JPS6020432B2 - Mixed cholesteric liquid crystal composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has clear thresholds, fast response speed,
The present invention relates to a Namiai cholesteric liquid crystal composition suitable for Y matrix display devices.

It is desired to develop a liquid crystal material having display characteristics superior to conventional materials.

At present, several nematic liquid crystals that can be used in display devices are known and are also being manufactured and sold. However, they have a drawback in that they do not have a clear threshold or value, and there are also liquid crystals that have a clear threshold value, such as nematic liquid crystals mixed with cholesterin concessionaires, but their response speed is slow, and these cannot be used for XY matrix display, which is advantageous for multi-pixel display, or has poor display performance. The x-Y matrix display is a matrix formed at the intersection of a plurality of parallel strip-shaped × electrode groups extending in the X direction and a plurality of parallel strip-shaped Y electrodes extending in a direction perpendicular to the X direction.
This is intended to address and display n picture elements (m: number of X electrodes, n: number of Y electrodes) using X electrodes and Y electrodes.

The advantage of this case is that only m+n lead wires are required to be connected to each electrode to control mn picture elements, and m
+ Only n drivers are required. However, this display method has a problem called crosstalk. Crosstalk is the interaction between one × electrode in the X electrode group and Y
When a picture element at the intersection with one Y electrode in the electrode group is selected and a voltage V is applied between both the × and Y electrodes, V/2 is applied to the picture elements arranged in a cross shape with this intersection as the center. voltage is applied, resulting in a half-selected state. To prevent this, the liquid crystal sandwiched between the × electrode group and the Y electrode group must be made such that it does not cause any visual change (for example, scattering light) up to a voltage of V'2. A liquid crystal with a value is required. Furthermore, since scanning (sequential addressing) means must necessarily be used in the XY matrix display, a liquid crystal material with a fast response speed is required. The present invention provides a liquid crystal material suitable for a ×1 Y matrix display device, which has a threshold value and is advantageous for a multi-pixel display with a fast response speed.

The present invention will be described in detail below with reference to examples. A mixed liquid crystal containing (10)-8-methylbutyl-4-(p-n-hexylphenyl)penzoate (smectic - isotropic liquid transition temperature 14°C) represented by the following structural formula (hereinafter this compound is referred to as MBHPB) All exhibit a cholesteric phase and have a threshold.

*(10) 13-Methylbutyl-4-(p-n-hexylphenyl)penzoate The above compound was prepared as follows.

4-(p-n-hexylphenyl)benzoic acid 8.5 hours,
A mixture of 20 ml of thionyl chloride is heated at 100 ml until hydrogen chloride no longer evolves.

Thereafter, thionyl chloride is completely removed under normal pressure and finally under reduced pressure. Thereafter, optically active (1)-2-methyl-1-butanol was added and the mixture was heated to reflux. When hydrogen chloride is no longer generated, heating is stopped, and after cooling, the target product is extracted with toluene.
The toluene solution is washed with water until the washing liquid becomes neutral, and then dried with sodium sulfate. After removing the toluene, it is dissolved in n-hexane, and column chromatography is performed using neutral alumina having an activity of 1 and using n-hexane as a screening agent. After removing the n-hexane, recrystallization twice from n-hexane using a cryogen (dry ice-methanol) yields 31 grams of (10)-18-methylbutyl-4-(p-n-hexylphenyl)penzoate, which is liquid at room temperature. It was done. Specific rotation [Q] of this target object. is 6.1 (100 cc of CHC
Target object in 13 solvents 2.6? ). The results of elemental analysis are C (%) calculated value 81.76 days, measured value 81.55 days (%).
) A calculated value of 9.17 and an actual value of 9.02 were obtained.

Therefore, it is considered that the desired compound was obtained. The case where the parent liquid crystal is p-nematic or n-nematic will be explained below.

[1] Mixed liquid crystal of p-nematic liquid crystal and MBHPB (referred to as p-mixed cholesteric liquid crystal composition).

) A p-nematic liquid crystal is a nematic liquid crystal whose yield coefficient in the longitudinal direction of liquid crystal molecules is larger than the dielectric constant in the perpendicular direction, and is called a nematic liquid crystal with positive dielectric constant anisotropy.

The curve in Figure 1 represents the p-
General electro-optical properties of cholesteric mixed liquid crystals are shown. The characteristics of the same machine are shown whether the applied voltage is DC or AC. The threshold value h' is the point at which the light transmittance starts to change rapidly, and it changes depending on the ratio of M old HPB, and increases as the ratio of M old HPB increases. The abrupt change in the curve is the phase transition from cholesteric to nematic phase.
The voltage is in the cholesteric phase below the threshold voltage Vth, and is in the nematic phase above the saturation voltage Vsat. With p-nematic liquid crystal alone, there is no large change in light transmittance as described above, and the threshold value can be observed and removed (although there is some variation in light transmittance due to the rotation of molecules when an electric field is applied, at most the light transmittance changes). (The transmittance varies between 100% and 90%). P-nematic liquid crystals contain p-alkoxybenzylidene-p'-cyanoaniline, p-cyanobenzylidene-b-alkoxyaniline, p-alkylbenzylidene-b-cyanoaniline, p-cyanobenzylidene-p'-alkylaniline, and P-acyloxy. Benzylidene-p'-cyanoaniline, p-cyanobenzylidene-p
'-acyloxyaniline, p-cyanophenyl-p'-
Alkylbenzoate, p-cyanophenyl-p'-alkoxybenzoate, p-alkylphenyl-p'-
Cyanobenzoate, p-alkoxyphenyl p'-
Cyanobenzoate, p-alkoxybenzylidene-p
'-aminobenzene, n-alkyl p-thia/penzylidene-p'-aminocynamite, p-n-alkyl-
p'-n-alkylazobenzene, p-alkyl-p'
There are nematic liquid crystal compounds such as -cyanobiphenyl and P-alkoxyp'-cyanobiphenyl. Mixtures of some of these are also p-nematic liquid crystals.

Other p-nematic liquid crystals include liquid crystals obtained by mixing the above p-nematic liquid crystal with n-nematic liquid crystal, which will be described later. Whether this mixed liquid crystal is a p-nematic liquid crystal is determined by the fact that the average dielectric constant in the orientation direction of the liquid crystal (the most axial direction of the molecules) is larger than the average dielectric constant in the direction perpendicular to the orientation direction. be done. In this case, therefore, the amount of n-nematic liquid crystal mixed must be adjusted. For example, p-butoxybenzylidene-p'-cyanoaniline and n
It is known that a mixed liquid crystal of p-methoxybenzylidene-p'-butylaniline, which belongs to the nematic liquid crystal, becomes a p-nematic liquid crystal if 5 mol% of p-butoxybenzylidene-cyanoaniline is contained. (Example 1) p-nematic liquid crystal, p-n-hexylbenzylidene-p'-cyanoaniline 7% by weight Ship H
PB female content % This mixed cholesteric liquid crystal composition has a clear threshold value when a square wave 250 days 2 alternating current is applied at a temperature of 10°C and an electrode spacing of 6 μm, and the threshold value voltage Vth is 6 volts, and the saturation voltage Vsat is 12 volts.

When a voltage of 15 volts is applied, the rise time is 5 hsec and the decay time is 80 hsec. These values (
The characteristics (rate of light transmittance with respect to applied voltage and response speed) are much better than those of n-nematic liquid crystal (p-methoxybenzylidene-p'-n-butylaniline, abbreviated as M former BA) which will be described later. (Example 2) P-nematic liquid crystal, p-n-octyloxybenzylidene-p'-cya/aniline 3% by weight n-nematic liquid crystal, p-methoxybenzylidene-p'-1-butylaniline 5% by weight Ship H
PB Female amount % This mixed liquid crystal has a temperature of 40°C, an electrode spacing of 6 peaks, and a threshold voltage yth of 6 volts when a 250 Hz square wave alternating current is applied.
The saturation voltage Vsat is 12 volts.

When applying a voltage of 15 volts, rise time is 38 hsec
, the decay time is 200 hsec. In general, M-old HPB mixes well with other liquid crystals, but if it exceeds 3% by weight, it will no longer be a liquid crystal at room temperature and cannot be used at room temperature. This example also has better characteristics than MBBA, which will be described later. [
2]-Mixed liquid crystal of n-nematic liquid crystal and MBHPB (referred to as an n-mixed cholesteric liquid crystal composition).

) n - Nematic liquid crystal is a nematic liquid crystal in which the yield coefficient in the Nagato direction of the molecules is 4 points higher than the dielectric constant in the direction perpendicular to it, and the dielectric constant anisotropy is negative. It is.

The curve in FIG. 2 shows the general electro-optical properties of an n-cholesteric mixed liquid crystal sandwiched between two transparent electrodes. As shown in Figure 2, this n-cholesteric liquid crystal has a memory effect and initially has a high light transmittance, but when a direct current or an alternating current below a certain limit frequency fc is applied to it, It moves from the transparent state of 2 to the opaque state of 2, and remains in the opaque state of 3 even if the fin pressure is lowered. This opaque state 3 returns to the transparent state 1 by applying an alternating current with a frequency higher than the limit frequency fc. This limit frequency fc varies depending on the temperature and the properties of the n-nematic liquid crystal, such as viscosity, conductivity, dielectric constant, etc., and is normally in the range of several tens of Hz to several kHz. An example is shown in Example 3.

If the amount of MBHPB is less than 15% by weight, the above-mentioned memory effect will be reduced and the well-known dynamic scattering will be exhibited, but as long as it contains more than 2% by weight of MBHPB, the threshold value will be lower than MBHPB. It is sharper and clearer than without it. For example, in the case of M old BA, when a voltage is applied to a cell with an electrode spacing of 12 μm, so-called dynamic scattering occurs.
The light transmittance changes slowly at a value of V of about 5 volts, and the saturation voltage of V becomes about 20 volts. When applying 20 volts at 25 qo, the rise time exceeds lowhs and the decay time exceeds 50 ksec.

Examples of n-nematic liquid crystals include p-alkoxy-pn-alkylazoxybenzene, p-n-alkylumealkoxyazoxybenzene, p-alkoxyp'-alkoxyazoxybenzene, p-n -alkyl-p'-alkoxyazobenzene, p-alkoxylyalkylazobenzene, p-alkoxyp'
-Alkoxyazobenzene, P-alkoxybenzylidene-p'-acyl. xyaniline, p-n-alkylbenzylidene-p'-acyloxyaniline, p-n-alkylbenzylidene-p'-alkoxyaniline, p-alkoxybenzylidene-p'-n-alkylaniline, p
-n-alkyl-p'-acyloxyazoxybenzene and the like. Some of these mixed liquid crystals are also n-nematic liquid crystals. (Example 3) n-nematic liquid crystal, p-methoxybenzylidene-p'-n-butylaniline 7% by weight Ship H
PB 3 Koshitaka% This liquid crystal has a temperature of 20°C, an electrode spacing of 12〃, an applied AC voltage of 70 days 2, a square wave, a threshold V ratio of 10 volts, a saturation voltage Vsat of 25 volts, and a voltage of 40 volts applied. When , the rise time is 80 hsec and the limit frequency fc is 140 days2.

When a rectangular wave alternating current of 280 Hz and 40 volts is applied, the erasing time is 150 hsec.

In addition to the above-mentioned p-mixed cholesteric liquid crystal composition and n-mixed cholesteric liquid crystal composition, liquid crystals in which cholesteric liquid crystals made of cholesteric derivatives are added to each of these also essentially have their respective electro-optical properties (first Some of the cholesteric derivatives, as shown in Example 4 without changing the shape of the curves in FIG.
For example, cholesteric nonanoate lowers the threshold voltage.

Cholesteric liquid crystals made of cholesteric derivatives are
Examples include cholesterol chloride, cholesterol bromide, cholesterin carboxylic acid esters such as cholester nonanoate, and cholesterin carbonate esters such as cholesteryl oleyl carbonate. (Example 4) p-nematic liquid crystal, p-n-hexylbenzylidene-p'-cyanoaniline 6% by weight Ship HP
B Weight increase% cholesteric nonanoate 1% by weight This liquid crystal exhibits the electro-optical characteristics shown in FIG. 1, temperature 1 is 0, electrode spacing 6A,
When 250Hz, square wave alternating current is applied, the threshold value Vt
h is 1.6 volts, saturation voltage Vsat is 10 volts,
When a voltage of 10 volts is applied, the rise time is 60 hsec,
The decay time is 10 hsec.

As is clear from the above explanation, mixed cholesteric liquid crystal compositions with various properties can be obtained by adding various liquid crystal matrix materials to MBHPB. However, in order to further improve performance, compounds that are not originally liquid crystals can be added. It can also be added to an extent that does not destroy the liquid crystal state. For example, P-n-
Alkylbenzylidene-p'-n-alkylaniline is effective in lowering the solid-to-liquid crystal transition temperature and obtaining high-speed response characteristics. Also, in order to obtain appropriate conductivity,
Organic electrolytes can also be added in quantity. For example, addition of trimethylammonium halide and the like is well known. Further, in the description of the display device of the present invention, a transmissive display device was used, but it is well known that a reflective display device can be obtained by using one electrode as a reflective surface. As is clear from the above explanation, the mixed cholesteric liquid crystal composition of the present invention has a clear threshold value, a long response speed, and can realize an ×Y matrix display device that is advantageous for multi-pixel display. be. It also exhibits excellent performance even when used in ordinary electro-optical display devices. Brief Description of the Drawings FIG. 1 is a diagram showing the electro-optical characteristics of a p-mixed cholesteric liquid crystal composition, and FIG. 2 is a diagram showing the electro-optical characteristics of an n-mixed cholesteric liquid crystal composition.

1 box of bamboo blinds Dance 2

Claims (1)

[Claims] 1. A mixed cholesteric liquid crystal composition comprising 2% to 30% by weight of (+)-β-methylbutyl-4-(p-n-hexyl phenyl)benzoate and a nematic liquid crystal compound.