JPS6027707B2 - liquid crystal composition - Google Patents

Description

Detailed Description of the Invention: Electrodes are formed on opposing surfaces of two substrates, and a nematic liquid crystal material is filled between the electrodes to form a transparent thin layer, and light is incident on the nematic liquid crystal layer. It is known that when a voltage is applied between the electrodes, the liquid crystal layer in the area where the voltage is applied becomes cloudy and blocks transmitted light.

Using this phenomenon, light blocking devices that block light, or display devices that display characters, numbers, symbols, figures, etc., have been manufactured. In such liquid crystal devices, various additives are added to the nematic liquid crystal material in order to increase the degree of cloudiness of the nematic liquid crystal layer or to speed up the response speed. However, in liquid crystal compositions in which quaternary ammonium halogen salts or carponate salts are added to nematic liquid crystals, which have been commonly used in the past,
Temperature dependence of conductivity (ratio of conductivity to temperature change)
However, if the electrical conductivity required in the low temperature range is guaranteed, the power consumption in the room temperature range becomes large.

By the way, in order to create cloudiness, additives are added to the liquid crystal system, and the conductivity (current) of the liquid crystal system is calculated by dielectric constant x driving frequency.
It is necessary to set the value above a certain value determined by the value of .

and the temperature dependence of conductivity in general. =0. exp(1△E/K・T) Represented by Z. however
.

: Electrical conductivity at temperature ToK.

o: Electrical conductivity at temperature oK △E: Activation energy in temperature dependence (unit: eV)
Z K: Borckmann's constant T: Absolute temperature In the above conductivity equation, the minimum conductivity that effectively causes clouding in the liquid crystal system at 0°C by applying a certain voltage (25V, 60Hz) is approximately 10-100, Arc-
It is 1.

Further, the electrical conductivity 〇 at any temperature T above 0° C. becomes smaller as the activation energy ΔE in the temperature dependence of the electrical conductivity becomes smaller. Therefore, in a liquid crystal display system using a clouding phenomenon, a liquid crystal display device using a liquid crystal composition containing the additive of the present invention can save unnecessary power consumption. The present invention has been made in view of the above points.

That is, an object of the present invention is to provide a liquid crystal composition that has excellent response speed and degree of cloudiness, and also has low temperature dependence of conductivity (current). As a result of intensive research, the present inventor found that [salts of aromatic amines and 3,5-dinitrobenzoic acid] or [double ring or polycyclic double ring nitrogen-containing compounds and 3,5-dinitrobenzoic acid] At least one type of salt] is added to the liquid crystal material as an additive (the amount added is 0.05
Weight%~2. % by weight, more preferably from 0.1% by weight
1.0% by weight) was found to be excellent in the degree of cloudiness and response speed, as well as having a small temperature dependence of conductivity (current).

Aromatic amines have the following structural formula, and the substituents R and R2 bonded to nitrogen are -CQ
, one C2 & or one C3 day 7, R,, R2 may be the same or different.

Also, X, is day or one CH3, X2, X3 is day, one C
H3, 1C, 1Br or -N02. In order to improve the temperature dependence of current and the response characteristics of the liquid crystal composition described later, it is necessary to set X instead of X2 and X3 to the above-mentioned substituents. As described above, the structure of the aromatic amine, which is a component of the compound constituting the additive of the present invention, is clearly specified and recognized. A compound of an aromatic amine and 3,5-dinitrobenzoic acid forms a pale yellow or yellow salt with good crystallinity. On the other hand, pyridine or quinoline, which are heterocyclic or polyhedral compound nitrogen-containing compounds, also form pale yellow or white crystalline salts with 3,5-dinitrobenzoic acid. It is difficult to obtain sufficient electrical conductivity even if only aromatic amines or Enomoto Ringsha nitrogen compounds are added to liquid crystal materials, and addition of only 3,5-dinitrobenzoic acid causes problems in liquid crystal materials having azomethine groups. Promotes decomposition.

That is, a liquid crystal material having an azomethine group is R: alkyl group)
However, the CH═N moiety is easily decomposed by acids and alkali, while 3,5-dinitrobenzoic acid is weakly acidic and thus accelerates the decomposition of the liquid crystal material. but,
The salts of aromatic amines and 3,5-dinitrobenzoic acid, or the salts of double ring nitrogen-containing compounds and 3,5-dinitrobenzoic acid, which are additives according to the present invention, do not promote decomposition of liquid crystal substances. That is, since the additive of the present invention is a crystalline salt,
Does not promote decomposition of liquid crystal substances containing azomethine groups. Therefore, a liquid crystal composition is formed which has a sufficient clouding effect and whose conductivity is less dependent on temperature. Additionally, this additive is effective for all N-type nematic liquid crystal materials (negative dielectric anisotropy), such as azoxy compounds such as P-azoxyanisole, P-benthylphenyl 2-chloro-4- (P-phenylbenzoyloxy)
Good results can be obtained when added to ester compounds such as penzoate or Schiff compounds such as P-alkoxybenzylidene-P'-butylaniline.
Next, the present invention will be specifically explained with reference to Examples.

First, a synthesis example for forming the additive as described above will be shown.
{1) Salt of aromatic amine and 3,5-dinitrobenzoic acid.

Aniline, 0-toluidine, m-toluidine, P-toluidine, 0-chloroaniline, m-chloroaniline, p
-Chloroaniline, P-bromoaniline, m-nitroaniline, P-nitroaniline, N-methylaniline, N
, N-dimethylaniline, N-ethylaniline, N,N
- 0.01 mol of aromatic amine such as diethylaniline, N,N-dibropylaniline, etc. and 2.1 mol equivalent to this
Reaction of two days of 3,5-dinitrobenzoic acid in ethanol gives a pale or yellow crystalline salt.

They can be purified by the recrystallization method using ether/benzene as solvent. '2} A salt of a heterocyclic or polycyclic heterocyclic nitrogen-containing compound and 3,5-dinitrobenzoic acid.

When 0.01 mole of pyridine or quinoline and 0.01 mole (=2.12 moles) of 3,5-dinitrobenzoic acid are reacted in ethanol, a pale yellow or white crystalline salt is obtained.

They can be purified by the recrystallization method using ethyl/benzene as solvent. A liquid crystal mixture is prepared by adjusting various liquid crystal materials in the proportions shown in Table 1 below.

Table 1 The temperature range showing the nematic liquid crystal phase of the above liquid crystal mixture is -
The temperature is 16°C to 6°C.

Two glass plates with transparent electrodes made of indium oxide on their surfaces were prepared, and the two glass plates were placed in parallel with the transparent electrodes on the inside to create a transmission type liquid crystal cell with a distance of 201 m between the electrodes. do.

Next, the above liquid crystal mixture, a liquid crystal composition containing tetrabutylammonium bromide, which is an additive commonly used in the past, and various additives according to the present invention were added in various proportions to the above liquid crystal mixture. Fill the cell with a liquid crystal composition to form a transparent thin layer, and apply 60H between the transparent electrodes.
25V AC voltage is applied at Z, and the current flows during that time.
response. time. The results of determining the threshold voltage and light transmittance are shown in Table 2. In addition, the temperature dependence of current (conductivity) was determined in the same manner, and as a result, data as shown in Table 3 and the drawings were obtained. Here, the drawings show 3,5-dinitrobenzoate of tetrabutylammonium conventionally used in the liquid crystal mixture shown in Table 1 and 3,5-dinitrobenzoate of N,N-jethylaniline according to the present invention. Liquid crystal composition A. o benzoate or 3,5-dinitrobenzoate of pyridine added. B. 2 is a graph showing the temperature dependence of conductivity of C. 't2 However, a: No additive b: Tetrabutylammonium bromide c: N,N-
3-5-dinitrobenzoate of diethylaniline d: 3,5-dinitrobenzoate of pyridine'1): Addition amount (
Weight%) [2}: Threshold voltage (Vnns)
'3': Current (rA/) [4}: Transmittance (%) ■: Response speed (m sec) (51): Rise, (52): Fall Setting conditions 25V, 25℃, 60Hz, cell thickness 20 mountain m
Table 3: However, e: 3,5-dinite of tetrabutylammonium.

Benzoate c: 3,5-dinitrobenzoate of N,N-diethylaniline d: 3,5-dinitrobenzoate of pyridine (1}: Addition amount (mol/night) ■: Temperature (00) '3 ': Current (French A/) Measurement conditions 25V, 60Hz, cell thickness 20 m '7':
Conductivity (Hi, Sup-1) side: Rate of increase in current (current at 25oo/current at 0°C) '91: Activation energy of conductivity (
eV) If the DC component of the current J flowing here is Joc, and the AC component is JAc, then J is expressed as J2=Joc2+J^c2.

Also each J. c, 1^c are as follows. JDC=sha・
EJ^.

= Bones 2mfCV = 2汀f●Gosho・Edict.

: Electrical conductivity d: Liquid crystal layer thickness E: Electric field strength V: Applied voltage Z: Impedance f: Frequency C: Capacitance per unit of liquid crystal z: Dielectric constant of liquid crystal o: Dielectric constant (8.85 x 10-1 tsubo /m) As is clear from Table 2, 3,5-dinitrobenzoate of N,N-jethylaniline, which is an aromatic amine, or a double ring nitrogen-containing compound was added to the liquid crystal mixture shown in Table 1 above. By adding a certain 3,5-dinitrobenzoate of pyridine as an additive, the current value, transmittance, response speed, falling IJ time and threshold voltage of the liquid crystal composition can be changed by adding it as an additive, which is conventionally used. can be significantly improved compared to the case where .

Furthermore, as is clear from Table 3 and the drawings, compared to the conventional 3,5-dinitobenzoate of tetrabutylammonium, the additive of the present invention, 3,5-dinitobenzoate of aromatic amine or pyridine, By adding dinitrobenzoate, the temperature dependence of conductivity (current) can be reduced. That is, the equation for the temperature dependence of conductivity.

=0. ΔE at exp(-ΔE/k, T) can be lowered from 0.4 steps v to 0.31 eV compared to the conventional example.

Furthermore, as is clear from Table 3 when compared at 0 current value, the additive according to the present invention can reduce the temperature dependence of current by about 1/3 at 25 oo compared to the conventional example. can. That is, as shown in Table 3, the rate of increase in current (current at 2 C/current at 0 C) can be reduced to about 1/35. Even when the above results are compared with 3,5-dinitrobenzoate of tetraethylammonium as a secondary example, 3,5-dinitrobenzoate of tetrabutylammonium and 3,5-dinitrobenzoate of tetraethylammonium are compared.
Since the temperature characteristics and the like are almost the same as that of dinitroben 0zoate, the same results can be obtained. In addition, in the additive according to the present invention, the alkyl group of R, , R2 is CnH
It is expressed by R. , R2=CH3~C44
At a certain length, the effect as an additive is the same regardless of the value of n.

The fact that the temperature dependence of the current value is small in this way means that if the current value is set to 5.7 A/A when the minimum operating temperature is 0°C, it can be used in the high temperature range above 0°C, such as the conventional one of 25qC. At about 55〃A/(25V, 60Hz, cell thickness 20
m), but in the liquid crystal composition of the present invention, it is about 19 mA/
(25 V, 60 days 2, cell thickness 20 rm), which provides an extremely excellent effect of driving a liquid crystal display with low power consumption. As explained in detail above,
According to the present invention, the fall time of the response speed of the liquid crystal composition,
Transmittance and threshold voltage can be significantly improved compared to conventional ones, and the temperature dependence of current (conductivity) can be reduced, contributing to a reduction in power consumption.

[Brief explanation of the drawing]

The drawings show 3,5-dinitrobenzoate of tetrabutylasomonium (1.1×io-3 mol/s) conventionally used in the liquid crystal mixture shown in Table 1, N, according to the present invention,
3,5-dinitrobenzoate of N-jethylaniline (
1.1xlo-3 mol/so), 3,5-dinitobenzoate of pyridine (0.11 mol/so) is added to the liquid crystal compositions A, B, and C. It is a graph.

Claims (1)

[Claims] 1 The following structural formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [However, X_1 to X_3 are from the group of H, CH_3, Cl, Br, and NO_2 The selected ones, R_1 and R_2 are C
An alkyl group represented by nH_2_n_+_1 (n=1 to 3). A liquid crystal composition comprising a nematic liquid crystal material having negative dielectric anisotropy containing at least one of the compounds represented by the following as an additive.