JPS6251996B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention describes the use of nematic liquid crystal mixtures in electro-optical devices for the modulation of transmitted or reflected light or for the coloring or black and white display of numbers, symbols and moving or stationary figures. Concerning the application of

It is known that liquid crystal materials can be used for modulating light as well as for displaying measured values or reproducing information.
These methods are based on the fact that the preferred orientation in a thin layer of liquid crystal material can be changed by applying an electric field. This orientation change is associated with a change in optical behavior (birefringence, polarization, light absorption). Depending on the initial orientation, dielectric anisotropy, conductivity, dichroism and the strength and direction of the applied electric field, achieved by special pretreatment of the surrounding electrodes or by the addition of appropriate substances, Electro-optical effects are observed and used technically (M. Tobias: International Handbook of Liquid Crystal Displays 1975-1976, Obham Limited, London 1976, J. Meyer,
I, Satsukuman, Zei. J. Grubmeier:Associations Off Liquid Crystals Springer Fuerlag Berlin-
Heidelberg-New York 1975 [M.
tobias：International Handbook of Liquid
Crystal Displays 1975―1976, Ovum Ltd.
London 1976; G.Meier, E.Sackmann, JG
Grabmaier: Applications of Liquid Crystals,
Springer Verlag, Berlin-Heidelberg-New
York 1975]). For example, in one known method, by applying an electric field, a layer of a twisted structure loses its polarizing properties, so that transmission (annihilation) of the projected light is observed when placed between parallel (crossed) polarizers. Based on (M. Schat, V. Helfrich)
Applied Physics Letters [M.
Schadt, W. Helfrich: Applied Physics
Letters] Vol. 18, p. 127 [1971]).

Depending on the underlying electro-optical effect, the substances used must meet specific requirements: melting point well below room temperature (preferably below 0 °C), clearing temperature above 50 °C, low viscosity. , high chemical and thermal stability and durability under the action of sustained sunlight. Moreover, these materials must exhibit a certain (often as positive as possible) dielectric anisotropy and low electrical conductivity.
Pure substances that meet all these requirements simultaneously are not available. Mixtures of different substances, often including those belonging to different substance classes, are therefore used. However, there are limits to the possibilities of mixing, so it is not possible to combine arbitrary substances.

general formula (However, R ¹ and R ² may be the same substituent or different, such as CnH ₂ n ₊₁ ^- , CnH ₂ n ₊₁ O _- ,
CnH ₂ n ₊₁ COO− or CnH ₂ n ₊₁ CO _- )
It is known to use compounds of the homologous series of phenylpyrimidines in the production of electro-optical display tubes (H. Zaschke, H. Schubert, F. Kusiel, F. Deinger, De Dehms). H. Schubert, F. Kuschel, F.
Dinger, D. Demus]: East German General Purpose Patent No. 95892
issue). So, for example, the mixture Mi3 contains two components of this substance class, 5-n-hexyl-2-(4-n-
It consists of 68.5 mol% of hexyl-oxyphenyl)-pyrimidine and 31.5 mol% of 5-n-hexyl-2-(4-n-nonyloxyphenyl)-pyrimidine. This mixture has the following properties: melting point +
4℃, transparent temperature 6.0℃, dielectric constant anisotropy +0.7, voltage required for electric field effect applied to the twisted layer 10% - voltage
6.0V, 90% - voltage 8.2V, excitation time (25℃, layer thickness
After applying a voltage of 4 times the threshold voltage to the twisted layer at 25 μm) 170 ms and a decay time of 320 ms. Regarding the melting behavior and the required voltage for the electric field effect for the twisted layer, this mixture meets the usual requirements (thermodynamically stable). The melting point of the crystalline solid phase is preferably below 0℃, 10% -
voltage is less than 2V).

In addition, general formulas are used for manufacturing liquid crystal display devices. (However, R is -CmH2n+1, -OCmH2m+1,
It is known to use compounds of the homologous series of 4-substituted cyclohexanecarboxylic acids [4-substituted phenyl esters] of -COCmH2m+1, -CN or _-NO2 (c. J. Deutscher, F. Kussier, H. Schubert, Deutscher, F.
Kuschel, H. Schubert, D. Demus]: East German General Purpose Patent No. 105701). So, for example, the mixture Mi14 contains the three components of this substance class: 34.5 mol % 4-n-propyl-cyclohexanecarboxylic acid-[4-cyan-phenyl ester], 34.5 mol% 4-n-butyl-cyclohexanecarboxylic acid-[4-cyanide], Phenyl ester] 31 mol%, 4-n-pentyl-cyclohexanecarboxylic acid-[4cyanophenyl ester]
Consisting of 34.5 mol%.

This mixture has the following properties: melting point +12.5
~16℃, transparent temperature 72℃, dielectric constant anisotropy +
6.5, 10% - voltage 1.4 V, 90% - voltage 2.1 V, excitation time 115 ms, decay time 240 ms This mixture does not meet the above requirements regarding its melting point.

There is also a general formula for manufacturing display devices using liquid crystals. (However, R means CnH2n+1 ^- or CnH2n+1O-) Compounds in the homologous series of 4-substituted benzoic acid [4-cyanphenyl ester] can also be used (A. Bora, H. Schierer, M. Shat) ; Proceedings off the they.i.
stomach. stomach. [A. Boller, H. Scherrer, M. Schadt:
Proceedings of the JEEE] Volume 60, Page 1002 (1972), c. - Yotsuto. German Cheer, F.
Kuushiel, E. Bargenda, ha. Schubert, de. Demus [H.--J. Deutscher, F.
Kuschel, E. Bargenda, H. Schubert, D.
Demus]: East German General Purpose Patent No. 106120). For example, the mixture Mi16 consists of three components of this substance class and has the following composition: 4-n-hexyl-benzoic acid-[4-cyanphenyl ester] 36 mol%;
4-n-heptyl-benzoic acid-[4-cyan-phenyl ester] 37 mol%, 4-n-octyl-
Benzoic acid-[4-cyan-phenyl ester]27
Mol% This mixture has the following properties: Melting point: +13
°～21℃, transparent temperature: 53℃, dielectric constant anisotropy:
Approximately +20, 10% - voltage 1.7V, 90% - voltage 2.3V, excitation time: 420ms, decay time 600ms Although this mixture Mi16 has a high melting point and relatively advantageous dielectric properties, it is difficult to Use is not recommended.

The purpose of the present invention is to use materials for optoelectronic components that are chemically and thermally stable, have a melting point much lower than room temperature, a clearing point higher than 50° C., and require as low a voltage as possible. That's true.

The object of the invention is to find a mixture of liquid crystal substances which has a lower melting point and a lower voltage requirement than the respective components of the mixture.

For this task, each mixture component has a general formula (In the formula, n is 1 to 12.) One or more compounds among the congeners of 4-alkyl-cyclohexanecarboxylic acid-[4-cyan-phenyl ester] and the general formula (In the formula, n is 1 to 12.) One or more compounds of the congeners of 5-alkyl-2-(4-alkoxy-phenyl)-pyrimidine and/or the general formula (In the formula, n is 1 to 12). The liquid crystal mixture can be used in electro-optical devices for displaying numbers, symbols and images by modulation of transmitted or reflected light.

Example 1 A mixture is made with the following composition: Mi14 70 mol% 5-n-butyl-2-(4-n-heptyloxy phenyl)-pyrimidine 30 mol% This nematic mixture has the following properties: Melting point +1° ~ 3℃ Clearing temperature 58℃ 10% - Voltage 1.45V 90 - Voltage 2.2V Excitation time (25℃, layer thickness 20μ
After applying twice the voltage) 190ms Decay time 280ms Example 2 A mixture having a composition of 70 mol% Mi14 and 30 mol% Mi3 is prepared. This mixture has the following properties: Melting point: In microscopic specimens, no crystallization could be observed when the nematic mixture was kept at -20 DEG C. after 36 hours.

Clearing temperature: 60°C 10%-voltage: 1.6V 90%-voltage: 2.2V Excitation time: 150ms Decay time: 240ms The mixture obtained by mixing the phenylpyrimidine compounds corresponding to Example 1 and 2 The melting temperature range is significantly reduced compared to that of mixture Mi14 without adversely affecting the electro-optical properties.

Example 3 A mixture with a composition of 53 mol% Mi14 and 47 mol% Mi16 has the following properties: Melting point: -6° to 0°C Clearing temperature: 59°C 10%-voltage: 1.2V 90%-voltage: 1.9 V Excitation time: 310 ms Decay time: 450 ms In addition to the extension of the melting point temperature range to the lower end, the reduction in the voltage required for the electro-optic effect on the torsion layer offers particular practical advantages.

Example 4 0.4% of the dichroic dye Indophenol Brau is added to the mixture described in Example 4. The dye dissolves when the sample is heated. This mixture is used to make specimens with oriented, lying layers of 20 μm thickness between transparent conductive electrodes.

When transmitting white polarized light, this layer appears blue when the preferred direction of the nematic specimen is in the plane of polarization of the light. When an electric field (2V, 50Hz) is applied, the lying layers are reoriented in the direction of the field. The dye molecules dissolved in the nematic material are then also brought into a position parallel to the direction of field and light transmission with respect to the direction of maximum light absorption. The color changes from blue to colorless. This color change can be repeated any number of times depending on the situation.

Claims (1)

[Scope of Claims] 1. Nematic liquid crystal mixtures for electro-optical devices displaying numbers, symbols and images by modulation of transmitted or reflected light, according to the general formula (In the formula, n is 1 to 12.) One or more compounds among the congeners of 4-alkyl-cyclohexanecarboxylic acid-[4-cyan-phenyl ester] and the general formula (In the formula, n is 1 to 12.) One or more compounds among the congeners of 5-alkyl-2-(4-alkoxy-phenyl)-pyrimidine and/or the general formula (In the formula, n is 1 to 12) The above nematic liquid crystal mixture. 2. A nematic liquid crystal mixture according to claim 1, wherein said mixture is a mixture containing other liquid crystal- or non-liquid crystal substances, in particular pigments.