JPS6020431B2 - Mixed cholesteric liquid crystal composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a clear threshold, fast response speed,
The present invention relates to a mixed 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 starting point 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 derivatives, but their response speed is slow, and these cannot be used for ×1 Y matrix display, which is advantageous for multi-pixel display, or has poor display performance. An X-Y matrix display is a matrix formed at the intersection of a plurality of parallel strip-shaped X electrodes extending in the x direction and a plurality of parallel strip-shaped Y electrodes extending in a direction perpendicular to the X direction.
The purpose is to address and display n picture elements (m: x number of electrodes, n: Y number of electrodes) using X electrodes and Y electrodes.

The advantage in this case is that only m+n lead wires are 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
If 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 X and Y electrodes, the picture elements arranged in a cross shape with this intersection as the center will be voltage is applied, resulting in a half-selected state. In order to prevent this, the liquid crystal sandwiched between the X electrode group and the Y electrode group should not cause any visual changes (for example,
A liquid crystal that does not scatter light (i.e., has a threshold) is required. Furthermore, since scanning (sequential addressing) means must necessarily be used in the X-Y matrix display, a liquid crystal material with a fast response speed is required. The present invention provides a liquid crystal material which has a threshold value and is directly suitable for an x-Y matrix display which 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. (10)-P-methylbutyl-4-(P1n-
Bentyloxyphenyl) penzoate (spots ℃ ~ 64℃
shows a smectic liquid crystal state.

All mixed liquid crystals containing this compound (hereinafter referred to as MBPP) exhibit cholesteric properties and have a threshold value. -8-Methylbutyl-4-(P-n-bentyloxyphenyl)penzoate The above compound was prepared as follows.

4-(P-n-besothyloxyphenyl)benzoic acid 85
In the evening, a mixture of 20 ml of thionyl chloride was heated at 100 qo until hydrogen chloride was no longer generated.

Thereafter, thionyl chloride is completely distilled off under normal pressure and finally under reduced pressure. Later activated aluminum optically active (1)2-methyl-1
-Add 3 portions of butanol alcohol and heat 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 distilling off toluene, it is dissolved in n-hexane, and column chromatography is performed using neutral alumina with an activity of 1 and n-hexane as a developing agent. After removing n-hexane, recrystallization is performed twice from ethanol, and the liquid crystal temperature becomes uneven ~ 64. ○(10)-8
-Methylbutyl-4-(P-n-bentyloxyphenyl)penzoate was obtained in the form of 6.9 tons of white crystals.
Specific rotation [Q] of this target object. is 37 (10
(at a concentration containing 2.4 t of the target product in 0 cc of CHC13 solvent). The result of elemental analysis is C (%) as C23 days 3 minus 3 Calculated value 77.91 Actual value 7812 days (%)
A calculated value of 8.55 and an actual value of 8.71 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 M old PPB (referred to as P-mixed cholesteric liquid crystal composition).

) A P-nematic liquid crystal is a nematic liquid crystal in which the dielectric constant in the long axis direction of the liquid crystal molecules is larger than the yield ratio in the perpendicular direction, and the yield ratio anisotropy is positive.

The curve in FIG. 1 shows the general electro-optical properties of a P-cholesteric mixed liquid crystal sandwiched between two transparent electrodes. It exhibits similar characteristics whether the applied voltage is direct current or alternating current. The threshold voltage y ratio is the point at which the light transmittance starts to change rapidly, and changes depending on the ratio of MBPPB, and increases as the ratio of MBPPB increases. The abrupt change in the curve is the phase transition from the cholesteric phase to the nematic phase. Below the threshold value Vth, the cholesteric phase occurs and the saturated fin pressure Vs
Above at, there is a nematic phase. With P-nematic liquid crystal alone, there is no large change in light transmittance as described above, and the threshold value is difficult to observe (although there is a change in light transmittance due to the rotation of molecules when an electric field is applied). (at most, the light transmittance varies between 100% and 90%). P-nematic liquid crystal contains P-alkoxybenzylidene-P'-cyanoaniline, P-cyanobenzylidene-P'-alkoxyaniline, P-alkylbenzylidene-P'-cyanoaniline, P-cyanobenzylidene-P'-alkylaniline, P-acyloxybenzylidene-P'-cyanoaniline, P-cyanobenzylidene-
P'-acyloxyaniline, P-cyanophenylene-P'
-Alkylbenzoite, P-cyanophenylene P'-
Alkoxybenzoate, P-alkylphenyl-P'
-Cyanobenzoate, P-alkoxyphenyl-P'
-Sia/penzoite, P-alkoxybenzylidene-P'-aminobenzene, n-alkyl-P-sia/penzylidene-P'-aminocinamiite, P-n-alkyl-P'-n-alkylazobenzene, P-alkyl-
There are nematic liquid crystal compounds such as P'-cyanobiphenyl and P-alkoxy-P-cyanobiphenyl. Mixtures of some of these are also P-nematic liquid crystals. Other P-nematic liquid crystals include the P-
There is a liquid crystal that is a mixture of nematic liquid crystal and 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 (long axis direction) of the liquid crystal is larger than the average dielectric constant in the direction perpendicular to the orientation direction. Ru. Therefore, in this case, the amount of n-nematic liquid crystal that is added must be adjusted. For example, in a mixed liquid crystal of P-ptoxybenzylidene-P'-cyanoaniline belonging to P-nematic liquid crystal and P-methoxybenzylidene-P-butylaniline belonging to n-nematic liquid crystal, P-butoxybenzylidene-P'-cyanoaniline is 5 mol%. It is known that if there is a P-nematic liquid crystal.

(Example 1) P-nematic liquid crystal, P-n-hexylbenzylidene-P-cyanoaniline 7% by weight PPB
This mixed cholesteric liquid crystal composition has a clear threshold when a square wave 250 Hz alternating current is applied at a temperature of 30° C. and an electrode spacing of 6 μm, and the threshold voltage Vth is 6 volts. Saturation voltage V
sat is 12 volts.

When a voltage of 15 volts is applied, the rise time is 4 hsec and the decay time is 8 hsec. These values (
The ratio of light transmittance to applied voltage and response speed) are much better than those of n-nematic liquid crystal (P-methoxybenzylidene-P'-n-butylaniline, abbreviated as MBBA), which will be described later. (Example 2) P-nematic liquid crystal, P-n-octyloxybenzylidene-P'
- Cyanoaniline 3% - Nematic liquid crystal, P
-Methoxybenzylidene-P'-n-butylaniline
5% by weight (10) 18-methylbutyl-41 (P-
Weight % of n-bentyloxyphenyl) penzoate 2
This mixed liquid crystal has a threshold voltage Vth of 2 volts and a saturation pressure Vsat of 9 volts when a 250 Hz rectangular wave alternating current is applied at a temperature of 40 degrees centigrade and an electrode spacing of 6 degrees.

When a voltage of 10 volts is applied, the rise time is 2 seconds,
The decay time is 6 hsec. In general, M old PPB mixes well with other liquid crystals, but if it exceeds 80% by weight, the liquid crystal temperature range becomes narrow and it becomes difficult to use. This example is also superior to the MBBA described below. [2] Mixed liquid crystal of n-nematic liquid crystal and M old PPB (referred to as n-cholesteric mixed liquid crystal).

) An n-nematic liquid crystal is a nematic liquid crystal in which the dielectric constant in the direction of the long axis of the molecules is smaller than the dielectric constant in the direction perpendicular thereto, and is called a nematic liquid crystal with negative yield anisotropy. The curve in FIG. 2 shows the general electro-optic properties of an n-mixed cholesteric liquid crystal composition interposed 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, as shown in Figure 2. It moves from the transparent state (1) to the opaque state (2), and remains in the opaque state (3) even if the voltage 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 is
It varies depending on the temperature and the properties of the n-nematic liquid crystal, such as viscosity, conductivity, dielectric constant, etc., and normally ranges from several tens of Hz to several K.
It is Hz. An example is shown in Example 3. When the base content of MBPPB is 15% by weight or less, the above memory effect decreases and the well-known dynamic scattering is exhibited.
As long as it contains 2% by weight or more of M old PPB, the threshold is MBP.
It is sharper and clearer than without PB. For example, in the case of M old BA, when a voltage is applied to a cell with 12 electrodes apart, so-called dynamic scattering occurs, and the light transmittance changes slowly at a value of V of about 5 volts, and the saturation voltage Vth
is about 20 volts. At 2yo, when 20 volts are applied, the rise time exceeds 10 hs and the decay time exceeds 50 hs.

Examples of n-nematic liquid crystals include P-alkoxy P-n-alkylazoxybenzene, P-n-alkyl-P'-alkoxyazoxybenzene, P-alkoxyP'-alkoxyazoxybenzene, P-n-alkyl-P'- Alkoxyazobenzene, P-alkoxyP'-alkylazobenzene, P-alkoxyP
'-Alkoxyazobenzene, P-alkoxybenzylidene-P'-alkoxyaniline, P-n-alkylbenzylidene-P'-acyloxyaniline, P-alkylbenzylidene-P'-alkoxyaniline, P-alkoxybenzylidene-P '-n-alkylaniline,
P1n-alkyl-? - There are nematic liquid crystal compounds such as acyloxyazoxybenzene. Of course, some of these mixed liquid crystals are also n-nematic liquid crystals. (Example 3) n-nematic liquid crystal, P-methoxybenzylideso-P'
1n-butylaniline 7% by weight PPB
% Increase This liquid crystal has a rise when the temperature is 2 mm, the electrode spacing is 12 peaks, the applied AC voltage is 50 Hz, and a square wave is applied. Time 1 hsec
, the limit frequency fc is 100Hz.

When a rectangular wave alternating current of 600 Hz and 30 volts is applied, the erasing time is 10 hsec.

In addition to the above-mentioned P mixed cholesteric liquid crystal compositions and n-mixed cholesteric liquid crystal compositions, liquid crystals in which cholesteric liquid crystals made of cholesteric derivatives are added to each of these also have essentially the same electro-optical properties (see Fig. 1). As shown in Example 4, some of the cholesteric derivatives, such as cholesteric/nanoates, do not change the voltage (and the shape of the curve in FIG. 2) but lower the value voltage. Cholesteric liquid crystals made of cholesteric derivatives include, for example, 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, P1n-hexylbenzylidene-P
-cyanoaniline 6% by weight female PPB
Female amount %Cholesteric/N/Eight Weight of 1;% This liquid crystal exhibits the electro-optical characteristics shown in Figure 1, at a temperature of 30 cm, an electrode spacing of 6 mm, 250 Hz,
When square wave alternating current is applied, the threshold value Vth is 1 volt, the saturated fin pressure Vsat is 8 volts, and when the voltage is 10 volts, the rise time is 20 hshc, and the decay time is 50 hshc.
It is Sec.

As is clear from the above explanation, mixed cholesteric liquid crystal compositions with various properties can be obtained by adding various liquid crystal matrixes to MBPPB, but in order to further improve performance, it is possible to obtain compounds that are not the original liquid crystal. It can also be added to an extent that does not destroy the liquid crystal state.

For example, P-n-alkylbenzylidene-P'-n-alkylaniline lowers the solid-to-liquid crystal transition temperature,
This is effective in obtaining high-speed response characteristics. Additionally, an organic electrolyte may be added in order to obtain a suitable electrical conductivity. 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 transmission type display device was used, but it is well known that a reflection type display device can be obtained by using one electrode as a reflective surface. As is clear from the above description, the mixed cholesteric liquid crystal composition of the present invention has a clear threshold value, has a fast response speed, and is advantageous for multi-pixel display →
This realizes a x-Y matrix display device.
It also exhibits excellent performance even when used in ordinary electro-optical display devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the optical characteristics of a P-mixed cholesteric IJ liquid crystal composition, and FIG. 2 is a diagram showing the electro-optical characteristics of an n-mixed cholesteric liquid crystal composition. Momme 1 figure Fin 2 figure

Claims (1)

[Claims] 1. A mixed cholesteric liquid crystal composition comprising 2% to 80% by weight of (+)-β-methylbutyl-4-(Pn-pentyloxyphenyl)benzoate and a nematic liquid crystal compound.