JPS63191890A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:To prepare a ferroelectric liq. crystal compsn. which exhibits a ferroelectric liq. crystal phase over a wide temp. range and enables a high speed response, by using a particular liq. crystal compd. having strong biphenyl or terphenyl conjugation. CONSTITUTION:A liq. crystal compsn. comprising at least one compd. of formula I (wherein l is 0 or 1; R is alkyl or alkoxy and R' is acyloxy or carbonyloxy, optically active acyloxy or carbonyloxy) having strong conjugation. In the above compsn., e.g., a binary mixture comprising a compound of formula I and an ester compound of formula II exhibiting a non-chiral smectic C phase exhibits a high speed response of 120musec when the concentration of the non- chiral component is 50wt.%. Further, a binary mixture comprising a compound of formula I and an ester compound of formula IV exhibiting a non-chiral smectic C phase exhibits a high speed response of 65musec when the concentration of the non-chiral component is 50wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to liquid crystal compositions containing novel liquid crystal substances, and more particularly to liquid crystal compositions.

2. Description of the Related Art In recent years, liquid crystal displays have come to be widely used not only in wristwatches, calculators, etc., but also in video equipment, and liquid crystal color televisions have also begun to appear on the market. Currently, the mainstream color display liquid crystal panels are those using nematic liquid crystals. but,
The characteristics of nematic liquid crystals are far from ideal and include many problems. Ferroelectric liquid crystals have various properties not found in nematic liquid crystals, such as fast response speed and memory properties, and are being studied in a variety of fields for potential applications in display devices. (e.g. Optronics, 198
3, No. 9) The ferroelectric liquid crystal will be explained below with reference to the drawings. Figure 6 is a schematic diagram of ferroelectric liquid crystal molecules. Ferroelectric liquid crystal is a liquid crystal that usually has a layered structure called smectic liquid crystal, and the liquid crystal molecules have a structure tilted by θ with respect to the normal direction of the layers. There is. Furthermore, ferroelectric liquid crystal molecules are usually composed of optically active liquid crystal molecules that are not racemic.

In FIG. 6, 7 is a liquid crystal molecule, 8 is spontaneous polarization, 9 is a C director 510 is a cone, 1) is a layer structure, 12 is a layer normal direction, and 13 is an inclination angle θ.

As shown in Figure 6, ferroelectric liquid crystal molecules have spontaneous polarization, and in the chiral smectic C phase, the sixth
It can move freely outside the cone 10 (cone) shown in the figure. The direction of the long axis of the molecules deviates slightly from layer to layer, resulting in a twisted structure as a whole. Next, we will discuss the display principle of ferroelectric liquid crystal. FIG. 7 is a diagram showing the operating principle of a ferroelectric liquid crystal. Figure 7+al shows the state where no voltage is applied, and Figure 7fbl shows the case where voltage is applied from the back side of the paper to the front side.
Figure 7 (C1 is a diagram of the principle of operation when voltage is applied in the opposite direction. 14 is a liquid crystal molecule whose long axis of the molecule is tilted by +θ degrees with respect to the layer normal; 15 is a liquid crystal molecule whose long axis is tilted by 10 degrees; 16 is a dipole moment facing toward the front of the page, 17 is a dipole moment facing toward the back of the page, and 18 is the direction of the two polarizing plates.0 A glass substrate with a ferroelectric liquid crystal and a transparent electrode. If the thickness of the panel is made equal to or less than the helical pitch, the helix will unravel as shown in Figure 7 (al), and the molecules will be +θ
It is divided into a region tilted by 10 degrees and a region tilted by −0 degrees. By applying a voltage between the upper and lower electrodes from the back side of the paper toward the front side, the entire cell becomes a monodomain tilted by +θ degrees as shown in Fig. 7 (mountain). Furthermore, when a reverse voltage is applied, the entire cell becomes a monodomain tilted by −0 degrees as shown in FIG. 7 (C1).

Therefore, when applying a ferroelectric liquid crystal to a display device, which can express brightness and darkness in two states tilted by +θ degrees by utilizing birefringence or dichroism caused by the electro-optic effect, the following conditions are required for the liquid crystal material: The following can be mentioned.

+1) Ferroelectric liquid crystal phase (
For example, chiral smectic C phase).

(2) The response speed τ of the ferroelectric liquid crystal to the electric field is τ=
η/P s-E However, η; viscosity P3; spontaneous polarization E; given by applied electric field. Therefore, in order to achieve a high-speed response on the order of several microseconds, it is necessary to have a large spontaneous polarization.

(3) As mentioned earlier, the optical response of a ferroelectric liquid crystal is first realized in a stable two-state state. According to Clerk et al., in order to realize this state, the cell gap It is necessary to make d less than the spiral pitch and unwind the spiral.
erk, S., T.

LagerwallHApH, Phys, L-et
t, 36899 (1980)) Therefore, in order to utilize a cell with a thick cell gap that is easy to fabricate, it is necessary to lengthen the helical pinch of the ferroelectric liquid crystal phase.

(4) The alignment state of the ferroelectric liquid crystal varies depending on the phase series of the liquid crystal material. In particular, liquid crystal materials that have a smectic A phase (SmA) and a cholesteric phase (Ch) on the high temperature side of the ferroelectric liquid crystal phase exhibit good alignment. It is believed that the state can be obtained. That is, when the phase series of the ferroelectric liquid crystal material is, for example, chiral smectic C phase, Iso -* Ch -e SmA
-4SmC+ However, it is desirable that the liquid be a summer so H isotropic liquid Ch; cholesteric phase SmA i smectic 7ri A phase S m C* i chiral smectic C phase.

Furthermore, among the liquid crystal materials having the above phase series, Ch
It is believed that the longer the phase pitch, the better the orientation state.

In addition to the conditions described above, there are various requirements such as requirements for the tilt angle θ of liquid crystal molecules.

There are only a few conventional ferroelectric liquid crystal materials that are practical in terms of temperature range, and at present there are almost no materials that meet all of the above conditions and can be put to practical use. Furthermore, conventionally, ferroelectric liquid crystal materials using chemically stable ester compounds have been mainly used.

The characteristics of a mixed system using conventional ester compounds are shown below.

RO◎coo◎OR' Transition temperature Iso -4Ch -1)SmA -* Sm
C*73℃ 67℃ 57℃ Response speed (25℃) 1, 2m5ec (24Vpp) Problems to be solved by the invention Conventional ferroelectric liquid crystal materials use chemically stable ester compounds. was the majority.

However, ester compounds have a problem in that although they have high S m C properties, they also have high viscosity and considerably poor electro-optical response characteristics. Therefore, the ferroelectric liquid crystal composition of the present invention is a ferroelectric liquid crystal composition that exhibits a ferroelectric liquid crystal phase over a wide temperature range and can respond at high speed by using a strongly conjugated biphenyl-based or terphenyl-based liquid crystal compound. It is something that provides something.

Means for Solving the Problems In order to solve the above problems, the present invention uses a highly conjugated liquid crystal material such as biphenyl-based or terphenyl-based ferroelectric liquid crystal material, so that it can be used in a wide temperature range. The present invention provides a ferroelectric liquid crystal composition that exhibits a ferroelectric liquid crystal phase and is capable of high-speed response.

Effect Since the ferroelectric liquid crystal composition of the present invention contains biphenyl-based or terphenyl-based liquid crystal materials, the conjugated system is stronger than that of conventional ester-based liquid crystal materials, resulting in a structure closer to a rigid body, which is useful for elasticity. Therefore, the electro-optical response speed becomes extremely fast.

EXAMPLE A liquid crystal composition according to an example of the present invention will be described below with reference to the drawings. First, FIG. 5 shows the structure of a liquid crystal cell in which the response characteristics of the ferroelectric liquid crystal material were measured in this example. Here, 1 is a polarizing plate, 2 is a glass substrate, 3 is a transparent electrode, 4 is an organic polymer film subjected to alignment treatment by rubbing, 5 is a ferroelectric liquid crystal layer, and 6 is a layer for keeping the cell thickness constant. It represents a spacer. A ferroelectric liquid crystal material was sealed in a cell with such a structure, and its response characteristics and spontaneous polarization were measured. Spontaneous polarization was measured using the triangular wave method.

In addition, regarding the phase transition temperature, the text
Measurements were performed by ure observation and DSC (differential scanning calorimetry needle).

Example 1 A two-component product in which the compound described in claim (1) is a compound represented by formula (1), and this compound is mixed with an ester compound (n) exhibiting a non-chiral smectic C phase. The phase transition temperature and response speed of the mixed system were measured. 1st
The figure shows the concentration dependence of the spontaneous polarization at 25°C and the response speed when applying 24 Vp/application, and the phase diagram of this mixed system is shown in Fig. 2.

For comparison, the response speed of a mixed system of an ester-based chiral smectic liquid crystal compound and a non-chiral ester compound having the same chiral properties is shown below.

1200μs at a non-chiral component concentration of 5Qwt%
In the case of ec and the biphenyl-based mixture of this example, a high-speed response of 120 C1 sec was shown under the same conditions.

......(1) RO◎coo◎OR' ......(II) Example 2 The compound described in claim (1) is a compound represented by formula (1) This compound is a phenylpyrimidine compound (II) that exhibits a chiral smectic C phase.
The phase transition temperature and response speed of the two-component mixed system containing I) were measured. Figure 3 shows spontaneous polarization at 25°C and 24Vp.
Figure 4 shows the concentration dependence of the response speed when p is applied, and the phase diagram of this mixture system is shown in Figure 4.
It showed a fast response of c.

Effects of the Invention As described above, the present invention uses a highly conjugated biphenyl-based or terphenyl-based liquid crystal compound as a ferroelectric liquid crystal material, thereby easily exhibiting a ferroelectric liquid crystal phase over a wide temperature range including room temperature. The present invention provides a ferroelectric liquid crystal composition capable of high-speed response.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram of the concentration dependence of response speed and spontaneous polarization of a ferroelectric liquid crystal cell in Example 1 of the present invention, Figure 2 is a phase diagram of a mixed system in Example 1 of the present invention, and Figure 3 is A characteristic diagram of the concentration dependence of the response speed' and spontaneous polarization of the ferroelectric liquid crystal cell in Example 2 of the present invention, Figure 4 is a phase diagram of the mixed system in Example 2 of the present invention, and Figure 5 is the ferroelectric liquid crystal cell. FIG. 6 is a schematic diagram of a ferroelectric liquid crystal, and FIG. 7 is a schematic diagram showing the operating principle of a ferroelectric liquid crystal. Engineering: polarizing plate, 2: upper and lower glass substrates, 3: transparent electrode, 4: organic alignment film subjected to alignment treatment, 5... ...ferroelectric liquid crystal phase,
6...Spacer to keep cell thickness constant,
7... Ferroelectric liquid crystal molecules, 8... Spontaneous polarization, 9... C director-1) 0...
・Cone, 1)...Layer, 12...Layer normal, 13...Tilt angle θ of the molecule with respect to the layer normal,
14...Liquid crystal molecules whose long axis of the molecule is tilted by 10 degrees with respect to the layer normal, 15...Liquid crystal molecules whose long axis of the molecule is tilted by 10 degrees with respect to the layer normal, 16...Dipole moment facing toward the front of the page, 17...Dipole moment pointing toward the back of the page, 18...
・Direction of the two polarizing plates. Name of agent Patent attorney Toshio Nakao 1 person Figure 1 Q 5Q 100 Chiral Figure 4 0.5+7
/(X)Figure 5Figure 6Figure 7

Claims (9)

[Claims] (1) General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the formula, 1 is an integer of 0 or 1, R is an alkyl group or alkoxy group, and R' is an acyloxy group, a carbonyloxy group, or an optically active acyloxy group. 1. A liquid crystal composition comprising at least one strongly conjugated compound represented by the following formula. (2) The liquid crystal composition according to claim (1), wherein R is an optically active 2-methylbutyl group (numerical formula, chemical formula, table, etc.). (3) The liquid crystal composition according to claim (1), wherein R is an optically active 2-octyl group (numerical formula, chemical formula, table, etc.). (4) General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the formula, 1 is an integer of 0 or 1, R is an alkyl group or alkoxy group, and R' is an acyloxy group, a carbonyloxy group, or an optically active acyloxy group. There are strongly conjugated compounds such as those represented by the following formulas (representing groups, carbonyloxy groups) and general formulas ▲ mathematical formulas, chemical formulas, tables, etc. A ferroelectric liquid crystal composition comprising at least one compound each represented by an optically active alkyl group or an alkoxy group. (5) The liquid crystal composition according to claim (4), wherein R in the general formula is an optically active 2-methylbutyl group (numerical formula, chemical formula, table, etc.). (6) The liquid crystal composition according to claim (4), wherein R in the general formula is an optically active 2-octyl group (numerical formula, chemical formula, table, etc.). (7) General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the formula, 1 is an integer of 0 or 1, R is an alkyl group or alkoxy group, and R' is an acyloxy group, a carbonyloxy group, or an optically active acyloxy group. There are strongly conjugated compounds such as those represented by the following formulas (representing groups, carbonyloxy groups) and general formulas ▲ mathematical formulas, chemical formulas, tables, etc. 1. A liquid crystal composition comprising at least one compound each represented by an optically active alkyl group or an alkoxy group. (8) The liquid crystal composition according to claim (7), wherein R in the general formula is an optically active 2-methylbutyl group (numerical formula, chemical formula, table, etc.). (9) In the general formula, R is an optically active 2-octyl group ▲ mathematical formula,
The liquid crystal composition according to claim (7), which has chemical formulas, tables, etc. ▼.