JP2956946B2 - Trifluoromethyl compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel trifluoromethyl compound having a positive dielectric anisotropy and a liquid crystal composition containing the compound.

[0002]

2. Description of the Related Art Display devices using liquid crystals are widely used in watches, calculators and the like. These liquid crystal display devices utilize the optical anisotropy and the dielectric anisotropy of a liquid crystal material. The liquid crystal phase includes a nematic liquid crystal phase, a smectic liquid crystal phase, and a cholesteric liquid crystal phase. Among them, a liquid crystal phase using a nematic liquid crystal has been most widely put to practical use.

There are TN (twisted nematic) type, D type, and D type, corresponding to the electro-optic effect applied to liquid crystal displays.
There are display devices of S (dynamic scattering) type, guest post type, DAP type and the like, and it is desirable that the liquid crystal substance used for each display a liquid crystal phase in a temperature range as wide as possible in nature.

At present, no single liquid crystal material satisfies such conditions, and several liquid crystal materials or non-liquid crystal materials are mixed for practical use. These substances are required to be stable to moisture, light, heat, air and the like.

In recent years, it has been desired to increase the size of the display element.
Since the display quality is inferior in the conventional TN type, a new series of STN (super twist) type display devices are newly developed. Shut, F.S. Rinfutsu (Appl. Phys. Lett., 50. 236 (1
987)), and the display quality is not inferior even if it is enlarged.

The property of the liquid crystal desired for this method is K ₃ / K
₁ is large, K ₂ / K ₁ is small, and Δε / ε is desired to be small (M. Schadt, F. Leenhouts Society fo).
rInformation Display International Symposium Diges
t of Technical PaparsVol.X VIII New Orleans.Lous
iana May 12-14, (1987) 372-375).

Where K ₁ is the elastic constant of expansion, K ₂ is the elastic constant of torsion, and K ₃ is the elastic constant of bending, and is determined from the threshold value when a magnetic field or an electric field is applied to a uniformly oriented cell. Can be When ε⊥ is a dielectric constant in a direction perpendicular to the orientation vector and ε‖ is a dielectric constant in a direction parallel to the orientation vector, Δε = ε∥−ε⊥, which indicates dielectric anisotropy.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide K ₃ /
K ₁ is large, Δn is small and excellent in compatibility,
An object of the present invention is to provide a novel compound which has a positive value of Δε and can be used in the above-mentioned STN-type display element, and is useful as a liquid crystal composition. Another object is to provide a liquid crystal composition characterized by containing the compound.
Here, Δn = n‖−n⊥, which is the difference between the refractive index in the direction parallel to the orientation vector and the refractive index in the direction perpendicular to the orientation vector.

[0009]

According to the present invention, there is provided a compound of the general formula

Embedded image (In the above formula, R ¹ is a linear or branched alkenyl group having 2 to 15 carbon atoms, and R ² is a linear or branched C 1 -C 1 alkenyl group.)
And n is 1 or 2, and m is 0 or 1.) and a liquid crystal composition containing at least one of the above compounds.

Other components other than the compound of the present invention that can be used as components of the liquid crystal composition of the present invention include, for example, liquid crystal compounds of ester type, Schiff base type, biphenyl type, phenylcyclohexane type, heterocyclic type and the like. be able to.

The production method of the compound of the present invention is shown, for example, by the following reaction.

Embedded image (In the above formulas ^R 2, m is as defined above, ^{R 3} represents a hydrogen atom or a straight-chain or branched alkyl group having 1 to 12 carbon atoms, PhNMe ₂ is N, the N- Jimechirua two phosphorus Shown.)

Namely, known ω- alkyl allyloxyphenyl ethers (e.g. JP 64-63533, JP-A 1-110649 Patent forth) N, the N- Jimechirua two <br/> phosphorus as a solvent, it was heated To carry out a Claisen rearrangement reaction to produce α-alkylallylphenols. Then, the phenols and 4-trifluoromethylbenzyl bromide (when n = 0) or 4-trifluoromethoxybenzyl bromide (when n = 1) are dried in N, N-dimethylformamide (hereinafter abbreviated as DMF) solvent. By reacting with potassium carbonate, the desired trifluoromethyl compound was obtained.

[0013]

The present invention will be described in more detail with reference to the following examples. Example 1 1- (4-trifluoromethyl) benzyloxy-2-
Allyl-4- (trans-4-propylcyclohexyl-trans-4-cyclohexyl) benzene (R in formula I
^{_{1 = CH 2 = CHCH 2 -}} , R 2 = C 3 H 7 -, l = 2,
m = 0).

JP-A-64-63533, JP-A-1-11
1-hydroxy- 2 -allyl-4- (trans-4-propylcyclohexyl-trans-4-cyclohexyl) benzene (3.5 g, 0.01 mol) produced by a known method described in No. 0649 or the like is mixed with 200 ml of DMF. Was added thereto, and 50 g of anhydrous potassium carbonate was added thereto. 3.6 g of 4-trifluoromethylbenzyl bromide with stirring
(0.015 mol) and reacted at 80 ° C. for 12 hours.

After completion of the reaction, water was added to the reaction solution, and the precipitated oil was extracted with toluene. The toluene layer was washed with 2N sodium hydroxide and then with water until neutral. After drying the toluene layer with anhydrous sodium sulfate, the toluene was distilled off under reduced pressure. The remaining crystals were recrystallized with acetone. The crystal-nematic phase transition point was 93.6-94.4 ° C., the nematic phase-clearing point was 109.1 ° C., and the yield was 4.0 g (72% yield).

Examples 2 to 6 In the same manner as in Example 1, 4-trifluoromethylbenzyl bromide or 4-trifluoromethoxybenzyl bromide was reacted with various 2-alkenylphenols to obtain the desired trifluoromethyl compound. Manufactured. The results are shown together with the results of Example 1 in Table 1.

[0017]

[Table 1]

Example 7 (composition example) trans-4-propyl- (4-cyanophenyl) cyclohexane 30% by weight trans-4-pentyl- (4-cyanophenyl) cyclohexane 40% by weight trans-4-heptyl- ( The liquid crystal composition (A) having a composition of 30% by weight of 4-cyanophenyl) cyclohexane has a NI point of 52.1 ° C.
Δε is 11.2, and the viscosity at 20 ° C. is 23.4 mPa.
S and Δn are 0.119, and K ₃ / K ₁ is 1.82. As a liquid crystal cell, a silicon oxide-coated, rubbed tin oxide transparent electrode assembled with the substrate facing each other, a distance between the electrodes of 10 μm was prepared,
When the above liquid crystal composition (A) was sealed and its characteristics were measured at 20 ° C., the threshold voltage (hereinafter abbreviated as _Vth ) was 1.55 V.

1- (4-trifluoromethyl) produced in Example 1 of the present invention was added to 90% by weight of the liquid crystal composition (A).
The NI point of the composition in which 10% by weight of benzyloxy-2-allyl-4- (trans-4-propylcyclohexyl-trans-4-cyclohexyl) benzene was dissolved was 55.5 ° C., Δε was 10.5, Δn Is 1.115, Vth
Was 1.55V. Further, K ₃ / K ₁ is increased to 1.92 and the NI point can be raised, which is suitable for STN.

[0020]

The compound of the present invention has good compatibility with many other liquid crystal compounds, that is, liquid crystals of ester type, ship base type, biphenyl type, phenylcyclohexane type, heterocyclic type and the like. Is added to the liquid crystal composition, Δn can be kept small, and the threshold voltage does not increase so much. Further, since the value of K ₃ / K ₁ can be increased, the compound is suitable for a liquid crystal composition for an STN display device.

Claims (2)

(57) [Claims] 1. A compound of the general formula (In the above formula, R ¹ is a linear or branched alkenyl group having 2 to 15 carbon atoms, and R ² is a linear or branched alkenyl group having 1 to 15 carbon atoms.
And n is 1 or 2, and m is 0 or 1. )
A trifluoromethyl compound represented by the formula: 2. A liquid crystal composition comprising at least one trifluoromethyl compound according to claim 1.