JPH03141237A - Fluorine-containing tricyclic compound having oxymethylene bond - Google Patents

Abstract

NEW MATERIAL:A compound of formula I (R<1> and R<2> are straight chain or branched 1-18C alkyl; X is H or F). EXAMPLE:3-Fluoro-4-decyloxy-4'-(e-octylbenzyloxy)biphenyl. USE:A material for ferroelectric liquid crystals having excellent high responsibility. PREPARATION:A phenylphenol derivative of formula II is reacted with a 4- alkylbenzyl bromide of formula III in the presence of a base to prepare the compound of formula I. The compound of formula II having F as the X is prepared by subjecting a compound of formula IV to a mono-coupling reaction using Mg in the presence of PdCl2, demethylating the resultant 3,3'-difluoro-4,4'- dimethoxybiphenyl with HBr and subsequently alkylating one of the resultant OH groups.

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 due to their excellent characteristics (low voltage operation, low power consumption, thin display capability, and can be used even in bright places without causing eye strain).

However, in the most common TN type display system,
Compared to light-emitting display systems such as CRTs, the response is extremely slow and the display cannot be memorized (memory effect) when the applied electric field is turned off. There are many restrictions on the application to moving picture screens of televisions and the like, which require a high resolution, and it could not be said to be suitable.

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 C phase (hereinafter abbreviated as "sc"), which has the lowest viscosity among them. phase is most desirable.

Many liquid crystal compounds exhibiting the sc" phase have already been synthesized and studied, but the conditions for use as ferroelectric display elements are: (a) sc" phase in a wide temperature range including room temperature;
(b) In order to obtain good orientation, sc”
It has an appropriate phase series on the high temperature side of the phase, and its helical pitch is large; (c) it has an appropriate tilt angle;
D) It is preferable that the viscosity is low, and (E) that the spontaneous polarization is large to some extent, but there is no known material that satisfies these requirements alone.

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

Until now, the upper limit temperature (Tc point) of the SC phase or S phase
Compounds that have been used to increase
Compounds such as those represented by the following general formulas (IV) a to (IV) b, including ester compounds, are known, all of which have an SC phase (or sc'' phase) with a high Tc point.

... (IV) a ... (IV) b However, the above general formula (III) a to (II)
Directly bonded three-ring compounds such as the compound represented by e have poor compatibility with other liquid crystal compounds, so precipitation tends to occur and it is difficult to lower the melting point.
The ester compounds represented by V) a and (IV) 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 a compound represented by the following general formula (V), an ester compound such as a compound represented by the general formula (TV) a or (IV) b In comparison, the viscosity was considerably improved, but it was still not sufficient. Therefore, it has an even lower viscosity (and excellent compatibility, and Tc
There has been a desire for a compound that is highly effective in raising the score.

[Problem to be solved by the invention]

The problem to be solved by the present invention is to have excellent compatibility with other parent liquid crystal compounds, to have a low viscosity, and to exhibit an SC phase, and to have an upper limit temperature of the SC phase (or SC" phase) by mixing. To provide a compound that has a large effect of increasing the Tc point), and by using it, the Tc point is high, and
The object of the present invention is to provide a liquid crystal composition exhibiting a low viscosity SC (or sc'' phase) and 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 problems, the present invention provides the following general formula (A)
Provided are compounds represented by

In the above general formula, R1 and Rt each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms,
Preferably R1 and Rt each independently have 4 to 4 carbon atoms.
12 straight-chain alkyl groups. X represents hydrogen or fluorine.

The present invention also provides a liquid crystal composition containing at least one compound represented by the above general formula (A). In particular, the composition according to the present invention is suitable for use in chiral smectic liquid crystals for ferroelectric liquid crystal displays, Alternatively, it is preferable to use it as a base liquid crystal exhibiting an SC phase for preparing a chiral crystal liquid crystal, and it is preferable that the proportion of the compound represented by the general formula (A) in the composition is 2 to 60% by weight. Preferably 5
Particularly preferred is ~50% by weight.

Furthermore, the present invention provides a liquid crystal display element comprising the above composition, 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 (A) according to the present invention can be produced, for example, according to the following production method.

That is, it can be produced by reacting a phenylphenol derivative represented by the general formula (B) with a 4-alkylbenzyl bromide represented by the general formula (C) in the presence of a base. Here, in formula (B) and formula (C), Rt, Rg and X all have the same meaning as in formula (A).

The compound of formula (B) can be produced, for example, as follows. In the compound of formula (B), when X is F, F F That is, 2-fluoro-4-bromoanisole is homocoupled by reacting with magnesium in the presence of palladium chloride to form 3,3'-difluoro- 4,4'-dimethoxybiphenyl. This compound can be demethylated with hydrogen bromide to give 3,3'-difluoro-4,4'-biphenol, and one hydroxyl group of this compound can be alkylated.

In the compound of formula (B), when X is hydrogen ■) HzOz/HCOOH That is, after alkylating 2-fluoro-4-bromophenol, it is made into a Grignard compound and reacted with iodobenzene in the presence of palladium chloride. 3-fluoro-4-alkoxybiphenyl is obtained. It can be obtained by acetylating this by a conventional method and then reacting it with hydrogen peroxide in formic acid.

The compound of formula (C) can be produced, for example, as follows.

Table 1 ■ LjA I H4 ■ Brx That is, by esterifying commercially available 4-alkylbenzoic acid, reducing it with lithium aluminum hydride to form 4-alkylbenzyl alcohol, and brominating this with phosphorus tribromide, etc. Obtainable.

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

(In Table 1, Cr represents a crystalline phase, SF represents a smectic F phase, SC represents a smectic C phase, and l represents an isotropic liquid phase, but the SF phase may also be another smectic phase. ) Generally, in order to reduce the viscosity of a liquid crystal compound, the side chain is made into an alkyl chain, or the linking group -COO- is replaced with -CH,0-, -CH,CI!, which has less polarity. However, among the low-viscosity liquid crystal compounds obtained in this way, almost no compounds exhibiting an SC phase are known. For example, a compound represented by the general formula, which shows only a smectic E (hereinafter referred to as SE) phase and a smectic B (hereinafter referred to as SR) phase,
SC phase is not shown.

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.

In other words, the following parent liquid crystal (JLF) exhibits an SC phase below 57°C, an SA phase below 64.5°C, and an N phase below 69°C, and becomes an isotropic liquid at higher temperatures. (1)
However, the "sc" liquid crystal composition consisting of 84% by weight of this base liquid crystal (A) and 16% by weight of the following chiral dopant (B) exhibits the "SC" phase at 58°C or below, and its electro-optic response speed (0 -50%) is 86 μsec.

However, the liquid crystal composition s was prepared from this base liquid crystal (A) at 75.6% by weight, 8.4% by weight of compound (A-1) added, and 16.0% by weight of the chiral dopant (B). However, the upper limit temperature of the "sc" phase rose to 62.5°C, and when its electro-optic response speed was similarly measured, it was found to be 65μ
It was confirmed that the response time was faster than that in seconds.

The base liquid crystal (A) used here consists of , and the chiral dopant (B) consists of . The helical pitch induced in the N9 phase at around 70'C is long, and the helical pitch induced in the SC1 phase is long. This is a liquid crystal composition with extremely large spontaneous polarization.

Moreover, almost the same results were obtained when the compound of formula (A-2) was used instead of the compound of formula (A-1).

Since the parent liquid crystal used (A) itself consists of a bicyclic compound and has a fairly low viscosity, it is necessary to add a compound that can improve both its temperature range and response at the same time. 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 compound 1lhA-1 in Table 1) 4
-(3-Fluoro-4-decyloxy)phenylphenol 0.080 g was dissolved in dimethylformamide (DM
F) sl, 0.050 g of t-butoxypotassium was added to this solution, and the mixture was stirred at room temperature.

To this mixed solution was added 0.073 g of 1-bromomethyl-4-octylbenzene in 10mj! of DMF! Drop the solution,
The mixture was stirred at room temperature for 4 hours and then at 70°C for 2 hours.

After the reaction mixture was acidified with hydrochloric acid, water and ether were added, and the ether layer was washed with water and saturated brine, and then dehydrated with anhydrous sodium sulfate. The crude product obtained by distilling off the solvent was purified using silica gel column chromatography (solvent: n-hexane: ethyl acetate = 5:1) to obtain 3-.
0.095 g of white crystals of fluoro-4-decyloxy-4'-(4-octylbenzyloxy)biphenyl was obtained. The structure was confirmed by nuclear magnetic resonance spectrum (NMR) and infrared absorption spectrum (IR).

NMR (CDCNi) '0.884-0-93(+
6H), 1.19-1.67 (m, 2411),
1.79-1.88 (m, 2H).

2.6Ht, J=8Hz, 2B), 4.05(t
.

J=8.5Hz, 2H), 5.06(s, 2H)
.

6.97-7.03 (m, 3B), 7.20-7.
23 (++, 4H), 7.35 (d, J=8Hz
, 2H).

7.45(d, J=8Hz, 2H)IR(Nu
jol): 1605. 1590. 1520
-, 1300. 12B5゜1250, 1190.
1140. 1040. 1010°835, 81
0 (am-') Furthermore, when the phase transition temperature of the compound obtained by recrystallizing this white crystal from ethanol was measured, it was 1, and the melting point was 9.
4°C, showed an SF phase up to 115.5°C, an SC phase up to 133°C, and turned into an I phase at higher temperatures.

Note that the phase transition temperature was measured using a polarizing microscope equipped with a temperature control stage.

Example 2 (Synthesis of compound 11kLA-2 in Table 1) In Example 1, in place of 4-(3-fluoro-4-decyloxy)phenylphenol, 2-fluoro-4-
I' in Table 1 was carried out in the same manner as in Example 1 except that (3-fluoro-4-decyloxy)phenylphenol was used.
Compound hA-2 was obtained.

NMR (CDC13): 0.84-0.93 (1m
, 6H), 1.18-1.00 (m, 248),
1.79-1.89 (++, 2H).

2.61 (t, J=8Hz, 2)1), 4.05
(t.

J=7Hz, 28), 5.13(s, 2H).

6.96-7.00 (m, 2B), 7.17-7.
28 (m, 4H), 7.30 (d, J=8.5H
z, 2H) IR (Nujol): 1615.
1570.1520.1310.1275°1210,
1135.1045. 1000.865°800(c
+a-') Example 3 (Creation of SC" liquid crystal composition and display element) 8.4% of the NIA-1 compound obtained in Example 1, 75.6% of the above-mentioned base liquid crystal (A), and chiraldono. A liquid crystal composition containing 16.0% of <SC> was prepared.

This sc" liquid crystal composition exhibits an sc" phase at temperatures below 62.5°C.
Each exhibited SA phase at temperatures below 67.5°C, and became I phase at temperatures above that temperature.

This "sc" liquid crystal composition was filled into a cell having a thickness of approximately 2 μm and consisting of two glass transparent electrode plates that had been subjected to alignment treatment (polyimide coating and rubbing).

! The phase was slowly cooled to room temperature to uniformly orient the S phase. To this, the electrolytic strength io vp-p/μm is 5011
Applying a square wave of z, its electro-optic response speed (0-5
0%) measurement showed a high-speed response of 65 μsec at 25°C. The tilt angle at that time was 30.10, and the contrast was also good.

Example 4 Preparation of a sc" liquid crystal composition and electro-optics in the same manner as in Example 3 except that the compound l1hA-2 obtained in Example 2 was used instead of the compound l1hA-1 in Example 3. The response speed was measured.

This S liquid crystal composition has a sc” phase at 62°C or lower, and a 65°C
It showed an SA phase at temperatures below .degree. C. and an N* phase at temperatures below 66.5.degree.

The electro-optical response speed at 25° C. was as fast as 65 μsec, the tilt angle was 29.4°, and the contrast was very good.

Comparative Example In Example 3, the compound l1hA-1 was not used, and the parent liquid crystal (A) was 84.0% and the chiral dopant (B) was 16.
The SC" liquid crystal composition prepared from 0%
c” phase, SA phase at 63.5℃ or below, N at 65℃ or below.
''' phase, becomes one phase at higher temperatures, and sc
``The upper limit temperature of the phase has been lowered by 3 degrees Celsius.

Further, the electro-optical response speed measured in the same manner as in Example 3 was 86 μsec at 25° C., which was slow.

〔Effect of the invention〕

The compound of formula (A) of the present invention exhibits an SC phase in a wide temperature range up to a high temperature range, and when mixed and added to a liquid crystal composition, a liquid crystal composition exhibiting an SC phase whose temperature range is particularly expanded to a high temperature range. , or sc” liquid crystal compositions can be obtained.

Furthermore, since the compound of formula (A) 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.

In addition, as shown in Examples, it can be easily produced industrially, the compound itself is colorless, and 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.

Procedural amendment (voluntary) October 9, 1990

Claims (1)

[Claims] 1. General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R^1 and R^2 each independently represent the number of carbon atoms of 1
~18 linear or branched alkyl groups, and X represents hydrogen or fluorine. ) A compound represented by 2. A liquid crystal composition containing the compound according to claim 1. 3. The liquid crystal composition according to claim 2, which exhibits a ferroelectric chiral smectic phase. 4. A liquid crystal display element comprising the liquid crystal composition according to claim 2 or 3 as a constituent element.