JPS6289650A - Liquid crystal compound, composition containing same and light switching element - Google Patents

Abstract

NEW MATERIAL:A compound shown by the formula I (R is 1-20C alkyl or alkoxy; R* is optically active alkyl; m is 1 or 2). EXAMPLE:4-[(S)-2-Methylbutyliminomethyl]phenyl 4-n-decyloxybenzoate. USE:A liquid crystal composition having ferroelectricity, especially usable as a liquid crystal display element having high-speed response and improved memory properties. PREPARATION:An acid chloride shown by the formula II is reacted with p- hydroxybenzaldehyde to give an aldehyde shown by the formula III, which is condensed with an alkylamine shown by a formula H2NR*, to give a compound shown by the formula I.

Description

[Detailed description of the invention] Industrial application field> The present invention relates to a novel liquid crystal compound and liquid crystal composition, and in particular provides a liquid crystal material having ferroelectricity, which is different from conventional liquid crystal materials. In comparison, the present invention provides a liquid crystal material that can be used for liquid crystal display elements that have particularly excellent high-speed response and memory properties.

<Prior art> Liquid crystal display elements have excellent characteristics such as low voltage operation, low power consumption, thin display, and light-receiving type that does not cause eye strain, so they are widely used as various display elements. It is used.

At present, the most common display system is one that uses nematic liquid crystal as a material, called a twisted nematic type (TN type). However, although this TN type display element has all of the above-mentioned excellent features, it has the drawback that its response is extremely slow compared to other light-emitting display systems such as CRT. Therefore, various restrictions have been imposed on the application to display elements that require a fast response, such as moving picture screens on televisions and heads of high-speed printers.

In addition to the TN type, liquid crystal display elements include the guest-host (GH) type, birefringence control (ECB) type, and phase change (PC) type.
type, thermal effect type, etc. have been developed, and each has its own characteristics, but none of them can be said to provide particularly high speed response compared to the TN type. For these display elements, a dual-frequency drive type was developed as a display system capable of obtaining high-speed response, and although significant improvements were made in response, it was still difficult to say that it was fully satisfactory.

For this reason, attempts have been made to develop new display systems with even better responsiveness.

In line with this objective, ferroelectric liquid crystals have recently been announced. (Mayer et al.: Journal de Fuisique.

56 L69 (1975)) Display elements using this ferroelectric liquid crystal are capable of a high-speed response of 100 to 1000 times compared to conventional liquid crystals and a memory effect due to bistability (Clark et al.・Fix Letters, 36 899 (19
80)), and can be expected to be applied to a wide variety of display devices, including moving images on televisions, high-speed optical cameras, and the like.

The liquid crystal phase of the ferroelectric liquid crystal belongs to the tilted chiral smectic phase, and among these, the chiral smectic C phase (hereinafter abbreviated as "SC" phase) has the lowest viscosity and is practically desirable. .

Liquid crystal compounds exhibiting the "SC" phase have been extensively studied and many are already known.

A typical example is (m)-2-methylbutyl-p-decyloxybenzylidene aminocinnamate (DOBA), which is known as the first ferroelectric liquid crystal synthesized.
Examples include Schiff base liquid crystals (abbreviated as MBC) and their homologues. It is still one of the most commonly used liquid crystal compounds for studying the physical properties and orientation of ferroelectric liquid crystals, and is one of the fundamentals of important physical properties in ferroelectric liquid crystals, such as spontaneous polarization and pitch. It is also used as salt. However, DOBAMBC and its series compounds: ■ lack stability against light, ■ lack stability against moisture, ■ themselves are colored, and ■ exhibit SC phase. It has drawbacks such as narrow temperature range of 32° when the temperature is lowered, and a high temperature range. In particular, type (3) is fatal for use as a display element and lacks practicality.

In order to improve these drawbacks, many studies have been made on ester systems, and also on thick base systems.

(a) p-Aminocinnamic acid derivative (Yoshino et al.: Japanese Journal Fist Op Applied Fixtures, 2
3L175 (1984)), (0) p-7mi/benzoe
84 bodies (Kiguru et al.: JP-A-59-98051), (c) M
ORA series (Czezczynski et al.: Molecular Crystals and Kid Crystals, 88 55 (
1982)) etc. were synthesized. However, although a large spontaneous polarization is obtained in (a), the drawbacks of ■ to ■ are not improved, and in (b), although ■ is improved, the SC'' phase appears only during cooling. This is the so-called monoto-a big liquid crystal, and in (c) ■
Although ~■ has been greatly improved, it has not been reported that the spontaneous polarization is so small that a fast response speed of p1 cannot be expected.

<Problems to be Solved by the Invention> The present inventors have developed a novel method that is particularly stable against light, is colorless in itself, and can assume a liquid crystal phase (especially an SC phase) with ferroelectric properties even near room temperature. The present invention was developed after intensive research into whether it would be possible to obtain a liquid crystal compound.

Furthermore, the present invention aims to provide a liquid crystal display element having high-speed response using such a novel liquid crystal compound or a composition containing at least one thereof.

Means for Solving Problems> The liquid crystal compound in the present invention is an ester derivative of 4-((@)-2-methylbutyliminomethyl)phenol represented by the following general formula 1 (wherein R is R" is an alkoxy group or an alkyl group having 1 to 20 carbon atoms; R" is an optically active alkyl group;
m stands for 1 or 2. ).

In addition, the liquid crystal composition in the present invention is composed of a plurality of compounds represented by the general formula 1 (hereinafter abbreviated as compound I), or a liquid crystal composition composed of at least one compound 2 and a liquid crystal compound other than compound I. It is a composition.

Ferroelectricity in liquid crystals appears when the liquid crystal takes a tilted chiral smectic phase, and Compound I has the SC'' phase, which is considered the most practical. The 2-cold compound #1 exhibits the SC'' phase in a relatively low temperature range, and the 3-cold compound with m=2 exhibits the SC'' phase in a relatively high temperature range. m=1
In the case of , the SC" phase is so-called monotropic, which occurs only when the temperature decreases, and is not stable and is not suitable for use alone. It is possible to lower the melting point by mixing with m=
In the case of 2, the temperature range of the %SC phase is, for example, 93 to 14
5° (R = n-decyl oxychloride), but since it is much higher than room temperature, compounds with m = 1 and other liquid crystal compounds (SC" phase) are present, and the temperature range is slightly lower. (desirably) and use the temperature range near room temperature.

Compound I, as shown in general formula I, contains DOBA in the molecule.
It does not have a trans double bond that is unstable to light like MBC.

Therefore, it is completely stable against light. -DOBAM again
It is not colored like BC and is colorless itself.

Furthermore, Compound I is a thick base, and its stability against moisture cannot be said to have been improved much. However, since the liquid crystal cell itself is anhydrous, there is no problem in practice as long as the liquid crystal composition is handled with care until the cell is prepared.

In order for a liquid crystal to exhibit an SC phase ('! or other tilted chiral smectic phase), it must have a chiral carbon that is light-year active, and for this purpose, it must have a chiral carbon that is light-year active. A commonly used method is to introduce optically active groups into liquid crystal molecules.

In compound I, for example, (a)-2-methylbutylamine, which is easily available commercially, is used as an asymmetric source,
This purpose is achieved by introducing it into liquid crystal molecules through -CH=N- bonds. A method for introducing such asymmetry into liquid crystal molecules is completely unknown so far. Such optically active groups can be appropriately selected from optically active alkyl groups having asymmetric carbon atoms.

This is because although ferroelectric liquid crystals exhibit high-speed response, they have spontaneous polarization and therefore interact directly with the applied electric field. The larger the value of spontaneous polarization, the faster the response speed. Therefore, it is one of the most important physical properties of ferroelectric liquid crystal compounds.
It is one. In order to increase spontaneous polarization, it is considered desirable that a carbonyl bond (C=O), which is a large permanent dipole, and an asymmetric carbon exist in the vicinity, and currently a
All liquid crystal compounds having a spontaneous polarization of 7 cm or more have such a molecular structure. However, in this compound (2), even though the carbonyl bond does not exist near the asymmetric carbon, the spontaneous polarization (
approximately 4nC/cIL). This j-f--CH
This is thought to be because the polarization of the =N- bond acts as a permanent dipole instead of the carbonyl bond, but such an example has not been known so far.

Next, the method for producing compound (1) will be described.

1. First, by reacting an acid chloride ■ represented by the following general formula ■ (the meanings of the symbols in the formula are the same as those of the general formula ■) and p-hydroxybenzaldehyde, a reaction mixture represented by the following general formula II The aldehyde ■ (The meanings of the symbols in the formula are the same as in general formula I.) and (!
1) Compound I can be obtained by condensing an alkylamine having an asymmetric carbon such as -2-methylbutylamine.

The process is shown below using a reaction formula.

(n) (III) Here, the acid chloride ■, some of which are commercially available, is a carboxylic acid ■ expressed by the general formula ■ (the meanings of the symbols in the formula are the same as those of the general formula I). It can be easily obtained by reaction with a chlorinating agent such as thionyl, and in many cases the resulting acid chloride nt-t
After distilling off excess thionyl chloride, it can be used in the next step without any particular purification. If necessary, it can be used after V-purification by distillation or recrystallization.

Now, the obtained liquid crystal compound or composition is placed between two transparent electrode plates to a uniform thickness of 1 nIrL to 20 μm).
By forming a thin film, it can be used as a liquid crystal display cell.

In the display cell, liquid crystal molecules need to be homogeneous monodomains with their long axes parallel to the electrode planes, with uniform orientation. To achieve this, the cell surface may be subjected to an alignment treatment such as rubbing or vapor deposition, or a magnetic field may be applied across an electric field, or a temperature gradient may be created. Generally, a method is used in which the compound or composition of the present invention is gradually cooled to a liquid crystal phase and then oriented, and uniformly oriented monodomain cells can be obtained by such a method.

<Effects of the Invention> The present invention is as described above, and Compound I of the present invention is D, which was known as a typical ferro-linear liquid crystal compound in the United States.
Compared to OBAMBC, it can be easily produced industrially, as shown in the examples below, and it is colorless itself and has superior chemical stability to light. In addition, in the composition of the present invention, as with general liquid crystal compositions, a decrease in melting point was observed compared to a single compound,
Usage at room temperature is also possible.

Furthermore, the ferroelectric liquid crystal compound and composition 1 of the present invention! Similarly to conventional ferroelectric liquid crystals, /I has an extremely fast response speed of more than 100 times that of nematic liquid crystals. Therefore, it is extremely effective as a display switching element.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but of course the gist and scope of the present invention are not limited by these Examples. In addition, the temperature a degree Celsius is assumed to be X.

Example 1 [Synthesis of 4-((s)-2-methylbutyliminomethyl)phenyl 4-n-7' syloxybenzoate] 1-a, (Synthesis of 4-n-decyloxybenzoic acid chloride) 26. 2! j (100 Mmol) of 4-n-decyloxybenzoic acid, 6017 of thionyl chloride and 0.5
Pyridine (d) was added, and the mixture was heated and stirred under reflux for 6 hours. Excess thionyl chloride was distilled off under reduced pressure, and 10% of toluene was added to the residue.
After removing insoluble matter, toluene and remaining pyridine were distilled off under reduced pressure to obtain oily A-n-decyloxybenzoic acid chloride 26.1.9 (resolution: 92%).

1-b, (Synthesis of 4-formylphenyl 4-n-7' syloxybenzoate) 6.71# (55 mmol) of p-hydroxybenzaldehyde was dissolved in pyridine 15atVC, and under water cooling,
To this was added 1 of the 4-n-decyloxybenzoyl chloride'$lJ14.83/7 (50rrLmol) obtained in 1-a.
A dichloromethane solution was added dropwise.

After the addition was completed, the mixture was stirred for 1 hour at the reflux temperature of methylene chloride.

100 M of ethyl acetate was added to the reaction solution, and the mixture was washed with 50 g of diluted hydrochloric acid, washed with water until the washing solution became neutral, and dried over sulfur salt. The solvent was distilled off to obtain crude crystals 17/I.

Ethanol and hexane-ethyl acetate mixed solvent (5:1
) to give 4-formylphenyl 4-n
-decyl oxy7penzoate 12.9V was obtained (yield 6
8%).

The structure was confirmed by infrared absorption spectrum (IR).

IR: 2750. 1740. 1700. 16
05°1520, 1270. 1220. 1170
゜1070.845. 760,515 cm, -' This thing shows a liquid crystal phase, and its phase transition temperature is 9 as follows.

Transition temperature from nematic (N) phase to isotropic liquid (I) phase (abbreviated as N-I. The same applies hereinafter) 72', 5A-N
62°, melting point 63° 1-c, (Synthesis of 4-((s) 2-methylbutyliminomethyl)phenyl 4-n-7' syloxybenzoate) 4-formylphenyl A obtained in 1-b) -n-7
"Fluoxybenzoate 582J? (1011101
CI+)-2-methylbutylamine 1.25.9 (
14 #1 mol) and 100 d of benzene were added, and the mixture was heated under reflux for 3 hours. The solvent was distilled off under reduced pressure, and the resulting crude crystals were recrystallized from a small amount of ethanol to give white needle-like 4-
((s)-2-methylbutylimino)methylphenyl A-n-decyloxybenzoate 4.50.9 was obtained as 7'C (yield 993%).

Nuclear magnetic absorption spectroscopy (NMR) and IR are used to confirm the structure.

and by mass spectrometry (MS).

NMR: δ8.28 (S, IH, -CH=N
-), δ8.08 (d, 2H, aromatic H)
, δ7.75 (d, 2H, aromatic H),
δ7.22 (d, 2H, aromatie H),
δ6.91 (d, 2H, arnmatlc H), δ
3.97 (t, 21.-CH,-0-), δ15(
m, 2H, -CH, -N-), δt6-1.9 (m, 3
H), δt2~1.6 (m, 16H, -CH, -), δ
0.8-1.1 (m, 9H, CH3), IR: 1
740. 1650. 1615. 1520. 12
60°1200, 1180. 1080. 860.
770°665 (crn-') MS: %/1! =451 (M") This compound exhibits an SC phase, and its transition temperature is shown below. Measurements were carried out using a differential scanning calorimeter and a polarized light microscope equipped with a temperature control stage. 5A-177" , SC-8A 6
4.5°, melting point 68°, the spontaneous polarization of this compound at 50″ is 4.2 nC/cm, and the helical pitch is approximately 2 μ
It was a door.

Example 2 (Synthesis of 4-((s)2-methylbutyliminomethyl)phenyl d-n-dodecyloxybenzoate) 2-a (Synthesis of 4-n-dodecylox7benzoate chloride) 4-n-dodecyl Using 290 g of oxybenzoic acid, 1
The reaction was carried out in the same manner as in -a) to obtain crystals of 4-n-dodecyloxybenzoic acid chloride '27.1 II (yield: 88
%).

2-b (Synthesis of 4-formylphenyl A-n-dodecyloxybenzoate) A-n-dodecyloxybenzoate fp! 15. ,12.9
was reacted with 1-b) in the same manner as in 18 using
323i' was obtained (yield 65%).

This compound exhibits a liquid crystal phase, and its phase transition temperature is as follows.

5A-I77°, melting point 73°2-e (Synthesis of 4-((g)-2-methylbutylimino)methylphenyl A-n-dodecyloxybenzoate) 4-formylphenyl obtained in 2-b) 4 -n-)
"1-c using 2.05g of decyloxybenzoate
), 2.28 JI of A-((g)-2-methylbutylimino)methylphenyl A-n-dodecyloxybenzoate (yield 95%) was obtained. This compound has an "sc" phase, and its phase transition temperature is described below.

5A-I76', SC''-8A 6Q, 5°, melting point 7
3゜Example 5 [Synthesis of d-((g)-2-methylbutyliminomethyl)phenyl 4'-n-7'' siloxybiphenyl-4-carboxylate] 3-a (4'-n-decyloxy biphenyl-4-
Synthesis of carboxylic acid chloride) 4'-n-7' Siloxybiphenyl-4-carboxylic acid 17,7 and Si' were reacted in the same manner as in Example 1-a) to form 4'-n-7 'Syloxybiphenyl-4-
Crystals of carboxylic acid 15.1.9 were obtained (yield 83
%).

3-b (Synthesis of 4-formylphenyl 4'-n-decyloxybiphenyl-4-carboxylate) 3-a)
The 4'-n-decylox7biphenyl-4-carboxylic acid chloride 7.10.9 obtained in 7.10.9 was reacted with p-hydroxybenzaldehyde in the same manner as in 1-b) to give 4-formylphenyl 4'-n-7. 'Syloxybiphenyl-4-
Carboxylate 6.70. f was obtained (yield: 73%).

The structure was confirmed by IR.

IR: 2750. 1735. 1710. 16
-05°1510, 1400. 1295. 122
0°1t65. 1090. 1030. 835°7
05 Biji - This material exhibits a liquid crystal phase, and its phase transition temperature is as follows.

N-I211°, 5A-N178', melting point 111°3
-c (Synthesis of 4(II) 2-methylbutyliminomethyl)phenyl 4'-n-decyloxybiphenyl-4-carboxylate) 4-formylphenyl 4'-n- obtained in 3-b)
Decyloxybiphenyl-4-carboxylate) 3.9
．． 9 and reacted with (a) -2-methylbutylamine in the same manner as in 1-c) to produce A-((s) -2-methylbutyliminomethyl)phenyl 4'-n-7'yloxyhyphenyl. -4-carboxylate crystals 3.2g
was obtained (yield 49%).

NMR: δ8.23 (s IH, -CH=N-)
, δ6.9-8.2 (m 12H, aromatic
-H), δ3.96 (t 2H, -CH, -0-),
δ14 (m 2H, -N-CHl)% δ1.6 ~ t9
(m 3H), δ1.2-1.6 (m 16H9CHt ), δ[
L8-11 (m 9H, CH,), IR: 173
5. 1640. 1605. 1505°1290,
1200.・1160. 1080°830, 7
65 (cR-) MS: m/a=527 (M) This compound has an SC phase, and its phase transition temperature is shown below.

SA-4197", SC"-8A 115°, 5
x-sc"93° (SX is a smectic phase that is closer to a crystalline phase), melting point 76° Example 4 [4-((s)-2-methylbutyliminomethyl]phenyl 4'-n-tetradecyloxy Synthesis of biphenyl-4-carboxylate] Using 4'-n-tetradecyloxybiphenyl-4-carboxylic acid, the reaction was carried out in exactly the same manner as in Example 3, and 4-((s)-2-
Methylbutyliminomethyl)phenyl 4'-n-tetradecyloxybiphenyl-4-carboxylate was obtained.

This compound (shows an SC'' phase, and its shift temperature is shown below.

5A-1172°, SC"-8A114°, 5x-sc
"9A', melting point 86u Example 5 [Preparation of liquid crystal composition exhibiting SC" phase] Example 1
d-C(s)-2-methylbutyliminomethyl)phenyl, 4-n-decyloxybenzoate 42 obtained in
parts, 6 parts of 4-((m)-2-methylbutyliminomethyl)phenyl, 4'-n-decyloxybiphenyl-4-carboxylate obtained in Example 3 and 3-fluoro-4-((s )-2-methyloxycarbonyl)phenyl% 47yloxybenzoate 62 parts, (s)
20 parts of -2-methylbutyl 4'-nonanoyloxybiphenyl-4-carboxylate was blended to prepare a liquid crystal composition.

This liquid crystal composition changed to the SC phase at temperatures below 40°, did not crystallize below room temperature, and stably maintained the S02 phase. As a result, a monocrystalline composition exhibiting ferroelectricity at room temperature was obtained.

Note that the 5A-melting point of this composition was 70°.

Example 6 [Creation of a liquid crystal display element] The composition obtained in Example 5 was heated between two glass transparent electrodes that had been subjected to an alignment treatment by rubbing with a spacer having a thickness of 3 μm interposed therebetween, and an isotropic Fill it as a liquid and create a thin film cell.

Cooling was performed slowly at a rate of 0.2° per minute to orient the smectic phase and obtain a uniform monodomain.

The cell was cooled to the SC” phase at 30°, and the electric field (5V
, 0.1 Hz rectangular wave) was applied, and the optical switching operation was detected using a photomultiplier, and the response speed was approximately 120 μsec. This means that a liquid crystal display element with a fast response speed can be obtained.

Claims (1)

[Claims] 1. General formula I ▲ Numerical formulas, chemical formulas, tables, etc. are included ▼... (I) (In the formula, R is an alkyl group or alkoxy group having 1 to 20 carbon atoms, R^* is , an alkyl group having optical activity, m
represents 1 or 2. ) A liquid crystal compound represented by 2. The liquid crystal compound according to claim 1, wherein R^* is an optically active 2-methylbutyl group. 3. General formula I ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼... (I) (In the formula, R is an alkyl group or alkoxy group having 1 to 20 carbon atoms, and R^* is an optically active alkyl group. base, m
represents 1 or 2. ) A liquid crystal composition containing at least one compound I as a compounding component. 4. The liquid crystal composition according to claim 3, wherein R^* is an optically active 2-methylbutyl group. 5. The liquid crystal composition according to claim 3 or 4, which contains two or more kinds of compound I. 6. The liquid crystal composition according to claim 3 or 4, which contains at least one compound I and a liquid crystal compound other than compound I. 7. The liquid crystal composition according to claim 2, 3 or 4, which has a chiral smectic phase. 8. General formula I ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼... (I) (In the formula, R is an alkyl group or alkoxy group having 1 to 20 carbon atoms, and R^* is an optically active alkyl group. base, m
represents 1 or 2. ) An optical switching element comprising at least one liquid crystal compound represented by the following.