JPS62205190A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:A liquid crystal composition, containing a mixture of novel liquid crystal compounds having mutual opposite helical twisting directions of a smectic liquid crystal exhibiting ferroelectricity and the same polarity of spontaneous polarization and capable of exhibiting a ferroelectric liquid crystal phase within a wide temperature range. CONSTITUTION:A liquid crystal composition containing respective one or more kinds of liquid crystal compounds having mutually opposite directions of helical twisting directions of a smectic liquid crystal exhibiting ferroelectricity and liquid crystal compound having the same polarity of spontaneous polarization. The above-mentioned composition preferably contains liquid crystal compounds without exhibiting racemic modification of a chiral part expressed by the formula (R is alkyl or alkoxy). EFFECT:Capable of readily giving good orientation and providing high-speed response such as in the order of several musec.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to liquid crystal compositions containing novel liquid crystal materials, and in particular to ferroelectric liquid crystal materials.

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 a fast response speed and various properties not found in external nematic liquid crystals, and are being studied in many fields for potential applications in display devices. (Optronics, 1983, Volume 9
) The ferroelectric liquid crystal will be explained below with reference to the drawings.

FIG. 8 is a schematic diagram of ferroelectric liquid crystal molecules. A ferroelectric liquid crystal is usually a liquid crystal having a layered structure called a smectic liquid crystal, and the liquid crystal molecules have a structure tilted by θ with respect to the normal direction of the layers. Furthermore, ferroelectric liquid crystal molecules are usually composed of optically active liquid crystal molecules that are not racemic.

In Figure 8, 10 is a liquid crystal molecule, 11 is spontaneous polarization, and 12
is a C director - 113 is a cone, 14 is a layered structure, 15
indicates the layer normal direction, and 16 indicates the inclination angle θ.

As shown in Figure 7, ferroelectric liquid crystal molecules have spontaneous polarization, and in the chiral smectic C phase, the 8th
It can move freely outside the cone 13 (cone) shown. 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. 9 is a diagram showing the operating principle of a ferroelectric liquid crystal. Figure 9(a) shows the state with no voltage applied;
FIG. 9(b) shows the principle of operation when a voltage is applied from the back to the front of the paper, and FIG. 9(C) shows the operating principle when a voltage is applied in the opposite direction. 17 is a liquid crystal molecule whose long axis is +θ degrees heavier than the layer normal, 18 is a liquid crystal molecule that is 1θ head heavier, 19 is a dipole moment pointing toward the surface of the paper, and 20 is facing toward the surface of the paper. The dipole moment, 21, is the direction of the two polarizing plates. If a ferroelectric liquid crystal is sandwiched between glass substrates with transparent electrodes and the thickness of the panel is made equal to or less than the helical pitch, the ninth
As shown in Figure (al), the spiral is unraveled and the molecules are divided into a region where the molecules overlap the layer by +θ degrees and a region where the molecules overlap by 10 degrees.
As shown in b), the entire cell becomes a monodomain with an overlapping +θ degree.

Furthermore, when a reverse voltage is applied, the entire cell becomes a monodomain that is heavier by 1θ as shown in FIG. 9(C). Therefore, by utilizing birefringence or dichroism due to the electro-optic effect, brightness and darkness can be represented by two states tilted by θ.

When applying ferroelectric liquid crystal to display devices,
The following conditions are required for liquid crystal materials.

(2) Exhibits a ferroelectric liquid crystal phase (for example, chiral smectic C phase) over a wide temperature range including room temperature.

■ The response speed τ of ferroelectric liquid crystal to electric field is τ=η
/Ps-E where η; viscosity PS; spontaneous polarization E; given by applied electric field. Therefore, in order to achieve a high-speed response on the order of several μscc, it is necessary to have a large spontaneous polarization.

(2) As mentioned above, the optical response of a ferroelectric liquid crystal is first realized by a stable two-state g (bistable 5tate). According to C1erk et al., in order to achieve this state, it is necessary to make the cell gear d less than the helical pitch and unwind the helix. F. Nee, Clark;
Varnish, Tea, Raghaval; Apple, Huiz, Lett;
, 36899 (1980) (N. A. C1erk,
S, T, La-gerwall; ApH, Phys, L
ett, , 36899 (198(1)) For this reason,
In order to utilize a cell with a thick cell gap that is easy to fabricate, it is necessary to lengthen the helical pitch of the ferroelectric liquid crystal.

■ The alignment state of ferroelectric liquid crystal varies depending on the phase series of the liquid crystal material, and in particular, liquid crystal materials with smectic A phase (SmA) and cholesteric phase (Ch) on the high temperature side of the ferroelectric liquid crystal phase have a good alignment state. is believed to be obtained. That is, when the phase series of the ferroelectric liquid crystal material is, for example, chiral smectic C phase, *Iso −+ Ch −÷ SmA = S
mC* However, it is desirable that Iso; isotropic liquid Ch; cholesteric phase SmA; smectic A phase SmC*; chiral smectic C phase.

Furthermore, among liquid crystal materials with 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 regarding the tilt angle θ of liquid crystal molecules, etc.

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.

An example of a conventional ferroelectric liquid crystal material is shown below.

()) p-Decyl Oyashi, Sunjiriy'n, p'Amino 2-Methylphylene', Jite (100 OBA
MBC) C+ollzlO■ CH= N kuQ,>
CH=lh CII COOCItzCHCzilsISO-*
5rnA-*SmC*-5mC*12
0″c 91℃ 6
0°C However, Srn G *; Chiral smectic (JIPs E) 4~50C τ = several hundred μsec "" several m5ec Problems to be solved by the invention However, conventional ferroelectric liquid crystal materials can only be used within that temperature range. At present, there are few practical liquid crystal materials that satisfy all of the four conditions mentioned above and can be immediately applied to display devices.In the present invention, therefore, the polarity of the spontaneous polarization is the same. Ferroelectric liquid crystals can be produced over a wide temperature range by mixing liquid crystal materials that have a large spontaneous polarization and opposite twist directions, or by mixing liquid crystal materials that have thick spontaneous polarization and opposite twist directions. The object of the present invention is to provide a ferroelectric liquid crystal material that exhibits a phase, can easily obtain good alignment, and can respond at high speed on the order of several tens of microseconds.

Means for Solving the Problems In order to solve the above problems, the ferroelectric liquid crystal material of the present invention is a liquid crystal material that has large spontaneous polarizations, the same polarity, and opposite twist directions. By mixing or mixing liquid crystal materials with large spontaneous polarization and opposite twist directions, a ferroelectric liquid crystal phase can be obtained over a wide temperature range, good alignment can be easily obtained, and several 7μSe
It is a ferroelectric liquid crystal material capable of C-order high-speed response.

Function Generally, in order to expand the temperature range of liquid crystals, it is necessary to mix two or more types of liquid crystal compounds with different molecular shapes. However, when mixing ferroelectric liquid crystal materials, material constants such as the polarity of the spontaneous polarization of the compound, the direction of twist of the ferroelectric liquid crystal display layer, and the direction of 1 return of cholesteric 10 must be taken into account. Don't do it. Spontaneous polarization is
There are 10 as shown in Fig. 4 (, ++) and - as shown in Fig. 4 fb, and the polarity is determined by the configuration of the chiral center and the direction of the dipole moment. Figure 5 shows the change in spontaneous polarization when liquid crystal compounds with the same polarity of spontaneous polarization are mixed. (Figure 6 shows the change in spontaneous polarization when a 1-crystalline compound is mixed.
. Moreover, FIG. 6(a) shows the change in spontaneous polarization when the magnitudes of the spontaneous polarizations are almost equal, and FIG. When liquid crystal compounds with different polarities of spontaneous polarization are mixed, the value of spontaneous polarization becomes small, but by mixing liquid crystal compounds with the same polarity of spontaneous polarization, a liquid crystal compound with large spontaneous polarization can be easily obtained. Also, even when liquid crystal compounds with different polarities of spontaneous polarization are mixed,
When the magnitude of one spontaneous polarization is larger than the other, the decrease in spontaneous polarization is suppressed and a liquid crystal compound having a relatively large spontaneous polarization can be obtained.

The twist direction of the helical axis is thought to be determined by the absolute configuration of the chiral moiety and whether the number of molecules from the benzene ring to the chiral center is even or odd.

M, Tsukamoto, T, Otsuka, Kei, Morimoto, Soi. Murakami: Japan, Jay, Apple.

Fizz, , 141307 (1'175) (M, Tu
kamoto, T, 0tsuka.

K, Morimo to, Y, Murakami
Japan, J, App I, Phys.
, 141307 (1975)) That is, if the absolute configuration of the chiral center is eight bodies and the number of atoms from the benzene ring to the chiral center is an even number, the direction of twist is to the right, and if it is an odd number, the direction of twist is to the left. Moreover, if the absolute configuration of the chiral center is R-configuration, the configuration is reversed. In general, to extend the pitch, 2
There are two possible methods. One method is to mix a non-chiral liquid crystal material with a ferroelectric liquid crystal material, and the other is to mix a liquid crystal material whose tear direction is opposite to the ferroelectric liquid crystal material. According to the former method, in order to extend the pitch, it is necessary to mix a considerable proportion of a liquid crystal material that does not have chiral components, and the spontaneous polarization decreases as the non-chiral component increases, resulting in a very small amount. On the other hand, according to the latter method, as mentioned earlier, liquid crystal materials with the same polarity of spontaneous polarization and opposite pinch return directions are mixed, or even if the polarity of spontaneous polarization is opposite, only one spontaneous polarization A ferroelectric liquid crystal material with a large spontaneous polarization and a divergent pinch can be easily obtained by mixing liquid crystal materials which have a very large pitch and whose twist directions are opposite to each other.

Embodiment An embodiment of the present invention will be described with reference to the drawings. First, FIG. 7 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, 4 is a polarizing plate, 5 is a glass substrate, 6 is a transparent electrode,
7 is an organic polymer film subjected to alignment treatment by rubbing, 8
9 represents a ferroelectric liquid crystal layer, and 9 represents a spacer for keeping the cell thickness constant. 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, tex using a polarizing microscope
5C) The pitch of the k phase was determined using a cell subjected to alignment treatment with a cell thickness of 100 micrometers, and the pitch of the ch phase was determined by mixing the ch phase with nematic liquid crystal. Measurements were carried out using a model cell using a glass substrate with a thickness of 5 mm that had been subjected to an alignment process, using a conventional method.

Example 1 Compound (1) described in claim (2) has a steric configuration of the chiral moiety of 23,3S and R is an octoxy group, and the helical twist direction of compound (V) is to the right. ,
Compound (III
) The phase transition temperature, spontaneous polarization, pinch length, and response speed were measured using a compound (Vl) in which the configuration of the chiral moiety is 8 and R'' is an octoxy group. .

CI CI+3 C11゜Cu H+ t O■coo■OCHzCHCzHs(
Vl) Figure 2 shows the phase diagram of this two-return system. It can be seen that the material exhibits a ferroelectric liquid crystal phase over a wide temperature range, including room temperature, over almost the entire composition range. Figure 3 shows changes in spontaneous polarization and the reciprocal of pitch in the chiral smectic C phase depending on the composition. The pinch in the cholesteric phase also shows almost the same change as the pitch in the chiral smectic C phase. This figure shows that although the helical pinch of the compound containing 25% by weight of compound (V) extends almost infinitely, the magnitude of the spontaneous polarization is as large as 30 nC. Although the helical pitch of compounds with compositions other than those mentioned above is considerably elongated and good orientation is exhibited, the magnitude of spontaneous polarization is extremely large, ranging from several tens to several hundreds of nC. FIG. 1 shows the results of measuring the response speed of a cell using this liquid crystal composition. Figure 1 (al is 80t-t% of compound (V), Figure 1 (bl is 50wt% of compound (■), Figure 1 (C
) shows the response speed of a mixture containing 25 wt% of compound (V). Compound (V) with a b·t% of 50% showed a high-speed response of 25 μsec when ±20 V was applied near room temperature.

Example 2 Compound (I) described in claim (2) has a steric configuration of the chiral moiety of 23.3S, and the helical twist direction of compound (V) in which R is an octoxy group is to the right. ,
Compound (III) has an 8-configuration of the chiral moiety and R'' is an octoxy group as a left-handed compound of reverse twist, and Compound (IV) has an 8-configuration of the chiral moiety of Compound (IV). The phase transition temperature, spontaneous polarization, pitch length, and response speed of a three-component system using a compound (■) in which R'' is an off-1-oxy group were measured. In addition, the composition of the compound measured was compound (V)
is 72i%, compound (Vl) is 18-t%, compound (■
) was 10 wt%. The results are shown below.

CL C1h dislocation temperature IsO-) SmA --SmC* → 5II
I*76°C57°C 15'C Spontaneous polarization; 143nC ch-phase helical polarization; 17 micron SC*-phase helical polarization; infinite response speed; 35μ5ec (30'C) Example 3 Claim No. (2) Compound (V) in which the configuration of the chiral moiety of compound (1) is 25,3S and R is an octoxy group, and compound (II) in compound (II) as described in claim (5) The configuration is 2S, 3S
Since the twist direction of the compound (■) in which R is a -butyl group is right, the chiral part of the compound (IN) is an S configuration as a compound with a left-handed twist instead of a reverse twist, and R゛ is octoxy. The phase transition temperature, spontaneous polarization, pinch length, and response speed of the three-component system using the compound (VT) as a group were measured. The composition of the mixture in which the measurement was performed was 22.5 wt% of compound (V), 12.5 ht% of compound (■), and 75-t% of compound (VI). The results are shown below.

Cgll+, OσX■oco◎OC! 1□ClIC mountain (
■) Phase transition temperature Iso = 5rnA -SmC* → SD
I*60°C 45°C 6.1°C Spontaneous polarization; 39 nC Ck+ phase spiral pitch; infinite Sc* phase spiral pitch; infinite response speed; 40 μsec As described above, the present invention has a large spontaneous polarization. Either ferroelectric liquid crystal materials with the same polarity and opposite pitch twist directions are mixed, or ferroelectric liquid crystal materials with large spontaneous polarization are used.
In addition, by mixing ferroelectric liquid crystal materials whose pinch twist directions are opposite, a ferroelectric material that exhibits a liquid crystal phase over a wide temperature range including room temperature, has a good alignment state, has large spontaneous polarization, and is capable of high-speed response. It provides liquid crystal materials.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram of the response of the ferroelectric liquid crystal cell in Example 1 of the present invention.
The phase diagram of the component mixture system. Figure 3 is a concentration dependence characteristic diagram of spontaneous polarization and the reciprocal of pitch in Example 1 of the present invention. Figure 4 is a schematic diagram showing the polarity of spontaneous polarization. Figure 5 is a diagram showing the spontaneous polarization. Figure 6 shows the concentration dependence characteristic diagram of spontaneous polarization when compounds with the same polarity of polarization are mixed.
Figure 7 shows the configuration of a ferroelectric liquid crystal cell, Figure 8 shows a schematic diagram of a ferroelectric liquid crystal, and Figure 9 shows the operating principle of a ferroelectric liquid crystal. It is a schematic diagram. 1...Layer normal direction, 2...Molecular long axis direction, 3...Direction of spontaneous polarization, 4...Polarizing plate, 5... ..." - Lower glass substrate, 6...
...Transparent electrode, 7...Organic alignment film subjected to alignment treatment, 8...Ferroelectric liquid crystal phase, 9...
Spacer to keep cell thickness constant, 10...
・Ferroelectric liquid crystal molecules, 11... Spontaneous scratching, 12
...C director-113 ... Cone, 14 ... Layer, 15 ... Layer normal, 16
...Inclination angle θ of the molecule with respect to the layer normal, 17...
...Liquid crystal molecules whose long axes are tilted by θ with respect to the layer normal, 18...Liquid crystal molecules whose long axes of the molecules are tilted by 10 with respect to the layer normal, 19... ...Dipole moment facing towards the front of the paper, 20...Dipole moment facing towards the back of the paper, 21...Direction of the two polarizing plates. Name of agent Patent attorney Toshio Nakao Name of the agent Figure 4 (-) ρkuO Figure 5 ('Ln (b)
Wty, Wty7゜Figure 7Figure 8Figure 9

Claims (15)

[Claims] (1) A liquid crystal composition comprising one or more types of liquid crystal compounds each of which has a smectic liquid crystal exhibiting ferroelectricity whose helical twist directions are opposite to each other and whose spontaneous polarization is the same. (2) In smectic liquid crystals that exhibit ferroelectricity, there are general formulas ▲mathematical formulas, chemical formulas, tables, etc.▼(I) (However, R in the formula represents an alkyl group or an alkoxy group). Claim No. (1) characterized in that contains a liquid crystal compound that does not form a racemate.
The liquid crystal composition described in . (3) In smectic liquid crystals that exhibit ferroelectricity, there are compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(I), and general formulas▲mathematical formulas, chemical formulas, tables, etc.▼(III ) (wherein R and R' represent an alkyl group or an alkoxy group), each of which contains one or more types of liquid crystal compounds in which the chiral moiety does not form a racemate. The liquid crystal composition according to item (1) or item (2). (4) In smectic liquid crystals that exhibit ferroelectricity, there are general formulas▲mathematical formulas, chemical formulas, tables, etc.▼(I) Compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(III) There are compounds represented by ▲mathematical formulas, chemical formulas, tables, etc.▼(IV) (However, in the formula, R and R'R'' represent an alkyl group or an alkoxy group). The liquid crystal composition according to claim (1) or (2), characterized in that each of the liquid crystal compositions contains one or more types of liquid crystal compounds. (5) In smectic liquid crystals that exhibit ferroelectricity, there are general formulas ▲mathematical formulas, chemical formulas, tables, etc.▼(II) (However, in the formula, R represents an alkyl group or an alkoxy group) Chiral moiety Claim No. (1) characterized in that contains a liquid crystal compound that does not form a racemate.
The liquid crystal composition described in . (6) In smectic liquid crystals that exhibit ferroelectricity, there are compounds represented by the general formula ▲mathematical formulas, chemical formulas, tables, etc.▼(II), and compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(III ) (wherein R and R' represent an alkyl group or an alkoxy group), each of which contains one or more types of liquid crystal compounds in which the chiral moiety does not form a racemate. The liquid crystal composition according to item (1) or item (5). (7) In smectic liquid crystals that exhibit ferroelectricity, there are compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(II), and compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(III ), and ▲mathematical formulas, chemical formulas, tables, etc.▼(IV) (However, in the formula, R and R'R'' represent an alkyl group or an alkoxy group.) The chiral moiety represented by the formula is racemic. The liquid crystal composition according to claim (1) or claim (5), characterized in that each of the liquid crystal compositions contains one or more types of liquid crystal compounds that do not have the following properties. (8) In smectic liquid crystals that exhibit ferroelectricity, there are general formulas such as mathematical formulas, chemical formulas, and tables. 1. A liquid crystal composition comprising at least one liquid crystal compound in which the expressed chiral moiety is not helical and one or more compounds in which the helical twist direction is opposite to this compound. (9) In smectic liquid crystals that exhibit ferroelectricity, there are general formulas ▲mathematical formulas, chemical formulas, tables, etc.▼(I) (However, R in the formula represents an alkyl group or an alkoxy group). The liquid crystal composition according to claim (8), characterized in that it contains one or more types of liquid crystal compounds each of which does not form a racemate and a compound whose spontaneous polarization is the same as that of this compound. (10) In smectic liquid crystals that exhibit ferroelectricity, there are compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(I), and general formulas▲mathematical formulas, chemical formulas, tables, etc.▼(III ) (wherein R and R' represent an alkyl group or an alkoxy group), each of which contains one or more types of liquid crystal compounds in which the chiral moiety does not form a racemate. The liquid crystal composition according to item (8) or item (9). (11) In smectic liquid crystals that exhibit ferroelectricity, there are compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(I), and general formulas▲mathematical formulas, chemical formulas, tables, etc.▼(III ), and ▲mathematical formulas, chemical formulas, tables, etc.▼(IV) (However, in the formula, R, R', and R'' represent an alkyl group or an alkoxy group.) The chiral moiety represented by the formula is racemic. The liquid crystal composition according to claim (8) or (9), each containing one or more types of intangible liquid crystal compounds. (12) In smectic liquid crystals that exhibit ferroelectricity, there are general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (II) (However, R in the formula represents an alkyl group or an alkoxy group). 1. A liquid crystal composition comprising at least one liquid crystal compound in which the compound does not form a racemate, and one or more compounds in which the helical twist direction is opposite to this compound. (13) In smectic liquid crystals that exhibit ferroelectricity, there are general formulas ▲mathematical formulas, chemical formulas, tables, etc.▼(II) (However, in the formula, R represents an alkyl group or an alkoxy group) Chiral moiety The liquid crystal composition according to claim (12), characterized in that the liquid crystal composition contains one or more types of liquid crystal compounds that do not form a racemate and one or more compounds that have the same polarity of spontaneous polarization as this compound. (14) In smectic liquid crystals that exhibit ferroelectricity, there are compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(II), and compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(III ) (wherein R and R' represent an alkyl group or an alkoxy group), each of which contains one or more types of liquid crystal compounds in which the chiral moiety does not form a racemate. The liquid crystal composition according to item (12) or item (13). (15) In smectic liquid crystals that exhibit ferroelectricity, there are compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(II), and compounds represented by the general formula▲mathematical formulas, chemical formulas, tables, etc.▼(III ), and ▲mathematical formulas, chemical formulas, tables, etc.▼(IV) (However, in the formula, R and R'R'' represent an alkyl group or an alkoxy group.) The chiral moiety represented by the formula is racemic. The liquid crystal composition according to claim (12) or (13), characterized in that each of the liquid crystal compositions contains one or more types of liquid crystal compounds that do not have the following properties.