JP2827463B2 - Fluorine-containing tricyclic compound having an oxymethylene bond - Google Patents

Description

The present invention relates to a fluorine-containing tricyclic compound having an oxymethylene bond useful as an electro-optical display material and a liquid crystal material using the same. The present invention relates to a ferroelectric liquid crystal display material having excellent responsiveness and memory properties.

(Prior art)

Liquid crystal display elements are currently widely used due to their excellent features (low voltage operation, low power consumption, thin display, use in bright places, and no eyestrain). However, the most common TN type display system has a very slow response compared to a light emitting type display system such as a CRT, and stores the display when the applied electric field is cut off (memory effect).
Therefore, there are many restrictions on the application to moving image planes such as optical shutters, printer heads, and televisions that require time-division driving, which require high-speed response, and display methods suitable for such applications. I couldn't say.

Recently, Meyer et al. Reported a display method using a ferroelectric liquid crystal.According to this, a high-speed response of 100 to 1000 times that of a TN type and a memory effect can be obtained. R & D is underway.

The liquid crystal phase of the ferroelectric liquid crystal belongs to a tilt-type chiral smectic phase, but practically, a chiral smectic C (hereinafter abbreviated as Sc ^* ) phase having the lowest viscosity among them is used. Most desirable. Many liquid crystal compounds exhibiting the Sc ^* phase have already been synthesized and studied, but for use as a ferroelectric display element, it is preferable that the following conditions be satisfied.

(B) Sc ^* phase should be exhibited in a wide temperature range including room temperature. (Ii) In order to obtain good orientation, an appropriate phase series on the high temperature side of Sc ^* phase and its helical pitch are large. (C) having an appropriate tilt angle, (d) having a small viscosity, and (e) having a spontaneous polarization to some extent. However, none of them satisfying these alone has been known.

Therefore, it is currently used as a liquid crystal composition exhibiting a Sc ^* phase (hereinafter, referred to as a Sc ^* liquid crystal composition).

Sc ^{* The} method for preparing the liquid crystal composition includes smectic C
(Hereinafter, this will be abbreviated as Sc.) A method of adding a chiral dopant composed of an optically active compound to a base liquid crystal exhibiting a phase or a Sc ^* phase is advantageous for achieving high-speed response. This is the method used.

Compounds that have been used to raise the maximum temperature (hereinafter referred to as the Tc point) of the Sc phase or Sc ^* phase are represented by the following general formulas (III) a to (III) e. Tc such as a compound having a structure in which three aromatic rings are directly connected, such as a compound, or a compound having an ester bond, such as a compound represented by the following general formulas (IV) a to (IV) b: A compound having a Sc phase (or Sc ^* phase) having a high point is known.

However, compounds of the three-ring direct-bonding type, such as the compounds represented by the general formulas (III) a to (III) e, have poor compatibility with other liquid crystal compounds, so that precipitation is likely to occur, and the melting point is lowered. On the other hand, the above (IV) a to (I
V) The compound having an ester bond represented by b has a disadvantage that the viscosity is large.

Therefore, it has been desired to provide a compound having a lower melting point, an excellent compatibility, and a low melting point having a large effect of increasing the Tc point.

[Problems to be solved by the invention]

The problem to be solved by the present invention is that the compound has excellent compatibility with other compounds for a base liquid crystal, has a low viscosity, and shows an Sc phase. By mixing, the maximum temperature of the Sc phase (or Sc ^* phase) can be reduced. By providing a compound having a large increasing effect, and by using the same, it is possible to provide a low-viscosity liquid crystal composition having a high Tc point and exhibiting a Sc (or Sc ^* ) phase in a wide temperature range. An object of the present invention is to provide a liquid crystal display device using a composition as a constituent element.

[Means for solving the problem]

The present invention provides a compound represented by the following general formula (I): 3 having a fluorine atom and an oxymethylene bond represented by
A cyclic compound is provided.

In the formula, R ¹ and R ² each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, preferably a linear alkyl group having 4 to 12 carbon atoms. Express.

Further, the present invention provides a liquid crystal composition containing the compound represented by the general formula (I). In particular, the liquid crystal composition of the present invention is preferably used as a chiral smectic liquid crystal for ferroelectric liquid crystal display or a base liquid crystal exhibiting an Sc phase for preparing a chiral smectic liquid crystal. ) Is preferably in the range of 2 to 60% by weight, particularly preferably in the range of 5 to 50% by weight.

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

The compound represented by the general formula (I) according to the present invention is
For example, it can be manufactured according to the following manufacturing method.

(In the above reaction, R ¹ and R ² are each R ¹ and R ² in the general formula (I) which has the same meaning.) In other words, the presence of a base and a compound of formula (B) compound formula (C) By reacting below, the compound of the formula (I) according to the present invention can be produced.

 Here, the compound of the formula (B) is a known compound.

The compound of the formula (C) can be produced according to the following production method.

That is, 2,3-difluorophenol can be obtained by methylation, acylation, reduction of the acyl group to an alkyl group, and demethylation.

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

In Table 1, Cr represents a crystal phase, and I represents an isotropic liquid phase.

As is clear from Table 1, the compound of the formula (I) has a low melting point, shows a Sc phase in a high temperature range, and has a Sc phase or Sc ^*.
Mixing with a liquid crystal composition having a phase has the effect of increasing the maximum temperature of the Sc phase or Sc ^* phase of the liquid crystal composition and expanding the temperature range.

To reduce the viscosity of the liquid crystal compounds generally or the side-chain alkyl group, a -COO- of the linking group are more less polar -CH ₂ O-or -CH ₂ CH ₂ - methods such as changing the is made However, among the low-viscosity liquid crystal compounds thus obtained, almost no compounds exhibiting the Sc phase are known. For example, a compound similar to general formula (I) but containing no fluorine The compounds smectic B (hereinafter, referred to as S _B.) And smectic E (hereinafter, referred to as S _E.) Shows only phase, Sc phase is not shown.

Accordingly, the inventors have determined that this compound of formula (I)
^{* When} added to a liquid crystal composition exhibiting a phase, it was found that the Tc point was raised, the temperature range was expanded, and the response was hardly affected.

That is, the following parent liquid crystal (A) showing the Sc phase has a Sc phase at 57 ° C. or lower.
Phase, S _A phases at 64.5 ° C. or less, 69 ° C. or less nematic (hereinafter, N referred.) Phase indicates each becomes a more I phase at a temperature, the mother liquid crystal (A) 84 wt% and The Sc ^* liquid crystal composition comprising 16% by weight of the following chiral dopant (B) is 58%
It shows a Sc ^* phase below ℃ and its electro-optical response speed at 25 ℃ is 100 μs. However, this mother liquid crystal (A)
To 75.6% by weight, and 8.4% by weight of the compound of No. 1 in Table 1 was added, and a Sc composed of 16.0% by weight of a chiral dopant (B)
^{* When a} liquid crystal composition was prepared, the maximum temperature of Sc ^* phase was 61.
The temperature was raised to 0 ° C., and the electro-optical response speed was measured in the same manner. As a result, it was confirmed that the electro-optical response speed was 117 μsec at 25 ° C., which also showed a high-speed response.

The base liquid crystal (A) used here is: Wherein chiral dopamine (B) is This is a liquid crystal composition having a long helical pitch induced in a chiral nematic (hereinafter, referred to as N ^* ) phase at around 70 ° C. and a very large spontaneous polarization induced in a Sc ^* phase.

The ferroelectric liquid crystal composition containing the compound of the general formula (I) of the present invention can be used as a display cell by being enclosed as a thin film of about 1 to 20 μm between two transparent glass electrodes. In order to obtain good contrast, it is necessary to form monodomains that are uniformly oriented. Many methods have been tried for this purpose.
Phase) → (N ^* phase) → (S _A phase) → (Sc ^* phase), and the helical pitch in the N ^* phase and Sc ^* phase, especially the N ^* phase, is good. It is known to exhibit orientation. The helical pitch mainly depends on the chiral dopant used, but the phase sequence of the Sc ^* liquid crystal composition depends on all the compounds used.

Compounds of formula (I) of the present invention, N-phase and the high temperature range of Sc phase, shows no other crystal phases such as S _A phase, and compounds for other base is used in accordance with the nature of the chiral dopant This makes it possible to easily maintain a desired phase sequence.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but of course, the gist and scope of the present invention are not limited by these Examples.

The structure of the compound was determined by the magnetic resonance spectrum (NM
R) and infrared absorption spectrum (IR). The measurement of the phase transition temperature was performed using a polarizing microscope equipped with a temperature control stage and a differential scanning calorimeter (DSC). (Nujol) in IR represents measurement in suspension in liquid paraffin. In NMR of (CDC1 ₃₎ a solvent, S is 1
Double line, d is double line, t is triple line, m is multiple line, broad
Represents a broad absorption, respectively.

In the examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively.

Example 1 Synthesis of 4- (2,3-difluoro-4-octylphenyloxymethyl) -4'-heptylbiphenyl (No. 1 compound in Table 1) 200 mg of 2,3-difluoro-4-octylphenol Was dissolved in 5 ml of dimethylformamide (hereinafter referred to as DMF), and 100 mg of potassium t-butoxide was added to the solution, followed by stirring at room temperature. 290 mg of 4-bromomethyl-4'-heptylbiphenyl was dissolved in 2 ml of DMF and added dropwise, and the mixture was further stirred at room temperature for 3 hours.

Water and ether were added to the reaction mixture, and the mixture was acidified with hydrochloric acid. The ether layer was washed with water and saturated saline, and dried over anhydrous sodium sulfate. The crude product obtained by evaporating the solvent was purified by silica gel column chromatography to obtain 270 mg of the title compound as white crystals.

_{NMR (CDC1 3): δ6.56~7.63 (} m, 10H), 5.10 (s, 2
H), 2.43 to 2.77 (m, 4H), 1.10 to 1.90 (m, 22H), 0.70
~ 1.10 (m, 6H) IR (Nujol): 1630, 1520, 1490, 1300, 1270, 1180,
1115, 1070, 1025, 930, 805 cm ^-1 Further, when the phase transition temperature of the purified product obtained by recrystallizing the white crystals from ethanol was measured, the melting point was 44.5 ° C.
Showed a Sc phase up to 98.5 ° C., and became an I phase at a temperature higher than 98.5 ° C.

Example 2 [Sc ^* Preparation of liquid crystal composition and display element] (1) 8.4% of compound obtained in Example 1, (2) Formula 35% compound of the formula 35% of the compound of formula Liquid crystal composed of 30% of compound (A) 75.6% and (3)
formula 73% of the compound of the formula A Sc ^* liquid crystal composition comprising 16.0% of a chiral dopant (B) composed of 27% of the above compound was prepared.

The Sc ^* liquid crystal compositions, the Sc ^* phase at 61 ° C. or less, the S _A phase at 63 ° C. or less, respectively show N ^* phase at 64.5 ° C. or less, was the I phase at higher temperatures.

This Sc ^* liquid crystal composition was filled in a cell composed of two glass transparent electrode plates having a spacing of about 2 μm and having been subjected to an alignment treatment (polyimide coating-rubbing). The phase I was gradually cooled from room I to room temperature to uniformly orient the Sc ^* phase. A 50 Hz rectangular wave having an electric field strength of 10 V _PP / μm was applied thereto, and the electro-optical response speed was measured. As a result, a high-speed response of 117 μsec at 25 ° C. was exhibited. At this time, the tilt angle was 26.3 °, and the contrast was good.

Comparative Example In Example 2, 84.0% of the host crystal (A) and the chiral dopant (B) were used without using the compound obtained in Example 1.
The Sc ^* liquid crystal composition consisting of 16.0% has a Sc ^* phase at 58 ° C or lower,
S _A phases at 63.5 ° C. or less, respectively show N phase at 65 ° C. or less, next I phase at higher temperatures, Sc ^* phase upper limit temperature (Tc) is 3
° C also dropped.

The electro-optical response measured in the same manner as in Example 2 was 100 μsec at 25 ° C., which was almost the same as that in Example 2.

〔The invention's effect〕

The compound represented by the general formula (I) of the present invention exhibits a Sc phase in a wide temperature range, and when used in addition to other Sc ^* liquid crystal compositions or Sc liquid crystal compositions, the Sc phase or Sc
^* It is possible to obtain a liquid crystal composition in which the phase temperature range has been extended to a high temperature range.

Further, the compound of the general formula (I) of the present invention is a low-viscosity compound having no strong polar ester bond or the like in the molecule, so that the above-mentioned Sc ^* liquid crystal composition can also respond at high speed.

Further, the compound of the general formula (I) of the present invention can be easily produced industrially as shown in Examples, and is colorless, water,
Excellent in chemical stability against light, heat, etc. and practical.

Further, the liquid crystal material comprising the chiral smectic liquid crystal compound or composition according to the present invention can realize a high-speed response of 40 μsec or less, and is extremely useful as an optical switching element for display.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C07C 43/225 C09K 19/20 G02F 1/13 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (4)

(57) [Claims] (1) General formula (Wherein, R ¹ and R ² each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms). 2. A liquid crystal composition comprising 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 device comprising the liquid crystal composition according to claim 2.