JPH0778064B2 - Liquid crystal material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ferroelectric liquid crystal compound useful as a display device having excellent image display responsiveness, and a chiral smectic liquid crystal composition containing the same.

At present, a display element made of a liquid crystal material is a light-receiving type display system, and has features such as low power consumption and the ability to create a thin display device, and is widely put to practical use. On the other hand, EL (electroluminescence) and plasma displays, which are light-emitting display systems and feature high-speed response, are also being actively developed.

[Conventional technology]

Most of the liquid crystals that have been used for display devices so far are nematic liquid crystals, and the mainstream is TN [Twisted Nematic (Tw
isted Nematic)] type. Although this TN type display system has advantages such as small size and low power consumption, it also has a drawback that the response speed of image display is slow. Various attempts have been made to improve this point, but Molecular Crystals and Liquid Crystals (Molecular Crys
tals and Liquid Crystals) Vol. 94, pp. 155-165, only the result of demonstrating the theoretical limit value seems to be the limit to the development of materials for TN type display.

Therefore, in order to overcome the above drawbacks, in recent years, interest has been shifted to the development of chiral liquid crystals in place of nematic liquid crystals, and considerable progress has been made especially in ferroelectric liquid crystals.

The first developed ferroelectric liquid crystal was A compound represented by (wherein * represents an asymmetric carbon atom) (hereinafter abbreviated as DOBAMBC), and its liquid crystal phase sequence and phase transition temperature (° C) are as follows.

(Where C is a crystalline phase, S _A is a smectic A phase, and ▲ S ^* _C ▼
Is a chiral smectic C phase, ▲ S ^* _H ▼ is a chiral smectic H phase, and I is an isotropic liquid).

Ferroelectricity is expressed in the chiral smectic C phase (hereinafter abbreviated as ▲ S ^* _C ▼) or chiral smectic H phase (hereinafter abbreviated as ▲ S ^* _H ▼) that is classified and named according to the molecular arrangement, and is based on the ferroelectricity. Since the response is expressed as the following formula [A] T = η / Ps · E [A] (where T is the response time, η is the viscosity of the liquid crystal material, Ps is the spontaneous polarization, and E is the electric field), theoretically 1μ
There is a possibility of obtaining a display element that can respond up to
Journal of Physics Fra by RBMeyer
nce) 36, 69 (1975).

Since then, various analogues of DOBAMBC have been synthesized, but ▲ S ^*
The lower limit of the temperature range belonging to _C ▼ or ▲ S ^* _H ▼ is higher than room temperature, and the compound itself is unstable to moisture and light. The focus of research has shifted to liquid crystal compounds [Liquid Crystals and Ordered Fluids, 4 , 1-32 (198
2)].

[Problems to be Solved by the Invention] As a result, although chemically stable compounds were obtained, as shown in Table 1, these liquid crystal compounds alone had a ferroelectric temperature range higher than room temperature, Not practical. In addition, when the compounds shown in Table 1 are mixed with each other, since the molecular structures are similar, a large melting point drop is not found as shown in Table 2.

Therefore, in the nematic liquid crystal material in the TN type display system,
This problem has been solved by mixing two or more kinds of liquid crystal compounds having significantly different molecular structures.

On the other hand, some pyrimidine-based compounds have a ferroelectric temperature range near room temperature, but the temperature range is narrow. Further, in the above formula [A], the Ps value is smaller than that of the analog of DOBAMBC (<4 nC / cm ² ), and high-speed response cannot be expected from the pyrimidine compound.

Therefore, it is strongly desired to develop a ferroelectric liquid crystal compound having a large Ps (spontaneous polarization) value, which is significantly different from these ester-based ferroelectric liquid crystal compounds in terms of molecular structure.

[Means for solving problems]

As a result of earnest research from the above viewpoints, the inventors of the present invention have found that a ferroelectric liquid crystal compound having excellent stability, a wide temperature range belonging to a ▲ S ^* _C ▼ phase or a ▲ S ^* _H ▼ phase, and a large Ps value, The present invention has been accomplished by finding a liquid crystal composition containing it.

That is, the present invention has the general formula [I] (Wherein R represents an alkyl group having 1 to 18 carbon atoms, and * represents an asymmetric carbon atom).

The present invention is also a chiral smectic liquid crystal composition containing at least one compound represented by the above general formula [I].

The boron-containing skeleton in the general formula [I] is named as follows.

In the general formula [I], R represents an alkyl group having 1 to 18 carbon atoms, preferably a linear alkyl group having 8 to 16 carbon atoms. Therefore, the compound represented by the general formula [I] is named as 2- {4 '-[4- (1-methylheptyloxy) phenyloxycarbonyl] phenyl} -5-alkyl-1,3,2-dioxaborinane. can do.

The method for producing the compound represented by the general formula [I] will be described in detail below, but a phenol compound having an optically active group is used as one of the starting materials. This phenolic compound Can be synthesized by the method described in JP-A-61-22051, and can be obtained from Teikoku Chemical Industry Co., Ltd.

The outline of the method for producing the compound represented by the general formula [I] is as follows.

[Wherein R ^* is And R each represents an alkyl group having 1 to 18 carbon atoms] [Action] The compound of the present invention exhibits the following actions and characteristics.

First, in an atmosphere containing water, it does not have a group that can be easily decomposed, an azomethine group (-CH = N-),
The conjugated system based on the double bond is an extremely short system with one benzene ring, so it is extremely stable against moisture and light. Then the dioxane borinan ring As in the case of 1, the polarization of the long axis of the molecule becomes large, and the ▲ S ^* _C ▼ phase is stably present due to the intermolecular interaction. Furthermore, in terms of stericity, the dioxaborinane ring has a slightly bent structure and does not exist on the same plane as the benzene ring, so that it can take the ▲ S ^* _C ▼ phase in a relatively low temperature range.

Further, when the compound of the present invention is mixed with other liquid crystals having a planar structure such as ester liquid crystals, biphenyl liquid crystals, and phenylpyrimidine liquid crystals, intermolecular packing becomes poorer and the thermal stability of the phase decreases. To do. This effect is
It is most prominent in the crystalline phase that requires the most regularity.
Thus the melting point is significantly reduced in the composition to provide a liquid crystal composition of the present invention having ▲ S ^* _C ▼ phase in a wide temperature range including the temperature of the room vicinity. Since the compound of the present invention has a large Ps (spontaneous polarization) value of 30 nC / cm ² or more, when it is used as a blending material for a mixed system, it achieves the above-mentioned purpose of lowering the melting point and improves the Ps value of the mixed system. It is possible.

〔Example〕

Hereinafter, the present invention will be described with reference to examples, but% in the examples means% by weight.

Production Example 1 Synthesis of 2-alkyl-1,3-propanediol 2 equipped with stirrer, thermometer, dropping funnel and reflux condenser
Lithium aluminum hydride 15g in a three-necked flask
(0.4 mol) and 600 ml of anhydrous ether were charged, and 0.2 ml of 2-alkylmalonic acid was added to the suspended liquid by vigorous stirring.
A solution of 20 mol of anhydrous ether was added dropwise at an internal temperature of 5 ° C. After the dropping was completed, the reaction was carried out at the reflux temperature for 6 hours. After completion of the reaction, the reaction product was ice-cooled, and in order to decompose excess lithium aluminum hydride, 50 ml of ether saturated with water and then 10 ml of 5% aqueous sodium hydroxide solution were added dropwise, and the mixture was stirred at 25 ° C. overnight. The white inorganic substance formed was removed, and the mother liquor was concentrated to obtain a white solid substance. Recrystallization was carried out with n-hexane, and 2-alkyl-1,3 shown in Table 3 below.
-Propanediol was obtained.

Production Example 2 Production of 2- (4'-carboxyphenyl) -5-alkyl-1,3,2-dioxaborinane [B] A stirrer, a thermometer and an azeotropic dehydrator with a reflux condenser were provided.
A 200 c.c. four-necked flask was charged with 0.01 mol of the 2-alkyl-1,3-propanediol obtained in Preparation Example 1 and 1.6 g (0.01 mol) of paracarboxyphenylphoronic acid together with 50 ml of toluene at a reflux temperature. Azeotropic dehydration was performed. About 1-2
The reaction was completed in time and 2- (4'-carboxyphenyl) -5-alkyl-1,3,2-dioxaborinane of Table 4 was obtained.

The results are shown in Table 4 together with the physical properties of the obtained compound.

Example 1 2- {4 '-[4-((S) -1-methylheptyloxy) phenyloxycarbonyl] phenyl}
-5-dodecyl-1,3,2-dioxaborinane (Table 5:
Preparation of Compound No. 4) 2- (4'-carboxyphenyl) -5-dodecyl-1,3 obtained in Preparation Example 2 was placed in a 100 c.c. three-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 2,2-Dioxaborinane (5 mmol) and 2.0 g of thionyl chloride were charged, dissolved with stirring and reacted in an oil bath at 70 ° C for 2 hours, and then excess thionyl chloride was distilled off under reduced pressure to remove the corresponding acid. Chloride was obtained. On the other hand, 4-((S) -1-
1.12 g (5 mmol) of methylheptyloxy) phenol (manufactured by Teikoku Chemical Industry Co., Ltd.) was charged, and 20 ml of tetrahydrofuran and 10 ml of pyridine were added and dissolved. The acid chloride synthesized above was added to this tetrahydrofuran solution at room temperature, and then the mixture was brought to reflux temperature and stirred for 6 hours. After completion of the reaction, tetrahydrofuran and pyridine were distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography (200 mesh silica gel 60 g, developing solvent dichloromethane / tetrahydrofuran = 95/5) for isolation and purification, and 2- {4 ' -[4
-((S) -1-Methylheptyloxy) phenyloxycarbonyl] phenyl} -5-dodecyl-1,3,2-dioxaborinane was obtained in a yield of 78%.

The structure of this compound was confirmed by IR and NMR spectra.

By recrystallizing from petroleum ether, a compound with higher purity can be obtained. The phase transition temperature of this compound is as shown in Compound No. 4 of Table 5. The spontaneous polarization of this compound was 32 nC / cm ² (39 ° C).

Similarly, in the general formula [I], R is a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group,
A compound that is a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, or a hexadecyl group can be produced.

The results of each compound obtained in the same manner as in Example 1 above are shown in Table 5 together with the phase transition temperature.

The symbols in the table below indicate the following.

C: Crystal phase, S ₁ : Smectic phase with undetermined features, ▲ S
^* _C ▼: Chiral smectic C phase, S _A : Smectic A
Phase, I: isotropic liquid phase, Ps: spontaneous polarization value (nC / cm ² ).

Example 2 Liquid crystal compositions of the following Table 6 were prepared using the liquid crystal compounds of the present invention of compounds No. 4, No. 5 and No. 6 of Table 5, and the phase transition temperatures thereof were measured. It was as shown in Table 6.

When this liquid crystal composition was applied to a cell having a transparent electrode in which a polyimide film was coated, the surface was rubbed for parallel alignment treatment and the cell thickness was controlled to 2 μm, ▲ S ^* _C ▼
A cell with uniform alignment was obtained. Also under the temperature of 39 ℃ ± 15
When a V rectangular wave voltage was applied, a display element with a response time of 0.4 ms and a contrast of 15 was obtained.

Example 3 A liquid crystal composition was prepared by mixing and dissolving 70% of the liquid crystal composition of the present invention obtained in Example 2 and 30% of the known ester-based liquid crystal composition described in Table 2, and the phase transition temperature thereof. As a result of measuring
It was as follows.

When this liquid crystal composition was injected into a cell similar to the cell used in Example 2, a cell having a uniform alignment could be obtained by (S ^* _C ). The cell had a response time of 1.3 ms at 25 ° C and a contrast of 13. It was possible to lower the melting point and expand the temperature range of ▲ S ^* _C ▼ by mixing with a biphenyl-based or pyrimidine-based liquid crystal compound in addition to the ester-based material.

〔The invention's effect〕

As shown in Example 1 (Table 5) above, the compound of the present invention is a compound that exhibits a ▲ S ^* _C ▼ phase in a wide temperature range and has ferroelectricity. From the results, it is clear that it is an effective component for obtaining a wide range of chiral smectic liquid crystal compositions including room temperature. Such an effect is first achieved by the present invention.

Claims (2)

[Claims] 1. A general formula [I] (Wherein R represents an alkyl group having 1 to 18 carbon atoms, and * represents an asymmetric carbon atom). 2. A general formula [I] A chiral smectic liquid crystal composition comprising at least one compound represented by the formula (wherein R represents an alkyl group having 1 to 18 carbon atoms and * represents an asymmetric carbon atom).