JPH05320140A - New ester compound, liquid crystal composition and optical switching element - Google Patents

Abstract

PURPOSE:To provide a new optically active ester compound useful as a liquid crystal composition exhibiting stable thermotropic crystalline state and giving a liquid crystal display element having quick response. CONSTITUTION:The new ester compound expressed by formula I (R and R' are 2-18C alkyl), e.g. 2-(4-butylphenyl)-5-[4-(2-fluoro-2-methylpentanoyloxy) phenyl]pyrimidine. The compound of formula I can be produced by esterifying a 2-(4-alkylphenyl)-5-(4-hydroxyphenyl)pyridine of formula II with a 2-fluoro-2- methylalkanoic acid of formula III. The compound of formula I has extremely excellent properties as a material for optoelectronic-relating elements, e.g. thermotropic liquid crystalline state of the compound and the formation of a ferroelectric liquid crystal composition having large spontaneous polarization and quick response when added to a non-chiral liquid crystal.

Description

Detailed Description of the Invention

The present invention relates to a novel ester compound, particularly a stable thermotropic liquid crystal state, for example, for a display such as a liquid crystal television, an optical printer head, an optical Fourier transform element, a light valve, etc. The present invention relates to a novel ester compound that can be used as a liquid crystal material useful as a material for optoelectronics-related devices utilizing liquid crystals and electrochemichromism, an optically active substance thereof, a liquid crystal composition containing the optically active compound, and an optical switching device.

[0002]

2. Description of the Related Art At present, liquid crystal compounds are applied as display materials in various devices and put to practical use in watches, calculators, small televisions and the like. For these, a cell having a nematic liquid crystal material as a main component is used, and a display method called TN type or STN type is adopted. Cell in this case is actuated based on a weak interaction (ΔεE ^2/2) of the dielectric anisotropy Δε and the electric field E of the liquid crystal compound, the response speed to the electric field is low and several msec is cited as disadvantages There is. Therefore, when it is used in a television, an active matrix system in which a switching element is arranged and added for each pixel is mainly used as a drive system, which is one of the obstacles in achieving a large screen. However, in 1975 R.
Appearance of ferroelectric liquid crystals typified by 4- (4-n-decyloxybenzylideneamino) cinnamic acid-2-methylbutyl ester (DOBAMBC) synthesized by B. Meyer et al., And NAClark using it Proposed a new display method (Ap
plied Phys. Lett. 1980, 36 , p899) has made possible a liquid crystal cell having a high-speed response on the order of μsec and a property (memory property) in which the orientation of liquid crystal molecules does not change even when the electric field is cut off. The use of display elements made of these materials enables LCD TVs with a simple matrix system that uses multiplex drive without using switching elements, etc., resulting in higher productivity, lower cost, higher reliability, and larger screens. It will be much more advantageous in terms of.

Therefore, many ferroelectric liquid crystal materials have been synthesized and proposed so far. In order to use these ferroelectric liquid crystal materials as display materials, some physical properties are required. Among them, the basic one is that they exhibit a smectic C phase in a wide temperature range near room temperature and have a large size. It has a spontaneous polarization and is chemically stable. However, the initial ferroelectric liquid crystals were chemically unstable because the spontaneous polarization was as small as 10 nC / cm ² or less, and many of them had a Schiff base in the molecule.

Recently, it has been reported that a large spontaneous polarization is caused by a chemically stable ester compound.
For example, the following formula 2

[Chemical 2] The compound of the above is a chiral smectic C phase in the temperature range of 78.7 ° C to 103.3 ° C, and 103.3 ° C to 120.8 ° C.
It is known that the liquid crystal becomes a cholesteric phase liquid crystal in the temperature range of, and the spontaneous polarization of the liquid crystal at 83 ° C. is 89 nCcm ² / (Japanese Patent Laid-Open No. 61-43).

On the other hand, bicyclic compounds have been synthesized in order to lower the temperature at which the chiral smectic C phase is exhibited. For example, the following formula 3

[Chemical 3] It has been reported that the biphenyl compound of the above exhibits a chiral smectic C phase at a temperature rise of 44 ° C. (JP-A-59-1).
18744 publication).

Further, a phenylpyrimidine compound having a stable chiral smectic phase near room temperature has been reported. For example, the following formula 4,

[Chemical 4] It is known that the compound (1) becomes a chiral smectic C phase liquid crystal at 40.7 ° C. to 82.8 ° C. and a smectic A phase liquid crystal at 82.8 ° C. to 89.1 ° C. (JP-A-61-20097).
3 gazette).

[0007]

However, the ester compound represented by the above chemical formula 2 is a chiral smectic C compound.
It has the disadvantage that the temperature range of the phases is high. Further, the temperature of the biphenyl compound represented by the chemical formula 3 above, which exhibits a chiral smectic C phase, is close to room temperature, but the temperature range is about 10 ° C., which is not sufficiently wide. Further, the phenylpyrimidine compound represented by the above chemical formula 4 has a slow response speed of 1500 μsec at 43 ° C., and it is presumed that spontaneous polarization is considerably small.

That is, a liquid crystal material such as a display device which is required to have high-speed response must have a large spontaneous polarization.
Physical properties such as having low viscosity or exhibiting a chiral smectic C phase in a wide temperature range including near room temperature are required, but up to now, no material has sufficiently satisfied these physical properties. is there.

As a result of intensive studies on the asymmetric structure and nuclear structure of a ferroelectric liquid crystal compound, we have found that a diphenylpyrimidine compound having a fluorine atom and a methyl group on the asymmetric carbon as a substituent is thermotropically stable. It has been found that they exhibit a liquid crystal state, exhibit a large spontaneous polarization in the chiral smectic C phase, and give a liquid crystal composition that responds rapidly when mixed with a base liquid crystal.

The present invention has been made on the basis of such findings, and an object of the present invention is to provide a novel ester compound useful as a liquid crystal composition and a liquid crystal capable of producing a liquid crystal display device having a high-speed response. To provide a composition.

[0011]

The present invention has the following general formula (5):

[Chemical 5] (In the formula, R and R'represent an alkyl group having 2 to 18 carbon atoms), particularly in the compound represented by the above general formula 5, a methyl group and a fluorine bond to each other. An optically active ester compound having an asymmetric center on the active carbon, and a liquid crystal composition containing at least one of the optically active ester compounds and at least one of the optically active ester compounds. It is an optical switching element consisting of elements.

As the compound of the above general formula 5 of the present invention, 2- (4-butylphenyl) -5- (4- (2-fluoro-2-
Methylpentanoyloxy) phenyl) pyrimidine, 2-
(4-Butylphenyl) -5- (4- (2-fluoro-2-methylhexanoyloxy) phenyl) pyrimidine, 2- (4-butylphenyl) -5- (4- (2-fluoro-2-methyl) Heptanoyloxy) phenyl) pyrimidine, 2- (4-butylphenyl) -5- (4- (2-fluoro-2-methyloctanoyloxy) phenyl) pyrimidine, 2- (4-butylphenyl)
-5- (4- (2-Fluoro-2-methylnonanoyloxy) phenyl) pyrimidine, 2- (4-butylphenyl) -5- (4-
(2-Fluoro-2-methyldecanoyloxy) phenyl) pyrimidine, 2- (4-pentylphenyl) -5- (4- (2-fluoro-2-methylpentanoyloxy) phenyl) pyrimidine, 2- (4 -Pentylphenyl) -5- (4- (2-fluoro-
2-methylhexanoyloxy) phenyl) pyrimidine,
2- (4-pentylphenyl) -5- (4- (2-fluoro-2-methylheptanoyloxy) phenyl) pyrimidine, 2- (4
-Pentylphenyl) -5- (4- (2-fluoro-2-methyloctanoyloxy) phenyl) pyrimidine, 2- (4-pentylphenyl) -5- (4- (2-fluoro-2-methylnonanoyl) (Oxy) phenyl) pyrimidine, 2- (4-pentylphenyl) -5- (4- (2-fluoro-2-methyldecanoyloxy) phenyl) pyrimidine, 2- (4-hexylphenyl)
-5- (4- (2-Fluoro-2-methylpentanoyloxy)
Phenyl) pyrimidine, 2- (4-hexylphenyl) -5-
(4- (2-Fluoro-2-methylhexanoyloxy) phenyl) pyrimidine, 2- (4-hexylphenyl) -5- (4-
(2-Fluoro-2-methylheptanoyloxy) phenyl)
Pyrimidine, 2- (4-hexylphenyl) -5- (4- (2-fluoro-2-methyloctanoyloxy) phenyl) pyrimidine, 2- (4-hexylphenyl) -5- (4- (2-fluoro
-2-Methylnonanoyloxy) phenyl) pyrimidine, 2
-(4-hexylphenyl) -5- (4- (2-fluoro-2-methyldecanoyloxy) phenyl) pyrimidine, 2- (4-heptylphenyl) -5- (4- (2-fluoro-2- Methylpentanoyloxy) phenyl) pyrimidine, 2- (4-heptylphenyl) -5- (4- (2-fluoro-2-methylhexanoyloxy) phenyl) pyrimidine, 2- (4-heptylphenyl) -5- (4- (2-Fluoro-2-methylheptanoyloxy) phenyl) pyrimidine, 2- (4-heptylphenyl) -5- (4- (2-fluoro-2-methyloctanoyloxy) phenyl) pyrimidine, 2 -(4-heptylphenyl)-
5- (4- (2-fluoro-2-methylnonanoyloxy) phenyl) pyrimidine, 2- (4-heptylphenyl) -5- (4-
(2-Fluoro-2-methyldecanoyloxy) phenyl) pyrimidine, 2- (4-octylphenyl) -5- (4- (2-fluoro-2-methylpentanoyloxy) phenyl) pyrimidine, 2- (4 -Octylphenyl) -5- (4- (2-fluoro-
2-methylhexanoyloxy) phenyl) pyrimidine,
2- (4-octylphenyl) -5- (4- (2-fluoro-2-methylheptanoyloxy) phenyl) pyrimidine, 2- (4
-Octylphenyl) -5- (4- (2-fluoro-2-methyloctanoyloxy) phenyl) pyrimidine, 2- (4-octylphenyl) -5- (4- (2-fluoro-2-methylnonanoyl) (Oxy) phenyl) pyrimidine, 2- (4-octylphenyl) -5- (4- (2-fluoro-2-methyldecanoyloxy) phenyl) pyrimidine, 2- (4-nonylphenyl)-
5- (4- (2-fluoro-2-methylpentanoyloxy) phenyl) pyrimidine, 2- (4-nonylphenyl) -5- (4-
(2-Fluoro-2-methylhexanoyloxy) phenyl)
Pyrimidine, 2- (4-nonylphenyl) -5- (4- (2-fluoro-2-methylheptanoyloxy) phenyl) pyrimidine, 2- (4-nonylphenyl) -5- (4- (2-fluoro -2-
Methyloctanoyloxy) phenyl) pyrimidine, 2-
(4-nonylphenyl) -5- (4- (2-fluoro-2-methylnonanoyloxy) phenyl) pyrimidine, 2- (4-nonylphenyl) -5- (4- (2-fluoro-2-methyl) Decanoyloxy) phenyl) pyrimidine, 2- (4-decylphenyl) -5- (4- (2-fluoro-2-methylpentanoyloxy) phenyl) pyrimidine, 2- (4-decylphenyl) -5-
(4- (2-Fluoro-2-methylhexanoyloxy) phenyl) pyrimidine, 2- (4-decylphenyl) -5- (4- (2
-Fluoro-2-methylheptanoyloxy) phenyl) pyrimidine, 2- (4-decylphenyl) -5- (4- (2-fluoro-2-methyloctanoyloxy) phenyl) pyrimidine, 2- (4-decyl Phenyl) -5- (4- (2-fluoro-2-
Methylnonanoyloxy) phenyl) pyrimidine, 2- (4
Examples thereof include -decylphenyl) -5- (4- (2-fluoro-2-methyldecanoyloxy) phenyl) pyrimidine. Among these, as an example of a particularly representative compound, 2
The physicochemical properties of-(4-hexylphenyl) -5- (4- (2-fluoro-2-methylheptanoyloxy) phenyl) pyrimidine are shown below.

¹ H-NMR (270 MHz, TMS standard, δ value) δ 0.92 6H m δ 1.2 to 2.2 16H m δ 1.75 3H d (J = 20H
z) δ 2.71 2H t (J = 7H
z) δ 7.25 2H d (J = 9H
z) δ 7.32 2H d (J = 9H
z) δ 7.64 2H d (J = 9H
z) δ 8.38 2H d (J = 9H
z) δ 8.98 2Hs IR (KBr method, cm ⁻¹ ) 2910, 2840, 1755, 1580, 1438,
1205, 1165, 1120

The ester compound represented by the above general formula 5 can be obtained by the reaction route shown in formula 1.

[Formula 1]

That is, 2- (4-alkylphenyl) -5-
(4-hydroxyphenyl) pyrimidine 1 and 2-fluoro-
It is obtained by esterifying 2 -methylalkanoic acid 2 . The esterification can be performed, for example, by a method using a dehydration condensing agent such as dicyclohexylcarbodiimide. Alternatively, the alkanoic acid 2 can be converted into an acid halide by using a halogenating agent such as thionyl chloride, and then reacted with the pyrimidine 1 in the presence of a base.
Here, when the optically active substance having an asymmetric center on the carbon where the methyl group and the fluorine are bonded is used as the 2-fluoro-2-methylalkanoic acid 2 , the ester compound represented by Chemical formula 5 is used. The optically active substance can be obtained.

The pyrimidine 1 used here is a journal
Full fracture cicada (Journal fuer Praktisc
he Chemie) Vol. 323, No. 2, page 119
It is obtained by the route shown in the following Expression 2.

[Formula 2]

The alkanoic acid 2 used here can be obtained by the route shown in the following formula 3.

[Formula 3]

That is, first, an amine-hydrogen fluoride complex or silicon tetrafluoride is allowed to act on 2-methyl-1,2-epoxyalkane to give 2-fluoro-2-methyl-1-alkanol (Japanese Patent Laid-Open No. H11 (1999) -242242). 2-235828). The alkanoic acid 2 can be obtained by oxidizing this with an oxidizing agent such as potassium permanganate (JP-A-3-14).
No. 1241). At this time, an optically active alkanoic acid 2 can be obtained by using an optically active substance having an asymmetric center on the carbon to which the methyl group is bonded as the 2-methyl-1,2-epoxyalkane.

The carbon number of the alkyl group of R and R'in the compound represented by the general formula 5 has an influence on the physical properties such as the temperature range in which the compound can assume a liquid crystal state,
It can be appropriately selected depending on the purpose.

[0020]

Examples (Example 1) (1) 2- (4-hexylphenyl) -5- (4- (2-fluoro)
Of 2-methylheptanoyloxy) phenyl) pyrimidine
Synthesis 2- (4-hexylphenyl) -5- (4-hydroxyphenyl) pyrimidine 3.06 g (9.22 mmol), 2-fluoro-2
-Methylheptanoic acid 1.49 g (9.20 mmol), dicyclohexylcarbodiimide 2.13 g (10.34 mmol), 4-dimethylaminopyridine 0.12 g (0.98 mmol) and dry dichloromethane 45 ml are placed in a flask and the mixture is allowed to stand at room temperature overnight. It was stirred. The resulting solid was removed by filtration, the solvent was distilled off, and the resulting crude crystal was purified by silica gel column chromatography and recrystallization from ethanol to give 2- (4-hexylphenyl) having the above-mentioned physicochemical properties. ) -5-
3.73 g (yield 85%) of (4- (2-fluoro-2-methylheptanoyloxy) phenyl) pyrimidine was obtained.

(2) Evaluation of liquid crystallinity The compound obtained above is coated with polyimide and rubbed to form a glass plate with a transparent electrode having a thickness of 3 μm.
When observed with a crossed Nicols polarization microscope while cooling at a rate of −2 ° C./min, it changed from an isotropic liquid to a chiral smectic C phase at 114 ° C.
It changed to a higher order smectic phase at ℃, and crystallized at 72 ℃. When the temperature was raised, the crystal changed to a higher order smectic phase at 80 ° C. Moreover, when a spontaneous polarization was measured by applying a triangular wave of 30 Vpp at 109 ° C., it was 290 nC / cm ^2.
And was very big.

Example 2 A matrix liquid crystal mixture A was prepared by mixing eight kinds of non-optically active liquid crystal compounds shown in Table 1 in the proportions shown in the right column of Table 1.

[Table 1] The liquid crystal composition A exhibited the phase transition behavior shown in Table 2.

This liquid crystal composition A exhibited the phase transition behavior shown in Table 2.

[Table 2] (Cr is a crystalline phase, Sc is a smectic C phase, S _A is a smectic A phase, N is a nematic phase, and I is an isotropic phase.)

Since this liquid crystal composition A does not contain a compound having an asymmetric carbon, it does not exhibit ferroelectric behavior.

96% by weight of this liquid crystal composition A was used in Example 1
A liquid crystal composition B was prepared by mixing 4% by weight of 2- (4-hexylphenyl) -5- (4- (2-fluoro-2-methylheptanoyloxy) phenyl) pyrimidine synthesized in 1. above.

This liquid crystal composition B exhibited the phase transition behavior shown in Table 3.

[Table 3] (Cr is a crystalline phase, Sc ^* is a chiral smectic C phase, S _A is a smectic A phase, Ch is a cholesteric phase, and I is an isotropic phase.)

The liquid crystal composition was poured into a cell having a thickness of 2 μm and made of a glass plate with a transparent electrode, which was coated with polyimide and rubbed, and the temperature was gradually lowered from the state of an isotropic liquid to obtain a cholesteric phase. Was oriented. When the temperature was further lowered and the state was changed to the chiral smectic C phase through the smectic A phase, a well-oriented cell was easily obtained. When an electric field was applied to the cell while observing the cell with a crossed Nicols polarization microscope, a clear switching operation was observed.

A rectangular wave of 20 Vpp was applied to the cell at 25 ° C., the amount of transmitted light was measured by a photodiode, and an optical switching operation was detected. The amount of transmitted light was 10%.
The time required to change from 10 to 90% is 104 μse
It was very fast with c.

(Example 3) Liquid crystal composition A obtained in Example 2
Liquid crystal composition C was prepared by mixing 15% by weight of the compound of Example 1 with 85% by weight of

The liquid crystal composition C exhibited the phase transition behavior shown in Table 4.

[Table 4]

Further, this liquid crystal composition was poured into a cell having a thickness of 2 μm and formed of a glass plate with a transparent electrode, which was coated with polyimide and rubbed, and was slowly cooled from the state of isotropic liquid to give smectic A. The phases were oriented. When the temperature was further lowered and the state of the chiral smectic C phase was obtained, a well-oriented cell was easily obtained. When an electric field was applied to the cell while observing the cell with a crossed Nicols polarization microscope, a clear switching operation was observed.

A rectangular wave of 20 Vpp was applied to the cell at 25 ° C., the amount of transmitted light was measured with a photodiode, and the optical switching operation was detected. The amount of transmitted light was 10%.
It takes 24μsec to change from 90% to 90%
And was very fast.

[0033]

The compound of the present invention can have a stable thermotropic liquid crystal state, and when added to a non-chiral liquid crystal, it becomes a ferroelectric liquid crystal composition having a large spontaneous polarization and a high response speed. It has an extremely excellent effect as a material for optoelectronic-related elements.

Therefore, the present invention provides a liquid crystal material useful as a material for liquid crystal and optoelectronics-related elements that utilize electrochemichromism, such as optical printer heads, optical Fourier transform elements, and light valves for displays such as liquid crystal televisions. I can say.

Claims (4)

[Claims] 1. The following general formula 1 (In the formula, R and R'represent an alkyl group having 2 to 18 carbon atoms). 2. The novel ester compound represented by the general formula 1 according to claim 1, which has a new asymmetric center on the carbon where the methyl group and the fluorine are bonded. Ester compound. 3. A liquid crystal composition containing at least one kind of the novel optically active ester compound according to claim 2. 4. An optical switching element comprising at least one kind of the novel optically active ester compound according to claim 2 as a constituent element. [0001]