JPH11256163A - Ferroelectric liquid crystall compound and composition therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new ferroelectric liquid crystal compound having a flexible chain of a symmetrical structure not containing a chiral component in its molecule, capable of exhibiting a high spontaneous polarization in a wide temperature range and forming a double smectic CA phase and useful for a liquid crystal display, or the like. SOLUTION: This ferroelectric liquid crystal compound is a compound of the formula: A-M1 -X1 -B-X2 -M2 -A A is a terminal chain; M1 , M2 are each a mesogen group, e.g. M1 and M2 are groups of formula I and II, respectively; X1 , X2 are COO and, OCO respectively; B is a flexible chain, e.g. the formula: (CH2 )n [(n) is 1-15]}. For example, 1,5-bis(4-dodecaneaniline-benzilidene-4'- carbonyloxy)pentane. The exemplified compound is obtained by reacting 1,5-bis(4- formylphenyl-4'-carbonyloxy) pentane with 4-n-dodecane aniline.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel ferroelectric liquid crystal compound and a ferroelectric liquid crystal composition comprising the same.

[0002]

2. Description of the Related Art Liquid crystal displays are thin, light, have low power consumption, and are excellent in portability, and have a wide range of application fields compared to other types of flat panel displays. Therefore, watches, calculators, personal computers, televisions, etc. Used in various end products. At present, TN, STN, and TFT drive systems are mainly used for liquid crystal displays. On the other hand, a new display technology called a light valve using a ferroelectric liquid crystal, that is, a so-called ferroelectric liquid crystal display has appeared. This is characterized by a 100 times faster response and memory property than the TN type, and is attracting attention as a next-generation liquid crystal technology. Currently known ferroelectric liquid crystals have a smectic C phase or smectic I phase in which the mesogen is tilted in the smectic layer, and a mesogen tilted in the smectic layer, but the tilt of the mesogen between the layers is alternately reversed. It is prepared by mixing an optically active group (chiral component) into a liquid crystal compound that forms a smectic CA phase facing the above. That is, the chiral smectic C phase, chiral smectic I phase, and chiral smectic CA phase exhibit ferroelectricity due to the reduced symmetry of the smectic structure due to the chiral component.

[0003] Ferroelectricity means that spontaneous polarization can be reversed by an external electric field when permanent dipole moments are aligned in the same direction even when no external electric field is applied. It has been pointed out that a ferroelectric liquid crystal phase is developed by introducing asymmetric carbon, and various attempts have been made to obtain a ferroelectric liquid crystal. As a result, the introduction of asymmetric carbon lowers the symmetry of the system and breaks the inversion symmetry, and it has been considered that the introduction of an optically active group is indispensable for the development of a ferroelectric liquid crystal.

However, optically active substances are generally expensive and often accompanied by difficulties in synthesis, so that they are inferior in mass productivity. Furthermore, since such a ferroelectric liquid crystal composition contains an optically active group in a molecular structure, a helical property is generated in a formed liquid crystal phase. The dipole generated in the system becomes isotropic due to this helical property, and cancels the generated spontaneous polarization. Due to this helical property, it is originally 100 to 2
The spontaneous polarization that will occur on the order of 00 nC / cm ² is
When actually measured, the value is low. The spontaneous polarization of ferroelectric liquid crystal compounds synthesized up to the present is generally 10
To 50 nC / cm ² .

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems associated with the prior art described above, and has a high spontaneous polarization without introducing an optically active group.
It is an object of the present invention to provide a ferroelectric liquid crystal composition exhibiting excellent ferroelectricity.

[0006]

In the present invention, a compound represented by the following general formula (I) containing no optically active group and a compound containing such a compound can be obtained by controlling the symmetry from the shape of the molecule. It was found that the resulting composition exhibited a ferroelectric liquid crystal phase.

That is, the ferroelectric liquid crystal compound according to claim 1 has the following general formula (I):

[0008]

Embedded image AM ₁ -X ₁ -BX ₂ -M ₂ -A (I) (wherein A is a terminal chain, M ₁ and M ₂ are mesogen groups, X ₁ and X ₂ And a binding group B represents a bent chain), and the bent chain B is a divalent aliphatic group composed of a non-chiral component.

The ferroelectric liquid crystal compound according to claim 2 is
2. The ferroelectric liquid crystal compound according to claim 1, wherein the mesogen groups M ₁ and M ₂ and the bonding groups X ₁ and X ₂ are respectively symmetrically arranged around the bent chain.

The ferroelectric liquid crystal compound according to claim 3 is:
3. The ferroelectric liquid crystal compound according to claim 1, wherein said bent chain B is represented by the following formula (II) or (III):

[0011]

-(CH ₂ ) _2n-1- (II) (wherein, n is an integer of 1 ≦ n ≦ 15)-((CH ₂ ) _m -O-) _2n-1- (CH ₂ ) _m -(III) (where m is an integer of 1 ≦ m ≦ 7, n is an integer of 1 ≦ n ≦ 7)
It is characterized by being represented by

The ferroelectric liquid crystal compound according to claim 4 is
The ferroelectric liquid crystal compound according to any one of claims 1 to 3, wherein the terminal chain A is

[0013]

Embedded image It is any one group of —O— (CH ₂ ) _n CH ₃ (0 ≦ n ≦ 30) and — (CH ₂ ) _n CH ₃ (0 ≦ n ≦ 30).

The ferroelectric liquid crystal compound according to claim 5 is
The ferroelectric liquid crystal compound according to claim 1, wherein the mesogen group M ₁ is

[0015]

Embedded image

And the mesogen group M ₂ is

[0017]

Embedded image

## STR1 ## is characterized by the fact that

The ferroelectric liquid crystal compound according to claim 6 is:
The ferroelectric liquid crystal compound according to claim 1, wherein the bonding group X ₁ is

[0020]

Embedded image —COO— and the bonding group X ₂ is

[0021]

Embedded image It is characterized by being a group of —OCO—.

The ferroelectric liquid crystal composition according to claim 7 is:
It comprises the ferroelectric liquid crystal compound according to any one of claims 1 to 6, and forms a double smectic CA phase.

The ferroelectric composition according to the eighth aspect is characterized by comprising at least one compound according to any one of the first to sixth aspects.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The novel ferroelectric liquid crystal compound according to the present invention has a structure represented by the following general formula (I).

[0025]

Embedded image AM ₁ -X ₁ -BX ₂ -M ₂ -A (I) In the formula (I), A is a terminal chain, M ₁ and M ₂ are mesogen groups, X ₁ and X ₂ bonds. The group, B, represents a bent chain.

In the above formula (I), B is a bent chain and represents a group comprising a divalent non-chiral component derived from an aliphatic. The bent chain B is typically represented by the following formula (II) or (III)
)

[0027]

Embedded image _{- (CH 2) 2n-1} - (II) ( wherein, n an integer of 1 ≦ n ≦ 15) - ( (CH 2) m -O-) 2n-1 - (CH 2) m -(III) (where m is an integer of 1 ≦ m ≦ 7, n is an integer of 1 ≦ n ≦ 7)
And does not contain a chiral component.

Examples of the bent chain B include a divalent bent chain represented by the following formula.

[0029]

_{Embedded image-} (CH ₂ ) _2n-1- (1 ≦ n ≦ 15) -CH ₂ -O-CH ₂ --CH ₂ CH ₂ -O-CH ₂ CH ₂ --CH ₂ CH ₂ CH _{2- O-CH 2 CH 2 CH 2} - -CH 2 CH 2 CH 2 CH 2 -O-CH 2 CH 2 CH 2
_{CH 2 - - (CH 2 CH} 2 -O) 3 -CH 2 CH 2 - - (CH 2 CH 2 -O) 5 -CH 2 CH 2 - - (CH 2 CH 2 CH 2 -O) 3 -CH 2 CH ₂ CH <sub>2
- - (CH 2 CH 2 CH</sub> 2 -O) 5 -CH 2 CH 2 CH 2
_{- - (CH 2 CH 2 CH} 2 CH 2 -O) 3 -CH 2 CH 2
_{CH 2 CH 2 - - (CH} 2 CH 2 CH 2 CH 2 -O) 5 -CH 2 CH 2
CH ₂ CH ₂ — In the formula (I), A is a terminal chain, and is an aliphatic group, preferably an alkyl group and an alkoxy group having 1 to 31 carbon atoms,
A methyl (poly) ethylene oxide group having 3-21 carbon atoms,
It is a methyl (poly) propylene oxide group having 4 to 31 carbon atoms. It is preferred that the two terminal chains A are identical to obtain molecular symmetry.

Specific examples of such a terminal chain include the following terminal chains.

[0031]

Embedded image (1) —O (CH ₂ ) _p CH ₃ (1 ≦ p ≦ 30) (2) — (CH ₂ ) _p CH ₃ (1 ≦ p ≦ 30) (3) —O (CH ₂ CH) ₂ O) _p CH ₃ (1 ≦ p ≦ 10) (4) —O (CH ₂ CH ₂ CH ₂ O) _p CH ₃ (1 ≦ p ≦ 10) Among these, the groups (1) and (2) are It is preferable in that the synthesis is easy.

In the above formula (I), M ₁ and M ₂ represent a mesogen group. As a mesogen group, two or more phenylene groups are bonded in a chain at the para position, or an oxycarbonyl group (—O— (CO) —) is formed between phenylene chains constituting such a chain phenylene bond. Carbonyloxy group (-(CO) O-), diazo group (-N = N-)
Or an azomethine group (-N = CH-, -CH = N-)
And a mesogen group in which a cyclohexyl group and a phenylene group are directly bonded at the para position.

Specific examples of such a mesogen group include a mesogen group represented by the following formula.

[0034]

Embedded image

In this, M ₁

[0036]

Embedded image

And M ₂

[0038]

Embedded image

Is suitable because it has symmetry and ferroelectricity is easily obtained. In addition, other mesogen groups have similar properties and can be used.

The skeleton of these mesogen groups may be partially substituted with a substituent such as a cyano group, a halogen group, a methoxy group or a methyl group.

In the above formula (I), X ₁ and X ₂ are preferably those having a dipole moment at the bonding group.
COO-, or -O-, and the like, the M ₁ -CO
Making O— and M ₂ —OCO— is suitable because it has symmetry, has a large dipole moment, and is easy to synthesize.

Specific examples of the ferroelectric liquid crystal compound represented by the general formula (I) having B, A, M ₁ , M ₂ , X ₁ and X ₂ include the following compounds. Can be

[0043]

Embedded image

In the compound of the above formula (1), the compound represented by the formula (2)
In the compound (1), the bonding group, the mesogen group, and the terminal chain are arranged so as to be linearly symmetric about the oxygen atom located at the center of the bent chain. Therefore, the molecule has a symmetrical structure containing no chiral component, and exhibits high spontaneous polarization.

The ferroelectric liquid crystal compound of the present invention can be prepared from a known starting compound by using a known reaction.

The novel ferroelectric liquid crystal composition according to the present invention has a double smectic CA in the liquid crystal formation temperature range.
Form a phase. Such a double smectic CA phase can have ferroelectricity due to the symmetry of the system even if it does not contain asymmetric carbon. In other words, in such a system, a double axis is generated in a direction perpendicular to the long axis of the molecule and there is no mirror surface orthogonal to the double axis. It is a symmetry that can express polarization and become ferroelectric. By controlling the symmetry based on the shape of the molecule as described above, ferroelectricity can be exhibited even in a non-optically active molecule containing no optically active group.

According to the ferroelectric liquid crystal composition of the present invention, a sharp phase reflection derived from the smectic CA phase in the direction of the alignment axis and the molecules in the smectic CA phase in the axis direction perpendicular to the alignment axis were measured by X-ray diffraction measurement. Diffuse reflections due to turbulent filling appear at 25 ° separation. Further, sharp (001) reflection and (002) reflection appear in the orientation axis direction. This comes from the molecular length and half the period of the molecular length, respectively.
This is phase reflection unique to the double smectic CA phase.

The ferroelectric liquid crystal compound of the present invention can be used alone or in combination of two or more as a ferroelectric liquid crystal composition for a display such as a liquid crystal monitor.

[0049]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The structure of the ferroelectric liquid crystal compound obtained in the following examples was confirmed by NMR and elemental analysis.

Example 1 1,5-bis (4-dodecaneanilinebenzylidene-
4'-carbonyloxy) pentane (di-12AM-
Synthesis of 5) 1,5-bis (4-dodecaneanilinebenzylidene-
4'-carbonyloxy) pentane (di-12AM-
The synthesis of 5) was performed through the following two steps.

1) Synthesis of 1,5-bis (4-formylphenyl-4'-carbonyloxy) pentane 5.0 g of terephthalaldehyde acid and 1.67 g of 1,5-pentanediol were added to 200 ml of ethyl acetate, and stirred. Then, 6.9 g of N, N'-dicyclohexylcarbodiimide and 0.4 g of dimethylaminopyridine were added.
After stirring at room temperature for one week, a white precipitate generated by the reaction was separated by filtration, the solution was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography of a mixed developing solution of hexane / methylene chloride. (Yield 65%).

2) 1,5-bis (4-dodecaneanilinebenzylidene-4'-carbonyloxy) pentane (d
Synthesis of i-12AM-5) 3.6 g of 1,5-bis (4-formylphenyl-4'-carbonyloxy) pentane and 6.2 g of 4-n-dodencananiline were dissolved in dehydrated ethanol, and the solution was dissolved at 60 ° C. 5
The mixture was heated and stirred for days. After cooling and crystallizing, the crystals were separated by filtration and then recrystallized twice with a mixed solution of isopropyl alcohol / hexane. (Yield 96%) ¹³ C-NMR (14.0, 22.5, 22.9, 30.
5,32.5,36.0,66.0,129.0,12
9.5, 130.0, 133.5, 142.0, 15
0.0, 164.0, 167.0 ppm) Elemental analysis C79.8%, H9.3%, N3.4%, O
7.5% (Example 2) 1,7-bis (4-octyloxyaniline benzylidene-4'-carbonyloxy) heptane (di-8AM)
Synthesis of O-7) 1,7-bis (4-octyloxyanilinebenzylidene-4′-carbonyloxy) heptane (di-8AM)
Synthesis of O-7) was performed through the following two steps.

1) Synthesis of 1,7-bis (4-formylphenyl-4'-carbonyloxy) heptane 5.0 g of terephthalaldehyde acid and 2.05 g of 1,5-pentanediol were added to 200 ml of ethyl acetate, and stirred. Then, 6.9 g of N, N'-dicyclohexylcarbodiimide and 0.4 g of dimethylaminopyridine were added.
After stirring at room temperature for one week, a white precipitate generated by the reaction was separated by filtration, the solution was concentrated under reduced pressure, and the residue was subjected to silica gel column chromatography of a mixed developing solution of heptane / chloroform to perform purification. The solvent of the product was distilled off, and the product was purified by recrystallization with a mixed solution of isopropyl alcohol and heptane. (Yield 53%).

2) Synthesis of 1,7-bis (4-octyloxyanilinebenzylidene-4'-carbonyloxy) heptane (di-8AMO-7) 1,7-bis (4-formylphenyl-4'-carbonyloxy) ) 4.2 g of heptane and 7.6 g of 4-n-octylaniline were dissolved in dehydrated ethanol, and the mixture was heated and stirred at 60 ° C for 5 days. After cooling and crystallizing, the crystals were separated by filtration and then recrystallized twice with a butanol / hexane mixed solution. (Yield 85%) ¹³ C-NMR (14.0, 23.1, 30.6, 62.
6, 66.0, 129.0, 129.5, 130.0,
133.5, 142.0, 150.0, 164.0, 1
67.0 ppm) Elemental analysis: C79.2%, H8.9%, N3.4%, O
8.5% (C79.4%, H8.6%, N3.6%, O
(8.3%) (Example 3) Synthesis of 2,2-bis ((4-octyloxyaniline benzylidene-4'-carbonyloxy) -2-ethoxy) ethane (di-8AMO-2O2) 2,2-bis The synthesis of ((4-octyloxyanilinebenzylidene-4'-carbonyloxy) -2-ethoxy) ethane (di-8AMO-2O2) was performed through the following two steps.

1) Synthesis of 2,2-bis ((4-formylphenyl-4'-carbonyloxy) -2-ethoxy) ethane 5.0 g of terephthalaldehyde acid and 2.5 g of diethylene glycol were added to 200 ml of ethyl acetate. With stirring, N, N'-dicyclohexylcarbodiimide 6.9
g and dimethylaminopyridine 0.4 g were added. After stirring at room temperature for one week, a white precipitate generated by the reaction was separated by filtration, the solution was concentrated under reduced pressure, and the residue was subjected to silica gel column chromatography of a mixed developing solution of heptane / chloroform to perform purification. The solvent of the product was distilled off, and the product was purified by recrystallization with a mixed solution of isopropyl alcohol and heptane. (Yield 43%).

2) 2,2-bis ((4-octyloxyanilinebenzylidene-4'-carbonyloxy) -2
Synthesis of -ethoxy) ethane (di-8AMO-2O2) 5.7 g of 2,2-bis ((4-formylphenyl-4'-carbonyloxy) -2-ethoxy) ethane, 4-n
7.5 g of octylaniline was dissolved in dehydrated ethanol, and the mixture was heated and stirred at 60 ° C. for 5 days. After cooling and crystallizing, the crystals were separated by filtration and then recrystallized twice with a butanol / hexane mixed solution. (Yield 72%) ¹³ C-NMR (14.0, 23.1, 30.6, 32.
5,36.0,67.1,69.0,129.0,13
0.0,133.5,142.0,150.0,16
4.0, 167.0 ppm) Elemental analysis: C78.1%, H8.8%, N3.1%, O
10.0% (C78.5%, H8.9%, N3.3%,
O9.3%) Example 4 Synthesis of 3,3-bis ((4-octyloxyanilinebenzylidene-4′-carbonyloxy) -3-propoxy) propane (di-8AMO-3O3) 3,3-bis The synthesis of ((4-octyloxyanilinebenzylidene-4'-carbonyloxy) -3-propoxy) propane (di-8AMO-3O3) was performed through the following two steps.

1) Synthesis of 3,3-bis ((4-formylphenyl-4'-carbonyloxy) -3-propoxy) propane 5.0 g of terephthalaldehyde acid and 2.8 g of dipropylene glycol were added to 200 ml of ethyl acetate. 5. Add N, N'-dicyclohexylcarbodiimide while stirring.
9 g and dimethylaminopyridine 0.4 g were added. After stirring at room temperature for one week, a white precipitate generated by the reaction was separated by filtration, the solution was concentrated under reduced pressure, and the residue was subjected to silica gel column chromatography of a mixed developing solution of heptane / chloroform to perform purification. The solvent of the product was distilled off, and the product was purified by recrystallization with a mixed solution of isopropyl alcohol and heptane. (54% yield).

2) 3,3-bis ((4-octyloxyanilinebenzylidene-4'-carbonyloxy) -3
-Propoxy) propane (di-8AMO-3O3)
Synthesis of 3,3-bis ((4-formylphenyl-4′-carbonyloxy) -3-propoxy) propane 6.1 g,
7.5 g of -n-octylaniline was dissolved in dehydrated ethanol and heated and stirred at 60 ° C for 5 days. After cooling and crystallizing, the crystals were separated by filtration and then recrystallized twice with a butanol / hexane mixed solution. (Yield 81%) ¹³ C-NMR (14.0, 23.1, 30.6, 32.
5,36.0,62.6,66.0,129.0,12
9.5, 130.0, 133.5, 142.0, 15
0.0, 164.0, 167.0 ppm) Elemental analysis C 77.2%, H 8.4%, N 3.3%, O
11.1% (C77.7%, H8.3%, N3.6%,
O. 10.3%) (Structural formula and characteristic test results)
Table 1 shows the structural formulas of the compounds and the results of characteristic tests of the compounds.
It was shown to.

The above characteristics were tested as follows.

(1) Phase transition temperature: The phase transition temperature was measured by a PYRIS1 type DSC (differential thermal analysis) manufactured by PerkinElmer. The phase states are indicated using the following abbreviations.

K: crystal S _CAb : double smectic CA phase I: isotropic phase (2) Spontaneous polarization: Spontaneous polarization in the double smectic CA phase was measured by a triangular wave method (± 10.0 μm ⁻¹ .1 Hz).

(3) Confirmation of double smectic CA phase: Using an X-ray generator R-axis manufactured by Rigaku Corporation, exposure was performed with a nickel filter, and measurement was performed using CuKα rays excluding Kβ rays. The camera used was a flat-panel camera. After the measurement sample is oriented on the glass thin film within the liquid crystal formation temperature range, it is mounted on a hot stage and directly installed on an X-ray generator, and the (001) reflection and (002) in the orientation axis direction are sharp.
The reflection was measured.

[0064]

[Table 1]

[0065]

The ferroelectric liquid crystal compound and the ferroelectric liquid crystal composition according to the present invention have a bent chain having a symmetrical structure containing no chiral component, so that the phase transition is the difference between the crystal and the isotropic phase. The behavior temperature shows a high spontaneous polarization over a wide temperature range, and the spontaneous polarization is the same as that of general ferroelectric liquid crystal compounds.
Double to four times higher, and double smectic C
A phase is formed. Furthermore, since no optically active substance is introduced, mass production is easy.

Claims (8)

[Claims] 1. A compound represented by the following general formula (I): A-M ₁ -X ₁ -BX ₂ -M ₂ -A (I) (In the formula (I), A represents a terminal chain, M ₁ and M ₂ is a mesogen group, X ₁ and X ₂ bonding groups, and B represents a bent chain, and the bent chain B is a divalent aliphatic group composed of an achiral component. Liquid crystal compound. 2. The ferroelectric substance according to claim 1, wherein said mesogen groups M ₁ and M ₂ and said bonding groups X ₁ and X ₂ are respectively symmetrically arranged around said bent chain. Liquid crystal compounds. 3. The method according to claim 1, wherein the bent chain B is represented by the following formula (II) or (II):
I) embedded _image- (CH ₂ ) _2n-1- (II) (wherein, n is an integer of 1 ≦ n ≦ 15)-((CH ₂ ) _m -O-) _2n-1- (CH ₂ ) _m - (III) (wherein, m is 1 ≦ m ≦ 7 integer, n represents ferroelectric according to claim 1 or 2, characterized by being represented by an integer) of 1 ≦ n ≦ 7 Liquid crystal compounds. 4. The terminal chain A is one of the following: -O- (CH ₂ ) _n CH ₃ (0 ≦ n ≦ 30) — (CH ₂ ) _n CH ₃ (0 ≦ n ≦ 30) 1 group, characterized in that
3. The ferroelectric liquid crystal compound according to any one of 3. 5. The method according to claim 1, wherein the mesogen group M ₁ is And the mesogen group M ₂ is The ferroelectric liquid crystal compound according to any one of claims 1 to 4, wherein 6. The method according to claim 1, wherein the bonding group X ₁ is a group of the formula: —COO— and the bonding group X ₂ is a group of the formula: —OCO—. 3. The ferroelectric liquid crystal compound according to item 1. 7. A ferroelectric liquid crystal composition comprising the compound according to claim 1 and forming a double smectic CA phase. 8. A ferroelectric composition comprising at least one compound according to any one of claims 1 to 6.