JPH03176443A - Biphenyl derivative and liquid crystal composition - Google Patents

Abstract

NEW MATERIAL:A racemic modification comprising a biphenyl derivative shown by formula I (R<1> is 4-18C linear chain alkyl; (m) is 2-8; (n) is 1-3). EXAMPLE:(+ or -)-4-(6-Methyloctyloxy)-4'-decylbiphenyl. USE:A material for ferroelectric liquid crystal display having excellent response characteristics and memory characteristics. PREPARATION:For example, a 4-(4-alkylphenyl)phenol shown by formula II is made to react with a bromide shown by formula III in the presence of a base to give a compound shown by formula I.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a racemic compound consisting of a novel biphenyl compound and a liquid crystal material using the same, and in particular to a ferroelectric liquid crystal with excellent responsiveness and memory properties. It relates to display materials.

[Prior art]

Liquid crystal display elements are currently widely used due to their excellent features (low voltage operation, low power consumption, thin display capability, and can be used in bright places without tiring the eyes). However, in the most common TN type display system, CRT
The response is extremely slow compared to luminescent display methods such as
In addition, the display cannot be memorized (memory effect) when the applied electric field is turned off, so optical shutters that require high-speed response,
There are many limitations to its application to printer heads and video screens such as TVs that require time-division drive, and it could not be said to be a suitable display method.

However, recently reported display systems using ferroelectric liquid crystals have high-speed response and memory effects that are 100 to 1000 times faster than TN display systems, so they are expected to be the next generation of liquid crystal display devices and are currently gaining popularity. Research and development is 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, which has the lowest viscosity, is the one that has the lowest viscosity. Most desirable.

Many liquid crystal compounds exhibiting the sc''' phase have already been synthesized.
Although it is being considered, the conditions for using it as a ferroelectric display element are (a) SC in a wide temperature range including room temperature;
``to exhibit a phase, (b) to obtain good orientation, SC
Having an appropriate phase series on the high temperature side of the 0 phase and having a large helical pitch; (c) having an appropriate tilt angle;
(2) 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, at present, SC0 compounds are mixed with other liquid crystal compounds exhibiting the 5011 phase (hereinafter referred to as SC0 compounds), etc.
SC*
A liquid crystal compound exhibiting a phase must have low viscosity and a certain level of large spontaneous polarization, especially in order to achieve high-speed response.

In addition, by adding it as a chiral dopant to other liquid crystal compounds or compositions exhibiting a smectic C (hereinafter referred to as SC) phase, it can be used as an "sc" composition, and in this case, the viscosity can be lowered. Therefore, faster response is possible, and this method is commonly used.The compound used as a chiral dopant alone can
Although it does not necessarily have to exhibit an SC* phase, it is necessary that it exhibit similar properties when used as an SC'' liquid crystal composition.

Compounds exhibiting an SC phase (hereinafter referred to as SC compounds).

is already well known. However, although SC compounds generally have a lower viscosity than SC''I compounds, their viscosity is currently not sufficient to ensure a wide temperature range. The viscosity is lower for two-ring compounds than for three-ring compounds, but since the upper limit temperature of the SC phase is not very high in two-ring compounds, it is difficult to maintain a sufficiently wide temperature range.

At present, the host liquid crystal composition exhibiting the SC phase (hereinafter referred to as S
It is called C matrix liquid crystal. ) is used as the main component of
The C compound is mainly a phenylbenzoate compound represented by the following formula (A) or a pyridine compound represented by the general formula (B).

(In the formula, R1 and Rh each independently represent a linear or branched alkyl group, alkoxyl group, alkoxycarbonyl group, alkanoyloxy group, or alkoxycarbonyloxy group, but do not represent an alkyl group at the same time.

(In the formula, R" and Rh have the same meanings as in the above-mentioned -Fukudai A.) In these compounds such as -Fukudai (A) and (B), an ester bond, a pyrimidine ring, etc. are present in the molecule. Therefore, its viscosity was by no means low. In addition, in order to expand the temperature range, the following
) to (C-5) are also used, but the viscosity of these three-ring compounds is higher than that of two-ring compounds, and the viscosity of the SC matrix liquid crystal obtained by mixing them is It wasn't low enough to satisfy me.

(In the formula, R'' and Rh represent the same meanings as in general formula (A).> (In the formula, Rc and R4 represent an alkyl group or an alkoxyl group.) [Problem to be solved by the invention] The above Therefore, the viscosity and temperature range of conventional SC compounds are insufficient to prepare SC host liquid crystals, and it is now possible to prepare SC0 liquid crystal compositions with fast response by adding chiral dopants from optically active compounds. There were problems in providing this service, and improvements were desired.

The problem to be solved by the present invention is to
``By providing a low-viscosity compound to be used in a parent liquid crystal exhibiting a phase, thereby providing a low-viscosity parent liquid crystal, and adding a chiral dopant consisting of an optically active compound to this, a high-speed response compound can be obtained. Our goal is to provide ferroelectric liquid crystal products.

[Means to solve the problem]

In order to solve the above problems, the present invention provides the following general formula (1
) provides a racemic form of the compound represented by

In the formula, R1 represents a linear alkyl group having 4 to 18 carbon atoms, and a linear alkyl group having 6 to 12 carbon atoms is particularly preferred. m represents an integer of 2 to 8, preferably an integer of 3 to 6; n represents an integer of 1 to 3, preferably 1 or 2.

The compound of general formula (1) of the present invention can be produced, for example, as follows.

That is, 4-(4-alkylphenyl)phenol represented by -Fukudai (II) (wherein R1 represents a straight chain alkyl group having 4 to 18 carbon atoms) and general formula (III) C)13 Br(CHz+CH←CH2→-, CHs -・-・
-(I[[) (wherein m represents an integer of 2 to 8 and n represents an integer of 1 to 3.

What is necessary is just to react with the bromide represented by in the presence of a base.

Here, the compound of -fukudai (n) is a known compound,
- The compound of Fukudai (III) can be produced, for example, as follows.

That is, it can be obtained by brominating the corresponding alcohol represented by general formula (III) using a conventional method. Although there are some commercially available alcohols represented by -Fukudai (■)', they can be easily produced using commercially available compounds as raw materials depending on their m and n.

When n=1 or n=2, it can be obtained by carrying out a commercially available carbon chain elongation reaction.

When n=3, commercially available 2-bromohexane is used to prepare the Grignard compound, then reacted with formaldehyde or with carbon dioxide and then reduced to alcohol (2-methylhexanol), as follows: It can be manufactured in a similar manner.

The compound of the general formula (I) of the present invention is obtained as described above, and the melting point, phase transition temperature, infrared absorption spectrum (IR), nuclear magnetic resonance spectrum (NMR) of each specific compound belonging to these are ), etc.).

Examples of representative compounds are shown in Table 1.

Table 1 (In the table, Cr represents a crystalline phase, SX represents an unidentified tilted smectic phase, and ■ represents an isotropic liquid phase.) The biphenyl derivative represented by the general formula (1) has the -form ( Ester bonds like the compound represented by A), -
Since it does not contain a highly viscous group such as a pyrimidine ring like the compound represented by formula (B), its viscosity is relatively low.

Further, as is clear from Table 1, as a two-ring compound, it has a tilted smectic phase up to a very high temperature, so it is very excellent as a compound for SC matrix liquid crystals.

As biphenyl derivatives having similar structures, compounds represented by the following general formula (D-1) and -form (D-2) are known.

(In the formula, R'' and R' each independently represent a linear alkyl group. (Frushige Kristallein Taberen P270 (1984)) Compounds represented by smectic B (SB) phase, smectic E (
It shows only a non-tilted smectic phase such as the (SR) phase, and does not show any tilted smectic phase, let alone the (SC) phase. Therefore, when it is added to the base liquid crystal, the upper limit temperature (Tc) of its SC (or sc'') phase is significantly lowered, making it unsuitable for use.

Furthermore, in the compound represented by the following general formula (D-3),
According to the studies conducted by the present inventors, the crystallinity was strong and did not exhibit liquid crystallinity.

In the compound represented by the general formula (1) of the present invention,
Although it does not exhibit an SC phase, it exhibits a tilted smectic phase up to relatively high temperatures, so by adding it to the host liquid crystal, the temperature range of the SC phase is hardly narrowed.
This makes it possible to lower its viscosity. Moreover, a major feature of the compound of the present invention is that its melting point is lower than that of other biphenyl compounds or parent liquid crystal compounds.

This is very convenient for obtaining a composition that exhibits a chiral smectic phase over a wide temperature range down to low temperatures.

Further, the present invention provides a liquid crystal composition. The liquid crystal composition of the present invention is composed of a racemic compound represented by the formula (1) and a liquid crystal composition other than the racemic compound represented by the formula (1). , especially when used as a ferroelectric liquid crystal display element, −
As a substance other than the compound represented by format (1), a composition consisting of a liquid crystal compound or liquid crystal composition exhibiting an SC phase as a main component and an optically active compound as a minor component is desirable, and a composition that is added in a small amount to a nematic liquid crystal is desirable. Accordingly, it can also be used for lowering viscosity and the like.

Examples of SC compounds that can be used as an SC matrix liquid crystal together with the compound represented by the general formula (1) of the present invention include:
For example, phenylbenzoate compounds represented by general formula (A), pyrimidine compounds represented by general formula (B), or general formulas (C-1) to (C-5
) can be mentioned as three prototype compounds.

By adding a chiral dopant made of an optically active compound to the SC base liquid crystal obtained in this way, a low-viscosity liquid crystal composition that exhibits the sc'' phase over a wide temperature range including room temperature can be easily obtained.

The ferroelectric liquid crystal composition containing the compound represented by the general formula (1) of the present invention has 1 to 2
By encapsulating it as a thin film of about 0 μm, it can be used as a display cell. In order to obtain good contrast, uniformly oriented monodomains are required. Many methods have been tried for this purpose, but the helical pitch and the phase series of the 5C11 phase in a high temperature range are important for liquid crystal materials. The helical pitch depends primarily on the chiral dopant used, whereas the phase sequence of the liquid crystal depends on the compound initiation used. Generally, it is required that the SA phase exists in the high temperature range of the SC''1 phase, but the compound represented by the general formula (1) of the present invention tends to expand the smectic A phase, so this point is There is no problem with that.Furthermore,
If a chiral nematic (N″1) phase is required,
It is also possible to maintain the desired phase series by using a strong nematic compound as another matrix compound.

〔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 to these examples.

The structure of the compound is determined by nuclear magnetic resonance spectrum (NMR).
, and infrared absorption spectra (IR), mass spectra (
Confirmed by MS). The phase transition temperature can be measured using a polarizing microscope equipped with a temperature control stage and a differential scanning calorimeter (D
SC) was used in combination.

(KBr) in IR is measured by tablet molding, (
neat) is for measurement using a liquid film, and (Nujol) is for measurement using a liquid film.
Each represents a measurement in suspension in liquid paraffin.

In NMR, (CDCl,) represents the solvent, S represents a singlet, d represents a doublet, t represents a triplet, q represents a quartet, m represents a multiplet, broad represents a broad absorption, and J represents a cup. Represents a ring constant. Moreover, temperature represents °C.

All "%" in the composition represents "% by weight".

Example 1 ((±)-4-(6-methyloctyloxy)
Synthesis of -4'-decyl biphenyl (compound No. 1 in Table 1) 439 ml of 4-(4-octylphenyl)phenol was dissolved in 10 ml of dimethylformamide (hereinafter referred to as DMF). To this solution was added 290 μ of potassium t-butoxy, and the mixture was stirred at room temperature. A solution of 351 μm of racemic 6-methyloctyl bromide dissolved in 5 μm of DMF was added dropwise to this mixture over 5 minutes, and the mixture was further stirred at 40° C. for 6 hours. After adding ethyl acetate to the reaction mixture and making it acidic with dilute hydrochloric acid, the organic layer was separated and washed successively with water and saturated brine.
Dehydrated with anhydrous sodium sulfate.

The residue obtained by distilling off the solvent was purified using silica gel column chromatography to obtain the title compound 542. The melting point of a purified product obtained by recrystallizing this compound from ethanol was 27°C. Also, when the temperature rises 6
A tilted smectic phase of unknown origin was exhibited up to 9.5°C.

NMR (CDC1s); 0.78-0.94 (m,
9H), 1.07-1.07 (m, 25H)
.

1.85-1.96 (n+, 2) 1), 2.62 (t,
J=8Hz, 2H), 3.98(t.

J=6.5Hz, 2H), 6.94(d, J=9Hz,
2B), 7.21 (d, J=9Hz, 2H), 7.45
(d, J=9Hz, 2f(), 7.49(d, J=9H
z, 2H) IR (Nujol); 1605, 1580,
1505.1275,1245,1180,1040°810 (cm-') Example 2 [(±)-4-(5-methyloctyloxy)
Synthesis of -4'-decyl biphenyl (compound Il & L2 in Table 1)] In Example 1, in place of 6-methyloctyl bromide,
The title compound was obtained in the same manner as in Example 1 except that racemic 5-methyloctyl bromide was used.

The phase transition temperatures are shown in Table 1.

Example 3 (SC” Preparation of liquid crystal composition and fabrication of display element
c) An "sc" liquid crystal composition having the following composition was prepared.

Compounds ll & 11 in Table 1 40% this S
Although the 01 liquid crystal composition Kaimono contained only four components, it stably exhibited the SC* phase even below room temperature. SC at 61 or below when increasing temperature
” phase and SA phase at temperatures below 69.5°C.

This "sc" liquid crystal composition was heated to form an isotropic liquid (I) phase, and this was subjected to alignment treatment (polyimide coating and rubbing) into a cell (cell 4, approximately 2
μm) and then slowly cooled to obtain uniformly oriented SC0 phase monodomains.

When the electro-optical response speed of this cell was measured by applying a rectangular wave with an electric field strength of 10 vp-p/μM and 50 Hz, it showed a high-speed response of 57 μsec at 25°C.

The tilt angle at this time is 26.2@, and the spontaneous polarization is 31.9n.
C/c11! The contrast was good.

Comparative Example In Example 3, when the compound of floor 1 in Table 1 was used at a ratio of 80%, it crystallized near room temperature.
It was not possible to measure the electro-optic response speed.

In addition, in Example 3, a composition was prepared in the same manner as in Example 3 except that the compound (D-2) was used instead of the compound +i in Table 1. The SC1 phase was not shown.

〔Effect of the invention〕

Compound (racemate) represented by general formula (1) of the present invention
shows a tilted smectic phase up to high temperatures, has a very low melting point, and has a relatively low viscosity, compared to other S
By using a C" liquid crystal compound or an SC liquid crystal compound as a host liquid crystal, a composition with a wide temperature range and low viscosity can be obtained. As a result, especially SC0
Liquid crystal compositions can provide high-speed response over a wide temperature range. Further, as shown in the Examples, the compound of the present invention can be easily manufactured industrially, is colorless, and has excellent chemical stability against water, light, heat, etc., and is therefore practical.

Furthermore, the liquid crystal material comprising the chiral smectic liquid crystal compound or composition of the present invention can achieve a high-speed response of 60 μsec or less, and is extremely useful as an optical switching device for display.

Claims (1)

[Claims] 1. General formula▲ Numerical formula, chemical formula, table, etc.▼ (In the formula, R^1 represents a linear alkyl group having 4 to 18 carbon atoms, and m is an integer of 2 to 8. , and n represents an integer of 1 to 3.) A racemic body consisting of a compound represented by the following. 2. The racemate according to claim 1, wherein n is 1 or 2. 3. A liquid crystal composition containing the racemate according to claim 1. 4. The liquid crystal composition according to claim 3, which exhibits a ferroelectric chiral smectic phase. 5. A liquid crystal display element constructed using the liquid crystal composition according to claim 3 or 4.