JPH04360864A - Ester compound and liquid crystal composition containing the same compound and liquid crystal display element using the same composition - Google Patents

Abstract

PURPOSE:To obtain a new compound useful as a TN type or STN type liquid crystal display element having high N-I point and capable of carrying out high- dimensionally divided driving. CONSTITUTION:A compound expressed by formula I (R1 and R2 are 1-10C alkyl), e.g. 4-(alkylthio)phenyl 4'-(trans-4''-alkylcyclohexyl)benzoate. The compound expressed by formula I is obtained by chlorinating a 4-(trans-4'-alkylcyclohexyl) benzoic acid expressed by formula II with thionyl chloride and then esterifying the chlorinated compound with a 4-(alkylthio)phenol expressed by formula III in diethyl ether in the presence of triethylamine. The compound has wide nematic liquid crystal temperature range and good steepness.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ester compound useful as a component of a liquid crystal composition used in a liquid crystal display element, a liquid crystal composition containing the same, and a liquid crystal display element using the liquid crystal composition.

0002

[Prior Art] Display methods of liquid crystal display elements that utilize the electro-optic effect unique to nematic liquid crystals include dynamic scattering type, guest-host type, twisted nematic (TN) type, birefringence control type, and super twisted nematic type. (STN) type, etc., and methods for driving these elements include a static drive method, a time division drive method, an active matrix drive method, etc.

Compared to other display elements, liquid crystal display elements (
1) It is easy to make small and thin, (2) the drive voltage is low and power consumption is extremely low, (3) it is compatible with LSI and the drive circuit can be simplified, and (4) it is a light-receiving type. It has the characteristics of being easy to see even under direct sunlight, and preventing eye fatigue even when used for long periods of time.

[0004] Taking advantage of these characteristics, they have been widely applied to displays for watches, calculators, audio equipment, games, cameras, and the like. Recently, they have been applied to displays with extremely large display capacities such as liquid crystal color televisions, word processors, and personal computers, and are attracting attention as display elements that will replace CRTs in the near future.

Next, although the characteristics required of the liquid crystal material used in the above-mentioned liquid crystal display elements differ depending on each field of application, some of the characteristics shown below are necessary for the liquid crystal material used in any field. It is essential. (1) Must be non-colored and stable in terms of heat, light, electricity, and science. (2) The practical temperature range should be around room temperature and as wide as possible. (3) The threshold voltage (Vth) of voltage-light transmittance characteristics is low and its temperature dependence is small. (4) The voltage-light transmittance characteristic has good steepness and viewing angle dependence. (5) Fast electro-optical response speed.

Among these characteristics, a large number of liquid crystal compounds that satisfy (1) have been developed, but (2)
There is no known liquid crystal compound that satisfies (6) with a single component. Therefore, as a method for obtaining these characteristics, a liquid crystal composition in which a plurality of nematic liquid crystal compounds or similar compounds thereof are mixed is used.

[0007]

[Problem to be solved by the invention] The lower limit of the practical temperature range of a liquid crystal composition can be lowered by bringing the composition of each component closer to the eutectic mixing ratio, and the upper limit can be lowered by nematic isotropy. It can be increased by mixing a liquid crystal compound with a high liquid phase transition temperature (N-I). In order to lower the threshold voltage, a liquid crystal compound or a similar compound thereof with a small elastic constant and a large dielectric anisotropy (Δε) may be added. The temperature dependence of the threshold voltage is generally N
- It is possible to make it smaller by increasing the I point. The steepness is determined by the ratio of elastic constants K33/K11 and △ε/ε
It can be made smaller by mixing liquid crystal compounds with small ⊥. Viewing angle dependence can be reduced by mixing a liquid crystal compound with small birefringence (Δn).

By the way, as liquid crystal compounds conventionally used to improve these characteristics, there are the following compounds.

[Formula 4] (Here, R3 and R4 represent an alkyl group.)
This compound has relatively small K33/K11 and Δn, but has the drawback that the NI point is not satisfactorily high.

[0009] Therefore, the object of the present invention is to provide K33/K11,
The object of the present invention is to provide a nematic liquid crystal compound with a small Δn and a high N−I point. A second object of the present invention is to provide a liquid crystal composition containing the compound with a small K33/K11, Δn and a wide practical temperature range. Furthermore, a third object of the present invention is to provide a liquid crystal display element capable of high time division driving using the liquid crystal composition.

0010

[Means for Solving the Problems] The present invention provides the general formula

[C5
] (Here, R1 and R2 have 1 to 10 carbon atoms.
represents an alkyl group. ), a liquid crystal composition containing the same, and a liquid crystal display element using the liquid crystal composition.

As is clear from Table 1, the ester compound of the present invention has a wider nematic liquid crystal temperature range than similar conventional compounds.

[Table 1] The compound of the present invention can be produced, for example, according to the scheme shown in Table 2 below. That is, step 1 4-(
trans-4'-alkylcyclohexyl)benzoic acid (
II) is chlorinated using thionyl chloride to obtain 4-(trans-4'-alkylcyclohexyl)benzoic acid chloride (III).

Step 2 Compound (III) and 4-(
Esterification of the alkylthio)phenol with triethylamine in diethyl ether provides 4-(alkylthio)phenyl 4'-(trans-4''-alkylcyclohexyl)benzoate (I).

[Table 2] Next, the liquid crystal composition of the present invention contains at least one type of compound (I), but it is more effective to add a combination of multiple components. In addition, compound (I) has good compatibility with other liquid crystal compounds, and the mixing ratio is 1 to 50%.
Weight% range, but if practicality is important, 3 to 3
0% by weight is preferred.

Although the liquid crystal compounds used in the liquid crystal composition of the present invention are not limited, for example, liquid crystal compounds of the following series can be mixed.

[Image Omitted] A liquid crystal display element using a liquid crystal composition in which a plurality of components of these liquid crystal compounds and the compound of the present invention are mixed appropriately depending on the application has a wide practical temperature range and good steepness.
High time division driving is possible.

FIG. 1 shows a TN type or STN type liquid crystal display element as an example of the liquid crystal display element of the present invention. The liquid crystal display element shown in the figure has substrates 1 and 2 made of transparent glass, plastic, etc. arranged in parallel at a predetermined interval, for example, 4 to 15 μm, and a sealant 6 such as inorganic glass or organic adhesive is applied around the substrates. The nematic liquid crystal composition of the present invention is sealed in this space. The predetermined spacing is obtained by mixing a spacer such as fiberglass, glass powder, Al2 O3 powder, etc. with the sealant.

Transparent electrodes 3 in a predetermined pattern are formed on the inner surfaces of the substrates 1 and 2, and a liquid crystal alignment control layer 4 for aligning liquid crystal molecules in a certain direction is further provided on the upper surface thereof. The orientation control layer is made by obliquely depositing SiO on the substrate or by applying a thin organic polymer film and rubbing the surface with cotton or nylon in a certain direction.

The orientation direction of the liquid crystal is such that the direction of the substrate 1 and the direction of the substrate 2 are different, and the liquid crystal molecules are twisted and oriented from the direction of the substrate 1 toward the direction of the substrate 2. The angle formed by substrates 1 and 2 is called the twist angle of liquid crystal molecules and can be selected arbitrarily, but it is 80-180 degrees for TN type and 180 degrees for STN type.
Selected from a range of 255 degrees.

A polarizing plate 5 is arranged outside the substrates 1 and 2, and its polarization axis is arranged parallel or perpendicular to the orientation direction of the substrates.

[0018]

[Examples] The present invention will be explained in more detail with reference to Examples below. [Example 1] (Production of liquid crystal compound) 4-(methylthio)phenyl 4'(trans-4''
-Production method of propylcyclohexyl)benzoate.

Step 1 24.6 g of 4-(trans-4'-propylcyclohexyl)benzoic acid and 23.8 g of thionyl chloride were refluxed for 3 hours. Excess thionyl chloride in the reaction product was distilled off under reduced pressure using an aspirator, and the residue was distilled under reduced pressure (160°C/1.0 mmHg) to obtain 24.7 g of 4-(trans-4'-propylcyclohexyl)benzoic acid chloride. Ta.

Step 2 2.8 g of 4-(methylthio)phenol was dissolved in 30 cm 3 of diethyl ether, and 2.4 g of triethylamine was added. 5.3 g of 4-(trans-4'propylcyclohexyl)benzoic acid chloride was added dropwise to this solution while stirring and cooling with ice water. Then, it was stirred at room temperature overnight. The reactants were mixed with water, 5% hydrochloric acid, water, 5%
% Na2 CO3 aqueous solution and then water, and diethyl ether was distilled off. The residue was recrystallized from acetone to give 4-(methylthio)phenyl 4'-(trans-4
5.6 g of ``propylcyclohexyl)benzoate were obtained.

The phase transition temperature of this compound was measured by DSC (temperature increase/decrease rate: 5° C./min) and the results were as follows.

C-N 132.5°C N-I 193.7°C In addition, the following compound was produced by the same production method as in Example 1.

4-(methylthio)phenyl 4'-(
Trans-4''-butylcyclohexyl)benzoate C-N 127.6°C N-I 181.6°C [Example 2] (Liquid crystal composition) Commercially available nematic liquid crystal composition ZLI-1565 (mother liquid crystal) and Example 1 4-(methylthio)phenyl 4'-
Liquid crystal compositions a and b were prepared by mixing (trans-4''-propylcyclohexyl)benzoate and 4-methoxyphenyl 4'-(trans-4''-propylcyclohexyl)benzoate at a weight ratio of 9:1.

[0024] The N-I point and △n of these liquid crystal compositions
The measurement results are shown in Table 2. [Example 3] (Liquid crystal display element) As shown in FIG. 1, a transparent electrode 3 made of an ITO film was formed on glass substrates 1 and 2, and an alignment agent made of polyimide was applied on this surface and rubbed. An orientation control layer 4 was formed.

Glass substrates 1 and 2 are coated with a sealant (8 μm
The liquid crystal compositions a and b of Example 2 and the mother liquid crystal are injected into this space, and the polarizing plate 6 is pasted on the outside of the substrates 1 and 2 to form the liquid crystal. Display elements A, B and O were produced.

Further, a TN type liquid crystal display element was used with a twist angle of 90 degrees. The voltage and voltage of the liquid crystal display element made in this way
Table 3 shows the results of measuring the light transmittance characteristics β and voltage margin M.

[Equation 1] (Here, V10 and V90 are the voltages when the light transmittance is 10% and 90%, respectively, T is the temperature (℃), and φ is the viewing angle (
M is the value when 1/3 bias - 1/3 duty. )

[Table 3] Although a TN type liquid crystal display element was used in the above example, it was confirmed that similar effects could be obtained when an STN type liquid crystal display element was used.

[0027]

Effects of the Invention As mentioned above, the compound of the present invention has high N
-I point, and high time division driving is possible by using a liquid crystal composition containing this compound in a liquid crystal display element.
It has become clear that a type or STN type liquid crystal display element can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cross section of a liquid crystal display element manufactured in Example 3 of the present invention.

[Explanation of symbols]

1, 2 Glass substrate 3 Transparent electrode 4 Orientation control layer 5 Polarizing plate 6 Sealant

Claims (3)

[Claims] Claim 1: General formula [Formula 1] (wherein R1 and R2 have 1 to 10 carbon atoms)
represents an alkyl group. ) An ester compound characterized by being represented by: Claim 2: General formula [Formula 2] (wherein R1 and R2 have 1 to 10 carbon atoms)
represents an alkyl group. ) A liquid crystal composition containing an ester compound, characterized in that it contains at least one type of ester compound represented by the following. Claim 3: General formula [Formula 3] (wherein R1 and R2 have 1 to 10 carbon atoms)
represents an alkyl group. ) A liquid crystal display element using a liquid crystal composition containing an ester compound, characterized in that the liquid crystal composition contains at least one type of ester compound represented by the following.