DE2920730A1 - LIQUID CRYSTAL SYSTEMS AND ELECTRO-OPTICAL DISPLAYS - Google Patents

Description

The invention relates to combinations of pleochroism N-substituted cyclic derivatives of mono- or diaminoanthraquinones with dielectrically positive nematic liquid crystals as well as electro-optical display systems in which these combinations are used.

Electro-optic devices using liquid crystals usually have two transparent flat plates of very thin thin transparent electrodes on their inward-facing surfaces that are a few microns to a few 10 microns apart and include a liquid crystalline material. These panels are shown below referred to as the container wall. When an electric field acts on the liquid crystal, these change optical properties of the liquid crystal layer.

In Heilmeier and Zanoni, Applied Physics Letters, Vol. 13, Pp. 91-92 (1968) describes that when combining pleochroic dyes with nematic liquid crystals in such a device the pleochroism

25 colors of the dye when the

electric field occur. Here the nematic liquid is called the "host" (host) and the pleochroic one Dye designated as "guest" so that there is a guesthost combination. Such systems are in the U.S. Patents 3,551,026, 3,597,044 and 3,960,751 used in the manufacture of electro-optical displays.

So an electro-optical device with nematic liquid crystals can be operated, the liquid crystal must have an oriented structure determined by the direction the applied electric field is influenced. Fluid-

909848/0789

Crystals (mesomorphic substances) usually have rod-like molecules. When the long axes of the liquid crystals are perpendicular are aligned to the container walls, one speaks of a homeotropic structure. Are the long axes of the liquid crystal on the other hand aligned parallel to the container walls, one speaks of a homogeneous structure due to the homogeneous boundary conditions. When two homogeneously orienting walls' at right angles to the orientation lines a twisted nematic liquid-crystalline structure is obtained.

Many nematic liquid crystals can be converted to a cholesteric phase by making a soluble optically active one nematic liquid crystalline material as dopant or a chiral compound, e.g.

(-) CH-, CH _O CHCH ^ O ^CH 3

'

(-) CH ₃ CH ₂ CHCH ₂ CH ₂ CH
CH,

the alkyl radicals being optically active amyl and heptyl groups are, clogs. In these cases the helix axis is the cholesteric one Phase homeotropically or homogeneously oriented.

Homogeneous boundary conditions can be achieved in various known ways, for example by

1. Rubbing, e.g. with an aqueous suspension of very fine Zirkonox: .d, in one direction; See U.S. Patent 3,694,053;

2. mechanical surface scribing or deformation; see D.W. Bergman, Phys. Rev. Lett., Vol. 28, p. 1683 (1972)

3. Separation of organic materials, e.g. trimethoxy

silane R-Si (OCH -) -. and then rubbing; see. F.J. Kahn, Appl. Phys. Lett., Vol. 22, p. 11 (1973) and Appl. Phys. Lett., Vol. 22, p. 386 (1973);

909848/0789

ORIGINAL INSPECTED

4. Deposition of inorganic materials, e.g. metal oxides or MgF, which are at an angle of 1-30 to the coated Surface are vapor-deposited [cf. J.L. Janning, Appl. Phys. Lett., Vol. 21, p. 173 (1972)] or at an angle of

5 more than 30 are deposited and then rubbed.

Homeotropic boundary conditions are generally of less importance Interest and are obtained e.g. by coating with metal oxides at an angle well above 30 ° or by treatment with surfactants.

Positive dielectric anisotropy occurs in liquid crystals that move lengthways when a field is applied relay a message. These compounds are of particular interest for the guest-host combinations according to the invention. In general it is only necessary that the overall effect correspond to a positive dielectric aniostropy so that the liquid crystalline host component in a high percentage made of negatively dielectrically anisotropic materials

20 and a smaller proportion of strongly positive dielectrically anisotropic materials.

Numerous pleochroism that can be used in the guest-host combinations Dyes usually also have molecules stretched in one direction, with little along their longitudinal axis or no absorption occurs and absorbs light from different regions of the visible spectrum along the short axis will. Other pleochroic dyes can align in opposite directions and are along the short axis

³⁰ colorless, colored along the longitudinal axis.

When combined with nematic liquid crystals with homeotropic structure, i.e. molecules perpendicular to the container wall, the former type of pleochroism aligns its molecules with those of the liquid crystal and it is no color visible until an electric field is applied.

909848/0780

~ '^ 7- 292073Q If the same pleochroic dye is combined with a nematic liquid crystal with a twisted structure, then align the molecules are parallel to the container walls and progressively at right angles, so that the combination is colored appears until an electric field is applied.

By combining the two types of pleochroism, devices are possible in which one color is converted into one other converts. Another effect can be achieved by using an isotropic, i.e. non-pleochroic Dye, combined with a pleochroism dye, so that the colors of both dyes are in one state add and the isotropic dye emerges in the other state of the field cycle.

So that a cycle between colorless and colored or between two colors is obtained in a certain device, the dye must be used in amounts which can be aligned by the nematic liquid crystal, i.

not in excess of the proportion of the quantity available Amount of liquid crystal can be aligned. This amount is usually up to about 5 percent by weight. In some Cases, the solubility of the pleochroism dye in the liquid crystal is insufficient to contain concentrations above 1 to achieve up to 5 percent by weight. Known combinations enable contrasts from 0 to the maximum electric field from about 2: 1 to about 4: 1. The object of the invention is to achieve greater solubilities and higher contrasts.

The invention relates to pie ochroic dyes of the general formula which can be used for guest-host combinations

(NRR ¹ ) _m 35 "<> ^ S. YV ss Qx

909848/0789

ORIGINAL INSPECTED

292073Q

* in which the substituents (NRR ¹ } and Q can be in positions 1 to 8 and the symbols have the following meanings:

Q = F, Cl, -NO ₂ , -NH ₂ . . · '/ -NH (AIk) or -OH; X = 0, 1, 2 or 3;
m = 1 or 2;

R = H;

R ¹ = cyclohexyl, bicyclohexyl or - (CH ₉ ) Ar?

ζ Ρ

whereby:

p = 0, 1 or 2;
Ar = aryl with 6 to 10 carbon atoms, which is represented in the 4 -position by -KHCOCH ₃ , -CN, ~ ^c _n ^H _2n + i '

-OC H, cyclohexyl,

4-alkfcyclohexyl or -Y - \ - / ~~ ^z , (where y = 0 or 1; Y = -CH ₃ -, -0-, -S- or ^Z = ^H '- ^N V ~ ^CN ' - ^C n ^H 2n ₊ 1 '- ° ^C n ^H 2n ₊ 1' ^F ' ^C1 or, if y = 0, also -C _fi H_)

and in 0 to 2 other positions by -CN,

-CH _n _, -OC H "^, -NH" or -OH is substituted; η 2η + 1 η 2η + 1 2.

η = 1 to 20 and
Alk = alkyl with 1 to 8 carbon atoms.

These substituted anthraquinones are particularly suitable for guest-host combinations with positive dielectrically anisotropic nematic compounds or mixtures, such as n-pentylphenyl cyclohexyl cyanide or p-heptyl-4-cyanodiphenyl or mixtures, which mainly contain these compounds, i.e. result in a positive dielectric net anisotropy. Under positive In the following, anisotropy is understood to mean a positive dielectric anisotropy. The compounds according to the invention can be used either alone or as combinations in up to equimolar amounts Proportions with the nematic compounds can be applied to achieve contrast ratios of up to about 20: 1 or to get about it.

The pleochroic dyes of the invention result in addition, an extremely high value for the optimal

see size parameter S. This parameter is a measure of the degree of orientation of a dye. It is determined by taking the light absorption as the reciprocal value of the percent permeability at ^ through a liquid crystal solution of the dye, which is located between electrode-coated plates in a cell, in the presence or absence of an electric field. The parameter S is calculated using the following formula:

10 Ä

Here, A ₁ and A denote the absorption in the presence and absence of a field, respectively. S is specified as a decimal number with a value below 1. Depending on each

^ 5 nematic liquid crystal used as the host component S can change somewhat for a given dye. Known pleochroic dyes give S values of about 0.3 up to 0.5. The dyes according to the invention allow S values of 0.5 and above, preferred compounds 0.7 and above. In the case of particularly suitable compounds, values of 0.9 and above are found. Such high values were after State of the art not to be expected.

The unusual properties of the pleochroism according to the invention Dyes make them suitable for combinations with nematic liquid crystals of positive net anisotropy, which can be used in display systems for computers, clocks, etc. They can also be used as electronic shutters for devices such as cameras or projectors, and for Spie-3Q Gel arrangement to be used, which is based on reflection can be switched transparently and are suitable for cameras or other mirror systems.

In the drawing show:

1 shows in cross section an electro-optical valve device, in the guest hdst combinations with the invention

009848/0780

appropriate pfeochroitisehen dyes are used? 2 shows, in cross section, a homeotropic guest-host combination of the invention in the idle state with no voltage applied; FIG. 3 shows the homeotropic guest-host combination of FIG. 2 with applied voltage; FIG.

4 and 5> guest-host combinations of homogeneously positive anisotropic nematic liquid crystals and dyes according to the invention with or without applied voltage;
6, 7 and 8 show the combinations of FIGS. 4 and 5, but with a right-angled cell wall orientation so that twisted nematic liquid crystals are present. In Fig. 6 no voltage is applied, in Figs. 7 and 8 a voltage;

Figures 9, 10 and 11 are transmittance curves of 5 percent solutions of 1,5-bis- (4-cyclohexylphenyl) -anthraquinone _# 1-methylamino-2-undecyl-4- (4-octylanilino) -anthraquinone and 1,4-bis, respectively - (4-phenylanillno) anthraquinone; Fig. 12 Comparative curves showing the decrease in optical density with an increase in the applied voltage.

In Fig. 1, a cell 8 is shown with walls 12 and 14, which on the inside with conductive coatings 16 made of tin and / or coated with indium oxide and a guest-host combination 18 made of a positively anisotropic nematic liquid crystal and a pleochroic dye. The cell 8 is between the light source 10 and the observer 24 together with a polarizer 28 and optionally

30 arranged in an analyzer 26. Cell 8 is with a

DC power source 20, e.g., a battery, but other power sources can be used. The power source is connected to the coatings 16 of the cell via a switch 22 connected.

909848/0789

ORIGINAL INSPECTED

2 and 3 show an enlarged view of the end of the cell 8 with a graphic representation of the molecules of the nematic liquid crystalline material 30 and the dissolved pleochroic dye 40. The cell walls of Figs have been treated as described above so that a homeotropic orientation occurs when, as in FIG Voltage is applied, and molecules 30 and -40 move in Align right angles to the walls.

The cell of Figures 4 and 5 is shown in front view. The inner cell walls are made of tin and / or coated Indium oxide with MgF "has been oriented at a small angle in a parallel arrangement. The orientation of FIG. 4 (no applied voltage) changes when a voltage of about 5 volts is applied and molecules 30 and 40 align, as shown in Fig. 5, in the field.

Figures 6, 7 and 8 show the behavior in a cell with a twisted orientation. The cell walls are like the ones 4 and 5, however, without voltage being applied, the orientation on the rear wall takes place in the vertical direction and on the front wall in the horizontal direction. When a voltage is applied in FIGS. 7 and 8, the orientate themselves Molecules with the field. In Fig. 6, a portion of the cell and the contents are cut away for orientation on the rear Wall to show.

To produce the guest-host combinations according to the invention it is necessary to use dielectrically positive anisotropic nematic compounds or mixtures. Specific examples for such compounds are given below together with the temperature at which the conversion from crystalline to nematic State (C-W) or »from nematic to isotropic state (N- * I), compiled:

9O9848 / G780

Table I.

N-p-m-hexylbenzylidene-p'-aminobenzonitrile

N-p - [(p-Methoxybenzylidene) amino] benzonitrile

N-p - [(Ethoxybenzylidene) amino] benzonitrile

N-p -cyanobenzylidene-p'-n-butoxyaniline

N-p-cyanobenzylidene-p'-octyloxyaniline

* Converting smectic to nematic. 15th

Other useful positive anisotropic nematic liquid crystals are the compounds

ON N- * I ( ⁰ C) - 51.5-52.5 105 125 106 118 70 93 83 * 107

-CN, 20

where R = alkyl or alkoxy with 1 to 7 carbon atoms and X »alkyl or alkoxy with 1 to 9 carbon atoms.

Eutectic mixtures and combinations of the above 25

compounds mentioned can be used. Special eutectic mixtures of 4'-substituted 4-cyano-4'-alkyl Diphenylenes are listed in Table II.

909848/0789

Table II

4 ¹ - substituent compound

(Mol%) c- »N nC _c H ,, 59 ~

3 37.5 41

^nC 7 ^H ll 10

^nC 5 ^H ll ° 15th ^nC 7 ^H 15 ° 13th HC ₈ H ₁₇ O 17th HC ₇ H ₁₇ 36 nC ₃ H _? O 18th HC ₅ H ₁₁ O 15th HC ₇ H ₁₅ O - 12th HC ₈ H ₁ O 12th

O 57.5

25 The above compounds with positive anisotropy can for example together with the specific examples of nematic liquid crystals given in Table III negative. anisotropy can be applied.

^L 909848/0780 -J

Table III

N-p-methoxybenzylidene-p * -n-butylaniline

ρ- [N- (p-methoxybenzylidene) amino] phenyl benzoate

N-p-methoxybenzylidene-p'-aminophenyl acetate

ρ-Az oxyani sol

p-n-Butylbenzoic acid p'-n-hexyloxyphenyl ester

butyl p- (p'-ethoxyphenoxycarbonyl) phenylcarboxylate

p- (p ¹ -ethoxyphenylazo) phenylheptanoate

p- (p'-ethoxyphenylazo) phenyl undecylenate 64 p-methoxybenzylidene-p'-butylaniline

N- (p-butyloxybenzylidene) -p'-pentylaniline

p-Ethoxybenzylidene-p'-n-butylaniline

C- * N HI ( ⁰ C) 19th 45 120 166 79 102 119 133 56 87 73 127 73 127 64 107 20th 44.5 41 80 38 78-9

Special compounds have the formula

and

where R and R denote C1-alkyl radicals;

where R is a C., ₇ -alkyl radical and R is a C. ^ - alkoxy radical or R is a C, "-alkoxy radical and R is a C,.

909848/0780

'45 -

where R and R C are --alkoxy radicals and a or b or Are hydrogen atoms or one is a chlorine atom;

where R is an alkyl or alkoxy radical having 1 to 10 carbon atoms is, as well as eutectic mixtures of these compounds.

When nematic compounds from Table III are combined with those from Table I or II, the combinations must have a positive net anisotropy. This can be achieved by using only a relatively low percentage Proportions of materials with high positive anisotropy sets in when the other materials have a relatively low have negative anisotropy. Examples of such combinations are combinations A and B in Table IV, both of which are nematic from at least -10 to +50 C.

Table IV

AWAY (%)

N-p-methoxybenzylidene-p'-n-butylaniline 57.3 51 N-p-Ethoxybenzylidene-p'-n-butylaniline 32.7 29

and
Np-hexylbenzylidene-p'-aminobenzonitrile 10, O 2O

A commercially available nematic liquid crystalline

Mixture contains about

13.9%. n-Pentylphenylcyclohexyldiphenylcyanide 26, ΐ%. n-propylphenylcyclohexyl cyanide

35.9% n-pentylphenylcyclohexyl cyanide 35 24.1%. n-heptylphenylcyclohexyl cyanide.

909848/0789

ORIGINAL

-ie -

Those used in the guest-host combinations according to the invention N-substituted aminoanthraquinones in which R = H are converted by methods known per se made by groups of anthraquinone molecules. Some of these reactions are illustrated in the following examples. In the examples, the melting points are measured with an electrothermal Kahn melting point device in a capillary tube on a heated block under use using an NBS calibrated thermometer (not corrected).

example 1

5 parts of 1,5-dichloroanthraquinone become 20 parts of 4-amino-1-cyclohexyl benzene given containing 5 parts of sodium acetate and 0.1 part of copper metal. The mixture is 2 hours heated to reflux with stirring to form a light red slurry which is cooled and washed with petroleum ether is mixed. The deposited 1,5-bis- (4-cyclohexylpheny 1) -anthraquinone is recrystallized as a dark red powder

20 sated.

10 mg of the bis (1,5-eyelohexylphenyl) anthraquinone obtained are heated gently in 1.0 g of a mixture of n-pentyl, n-propyl and n-heptylphenylcyclohexyl cyanide (35.9; 36.1 and 24.1%, respectively) in 13.9% n-pentylphenylcyclohexyldiphenyl anide solved, which has a positive dielectric anisotropy.

In order to determine the optical S-parameter of the received guest-host combination, a cell is used for the orientation of the nematic medium. Two about 5x7 cm and 5 mm thick glass plates are thoroughly cleaned by treating them successively with acid, alcohol, aqueous ammonia and distilled water and dry in an oven at 65 ° C. Each plate is then passed on to a surface Vapor deposition coated with indium oxide so that the surface is electrically conductive. The indium oxide surfaces are

^L 909846/0789 ^J.

292073Q

oriented, ie made anisotropic, by applying light to moderate pressure about 20 times with a cotton cloth
rubs, which is impregnated with an aqueous suspension of zirconium oxide. Each plate is carefully distilled with

Rinsed with water, placed in an oven and dried at 65C for 1 hour. Two strips of polytetrafluoroethylene film
12 in thickness are cut to a length of about 5 cm and applied to the oriented surface of one plate at a distance of about 5 cm, whereupon the other plate is placed in the direction of orientation perpendicular thereto. The arrangement is then firmly connected.

A solution of the pleochroic dye to be tested is prepared by heating about 0.5 g (10 drops) of the nematic combination of Table IV to 65 ° C (ie
above the isotropic melting temperature) and about 50 mg of the dye dissolves in it. This gives a at 655 nm
optical density of about 2. As long as the solution is still above the isotropic melting point, it becomes an edge of the cell

introduced into the dye solution, which the capillary action fills the cell. As the solution cools down, after a while the temperature of the solution drops below the isotropic point in the
nematic area and the experiment can be continued.

Optionally, about 0.1 to 50% of a chiral compound such as cholesteryl nonanoate can be added at this point. The amount used depends on what is intended
Effect. Smaller amounts (up to about 5 to 10%) are used to prevent the spontaneous reaction of such guest-host combinations.

combinations towards switching off the electric field

to enhance. Larger amounts result in a more cholesteric structure of the system instead of the more common twisted one
nematic structure, so that a polarizer is no longer required.

909848/0780

Using frog clips, electrical contacts are made to the indium oxide coatings on the exposed ends of the Glass plates that make up the cell are made, and these are connected to a direct current source that is 50 to 100 μΑ can deliver over a range of 0.8 to 10 volts or a sufficiently high fixed voltage. The cell will then be in the Sample beam of a spectrophotometer (e.g. Perkin Elmer model 350) introduced, the polarizing filter in both the Has reference as well as in the sample beam and analyzers arranged in parallel. The filters result in a when crossing neutral gray color. The transmittance is plotted over a range from 400 to 750 nm, where an the cell has no voltage (switch off) or a voltage above the threshold value for the respective host component (Switch on) is applied. The S-values are calculated from the transmission or absorption curves obtained. The color shifts from light red to colorless are shown in FIG. 9 using the absorption maximum at 555 nm.

20 Example 2

In a process similar to that in Example 1, 5 parts of i-butylamino-4-chloroanthraquinone are added to 20 parts of 4-aminodiphenyl, 0.1 g of copper and 5 g of sodium acetate and 100 parts of nitrobenzene are added. After about 2 hours of heating under The blue-green dye 1-butylaraino-4-diphenylaminoanthraquinone is obtained under reflux, which has an S-value of 0.7.

B e i s ρ i e 1 3

5 parts of 1- (n-pentylanilino) -4-hydroxyanthraquinone are refluxed in 20 parts of cyclohexylamine in the presence of a small amount of sodium hydrosulfite, the light blue dye 1 - (n-PentTlanilino ^ -cyclohexylaminoanthraquinone being formed.

By adding this pleochroism dye to the positive nematic liquid crystal mixture from Example 1

909848/0789

one holds a blue guest-host combination in which the dye has an S-value of 0.65.

Example 4

5 parts of leucoquinizarin are mixed with 20 parts of 4-n-butylcyclohexylamine to the sky blue dye bis (1,4-n-butylcyclohexylamino) anthraquinone condensed.

A 1% solution of this dye in a mixture of the nematic liquid crystals from Example 1 gives a blue guest-host mixture which becomes colorless. The S-value is 0.7 ..

Example 5

Leukochinizärin is made with ammonia in leuco-i-amino-4-hydroxyanthraquinone and then reacted with two amine bases, e.g. n-butylamine and p-toluidine. After heating for 2 hours at 90 ° C. and oxidizing with air and copper sulfate, i-n-butylamino-4-p-toluidinoanthraquinone is obtained as a clear blue one pleochroic dye with an S value of 0.7.

Example 6

1,5-diaminoanthraquinone is dissolved in o-dichlorobenzene and with sulfuryl chloride to 3,4,7,8-tetrachloroanthraquinone as Intermediate reacted, which is then condensed with two equivalents of p-n-Hexy! Aniline. When splitting off the Chlorine atoms form 4,8-bis-p-hexylphenylamino-1,5-diamino-2,6-dichloroanthraquinone as a pure blue dye with an S value of 0.75.

Example 7

i-Methylamino-Z-undecyl ^ -oetylanilinianthraquinone is made by Condensation of 1 equivalent of p-n-octylaminoaniline with 4-bromo-1-methylaminoanthraquinone, Cu and sodium acetate and subsequent alkylation of this dye with undecylaldehyde made in a mixture of nitrobenzene and piperidine.

909848/0789

This purple dye has an S value of 0.7. The passage Color shift characteristics are shown in FIG.

5 Example 8

1-nitroanthraquinone is refluxed with excess Cyclohexylamine in o-dichlorobenzene to 1-cyclohexylamine anthraquinone implemented, which then in aqueous pyridine to the corresponding i-cyclohexylamino-4-bromoanthraquinone is brominated. This compound is then further condensed with p-aminoacetanilide, the blue-green being pleochroic 1-Cyclohexylamino-4- (p-acetaminoanilino) anthraquinone dye with an S-value of 0.7.

15 Example 9

1 equivalent (2.4 g) 1,4-dihydroxyanthraquinone are in placed in a flask equipped with a reflux condenser and stirrer, which receives 1 g of boric acid and 0.5 g of tin (II) chloride and 30 g of 2-phenylethylamine. This is followed by stirring for 2 hours

at 130 ⁰ C and then pour the contents into 10 percent hydrochloric acid. This creates the blue pleochroic dye bis (1,4-phenethylamino) anthraquinone with an S value of 0.78.

Examples 10-19

A series of pleochroic dyes is prepared according to the method of Example 1, the meanings of Q, x, R ¹ and m and the position on the anthraquinone nucleus together with the color and the S value in Table V are given. The 1,4-cyclohexylene group is indicated by an H in the ring.

909848/0789

- 21 Table V

292073Q

Example

Fa.rbe positions

25 19

Red

2
2
2

0 ₇ 80

m .S-Wext

2 0.75 2

2 0.75 2

2 0.75

2> 0 ₇ 8

O ₇ O

0.7

0; 7

0.85 0.8

Examples 20-28 Other Pleochroic Dyes Used for Guest-Host Combinations can be used by condensation of substituted dichloroanthraquinones with various amines under reflux in an inert solvent such as nitrobenzene in the presence of sodium acetate and copper acetate manufactured. The dyes are listed in Table VI. The intermediates are known or can be based on known Manufacture way.

^L 909848/0789

03 UI

example

28

colour

20th yellow-green 21st . blue 90 9 8 22nd Red 4 ^
OO 23 Red O
αο
α> 24 Red 25th purple 26th blue 27 Red

Q position

5.8

Table VI R 'position

BM · ΒΒΒΜΒΜΒΜΒΒΒ> -ΜΜΒ1ΜΙ

OH 1.4

2.6 1.5 1.5 1.5 1.8 1.4 1.5 1.5

m x,

2

S-value ■■

⁰ T ⁷

0.68

0 ₇ 85

0.8

0 _; 75

0.85

0.8

0.85

0.9

1 . Example. 29

The procedure used in Examples 20 to 28 is based on the preparation of 1,5-bis- (benzylamino) -anthraquinone explained:

20 g benzylamine, 0.1 g copper acetate, 2.0 g sodium acetate and 10 g of nitrobenzene are mixed with 277 g of 1,5-dichloroanthraquinone in a suitable vessel. The mixture is 2 hours heated to reflux and then poured into methanol. The crude dye is separated and treated with hot nitrobenzene, which contains a small amount of piperidine. The red dye is purified from alcohol and washed with ether. It has an S value of 0.75.

Example 30

A useful method of introducing a substituted amino group in place of a hydroxyl group is to use the Hydroxyl substituted Änthraquinone with the amine in the presence of boric acid, usually in an inert solvent such as Nitrobenzene, to be heated. This process also enables the production of anthraquinones with two different ones Substituents; see examples 19 and 30.

1-Hydroxy-4-chloroanthraquinone is treated with 1 equivalent of p- (n-decyl) aniline in the presence of boric acid to form 1- [p- (n-decyl) -anilino] -4-chloranthraquinone condensed, which is then treated with 1 equivalent of 2-aminonaphthalene in the presence of copper acetate / sodium acetate condensed. After cleaning, the blue-green pleochroic dye 1-p- (n-decyl) -anilino-4-naphthylaminoanthraquinone is obtained with an S-value of 0.72.

Examples 31 to 39

Using the boric acid condensation described in Example 29 the pleochroic dyes listed in Table VII are prepared. In Examples 37 and 38 means the star that tin (II) chloride is used as in Example 9.

909ÖA8 / 0789

'CO cn

ω ο

ro cn

ro ο

cn

Table VII example

colour

Position g r »position mx

S value

COPY 31 reddish blue 5, 8th Cl 1.4 1.4 32 blue green 5, 8th OH 1.4 α *
O
CO
CO
Γ
ΟΟ
O 33
34 green
bluish green 5, r8 NO ₂
NO ₂
OH 1.4
4th
H -J
OO
α » U C ₅ H ii ^N - 35 -blue - -

36

blue .H

^C 8 ^H 17- °

H
-N-

-N-

0 ₇ 75

0.75

0 _; 68

0 ₇ 72

0 _; 8th

0 _; 8th

TO CD K) O

N) ul

Table VII - continued

cur α co OO * ■ * co

ο -j OO to

example

37

colour

Q position Q R ^ position

reddish blue 5.8

3 8 * bluish green

3 9 * blue-green

Cl

1.4 1.4 1.4 O-CH,

H
-N-

-N-

H
-CH ₂ N-

m
2
2

. S value

0.75

0.8

1 example 40

The guest-host combinations according to the invention are distinguished characterized by an unusual lightfastness. A field effect device is produced to demonstrate this property. A mixture is used as the nematic guest-host component of the nematic liquid crystals of Example 1, the 1% 1,4-bis (4-phenylanilino) anthraquinone (manufactured as the 1,5-isomer in Example 11) is used. The test sample is placed in an Atlas weathering apparatus at 60 ° C. for 100 hours, using a xenon UV light source

2 an output power of 0.115 nm / cni at 340 nm is used. The absorption spectra show no decrease in the pleochroic dye by 2 and over after 100 hours

* * Max

the electrode surfaces will be a current increase of less measured as 10%. The transmittance curves in terms of color shift are shown in FIG.

Example 41
The improvements achieved by the compounds according to the invention over unsubstituted bis-phenylaminoanthraquinones in guest-host combinations result from a comparison of a system (A) _r according to the invention in which the anthraquinone of Example 30 is used, in which each phenyl group is substituted by an octyloxy group ( in the 4-position of Ar), with a system (B) which has no substituents in the same position. Using the dielectrically positive nematic liquid-crystal mixture from Example 1, solutions are prepared in the same concentration, whereupon the transmittance curves are measured with increasing voltage. The results are shown in FIG. The higher S-value of system B (about 0.7) demonstrates the increased contrast ratio, the less colored background and the increased brilliance that can be achieved with electro-optical devices in which the inven-

35 appropriate combinations can be used.

909848/0789

2- »_ I

Similar S values as described in Examples 1 to 39 are obtained by considering the nematic liquid crystalline materials adding chiral compounds such as cholesteryl pelargonate in various amounts. at If small amounts are used, e.g. about 0.5%, a faster re-orientation is achieved when the voltage is switched off.

809846/0799

Blank page

Claims (1)

¹¹ liquid crystal systems and electro-optical ^ displays " Priority: May 23, 1978, v'.St.A. , No. 908 671 15 ' Claims 1. Liquid crystal systems with positive dielectric anisotropy, containing at least one nematic liquid-crystalline material with positive dielectric anisotropy and 0.01 to 50 percent by weight of a pleochroic dye of the general formula in which the substituents (NRR ¹ ) and Q can be in the positions 1 to 8 and the symbols have the following meanings: Q = F, Cl, -NO ₂ , -NH ₂ , -NH (AIk) or -OH; X = 0, 1 , 2 or 3;
m = 1 or 2; 35 K = H; R '= cyclohexyl, bicyclohexyl or - (CH ₂ ) Ar; 909848/0780 ORIGINAL INSPECTED .j where P = 0, 1 or 2; Ar = aryl with 6 to 10 carbon atoms, which in the 4-position by -NHCOCH-, -CN, -C H -... j η zn + ι, ~ ^0C n ^H 2n + 1 ' ^c Y ^clohex y ¹ ' ^^^ 4- {Alkfcyclohexyl or -Y -v_y-Z is substituted, (where y = 0 or 1; Y = -CH ₃ -, -0-, -S- or -OCH ₂ -; Z = H, -NO ₂ , -CN, -C _n H _{2n + 1} , -OC _n H _{2n + 1} , F, Cl or, if y = 0, also -C ₆ H ₁ -), "and in 0 to 2 further positions by -CN, -C _n H _{2n + 1} , - ° ^c _n ^H _{2n +} i '~ ^NH 2 ^or - ° ^H ; η = 1 to 20 and Alk = alkyl with 1 to 8 carbon atoms. _1t - 2. Systems according to claim 1, characterized in that they additionally contain about 0.1 to 10 percent by weight of an isotropic dye with a color contrast with respect to the normal color of the pleochroism dye. ₂₀ 3. Systems according to claim 1, characterized in that the nematic liquid-crystalline material comprises 10 to 20 percent by weight of Np-alkoxybenzylidene-p'-aminobenzonitrile. 2 ₅ 4. Systems according to claim 1, characterized in that the nematic liquid-crystalline material comprises n-pentylphenylcyclohexyldiphenyl cyanide in a combination of n-propyl, n-pentyl and n-heptylphenylcyclohexyl cyanide. ₃ q 5. Systems according to claim 1, characterized in that the nematic liquid-crystalline material comprises combinations of 4-cyano-4'-alkyl-di.phenylen. . 6. Systems according to claim 4, characterized in that the ^ ₅ pleochroic dye is 1,5-bis- [p- (4-n-pentylcyclohexyl) phenylamino] anthreiquinone. 909848/0789 7. Systems according to claim 4, characterized in that the pleochroic dye 1,5-bis (diphenylamino) anthrachi is non. 8. Systems according to claim 4, characterized in that the pleochroic dye bis- [4- (p-nitrophenylthio) phenylamino] anthraquinone, in which the substituents are in the positions 1.4- ", 1.5- or 1.8. 9. Systems according to claim 4, characterized in that the pleochroic dye 1,4-B.is- (4-n-decyloxyphenylamino) anthraquinone is. 10. Systems according to claim 1, characterized in that they are also about 0.1 to 50 percent by weight, based on the nematic liquid crystalline material, a chiral agent. 11. Systems according to claim 10, characterized in that the chiral agent is cholesteryl pelargonate. 12. Electro-optical displays in which an electrical Field can be switched off on a cell, which is a liquid-crystalline material in which a pleochroic dye is dissolved, contains between transparent glass plates provided with electrodes, characterized in that the liquid-crystalline material has a liquid-crystal system with positive dielectric anisotropy according to any one of claims 1 to Π. 30 ■ ■. L 909848/0789