JPS6261018B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel organic compound, and more particularly to a novel liquid crystal compound that can be used as a component of a liquid crystal material. As is well known, liquid crystal materials with positive dielectric anisotropy can be used in liquid crystal display devices that use nematic liquid crystals with twisted alignment, so-called TN cells, and can also be used as guest hosts by adding appropriate dye materials. It is also used in color liquid crystal display elements that apply this effect. As for these liquid crystal materials, there is currently no single compound that can withstand practical use due to its various properties, such as liquid crystal temperature range, operating voltage, response performance, etc., and for practical use, several types of liquid crystal compounds or non-compounds are suitable. Currently, liquid crystal compounds are mixed to obtain products that can withstand a certain level of use. An object of the present invention is to provide a liquid crystal compound useful as a component constituting such a stable liquid crystal composition with excellent practical performance. The present invention provides a novel liquid crystal compound with extremely small negative dielectric anisotropy, wide liquid crystal temperature range, high clearing point (N-I point), and excellent stability, which meets the above objectives. It is something to do. That is, the present invention is based on the general formula (However, in the above formula, R ₁ and R ₂ are H or carbon number 1 to
4-(trans-4'-alkylcyclohexylmethoxy)benzoic acid trans-4''-alkylcyclohexyl ester represented by 10 alkyl groups). The compounds of the present invention have a wide nematic temperature range, but have a melting point (C -N point), this compound alone is not practical for display devices.However, it has excellent compatibility with other liquid crystal compounds, and its high clearing point (N-I point) makes it difficult to use for display devices. Substances such as Schiff chlorine type, azoxy type, benzoic acid phenyl ester type, cyclohexanecarboxylic acid phenyl ester type, cyclohexanecarboxylic acid cyclohexane ester type, biphenyl type, phenylcyclohexane type, phenylpyridine type, phenylmetadioxane type It is useful as a so-called high-temperature liquid crystal component that increases the clearing point by mixing it with one type of liquid crystal, or a mixture of several types, such as cyanoterphenyl, which has been widely used for the same purpose. It has a relatively low viscosity compared to liquid crystal materials such as cyanobiphenylcyclohexane-based and cyanobiphenylcyclohexane-based materials, so by using this compound, it is possible to obtain a liquid crystal composition with excellent performance that has good response performance and less temperature dependence. Next, the method for producing the compound of the present invention will be shown. First, the chemical formula will be shown briefly. First, trans-4-alkylcyclohexanecarboxylic acid () is used as a starting material, and this and ethyl alcohol are reacted under an acid catalyst to obtain an ester compound () (Step A). Next, () is reacted with lithium aluminum hydride LiAlH ₄ in a solvent at low temperature to obtain a carbinol compound () (Step B). This ring reaction can also be carried out by hydrogen reduction using a catalyst. Next, () is reacted with a halogenating agent such as hydrogen bromide or phosphorus tribromide to obtain bromide () (Step C), and this () and p
-Hydroxybenzoic acid is reacted with 4-(trans-4'-cyclohexylmethyl)benzoic acid (Step D). to this ()
A halogenating agent such as SOCl ₂ is reacted to form an acid chloride (or acid halide) (Step E), and this is reacted with trans-4-alkylcyclohexanol in an inert organic solvent to achieve the desired purpose. A compound of formula () is obtained (Step F). Table 1 shows the physical properties (phase transition point) of the compound of formula () thus obtained.

[4-(trans-4′-n-propylcyclohexylmethoxy)benzoic acid-trans-4″-propylcyclohexyl ester (in the formula (), R ₁ is C ₃ H ₇ and R ₂ is C ₃ H ₇ )] Manufacturing]

[Step A] 170.24 g (1 mol) of trans-4-n-propylcyclohexanecarboxylic acid () was dissolved in 350 ml of ethyl alcohol, and 40 ml of 95% concentrated sulfuric acid was added thereto. After reacting under reflux for 2 hours, excess of ethyl alcohol was distilled off. The reaction product was extracted with 100 ml of n-hexane, the extract was washed with water, dried over anhydrous magnesium sulfate, the n-hexane was distilled off, and the residual liquid was distilled under reduced pressure to obtain 167.2 g of trans-4.
-n-propylcyclohexanecarboxylic acid ethyl ester () was obtained. Boiling point 73℃/1mmHg, yield 84.3%. [Step B] Ethyl ester obtained in Step A ()
198g (1 mol) of dried tetrahydrofuran
24 g of lithium aluminum hydride dissolved in 100 ml of tetrahydrofuran while drying
(0.633 mol) is suspended and the solution in () is added dropwise while stirring vigorously. After the addition is complete, the mixture is heated under reflux for 2 hours, and after cooling, ethyl acetate is carefully added to decompose the excess lithium aluminum hydride. Then 20% sulfuric acid was added until the inorganics were dissolved. The product was extracted with n-hexane, the extract was washed with water, dried over anhydrous magnesium sulfate, the n-hexane was distilled off, and the residual liquid was distilled under reduced pressure to obtain trans-4-n-propylcyclohexylcarbinol (). 148g (0.94 mol) was obtained. Yield 94.0%, boiling point 76℃/1mmHg. [Step C] 156.3 g of carbinol obtained in Step B
(1 mol) to 47% hydrogen bromide water 307g (1.784 mol),
93 g of 95% sulfuric acid was added and heated under reflux for 3 hours. After the reaction was cooled, the reaction product was extracted with n-hexane, and the extract was washed with a 2% aqueous sodium hydrogen solution and then with water, dried over anhydrous magnesium sulfate, and the n-hexane was distilled off. The residual liquid was distilled under reduced pressure to obtain 162.2 g (0.74 mol) of trans-4-n-propylcyclohexylmethyl bromide ().
Yield 74.0%, boiling point 64℃/1mmHg. [Step D] Dissolve 13.81 g (0.1 mol) of 4-hydroxybenzoic acid in 50 ml of ethylene glycol monomethyl ether, then dissolve 8 g (0.2 mol) of caustic soda in 15 ml.
Carefully add an aqueous alkaline solution dissolved in water of 30
Stir for a minute. Next, 21.92 g (0.1 mol) of the compound () obtained in Step C was added over 30 minutes.
The mixture was further heated under reflux for 5 hours. After cooling, 50% hydrochloric acid was added and the precipitated reaction product was filtered out, washed with water and dried. Recrystallize it with 150ml of glacial acetic acid and get 20.72g.
(0.75 mol) of 4-(trans-4'-n-propylcyclohexylmethoxy)benzoic acid () was obtained. Yield 75%, and this product is smectic (S)
It shows a nematic liquid crystal phase, and the C-S point is 213
℃, the SN point was 228°C, and the NI point was 235°C. [Step E, F] 13.82 g of benzoic acid () obtained in Step D
(0.05 mol) was dissolved in 50 g of thionyl chloride and reacted under reflux for 1 hour, and then excess thionyl chloride was distilled off to obtain acid chloride (2) (Step E).
On the other hand, trans-4-propylcyclohexanol
7.12 g (0.05 mol) was dissolved in 20 ml of dry pyridine, the above acid chloride was added thereto at room temperature, and the mixture was further heated and stirred at 70°C for 2 hours. After cooling, the reaction product was extracted with 100 ml of toluene, and the extract was washed with dilute hydrochloric acid, dilute alkali, and water in that order, and then dried using anhydrous magnesium sulfate, and then the toluene was distilled off. The obtained reaction product was recrystallized from a benzene-ethyl alcohol mixed solvent to obtain the desired 4-
(trans-4'-n-propylcyclohexylmethoxy)benzoic acid trans-4''-propylcyclohexyl ester () 9.61 g (0.024 mol) was obtained (yield 48.0%). Its melting point (C-N point) was 97
℃, the N-I point was 149℃. Moreover, the elemental analysis values agree well with the calculated values as shown below, indicating that it is the desired product. Analyzed value (%) Calculated value (%)
C ₂₇ H ₄₂ O ₃ ) C 78.18 78.01 H 10.12 10.00 Examples 2 to 8 In the same manner as in Example 1, R ₁ ,
Combinations of R ₂ as shown in Examples 2 to 8 in Table 1 were produced using the corresponding raw materials. The nematic liquid crystal temperature range is shown in Table 1 above. Example 9 (Application example 1) The NI point of the liquid crystal composition (A) having the following composition is 63.3°C. The following three compounds of the present invention are added to 85% by weight of this liquid crystal composition. When a liquid crystal composition (B) was prepared in which 5% by weight of each of I couldn't help it. Next, a SiO ₂ film was formed on the transparent electrode, and surface alignment treatment was performed by rubbing.
A TN cell (twisted nematic cell) with a cell thickness of 10 μm was made by sealing the two types of liquid crystal compositions between the glass substrates of the plate, and the threshold voltage was measured using a rectangular wave of 32 Hz. A) It is 1.62V,
That of composition (B) was 1.75V;
The temperature dependence between the two temperatures was -13.5 mV/°C for the former, while it was -11.5 mV/°C for the latter. In addition, the γ value (V ₅₀ −V ₁₀ /V ₅₀ ×10
0 (%); V ₁₀ and V ₅₀ have transmittance of 10% and 50%, respectively.
The former is 14.8% and the latter is 14.6%, and the temperature dependence of the γ value between 0 and 40°C is 0.81 (%/°C) for the former, but 0.65 for the latter.
(%/℃). Example 10 (Application example 2) The NI point of the liquid crystal composition (C) having the following composition is 72.5°C. The following three compounds of the present invention are added to 70% by weight of this liquid crystal composition. When a liquid crystal composition (D) was prepared in which 10% by weight of each of
No separation and precipitation of crystals was observed even after being left in the sun.
In addition, in the same way as in Application Example 1, a TN cell was made using this liquid crystal composition and its characteristics were measured. The threshold voltage of composition (C) was 1.80V, and that of composition (D). ) was 1.88V, but its temperature dependence between 0 and 40°C was -9.5mV/°C for the former, while it was -7.3mV/°C for the latter.
Furthermore, the γ value is 14.4% for the former and 13.3% for the latter, and its temperature dependence has decreased from 0.52%/°C for the former to 0.38%/°C.

Claims (1)

[Claims] 1. General formula (However, in the above formula, R ₁ and R ₂ are H or carbon number 1
-10 alkyl groups) 4-(trans-4'-alkylcyclohexylmethoxy)benzoic acid trans-4''-alkylcyclohexyl ester represented by 2 General formula (However, in the above formula, R ₁ and R ₂ are H or carbon number 1
A liquid crystal composition containing at least one type of 4-(trans-4'-alkylcyclohexylmethoxy)benzoic acid trans-4''-alkylcyclohexyl ester represented by the following formula (10 to 10 alkyl groups).