DD137117B1 - NEMATIC CRYSTALLINE-LIQUID SUBSTANCES - Google Patents

Description

Nematic crystalline-liquid substances Field of application of the invention

The invention relates to the use of nematic crystalline liquid substances in electro-optical arrangements for the modulation of the transmitted or incident light, in particular for the color reproduction of numbers, characters and images.

Characteristic of the known technical solutions

It is known that with the help of an electric field, the preferential orientation of crystalline crystalline liquid substances can be changed. This orientation change can be used in various ways for light modulation, especially for colored numeric and character representation and image reproduction. A known method is based homopropically orient nematic crystalline liquid substances with negative anisotropy of the dielectric constant between two glass panes, which have been provided with a transparent, electrically conductive coating (N-layer). If this arrangement is placed between two crossed polarizers, it appears after applying a

electric voltage the continuous or reflected light in color ("DAP effect" ') / M.P. Schiekel, K. Fahrenschon: Applied Physics Letters 19.391 (1971) / ·

Another known method is based on orienting a nematic liquid with positive dielectric constant anisotropy such that the longitudinal axes of the molecules are arranged on average in a direction parallel to the enclosing electrodes (P-layer). If this P layer is placed diagonally between crossed polarizers and an electrical voltage is applied to the electrodes, the color of the transmitted or reflected light can be controlled with the aid of the voltage ("DP effect") / H. Zaschke, H. Schubert , F. Kuschel, F. Dinger, D. Deraus: DDR , TP 95 892 /.

Both methods require the use of two polarizers, whereby part of the incident light is lost due to absorption. Eeondere special technological difficulties arise in both methods in that the layer thicknesses must be kept constant within very narrow limits (about - 1, to). In addition, the observed interference colors are usually very sensitive to fluctuations in the applied voltage and the temperature,

These disadvantages can be partially avoided by a likewise already known method. Electro-optical cells with twisted nematic or cholesteric layers of weak twist serve for the colored modulation of the light. To the crystalline liquid with the highest possible positive dielectric anisotropy is added to a suitable dye in the form of a non-crystalline liquid or a nematic, smectic or cholesteric compound. Between crossed polarizers, these cells result in transmitted or incident light

Light and after application of an electric field extinction / P. Kuschel, D. Demus, G. Pelzl: GDR WP 116 116 /. Although the layer thickness and voltage dependence of the color produced can be greatly reduced with this method, the disadvantage resulting from the use of two polarization filters is maintained.

There is also known a method which allows the color light modulation with a liquid crystal cell using only one polarizer. This process, which relies on the guest-host effect / G.H. Heilmeier, L. A. Zanoni: Applied Physics Letters 1_3_, 91 (1968) /, uses a dye with positive dichroism, which is dissolved in a nematic liquid. If this crystalline-liquid mixture has a positive dielectric anisotropy, then a P-layer is produced therefrom. This P-layer appears colored in the polarized light when the direction of the transition moment of the intercalated dye molecules coincides with the direction of oscillation of the light. After switching on an electrical voltage then a change from colored to pale colored or colorless is observed. For visual reasons, it is more advantageous if the crystalline-liquid mixture has a negative dielectric anisotropy and is based on an N-layer. Then this layer appears colorless or slightly colored in the de-energized state; On the other hand, it becomes colored when it is uniformly reoriented by an electric field. The goal to produce an electro-optical arrangement in which the electrically driven areas (numerals, letters, etc.) are strongly colored and stand out in contrast to their field-free environment, eich also with this method can not or only partially reach. Daa is due to the fact that the known nematic liquids suitable for

with negative anisotropy require too high operating voltages (10 V and more). On. Another disadvantage of the known method for the colored modulation of light is that the dyes used in the nematic liquid are often poorly soluble. In these cases, only weak color contrasts are achieved. In addition, there is a risk that the dye crystallized at lower operating temperatures. Furthermore, the light fastness of the previously used dyes is insufficient, so that the color contrasts decrease with increasing operating time.

Object of the invention

The object of the invention are electro-optical arrangements for the modulation of the transmitted or incident light as well as for the reproduction of numbers, characters and images, which provide strong color contrasts at low operating voltages and low operating temperatures.

Explanation of the essence of the invention;

The object of the invention consists in the use of new nematic crystalline-liquid substances which have a high chemical and thermal stability, a strong intrinsic coloration and a pronounced dichroism in the visible spectral region, sufficiently high clearing points at sufficiently low melting temperatures, and good lightfastness.

It has been found that nematic crystalline liquid substances of the general formulas

Such as

where R ¹ = Br, Cl-, C _n H _{2n + 1} -, Cj ₁ H _{2n + 1} O- where n * 1 to 10,

R ^{2 c} _n ^H 2n + i " ^{with n a 2 to}

^{r3 s C} n ^E 2n + 1- » ^C n ^H 2n-H ° ->» itη = 1 to 10, R ⁴ . C _n H _{2n + 1} -, C _n H _{2n + 1} O- with η. 1 to 10,

3 4 where R ^ and R are different,

mean, can be used in electro-optical arrangements for the modulation of the transmitted or incident light as well as the reproduction of numbers, characters and images. The substances have a high chemical and thermal stability, a strong intrinsic color and a pronounced dichroism in the visible spectral range, sufficiently high clearing points at sufficiently low melting temperatures and good lightness.

By producing mixtures of several of these substances or of these substances and other crystalline liquid compounds, the melting points can still be lowered and the operating temperature ranges can be increased considerably. The conversion temperatures of substances according to the invention are given in Tables 1 and 2 below. In the tables: K = crystal-solid state; S = smectic modification; N = nematic modification; I = isotropic-liquid state. Pips under these symbols indicate the existence of the modification in question; Dashes indicate the lack of modification. Bracketed indications designate conversions in the unstable area. The conversion temperatures are given in degrees Celsius.

The synthesis of the substances according to the invention can be carried out according to the following reaction schemes:

A. 3- (4-Substiphenyl) -b-n-alkyl-1,2,4,5-tetrazines variant 1:

P ¹

% Н »НС1 \ N ₂ H ₄ ^ H ₂ O

R ² -Cf -HCl ^ ^НН

I ₂ NaNO ₂ /

Acetic acid ^ -R ²

Variant 2:

W-NH

2 P ⁴ X

(X = Cl,, NH-

 "V.

Il 0

PCI,

I Cl Cl

N ₂ H ₄ -H ₂ O

N-N

V-R

I ί H H

NaNOp / acetic acid

⁴ N = N

For example, 3,6-bis (4-subst-phenyl) -1,2,4,5-tetrazines

^HC1

H ₂ O

N ₂ H ₄ -HO /

R чон / r (o) -R

⁴ N-N '

I i

H H

HCl

NaNOp / acetic acid

3- (4-n-alkyloxy-phenyl) -6- (4-substituted phenyl) -

1,2,4,5-tetrazines, OC ₂ H ₁ ,

NH

N ₂ HH ₂ O

NH ₂

HCl

N-N

H H

NaNOp / acetic acid

N-N,

N-N I I H H

table

, N-N

No.

R ¹

1/1 1/2 ° 6 ^Н 13 C ₇ H ₁₅ ° 5 ^Н 11 41. 55 ¹⁾ (. 27) - м » mm _# 59.5. 1/3 1/4 1/5 C ₄ H ₉ O ^С 4Ѵ ° 6 ^Н 13 ° 7 ^Н 15 с ₄ н ₉ 49 47. 48 ³ > (.43). , 49 57 62 1/6 1/7 C ₅ H ₁₁ O ° 5 ^Н 11 ^С 6 ^Н 13 60. 65 - - (. 59.5) ² } 58.5) 4 1.8 C ₅ H ₁₁ O O ₇ H ₁₅ 49 , 52.5. 63 1/9 1/10 ^С 6 ^Н 13 ° C ₅ H ₁₁ C ₇ H ₁₅ 55 58 , 68. 74 ⁴⁾ . 76

'Melting of an unstable solid modification at 53.5 ⁰ C.

Monotropic nematic

Melting of an unstable solid modification at 43 C

^ 'In the smectic range at 65 - 68 ⁰ C a conversion is observed

Table 2

-R *

R '

в:

2.18 с ₄ н ₉ 0 ^С 8 ^Н 1 7 - 127 2.19 ^C 6 ^H 1 3 ° C ₉ H ₁ 9 , 119 2/20 C ₇ H ₁ 5 ° H , 107 2.21 C ₇ H ₁ 5 ° ОН , 213 2.22 ^С 8 ^Н 1 7 ° H • 128 2.23 ^С 8 ^Н 1 7 ° ^С 8 ^Н 1 7 , 126

, 132.5. 180. 153.5 ♦ 175

161

• 128.5

131

, 172.5

EXAMPLES

Example 1:

3- (4-Substiphenyl) -6-n-alkyl-1,2,4,5-tetrazines (variant 1)

In a three-necked flask equipped with thermometer, stirrer and deetillation attachment 0.03 mol of N-alkanoyl-N '- [faith t-benzoyl] -hydrazine mixed with 20 g (0.09 mol) of PCIc and in vacuo and with stirring to 140 ⁰ C heated.

The reaction mixture liquefies and POCl-, and distilled off. The reaction is over when no POCl., More arises. Each cooling the flask contents are taken up in ether and cautiously added with ice cooling. Thereafter, the ether extract is washed with water and bicarbonate solution, over Na ₂ SO. dried and the solvent removed on a rotary evaporator. The 1,4-dichloro-1- [4-substituted-phenyl] -4-alkylazines are obtained in yellow-brown oils and are further processed as crude products.

The oil is suspended in 50 to 80 ml of absolute ethyl alcohol, and - 5 ⁰ C cooled. Then add enough ether to make a clear solution (about 20 ml). While stirring, 4 g of 80% hydrazine hydrate in 20 ml of ethyl alcohol are added dropwise so that the temperature does not exceed 0 ⁰ C. Thereafter, the mixture is stirred for 2 hours at room temperature. The resulting Dihydrotetrazin is filtered off and oxidized with NaNO ₂ / acetic acid to tetrazine. The product is purified by recrystallization or column chromatography. Yield: 10 - 20 % d. Th

Example 2:

3- (4-Substiphenyl) -6-n-alkyl-1,2,4,5-tetrazines (variant 2)

0.005 mol of 4-Subst.-benzimidoester hydrochloride, 0.015 mol of amidine hydrochloride and 10 - 30 ml of hydrazine hydrate (80%) are stirred for 2-5 hours at room temperature. Thereafter, the contents of the flask are poured into water, the precipitate is filtered off with suction and washed

 The precipitate is suspended in 30 - 40 ml of 10% NaNOp solution, covered with 70 ml of ether and oxidized with stirring with small portions of 10% acetic acid to tetrazine.

The ether extract is washed with NagSO. dried and the solvent removed on a rotary evaporator. The residue can be purified by chromatography on silica gel, using methylene chloride as the eluent. Yield: 20 - 50 % d. Th.

Example 3:

3,6-bis- (4-subs t -phenyl) -1,2,4,5-tetrazine

0.02 mol of 4-Subst.-benzimidoester hydrochloride are heated with 10 g of 85% hydrazine hydrate for 1 hour on the 7 / asserbad. After cooling, the yellow KristsllmasGe of the substituted dihydro-s-tetrazine is filtered off with suction and washed with ether.

The precipitate is suspended in 30-40 ml of 10% strength NaNO.sub.p solution, covered with 70 ml of ether and, with stirring, with small portions of 10% strength acetic acid, oxidized to give s-tetrazine. The formed tetrazine dissolves in ether. The oxidation is complete when the yellow starting material is consumed. The etheric phase is separated, with

Washed water, with HapSO. dried and then distilled off the solvent on a rotary evaporator. The residue is recrystallized from dioxane or ethyl alcohol / dioxane (7: 1). Yield: 40-70 % d. Th.

Example 4:

3- (4 ~ n-alkyloxy-phenyl) -6- (4-substituted phenyl) -1,2,4,5-tetrazines

0.005 mol of 4-n-alkyloxybenzimidoester hydrochloride, 0.015 4-Subst.-Benzamidine hydrochloride and 8 ml of 80% hydrazine hydrate are stirred for 3 hours on the water at 80 G and allowed to stand overnight. The precipitate is filtered off with suction and washed with water and ether. For oxidation, the precipitate (dihydro-s-tetrazine) is suspended in 30-40 ml of 10 $ sodium nitrite solution, covered with 70 ml of ether and treated with small portions of 10% acetic acid with stirring. The oxidation is complete when the yellow starting material is consumed and the tetrazines are dissolved in the ether.

The ethereal phase is separated, washed with water, with NagSO. dried and the solvent distilled off on a rotary evaporator. The residue is chromatographed on silica gel (0.05-0.2 mm particle size, Merck) with benzene / cyclohexane (1: 1). On a separation column of dimension 100 χ 3 cm is a complete separation of the resulting 3 tetrazines.

The yield of asymmetric tetrazine is 10 - 50% d. Th.

Example 5:

Of the substance no. 2/18 an approximately 10 ) xm thick oriented layer (P-layer) is produced between transparent, electrically conductive electrodes. When irradiated with white, polarized light, this layer appears slightly yellowish colored, if the direction of vibration of the light coincides with the preferred direction of the P-layer. After applying an electrical voltage of 15 V at 163 ⁰ C, a reorientation of the layer, which is then intensively colored red-violet. The switching can be repeated as often as desired.

Example 6:

Of the substance no. 1/4, a P-layer is prepared analogously to Example 5. This layer appears colorless without an electric field when the direction of oscillation of the incident polarized light coincides with the preferential direction of the P-layer. If an electrical voltage of 15 V is applied at 56 ^° C., the layer is colored red-violet after reorientation. The switch-on time is 30 ms, the switch-off time 90 ms. A color change from pale pink to red-violet and vice versa can also be observed in white, unpolarized light. If a green filter is switched on in the beam path, a change from light green to black occurs after the application of an electric field.

Example 7:

Ea a mixture of the following composition is prepared;

4-n-propyl-cyclohexanecarboxylic acid

- [4-cyanophenyl ester] 25.5 mol%

4-n-Butyl-cyclohexanecarboxylic acid

- [4-cyanophenyl ester] 24 mol%

4-n-pentyl-cyclohexane carboxylic acid

- [4-cyanophenyl ester] 25 »5 mol%

Substance No. 1/4 25 mol%

This Subsitanzmischung is nematic and red colored at room temperature. It shows a negative dichroism. From the mixture wii-d between transparent electrodes, an approximately 20 ^ m thick P-layer is produced. In the white, linearly polarized light whose direction of vibration coincides with the preferential direction of the P-axis, the transmitted or reflected light appears pale pink in color. When switching on an electrical voltage of 3 V, an intense red color appears. This arrangement was exposed to daylight for 600 hours.

Compared to the original state, no change in absorbance could be seen in the visible spectral range.

Example 8:

In the mixture according to Example 7, 0.9 wt .-% of the yellow dye "Wolfen 6", the following chemical

Constitution possesses

and having a positive dichroism. A P-layer prepared by this mixture appears yellow in the transmitted or reflected light when the preferential direction of the P-layer and the vibration direction of the irradiated polarized light coincide. After switching on an electrical voltage of 3 V (50 Hz), a color change to red occurs. Fig. 1 'shows the dependence of the permeability of a cell filled with this mixture on the wavelength at 20 μm layer thickness:

1- in the field-free state,

2- after applying 1.2V AC, 3- after applying 1.5V AC,

4- after application of 3.0 V AC voltage,

5- after applying 10 V AC.

Example 9:

In the mixture according to Example 8 additionally 0.4 wt .-% indophenol blue are dissolved. Indophenol blue is a dye with positive dichroism. From the mixture thus obtained, a 20μm thick P-layer is prepared, while the preference of this layer and the direction of oscillation of the incident polarized light agree, the read or reflected light appears green. After switching on an alternating voltage of 3 V, the layer is colored red.

Claims (2)

invention claim 1. Application of crystalline liquid substances on the Baaia of derivatives of tetrazine for electrooptic arrangements for the modulation of the transmitted or incident light and for the reproduction of numbers, characters and images, characterized in that substances of the general formulas where R ¹ = Br-, Cl-, tO with η = 1 to 10, R ² - C _n H _{2n + 1} with η = 2 to 10, ° η ^Η 2η ₊ Γ '° n ^H 2n ₊ 1 ° - with η = 1 to 10, ^С п ^Н 2п ₊ Г' ^С п ^Н 2p ₊ 1 ° - with η = 1 to 10 _s where R and R are different . be used. 2. Application of crystalline liquid substances according to item 1, characterized in that the substances of the general formulas 1 ул / ß ~ K \ ?
R ~ Of ⁴ V ^{R as well} For this 1 page drawings