JPH03135955A - Heterocyclic compound having ethylene chain - Google Patents

Abstract

NEW MATERIAL:The heterocyclic compound of formula I (R<1> and R<2> are independently 1-18C straight or branched chain alkyl; ring A is group of formula II to formula VI) having an ethylene chain. EXAMPLE:2-[2-(4-Heptylphenyl)ethyl]-5-(4-hexylphenyl)pyrazine. USE:Effective as a liquid crystal composition useful as an electro-optical displaying material. It is especially preferable to use as a chiral smectic liquid crystal for ferroelectric liquid crystal display or a matrix liquid crystal exhibiting SC phase and useful for the preparation of a chiral smectic liquid crystal. It exhibits high response from a low-temperature condition to a high- temperature condition. PREPARATION:A 4-alkylphenylacetic acid of formula VII is converted to ethyl ester and reduced with aluminum lithium hydride. The product is brominated with phosphorus tribromide and made to react with magnesium. The reaction product is reacted with a heterocyclic compound to obtain the objective compound of formula I.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a novel liquid crystalline compound useful as an electro-optical display material. In particular, the present invention provides compounds that are useful materials for obtaining liquid crystal materials having ferroelectric properties.

[Prior art]

Liquid crystal display elements are currently widely used as compounds due to their excellent characteristics (low voltage operation, low power consumption, thin display, can be used even in bright places, and are easy to see).

I'm tired. However, the most common TN type display system has an extremely slow response compared to light-emitting display systems such as CRTs, and does not retain the display when the applied electric field is turned off (memory effect), so it has a high speed. There are many restrictions and it cannot be said to be suitable for applications such as optical shutter printer heads that require response, and video screens such as televisions that require time-division driving.

Recently, Mayer et al. reported a display method using ferroelectric liquid crystal, which has a high-speed response 100 to 1000 times faster than the TN type and a memory effect, so it is expected to be the next generation of liquid crystal display elements, and currently, Research and development is actively underway.

The liquid crystal phase of ferroelectric liquid crystal belongs to the tilted chiral smectic phase, but in practical terms, the chiral smectic C (hereinafter abbreviated as "SC") phase is the one with the lowest viscosity. Most desirable.

A large number of liquid crystal compounds exhibiting an "sc" phase have already been synthesized and studied, but the conditions for use as a ferroelectric display element are (a) exhibiting an "sc" phase over a wide temperature range including room temperature; (b) In order to obtain good orientation, it must have an appropriate phase series on the high temperature side of the S phase and its helical pitch must be large; (c) it must have an appropriate tilt angle; (d) it must have a low viscosity. (e) It is preferable that the spontaneous polarization is large to some extent.
Nothing that satisfies these requirements alone is known.

Therefore, it is currently being used for research purposes as a liquid crystal composition exhibiting the S00 phase (hereinafter referred to as "sc" liquid crystal composition).

Until now, compounds that have been used to increase the upper limit temperature (Tc point) of the SC phase or sc'' phase include compounds represented by the following maximum (III) a to (I[I) e. Those with a structure in which three aromatic rings are directly connected,
Compounds such as those represented by the following maximum (■) a to (IV) b are known, including ester compounds, all of which have an SC phase (or SC0 phase) with a high Tc point.

Since 3-ring directly bonded compounds such as the compound represented by the above-mentioned compound have poor compatibility with other liquid crystal compounds, they tend to precipitate and it is difficult to lower the melting point.
The ester compounds represented by )a and (rV)b have a drawback of high viscosity.

In addition, in a compound having a pyrimidine ring and an oxymethylene bond in the molecule, such as the compound represented by -maximum (V) below,... (IV) a However, the above -maximum (I[I) a ~ (III )
Although the viscosity was considerably improved compared to ester compounds such as the compounds represented by e-maximum (IV)a or (IV)b, it was still not sufficient.

Therefore, it has lower viscosity, excellent compatibility, and T
A compound that is highly effective in raising the c point has been desired.

[Problems to be Solved by the Invention] The problems to be solved by the present invention are to have excellent compatibility with other compounds for parent fluid products, to have a low viscosity, and to form an SC phase (or SC0 phase) by mixing. To provide a compound having a large effect of increasing the upper limit temperature (Tc point), and by using the same, to provide a liquid crystal composition having a high Tc point and exhibiting a low viscosity SC (or sc'') phase; An object of the present invention is to provide a liquid crystal display element using such a composition as a component.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides the following - maximum (1)
Provides a compound represented by

...(1) In the above-mentioned maximum, R1 and at each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms,
Preferably R1 and R1 each independently have 4 to 4 carbon atoms.
Represents 10 linear alkyl groups.

The present invention also provides a liquid crystal composition containing at least two of the compounds represented by the above-mentioned formula (I). In particular, the composition according to the present invention is preferably used as a base liquid crystal exhibiting an SC phase for preparing chiral smectic liquid crystals for ferroelectric liquid crystal displays or for preparing chiral smectic liquid crystals. It is preferable that the proportion of the compound shown is 2 to 50% by weight.
Particularly preferred is ~30% by weight.

Furthermore, the present invention provides a liquid crystal display element comprising the above-mentioned composition as a component, and particularly provides a ferroelectric liquid crystal display element capable of high-speed response in a wide temperature range from a low temperature range to a high temperature range.

The compound of formula (I) according to the present invention can be produced, for example, according to the following production method.

(1) That is, 4-alkylphenyl acetic acid (A) is converted into ethyl ester (B), and then reduced with lithium aluminum hydride to obtain 2-(4-alkylphenyl)ethanol (C). This was brominated with phosphorus tribromide, and the obtained bromide (
D) is reacted with magnesium to form Grignard compound (E), which is converted into N1(Ph*P-CHzCFItP
In the presence of a Ni catalyst such as Ph*)C1g (Ph represents a phenyl group), it has the same meaning as in the heterocyclic compound (F), and X represents chlorine or bromine. ) The compound of -max (A) can be obtained.

Table 1 shows the phase transition temperatures of representative compounds of formula (A) thus produced.

(In the table, Cr represents the crystalline phase, 54 + 53 represents the tilted higher-order smectic phase, SB represents the smectic B phase, and S
A represents the smectic A phase, ■ represents the isotropic liquid phase,) As above, - compounds with maximum (1) S
Even if it shows C phase or does not show SC phase, it is possible to raise the Tc point by adding it as described below.

Generally, to reduce the viscosity of a liquid crystal compound, both chains are made into alkyl chains, or the linking group -COO- is replaced with -cogo- or -CHICH!, which have weaker polarity. However, among the low-viscosity liquid crystal compounds obtained in this way, almost no compounds exhibiting an SC phase are known.

Although the compound of formula (V) described above satisfies these conditions, it is possible to increase the Tc point of the liquid crystal composition by mixing the compound of formula (V), but it is difficult to improve its responsiveness. Rather, it increased the viscosity and had a negative effect.

However, the present inventors converted this compound of formula (A) to SC
When added to a liquid crystal composition exhibiting a phase, it was found that the viscosity was lowered and the response was improved, and the Tc point was increased to expand the temperature range of the SC phase.

That is, the following base liquid crystal (B) exhibiting an SC phase exhibits an SC phase at temperatures below 57°C, an SA phase at temperatures below 645°C, and an N phase at temperatures below 69°C, and becomes an isotropic liquid at temperatures above these. (I) phase, but this mother liquid crystal (B) 84% by weight and chiral dopane) (C
) 16% by weight S liquid crystal composition was heated at 57.5°C.
In the following, it shows an "sc" phase and its electro-optical response speed is 42 μsec.

However, 75.6% by weight of this base liquid crystal (B) was added, 18.4% by weight of compound k was added, and chiral dopant (C)
When an S liquid crystal composition was prepared from 16.0% by weight,
The upper limit temperature of the SC1 phase rose to 60.5°C, and when its electro-optical response speed was measured in the same manner, it was confirmed that it exhibited a faster response of 37 μsec.

The base liquid crystal (B) used here consists of: The xyl dopant (C) consists of 27% by weight, and is a liquid crystal composition with a very large spontaneous polarization induced in the S phase.

Furthermore, almost similar results were obtained when a Nα2 compound was used instead of the Na1 compound.

Although the base liquid crystal (B) used is itself composed of a two-ring compound and has a fairly low viscosity, by adding it to it, it is possible to simultaneously improve both its temperature range and response. was previously unknown.

〔Example〕

The present invention will be specifically explained with reference to Examples below.
Of course, the gist and scope of the present invention are not limited by these examples.

In addition, in the examples, "%" represents "weight %".

Example 1 Synthesis of 2-(2-(4-hebutylphenyl)ethyl)-5-(4-hexylphenyl)pyrazine L a 1 Synthesis of (2-bromoethyl)-4-heptylbenzene 4-hebutylphenyl 7.0 g of ethyl acetate (this compound was obtained by esterifying 4-hebutylphenyl acetic acid in ethanol with a sulfuric acid catalyst) was dissolved in ether 10c.
Dissolved in al. Add this solution to 20mJl of ether! 1.14 g of lithium aluminum hydride suspended in
After 0 dropwise addition was completed over 30 minutes while cooling with water, the mixture was further stirred at room temperature for 30 minutes.

Saturated brine was added to the reaction mixture to decompose excess hydride, and the formed precipitate was removed by decanting. The precipitate was washed with ether. The organic layers were combined and washed with saturated brine, followed by anhydrous sulfuric acid. Dehydrated and dried with sodium. The crude product obtained by distilling off the solvent was purified using silica gel column chromatography to obtain 4.72 g of an oily substance of 2-(4-hebutylphenyl)ethanol. (Yield: 84%) 4.70 g of this compound was mixed with 40 mj of dichloromethane! dissolved in While cooling with water, 2.12 g of phosphorus tribromide was added dropwise to this solution over 10 minutes. After stirring at room temperature for 2 hours,
Water was added slowly to destroy excess phosphorus tribromide. The organic layer was washed with an aqueous sodium bicarbonate solution, water, and saturated brine, then dehydrated and dried over anhydrous sodium sulfate.

The crude product obtained by distilling off the solvent was purified using silica gel column chromatography (distillation solvent: hexane-ethyl acetate mixed system) to obtain 1-(2-bromoethyl)-
2.29 g of 4-hebutylbenzene oil was obtained. (Yield 38%) ■-b) Synthesis of the title compound From 1.00 g of 1-(2-bromoethyl)-4-heptylbenzene obtained in 1-a) and 0.107 g of magnesium in 1SIIIl of anhydrous tetrahydrofuran. The Grignard compound (2-(4-hebutylphenyl)ethylmagnesium bromide) was prepared.

2-chloro-5-(4-hexylphenyl)piracif 1
．． 01g and Ni [PhzP-CHzCHzPPh
t] C1z (ph represents a phenyl group) 20■ tetrahydrofuran 10mj! The above Grignard compound solution was added dropwise into the solution at room temperature, and the mixture was further stirred for 4 hours.

After the reaction was completed, water was added to the reaction mixture to decompose the unreacted Grignard compound, and then ether was added to separate the organic layer. The organic layer was washed with dilute hydrochloric acid, water, then saturated brine, and dehydrated over anhydrous sodium sulfate.

The residue obtained by distilling off the solvent was purified using silica gel column chromatography (solvent: hexane L ethyl acetate) to obtain 0.32 g of the title compound.

Furthermore, the phase transition temperature of the product purified by recrystallization from ethanol was measured. The results are shown in Table 1.

The transition temperature was measured by observing the optical structure (Textme) using a polarizing microscope equipped with a temperature control stage and using a differential scanning calorimeter (DSC).

The structure of the compound was confirmed by nuclear magnetic resonance spectrum (NMR) and infrared absorption spectrum (IR).

CH δ0.70-1.00 (m, 6) 1. C1(s
)IR: 1520, 1485, 1415
, 1340, 1260.

1140, 1050, 1025, 10
10, 830.

820 ctn-” Real MN2 Synthesis of 2-(2-(4-hebutylphenyl)ethyl)-5-(4-octylphenyl)pyrimidine In Example 1, 2-chloro-5-(4-hexylphenyl) White crystals of the title compound were obtained in the same manner as in Example 1, except that 2-chloro-5-(4-octylphenyl)pyrimidine was used in place of pyrazine.

The phase transition temperatures are summarized in Table 1.

Hydrogen), 2.97-3.17 (+a, 4H.

(m, 8)1. other aromatic hydrogen), 63.06-3
．． 37 (m.

Other CL) 60.63-1.00 (In, 68.CH
3) IR: 1590, 1570, 154
0, 1520, 1000.

820, 650 cm+-' Example 3 (Preparation of SC" liquid crystal composition and creation of display element) Compound of the aforementioned base liquid crystal (B) 75.6% and xyl dopant CC) 16.0% and Nα1 8.4 s consisting of %
c''' liquid crystal composition was prepared.

This SC'' liquid crystal composition exhibited an SC'' phase at temperatures below 60.5°C and an SA phase at temperatures below 67 and 0'C.

Next, two glass transparent electrodes that have been subjected to alignment treatment (polyimide coating/rubbing) are placed together via a spacer with a thickness of approximately 2 μm, and the above sc''' liquid crystal composition is filled into this to create a cell. By slowly cooling the isotropic liquid (1) phase to room temperature, uniformly oriented S di-phase monodomains were obtained.

This cell has an electric field strength of 10V 5t-t/μm, 5
When a 0 Hz square wave was applied and the electro-optic response speed was measured, it was 37 μsec at 25°C. The spontaneous polarization at this time is 13.9nC/cd and the tilt angle is 27
．． The contrast was very good at 5°.

Example 4 SC'' liquid crystal compositions were prepared in the same manner as in Example 3, except that the Nα2 compound was used instead of the Nα1 compound, and the electro-optical response speeds of each composition were measured.

The results are shown in Table 2. Note that the reference example is an example in which the compound of formula (A) was not used, and instead, the base liquid crystal CB) was used at 84%.

〔Effect of the invention〕

The compound of formula (I) of the present invention exhibits an SC phase in a wide temperature range up to a high temperature range, or even if it is a compound that does not exhibit an SC phase, it can be mixed and added to a liquid crystal composition to increase temperature. It is possible to obtain a liquid crystal composition exhibiting an SC phase whose range is particularly extended to a high temperature range, or an "sc" liquid crystal composition.

Furthermore, since the compound of formula (1) of the present invention is a low-viscosity compound that does not have a highly polar ester bond or the like in its molecule, high-speed response is possible even in the above-mentioned sc'' liquid crystal composition.

Furthermore, as shown in the examples, it can be easily produced industrially, the compound itself is colorless, and it is chemically very stable.

Therefore, the compound of formula (A) of the present invention is useful as a ferroelectric liquid crystal material with excellent high-speed response.

Claims (1)

[Claims] 1. A compound represented by the general formula ▲There are numerical formulas, chemical formulas, tables, etc.▼ (wherein R^1 and R^2 each independently have a carbon atom number of 1)
Represents ~18 linear or branched alkyl groups, ▲ has mathematical formulas, chemical formulas, tables, etc. ▼ has ▲ has mathematical formulas, chemical formulas, tables, etc. ▼, ▲ has mathematical formulas, chemical formulas, tables, etc. ▼, ▲ mathematical formulas , chemical formulas, tables, etc. ▼, ▲ mathematical formulas, chemical formulas,
Represents ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼. ) A compound represented by 2. The compound according to claim 1, wherein ▲There are mathematical formulas, chemical formulas, tables, etc.▼ is ▲There are mathematical formulas, chemical formulas, tables, etc.▼. 3. The compound according to claim 1, wherein ▲There are mathematical formulas, chemical formulas, tables, etc.▼ is ▲There are mathematical formulas, chemical formulas, tables, etc.▼. 4. A liquid crystal composition containing the compound according to claim 1, 2 or 3. 5. The liquid crystal composition according to claim 4, which exhibits a ferroelectric chiral smectic phase. 6. A liquid crystal display element comprising the liquid crystal composition according to claim 4 or 5 as a constituent element.