of the present invention and a conventional liquid crystal composition, a liquid crystal composition having a high NI point and a wide viewing angle range can be obtained.

Therefore, the present invention is extremely useful as a liquid crystal material used for a TN type or STN type liquid crystal display device.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C07D 319/06 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] (1) The general formula is (In the above formula, R and R 'each represent a straight-chain alkyl group having 1 to 10 carbon atoms, and the cyclohexane ring and the 1,3-dioxane ring are trans-forms.) Liquid crystal compounds. 2. The general formula is (In the above formula, R and R 'each represent a straight-chain alkyl group having 1 to 10 carbon atoms, and the cyclohexane ring and the 1,3-dioxane ring are trans-forms.) A liquid crystal composition comprising: