DD201689A5 - LIQUID CRYSTAL MATERIALS AND ELECTROOPTICAL DISPLAY DEVICES - Google Patents

Abstract

The invention relates to liquid crystal materials for Guest-Horst liquid crystal display devices based on a solution of a pleochroic dye in a liquid crystal material, characterized in that the pleochroic dye comprises at least one anthraquinone compound having no water-solubilizing and ionic substituents of the formula I, in which Each Q is independently NH 2, OH, ALKYL, aryl, NO 2 or halogen; X are each independently H, -SR, where R is independently each alkyl, aryl and cycloalkyl, where Z is low and Z is deeply 2, independently of H, alkyl, aryl or cycloalkyl, or Q, and NO or an integer from 1 to 4 inclusive where at least two groups X are different e -SR groups.

Description

st

237666 7

Liquid crystal materials and electro-optical

display devices

Uses of the invention:

The invention relates to liquid crystal materials in which pleochroic dyes are dissolved and which are suitable, for example, for electro-optical display purposes

Chara kter istik of the known technical solutions:

Liquid crystal materials are well-known organic materials that form phases called liquid-crystalline phases or mesophases whose molecular order of degree is between that of the fully ordered crystalline solid state and that of the completely disordered isotropic liquid state.

The use of liquid crystal materials in 2 93-JX5976 / O6-SF-Bk

25FEB.1982 *! W2815

237666 7

Electro-optical display devices, such as digital display devices such as watches, calculators and digital voltmeters, are well known and widely used. In such devices, the optical contrast is exploited when an electric field is applied to a thin insulating layer of a suitable liquid crystal material. The molecules of the liquid crystal material, which are in a liquid crystalline phase at the operating temperature, are reoriented by the electric field, causing a change in the optical properties of the part of the liquid crystal layer to which the electric field has been applied, for example a change in scattering of omnidirectional light or optical transmission.

Liquid crystal materials have the property that their molecules can transfer their ordered state to molecules of other suitable dopant materials that have been incorporated into the liquid crystal material. Based on this property are the so-called guest-host display devices, such as display devices, where the host matrix liquid crystal material and guest introduced in the absence of an applied electric field have a particular molecular configuration and electrical potential applied to the material Field has a different molecular configuration. The doping material is usually a pleochroic dye whose molecular absorption properties depend on the orientation of the electrical vector of the

237665

depend on molecules of incident light.

Additions of such dyes can be used to increase the contrast between the OFF state (with no applied electric field) and the ON state (with electric field applied) of a liquid crystal display device, since the orientation of the dye molecules by the action of the applied electric field to the liquid crystal molecules and, consequently, the reorientation of the dye molecules by the so-called. Guest-host effect is switched as it were.

As will be explained in detail below, there are various types of liquid crystal effects which can make use of the guest-host effect in electro-optical display devices. The "liquid crystal properties depend on the type of liquid crystal material used and the configuration of its molecules in the AÜS state, which is predetermined, for example, by surface treatment of the substrates used, between which there is a layer of the liquid crystal material.

In order to achieve maximum contrast between the ON and OFF states in guest-host liquid crystal display devices, it is important that the molecules of the dopant material follow, as much as possible, the orientation of the liquid crystal material over time, but only because of the statistical thermal fluctuations in one

237666

limited extent can be realized. The extent to which the orientation deviates from the ideal state is measured by a variable known as order parameter S, which is defined by the following equation:

S = γ (3 cos ² e - 1),

where cos0 denotes the time averaging term and θ denotes the instantaneous angular orientation of the molecules with respect to the time average orientation of the liquid crystal molecules The determination of the value of the order parameter S is familiar to the person skilled in the art (cf., for example, DL White and G. N- Taylor, ¹ A new absorptive mode reflective liquid crystal display device ', Journal of Applied Physics 45 (1974) 4718-23).

When perfectly aligned, the value of the order parameter S is equal to 1, ie, θ equals O. Pleochroic dyes to be used in guest-host display devices should therefore have the largest possible order parameter in the liquid crystal matrix material as close to unity as possible should. However, the pleochroic dyes must also have sufficient chemical, photochemical and electrochemical stability, ie, for example, stability to atmospheric contaminants, electric fields, such as in operation of appropriate display devices, as well as ultraviolet radiation. They should also be nonionic or not

237566 7

be ionizable, otherwise the liquid crystal material would lose its insulating properties and become conductive, which would make a corresponding display device unusable. Suitable materials must also have sufficient solubility in liquid crystal materials; although the concentration of pleochroic dyes to be incorporated is generally very small, for example, not more than a few percent dye, to achieve the desired effect, many pleochroic dyes are still unsuitable because they are substantially insoluble in liquid crystal materials.

GB Patent Application 2 043 997A discloses liquid crystal compositions comprising symmetrical anthraquinone dyes of general formula A,

A,

in which R is hydrogen or a nonionic substituent. In the above GB patent application

237666 7

It is further stated that these dyes are intended for use only in liquid crystal materials having positive dielectric anisotropy.

GB Patent Application 2082196A also discloses symmetrical anthraquinone dyes of the formula B

RS 0 SR indicated, in the R optionally substituted alkyl or

aryl,

Q is halogen, hydroxy, amino, alkylamino, dialkylamino, arylamino, nitro, alkyl or aryl and y is an integer from 1 to 4,

which are intended for use in liquid crystal materials.

The symmetrical anthraquinone dyes of the formulas A and B, for example 1. 5-bis (phenylthio) anthraquinone and 1.4.5.8 tetrakis (phenylthio) anthraquinone have high order parameters and favorable stability, but their solubility in a number of liquid crystal materials is generally quite low for practical purposes; these dyes

-XS-

237666 7

also generally give a somewhat low contrast when used in electro-optical display devices.

Object of the invention:

The invention has for its object to provide liquid crystal materials with a pleochroic dye containing Anthrachinonfarbstoffe with good solubility, have a.high order parameters are stable and provide high contrast.

Dar legating. the ..Wesens invention:

The task is solved according to the claim.

The liquid crystal materials for guest-host liquid crystal display devices of the present invention consist of a solution of a pleochroic dye in a liquid crystal material and are characterized in that the polychoic dye comprises at least one anthraquinone compound having no water solubilizing and ionic substituents of the formula I.

X 0

XOX

in which mean

- is -

237666

Q is NH, OH, alkyl, aryl, NO ₂ or halogen, X are each independently H, -SR,

where R is independently alkyl, aryl or cycloalkyl, -NC ₁₇ I, where Ζ _Λ and Z _{n are} each independently H,

Alkyl, aryl or cycloalkyl,

or Q, and

η 0 or an integer from T up to and including 4,

where at least two of the substituents X. ' mean different -SR groups.

When one of the substituents in Formula I is an alkyl group, it preferably does not have more than 20 carbon atoms, and more preferably not more than 10 carbon atoms.

When one of the substituents in formula I is aryl or cycloalkyl, these groups preferably have not more than 15 carbon atoms and are preferably phenyl or cyclohexyl.

Preferred compounds of the formula I are

237666

and

(IV),

in which mean:

R ₁ aryl,

R-, Y ₁ to Y-. and T ₁ to T are each independently alkyl, aryl or cycloalkyl,

X ₁ - each independently H or -NZ ₁ Z ₃

with Z ₁ and Z ^ as above or Q as above

with the proviso that all groups and R or Y ₁ to Y are not identical.

and R or Y ₁ to Y or T ₁ to T.

When one of the substituents R, R ", Z ₁ , Z ^, Y ₁ to Y-. and T 'to T is an alkyl group, it preferably has not more than 20 C atoms.

Further, when one of these substituents is an aryl group, it preferably has not more than C atoms.

237666

By R, R ₂ , Z ₁ , Z ₃ , one of the substituents Y to Y or one of the substituents T to T shown alkyl groups may be straight or branched and are preferably lower alkyl groups, preferably containing 1 to 4 carbon atoms; Cycloalkyl groups are preferably cyclohexyl groups. The aryl group represented by R, R, R, Z ₁ , Z ", one of the groups Y ₁ to Y ₃ or one of the groups T ₁ to T ₄ is preferably a mono- or bicarbocyclic aryl group such as phenyl or naphthyl.

Alkyl groups represented by Q may be straight-chain or branched, and preferably contain 1 to 20 carbon atoms, and more preferably are lower alkyl groups. Aryl groups represented by Q are preferably monocarbocyclic aryl groups such as phenyl.

The alkyl, aryl and cycloalkyl groups represented by R, R ₁ , R ₂ , Z ₁ , Z ₃ , Y ₁ to Y-, T to T and Q may be substituted with nonionic groups. Phenyl groups are preferably substituted in the p position (4-position) with respect to the N or S atom or the anthraquinone skeleton, although in the case of methyl phenylthio substituents, compounds having a 3-methylphenylthio group are usually more soluble than the same compounds a 4-methylphenylthio group. Preferred substituents for alkyl groups are alkoxy, preferably C ₁ - to C ₁ -alkoxy, halogen, preferably chlorine, and also aryl, preferably monocyclic aryl, such as phenyl, preferred substituents for aryl groups,

237666 7

for example, by ti-, R, and T ₁ . to T _1n aryl groups as defined below and for cycloalkyl groups are alkyl and alkoxy, preferably lower alkyl and lower alkoxy and more preferably C. to C. alkyl and C. to C ₄ alkoxy, halogen, preferably chlorine, cycloalkyl , Preferably cyclohexyl, and aryl, preferably monocyclic aryl such as phenyl.

Lower alkyl groups or lower alkoxy groups are understood as meaning alkyl or alkoxy groups having 1 to 10 C atoms.

A preferred class of yellow to red dyes of the formula I includes dyes of the formula I where η = 0, in which two, three or four of the substituents X are -SR groups, with the remaining substituents -NZ ₁ Z- or more preferably H are.

A preferred class of red to blue dyes of the formula I are those in whose formula two substituents X-SR groups and two substituents X are substituents Q, in particular OH or NH groups. In this latter class of dyes, it is further preferable that η = 1 or 2, and that each of the substituents is QC.-C to alkyl groups adjacent to the -OH or NH.sub.4 groups.

It is generally preferred that at least one of -SR groups and more preferably all -SR groups are arylthio groups, most preferably phenylthio groups. The difference between the two

237666

The aryl groups may be in the aromatic nucleus, but are preferably in the nature and / or the position of a substituent of the aromatic nucleus. If only two -SR groups are present, they are preferably in the 1- and 5-positions.

The unsymmetrical substituted di-, tri- and tetra-thioanthraquinones are generally more soluble in liquid crystal materials than the equivalent symmetrical substituted di-, tri- and tetra-thioanthraquinones according to GB patent applications 2O43O97A and 2O82196A.

The term unsymmetrical in the context of polysubstituted thioanthraquinones means in the present case that at least two different substituted thio groups are present in the molecule, while under-symmetrical compounds in the same context is understood that all substituted thio groups in the molecule are identical. The invention also includes compositions comprising a mixture of symmetrical and unsymmetrical substituted polythioanthraquinones as well as the pure unsymmetrical compounds themselves and mixtures thereof.

However, it is preferred that such compositions contain at least 50% by weight of unsymmetrical substituted polythioanthraquinones and more preferably at least 75% by weight of these unsymmetrical compounds.

The unbalanced compounds are in pure form, ie without containing the structurally similar symmetry.

sfl ·

237666 7

See compounds, by chromatographic separation methods, in particular preparative or high-pressure liquid chromatography, accessible.

The main advantage of pure unsymmetrical compounds over compositions containing mixtures of these compounds with symmetrical compounds is their higher solubility, which, as mentioned above, is important for achieving high contrast in liquid crystal display devices.

However, solubility is only one of the factors affecting the achievement of good contrast in liquid crystal display devices; another factor is the extinction coefficient of the dyes in the liquid crystal material. A suitable parameter for the suitability of a dye to obtain a high level of contrast is the product of the molar extinction coefficient and the solubility (in mol / l). Solutions of dyes in liquid crystal compositions for electronic display purposes should have a value of this product which is preferably at least 500 cm and more preferably at least 750 cm. Since the molar extinction coefficient of a dye does not change significantly upon transfer from one liquid crystal material to another, the preferred value of this product for calculating the minimum solubility of a given dye in any liquid crystal

- 24a -

237666 7

be used to achieve a high Kcntrasts.

For a dye with a molar extinction,

2 - 1 coefficient of 11000 cm -mol, the solubility should preferably be at least 4.5-10 incl / 1 and still

-2 more preferably at least 6.8 x 10 mol / 1; the yellow dye of Example 1 has an extinction coefficient of such a value and a molecular weight of 480, so that the solubility (% by weight) of this dye should preferably be at least 2.2%, and more preferably at least 3.3%; the actual solubility of this dye in the liquid crystal material E43 (see Example 1) is 8.6%. ''

For dyes with a molar extinction

2 - 1 coefficient · of 1600C crn -mol should be the solution *

Preferably at least 3.1 * 10 mol / l and more preferably at least 4.6-10 mol / l; the red dye of Example 1 has such a value of extinction coefficient and a molecular weight of 650 that the solubility of this dye (% by weight) should preferably be at least 2% and more preferably at least 3%; the actual solubility of this dye in the liquid crystal material E43 is almost 15%.

For dyes with a molar extinction

2 -1 coefficients of 20000 cm-mol is the solvent

Preferably, at least 2.5 × 10 mol / l and

24b -

237866 7

even more preferably at least 3.8-10 mol / l.

The violet dye of Example 21 actually has such a value of extinction coefficient and a molecular weight of 590, so that the solubility should preferably be at least 1.5% and more preferably at least 2.2%; the actual solubility of this dye in the liquid crystal material E43 is 4.6%.

Dyes intended for use in liquid crystal display devices should preferably be as pure as possible, ie no inorganic or other ionizable materials which will interfere with operation. Display devices, or contain products that are sensitive to radiation and may degrade during operation within the display device. The dyes should also preferably contain no non-pochroitic or poorly pleochroic materials, such as the starting materials, intermediates and by-products, which do not contribute to the perceived contrast of such display devices for obtaining the dyes in a pure form, ie, substantially free of interfering or deleterious materials it is generally desirable to recrystallize the dyes repeatedly from organic solvents, for example from chloroform, and / or to use chromatographic separation techniques.

- 25 -

237666

The compounds of formula I have very high stability in liquid crystal materials as well as high order parameters, generally over. 0.7 lie. The substituted dithioanthraquinones are particularly valuable because stable yellow dyes with high order parameters and good solubility were previously inaccessible.

The addition of the dye to the liquid crystal material increases the viscosity of the system; Accordingly, when using such liquid crystal materials for electro-optical display devices, there is a tendency to prolong the response time of such devices. It is therefore desirable to keep the dye addition as small as possible, and the content must be sufficiently high to achieve adequate electro-optical contrast. In this regard, the dyes of the formula I used according to the invention are of particular value, since many of them have very high extinction coefficients and correspondingly only very small amounts must be present in the liquid crystal material, generally less than 7%.

It has also been found that the dyes of formula I have favorable ordering parameters and high solubility in many liquid crystal materials, both positive and negative dielectric anisotropic.

Among the most suitable liquid crystal matrix materials are:

237666 7

a. Mixtures with Cyanodiphenylen, preferably together with a few percent of one or more compounds having a clearing point {transition temperature from liquid crystalline to isotropic liquid state) 150 ⁰ C (for example, cyano-p-terphenyls), for example, the commercially available liquid crystal materials E7 and E4 3 (BDH Chemical Ltd., Broom Road, Poole, Dorset, England) whose composition is given below;

b. Mixtures with cyanophenylcyclohexane compounds, preferably also together with a few percent of one or more compounds having a high clearing point, such as cyanodiphenyl compounds, for example the commercial liquid crystal material ZL1132;

c. Mixtures with at least one Cyanodiphenylverbindung and at least one Cyanophenylpyrimidinverbindung, preferably also together with some percent of a compound with a high clearing point, for example a Cyanophenylpyrimidinphenylverbindung, for example, the commercially available liquid crystal material ROTN 30;

d. Mixtures with esters containing, for example, bicyclo (2.2.2) octane and benzene rings and which may have fluorine substituents.

It has been found that such liquid crystal matrix materials are particularly suitable which comprise a mixture of approximately equal amounts by weight of 4-n-alkyl- or -alkoxy-4-cyanodiphenyls and 1 - (4'-cyanophenyl) -

. #. 237666

4-n-aikyic icyclohexanes, the. together account for about SO to wt% of the mixture; contained together with one or more materials having a high clearing point (materials with a transition temperature from the nematic to the isotropic liquid state above 100 ⁰ C).

Any other liquid crystal materials having one or more compounds selected from the classes of compounds given below may also be used according to the invention as or in the matrix materials:

ii

iii

iv

vi

vii

viii

ix

xi

xii

xiii

xiv

xv

R RO 'RO R R RO RO RO RO

RO RO

0-GOO-XY ₁ \ __ / ₀ ι

237666 7

XVl xvii xviii xix

xx i xxii xxiii

²

In the above formulas: - represents a trans-1,4-substituted cyclohexane ring, an en 1,4-substituted bicyclo {2.2.2.) Octane ring,

one. 1 . 4-phenylene group \ fT> 7 a 4. 4'-diphenylyl group- <Q) - ^) - or a 2. 6-naphthyl

and CN,

, OR ₁ or

, in which

CN,

or

and R _{1 has} the meaning of R.

The dye-liquid crystal solution preferably contains at least 0.5% by weight of dye and more preferably about 0.75 to 10% by weight of dye and more preferably 1 to 5% by weight. The exact amount of dye is not critical within the preferred range, although the concentration is preferably not too low to provide the highest possible contrast

237666 7

on the other hand is not too high to slow the response speed of such electro-optical display devices.

Solutions of dye and liquid crystal material may be prepared in a conventional manner by simply mixing the dye and liquid crystal material together and then heating the mixture for about 10 minutes with stirring to about 80 ^° C. and then allowing the mixture to cool.

The pleochroic dyes of the above formula I can be mixed with other dyes, which need not necessarily have the formula I, for example to expand their spectral absorption properties in solution in the liquid crystal material.

For example, if a dye of formula I is colored yellow, it can be mixed with a blue and a red dye. The relative proportions of the combined dyes are determined according to the desired spectral response, which manifests itself in an absorption curve which is as flat as possible over the visible spectrum and, in turn, depends on the extinction coefficients of the dyes used as mixture constituents. The dye mixture is then used together with the liquid crystal materials described above or hereinafter.

_ *. 237666

The invention further relates to electro-optic liquid crystal display devices having two electrically insulating substrates, at least one of which is optically transparent, electrodes on their inner surfaces and a layer connected between the electrodes and the substrates made of or with a dielectric material according to the invention.

 The liquid crystal dye solutions of the present invention can be employed in any known electro-optical display devices known to those skilled in the art; Examples for this are:

a) Twisted nematic displays

In this case, a layer of nematic liquid crystal material having positive dielectric anisotropy is in the OFF state when the longitudinal axes of the liquid crystal molecules are in the plane of the inner surfaces of the substrate of the device which are normally parallel to each other or at a small angle to them from one substrate to another, due to the orientation caused by appropriate treatment of the surfaces, for example, by rubbing in one direction, prior to assembly, from one substrate to another are roughly roughly twisted by about JT / 2 helical. This condition is called a twisted, homogeneous texture.

By applying an electric field to the

'71

237666

Electrodes on the corresponding inner surfaces of the substrates in the ON state, a rearrangement of the liquid crystal molecules is caused, the longitudinal axes then lie practically perpendicular to the inner surfaces of the substrates, which is referred to as homeotropic texture-

Due to the molecular rearrangement changes

the optical activity (rotation) of the liquid

between crystal layer the ON and OFF states, wherein the observed optical effect can be enhanced by using a linear polarizer on one of the substrates and a pleochroic dye dissolved in the liquid crystal material. The polarization axis of the polarizer is parallel to the direction of the liquid crystal molecules on the adjacent inner surface of the substrate (or more precisely parallel to the central projection axis of the molecules on this surface).

Due to the guest-host effect of the dye, the liquid crystal layer in the OFF state appears relatively dark or strongly colored / while it appears bright or only slightly colored in the ON state.

b) Devices based on the Freedericksz effect in nematic liquid crystals with negative dielectric anisotropy

In such display devices using a nematic liquid crystal material having negative dielectric anisotropy, those are

237666

Molecules in the OFF state perpendicular to the inner surfaces of the parallel aligned substrates, ie in homeotropic texture, since these inner surfaces are subjected to a surface treatment prior to assembly of the cells. Adjacent to a substrate, a single polarizer is provided whose polarization axis is perpendicular to the normal to the inner surfaces of the substrates.

By applying an electric field to the electrodes on the corresponding inner surfaces of the substrates in the ON state, a rearrangement of the liquid crystal molecules is caused, which are then parallel to the substrate inner surfaces, ie. are in homogeneous texture. By introducing a pleochroic dye into the liquid crystal material, it is ensured that the liquid crystal layer in the OFF state appears relatively bright or only slightly colored while appearing dark or strongly colored in the ON state. The observed optical effect is further enhanced by the presence of the polarizer.

c) Devices based on the Freedericksz effect in nematic liquid crystals with positive dielectric anisotropy

In these devices, a nematic liquid crystal material having positive dielectric anistropy is used; the liquid crystal molecules are approximately parallel in the OFF state, ie in a more homogeneous state. Texture, and in the plane of the substrate interior

237666 7

surfaces, which are parallel to one another, since they were subjected to a pretreatment before assembly of the cell for orientation. Adjacent to a substrate, a single polarizer is provided whose polarization axis is parallel to the substrate inner surfaces.

Upon application of an electric field to the electrodes on the respective substrate inner surfaces in the ON state, a rearrangement of the liquid crystal molecules is caused, which are then oriented perpendicular to the substrate inner surfaces, ie in a homeotropic texture.

By introducing a pleochroic dye into the liquid crystal material, it is ensured that the liquid crystal layer appears relatively dark or strongly colored in the OFF state, while it appears colorless or only slightly colored in the ON state as in the above display devices described under a). The observed optical effect is enhanced by the presence of the polarizer.

d) Devices based on phase change (negative contrast)

In this case, a cholesteric liquid crystal material having a positive dielectric. Anisotropy and a long molecular helical pitch of typically 2 μm, with the molecules in the OFF state in random helical

237 666

arranged as a focal conical texture.

Upon application of an electric field to the electrodes on the respective substrate inner surfaces in the ON state, an order of the liquid crystal molecules is caused, which are then perpendicular to the substrate inner surfaces, ie in homeotropic texture as in the devices described under c), on the Freedericksz effect based.

By introducing a pleochroic dye into the liquid crystal material, the liquid crystal layer in the OFF state appears relatively dark or strongly colored and colorless or only slightly colored in the ON state.

e) Devices based on phase change (positive contrast)

In these devices, cholesteric liquid crystal materials having negative dielectric anisotropy and long molecular helical pitch are used; in the OFF state, the molecules are perpendicular to the substrate inner surfaces, ie in a homeotropic texture.

By applying an electric field to the electrodes on the corresponding substrate inner surfaces, a reorientation of the molecules is caused, which are then oriented in the plane of the substrate inner surfaces in a helical arrangement, ie in a twisted homogeneous texture.

When the liquid crystal material contains a pleochroic dye, the liquid crystal layer in the OFF state is relatively colorless or only slightly colored, while in the ON state it appears to be relatively dark or strongly colored.

f) Devices based on the Freedericksz effect in smectic liquid crystals

In this case, smectic A positive dielectric anistropy liquid crystal materials having a dielectric relaxation frequency fc below about 10 kHz are used, which means that the material has a negative dielectric anistropy above this frequency.

In the OFF state, the molecules are approximately parallel to the substrate inner surfaces, wherein the molecules are oriented in parallel on the two substrate inner surfaces as in the devices listed under c).

By applying an electric field with a frequency below fc in the ON state, a reorientation of the liquid crystal molecules is caused, which are then oriented perpendicular to the substrate inner surfaces, ie in homocotropic texture. The ON state persists when the electric field is turned off. The extinction of the ON state can be achieved by applying a high-frequency electric field having a frequency> fc.

237666 7

In these devices, as in the devices mentioned above under c), a single polarizer is used when the molecular orientation at the two substrate inner surfaces in the AUS state is parallel.

When the liquid crystal material contains a pleochroic dye, the liquid crystal layer in the OFF state is relatively dark or strongly colored while appearing bright or slightly colored in the ON state.

The use of the liquid crystal compositions according to the invention is not limited to electro-optical display devices of the abovementioned types, since the compositions according to the invention can also be used in any other known applications for colored liquid crystal materials. Examples of such non-electro-optical applications include thermally controlled display devices in which a symbol or a letter in a smectic or cholesteric material by selective heating of the material, for example with a laser beam (eg a He-Ne laser), with a local change in the molecular texture of the material is brought to display.

The dye enhances the contrast between the various areas of the display, ie, between the selectively heated and unheated areas.

23765

Of the dyes of the formula I used in the liquid crystal compositions of the invention, a preferred class of yellow dyes having two different -SR groups has the general formula V

Cv)

in the R ₁ aryl and

R _{9 is} one of the abovementioned groups R, where R 'and R _{2 are} not identical.

The groups R- include alkyl, aryl and cycloalkyl which may contain one or more nonionic substituents such as those listed above. When R _{2 is} aryl, this substituent must be different from the aryl substituent R. This difference can be in the aromatic nucleus as well as in the type and / or position of a substituent.

Conveniently suitable compounds of this type are, for example, compounds of the formula VI

S3

237666

/ TV

(VI),

in which R is hydrogen or a nonionic substituent and

R. represent a nonionic substituent, wherein R- with respect to constitution and / or position on the phenyl nucleus 'different from R.'

Of particular note are compounds of formula VII

(VII)

237666 7

in the R and and

have the above meaning

from

contractually

is divorced.

Particularly suitable compounds of this type are those in which der diees AIk ^ l, in particular t-butyl, mean.

Hydrogen and R. never

The dyes of formula V are accessible by reacting an equivalent of the thiol R ₁ SH and an equivalent of the thiol R ~ SH with one equivalent of a 1,5-dihaloanthraquinone. The reaction is conveniently carried out in a solvent, for example dimethylformamide, as well as in the presence of an acid acceptor, for example potassium carbonate , carried out. ·

The reaction product is a random mixture containing the compound of formula V as the main component in addition to symmetrical compounds of formulas VIII and IX

R ₁ S

(VIII)

and

237666 7

: Ϊ́χ)

contains.

The compounds of formula V can be prepared in a more pure form by reacting a 1-halo-5-nitroanthraquinone with one equivalent of the first thiol (R ₁ SH) under mild conditions and then reacting the product with one equivalent of the second thiol (R-SH) higher temperature can be produced.

As mentioned above, the known symmetrical dyes of formula I, such as 1, 5-bis (phenylthio) anthraquinone, have only fairly low solubility in liquid crystal materials. Mixtures of two or more compounds of formula A are also poorly soluble in liquid crystal materials.

In contrast, it is surprising that the unsymmetrical dyes of the formula V compared to the symmetrical dyes of the formula A have significantly higher solubility in liquid crystal materials. The pure unsymmetrical dyes have higher solubility than the above-mentioned products which are the symmetrical compounds of the formulas

- 23 7 66 8 7

VIII and IX as impurities. However, these mixtures of unsymmetrical and symmetrical dyes have sufficiently higher solubility than the pure symmetrical dyes, which is why they are commercially useful.

A preferred class of red dyes having four -SR groups, of which not more than three are identical, has the general formula XI

(ΧΙ!

in the T, T ", T and T each one of

above groups can be R with the proviso that not more than three of these substituents are identical.

Particularly useful compounds of formula XI are those in which T, T _? , T and T. aryl, of which not more than three substituents are identical. The differences between these substituents may be in the aromatic nucleus or in the nature and / or position of the substituents thereon.

237566.7

Conveniently suitable compounds of this type are, for example, compounds of the formula XII

(XII),

in the T _c , T,, T-. and T ₀ independently each

DO / O

Hydrogen or a nonionic substituent as defined above and at least one of the substituents T _n , T _r , T-, and T ₀ either kontxtutionell or

positionally different from the other substituents.

Of particular note are compounds of formula XIII

-S

S-

2.10

(XIII)

2376

in the T is hydrogen or a nonionic substituent and

represent a nonionic substituent, where are.

where Tq and T _{1n are} not particularly suitable compounds of this type are, for example, those in which T is hydrogen and T _{1 is} a lower alkyl group, especially t-butyl. ,

The dyes of formula XI can be prepared by reacting a 1.4.5.8-tetrahaloanthraquinone with one equivalent of each of the thiols SH, ^T 2 ^{SH /} Ti ^SH and T. SH, with no more than three of the substituents T, T ", T and T _{d are} identical. The reaction is conveniently carried out in a solvent such as dimethylformamide and in the presence of an acid acceptor, for example potassium carbonate.

The compounds of formula XIII are correspondingly prepared by reacting the tetrahalogenanthraquinone with two equivalents of a thiol of the formula

^t 9 - <Q) - ^sh

and two equivalents of a thiol of the formula

-237666 7

available. The product of these reactors is a random mixture in which compounds of formula XI are present as the major constituent besides minor amounts of compounds in which T., T ₂ , T and T are identical.

As mentioned above, the symmetrical dyes of formula B generally have lower solubility in liquid crystal materials than is required for practical applications.

In this connection, it is surprising that the asymmetrical dyes of the formula XI according to the invention have significantly higher solubility in liquid crystal materials than the symmetrical dyes of the formula XIV.

The preferred group of orange-colored dyes of formula III can be prepared by reacting two different substituted thiols with a trichloroanthraquinone in the presence of an acid acceptor to form a mixture containing mainly the unsymmetrical compounds in addition to minor proportions of the symmetrical compounds. Alternatively, a thiol with a nitro-dichloroanthraquinone can be reacted under mild reaction conditions to the corresponding dichloroanthraquinone, which is then reacted as an intermediate with the second thiol to form a single asymmetric anthraquinone with three substituted thiol groups and only minor amounts of the symmetrical products.

237886

The groups -NZ ₁ Z ^ and the groups Q are preferably introduced in front of the -SR groups by known methods, for example by reacting an amino compound HNZ ₁ Z- with the correspondingly suitable chloroanthraquinone.

Examples of other suitable compounds of formula I are:

1-phenylthio-5r (naphth-2-ylthio) -anthraquinone, 1-phenylthio-5-dodecylthicanthraquinone, 1-phenylthio-5- (4-nonylphenylthio) -anthraquinone, 1-phenylthio-4,5,8-tri cyclohexylthioanthraquinone,

1-phenylthio-4,5,8-tri- (4-phenyl-phenylthio) -anthraquinone,

1-phenylthio-4. 5. 8-tri- (4-t-butylphenylthio) anthraquinone, _

1-phenylthio-1-anilino-S- (4-methylphenylthio) -anthraquinone,

1-phenylthio-4.S-dibutylamino-S-butylthioanthrachinon

1-phenyl-thio-S-cyclopentylthioanth'rachinone.

EXAMPLES

The invention is explained in more detail below with reference to examples of the preparation and the properties of dyes of the formula I. In the examples, parts and percentages are by weight unless otherwise specified.

- 237666

example 1

1 . 4. 5. e -retrachloranthraquinone (12 g) was added with stirring to a mixture of dimethylformamide (100 ml), potassium carbonate (12 g), thiophenol (10.4 ml) and 4-t-butylphenylthiol (14.8 ml). The reaction mixture was heated to 130 to 140 ⁰ C and held at this temperature for 5 h. After standing overnight, the reaction product was filtered off; The filter cake was washed several times with a 50:50 mixture of ethanol and 2N NaOH solution. The washed product was then washed with strongly diluted acetic acid and then rinsed acid-free with water, dried at 50 ⁰ C in a vacuum, dissolved in the least amount of boiling toluene, filtered, by. Refilled with methanol, again. Filtration, washed with methanol and finally dried at 50 ⁰ C.

The product contained the following substituted anthraquinones.

Table 1

Ingredients Gew.-l

Tetrakis (phenylthio) anthraquinone 1 tris (phenylthio) -t-butylphenylthio

anthraquinone 19

Bis (phenylthio) -bis (t-butylphenyl)

thioanthraquinone 65

Tris (t-butylphenylthio) -phenylthio-

anthraquinone 11

Tetrakis (t-butylphenylthio) -

anthraquinone '4

237666

The solubility of the product was measured in the commercially available liquid crystal material E43 (BDH Chemicals Ltd., Broom Road, Poole, Dorset, England) containing the following compounds:

5 1 1

The solubility of the product in the liquid crystal material E4 3 at 2O ⁰ C is 14.7%.

For comparative purposes, the solubility of pure 1.4.5.8-tetrakis (phenylthio) anthraequinone and pure 1.4.5.8-tetrakis (4-t-butylphenylthio) -anthraequinone in the same liquid crystal material was also investigated; solubilities of <1% and 1.8%, respectively, were found.

Example 2

The procedure was as in Example 1, with the difference that the 4-t-butylphenylthiol was replaced by the equivalent amount of p-methylphenylthiol.

-237666 7

Example 3

Thiophenol (2.97 g), p-phenylphenylthiol (4.38 g) and potassium carbonate (3.73 g) were stirred in 23 ml of dimethylformamide (DMF) at 120 ^° C. for 1 h and then cooled to room temperature. After addition of 1.4.5.8-tetrachloroanthraquinone (3.46 g), the mixture 4 h at 120 ⁰ C and then cooled to room temperature. After adding 20 ml of ethanol, the mixture was worked up as follows.

After filtration and washing with a 50:50 mixture of 2N NaOH and ethanol, the crude product was slurried in 30 ml of the same solvent mixture, stirred for 30 minutes, filtered, washed successively with the mixed solvent of NaOH and ethanol and with water, and finally at 80 Dried ⁰ C.

The product of the work-up was heated to boiling point in 30 ml of chloroform and then filtered cold; The filtrate was added dropwise to 250 ml of petroleum ether (boiling range 100 to 120 ⁰ C). After 1 h of stirring, the precipitate was filtered off, washed with petroleum ether (boiling range 40 - β ο ⁰ C) and dried at 80 ⁰ C. The product contained about 90% unsymmetrical substituted tetrathioanthraquinones having both phenylthio and phenylphenylthio groups; the remainder consisted of symmetrical substituted tetrathioanthraquinones having either phenylthio groups or phenylphenylthio groups.

- 23 7 fi-fifi 7

3ί ^ J_ s ⁷ ^ i ο 1 4

Thiophenol (1.98 g), cyclohexylthiol (.2.07 g) and KOH (2.02 g in 30 ml of ethanol) were refluxed for 1 hour with stirring and then cooled to room temperature. After that, 1. 4. 5. 8-tetrachloroanthraquinone (2.31 g) was added, whereupon the mixture was refluxed for 16 h with stirring; after cooling to room temperature was worked up as in Example 3.

The solid crude product was dissolved in 100 ml of hot chloroform, strained and allowed to flow for 5 minutes in 300 ml of methanol. After stirring for 30 minutes, the solid was filtered off, washed with methanol and dried at 80 ^° C. (yield 2.8 g).

The main components of the product were unsymmetrical substituted tetrathioanthraquinones, which had both cyclohexlythio groups and phenylthio groups.

Example 5

To a mixture of dimethylformamide (100 ml), potassium carbonate (8.0 g), thiophenol (thiol · 1, 7.0 ml) and 4-t-butylphenylthiol (Thiol 2, 8.0 ml) were added 1.5-dichloroanthraquinone (12 g) added with stirring. The reaction mixture was then heated to 130 to 140 ⁰ C and held at this temperature for 5 h. After allowing to cool overnight, the

- £ -23 7 66 6

Filtered reaction product and the filter cake washed several times with a 50:50 mixture of ethanol and 2N NaOH solution. The washed product was then washed acid-free with very dilute acetic acid and then with water, dried in vacuo at 50 ⁰ C, dissolved in the lowest possible amount of boiling toluene, filtered, reprecipitated by the addition of methanol, filtered, washed with methanol and at 50 ⁰ C. dried.

The product contained 55% of 1- (4-t-butylphenylthio) -5-phenylthioanthraquinone; the remainder consisted of the two symmetrical 1,5-disubstituted anthraquinones.

The following four analogous products were prepared according to the procedure of Example-5 using equivalent amounts of the corresponding substituted thiols in place of the thiophenol and the 4-t-butylphenylthiol used in Example 5.

Example 6

Thiol 1: thiophenol

Thiol 2: 3-methylphenylthiol

Main components of the product :

1-phenylthio-5- (3-methylphenylthio) anthraquinone

Salary. Main ingredient in the product: 48%.

- 23 7 66 6

Example 7

Thiol 1: 3-Methylphenylthiol Thiol 2: 4-t-butylphenylthiol

Main component of the product:

1- (3-methylphenylthio) -5- {4-t-butyl-

phenylthio) anthraquinone Content of main constituent in the product: 6 4%.

Example 8

Thiol 1:, 3-methylphenylthiol Thiol 2: 4-methylphenylthiol

Main component of the product:

1- (3-methylphenylthio) -5- (4-methylphenylthio) -anthraquinone.

Example 9

Thiol 1: Thiophenol Thiol 2: 4-methylphenylthiol

Main component of the product:

1-phenylthio-5- (4-methylphenylthio;

anthraquinone.

Example 10

A mixture of 4-t-butylphenylthiol (thiol 2), (73.7 g), potassium hydroxide (25 g) and ethanol (640 ml).

-H-237666 7

was heated at reflux for 1 h and then cooled to room temperature. The mixture was treated with i-phenylthio-5-chloroanthraquinone (86.5 g) for 5 minutes; the mixture was then heated to reflux and held for 16h. After completion of the reaction, the mixture was cooled to room temperature; the solid product was filtered off and washed with 50% 2N NaOH in ethanol (200 ml). The crude product was reslurried in 200 ml of the same mixed solvent, stirred for 30 min, filtered again, washed successively with 100 ml of 50% 2N NaOH in ethanol and with 100 ml of water and finally dried at 80 ⁰ C.

The product was extracted with a 15: 1 mixture of petroleum ether (boiling range 100-120 ⁰ C) and chloroform (2 1) for 48 h at reflux; then the chloroform was distilled off. The residue in petroleum ether was cooled and filtered after 24 h at room temperature, washed with petroleum ether (boiling range 40 to 60 ⁰ C, 100 ml) and dried at 80 ⁰ C.

After repeated recrystallization from methanol the product (4-t-butylphenylthio) contained about 88% of 1-phenylthio-5- -anthraquinone possessed a melting point mp 241 ⁰ C.

The 1-phenylthio-5-chloroanthraquinone used above was added to a mixture of thiophenol (Thiol 1, 78 g), 32 g of potassium by addition of 1-nitro-5-chloroanthraquinone (72.5 g) and ethanol (500 ml).

- 5-3 "

237666 7

carbonate and 125 ml of dimethylformamide (previously held at 120 ⁰ C for 2 h at reflux and then cooled to room temperature) and heated to 40 ⁰ C for 16 h. After cooling and standing for 48 hours, the solid product was filtered off, washed with 40% aqueous ethanol (11), slurried in the same solvent (500 ml), stirred for 30 minutes, filtered and finally successively with 40% aqueous ethanol (200 ml) and water (1: 1). The product was then slurried in water (500 ml) for 30 minutes, filtered, washed with water and finally with ethanol (100 ml) and dried at 80 ^° C.

In Table -2, the solubilities of the dyes of Examples 5 and 10 are compared with those of the equivalent symmetrical dyes in the liquid crystal material E43 (see Example 1) at 20 ^° C.

Table 2

Attempt dye no.

1 1.5-bis (phenylthio) anthraquinone

2 1 .5-bis (4-t-butylphenylthio) anthra

quinone

3 50:50 mixture of compounds from

Trial 1 and 2

4 1-phenylthio-5- (4-t-butylphenylthio) -

anthraquinone (product of Beisp.10) .7,8

5 mixture of the compounds of experiments 1,

2 and 4 (product of Beisp.5) 3.2.

solubility .-%) (wt , 7 1 , 0 2 , 0 <2

237666 7

From the solubility data of Table 2 it can be seen that the unsymmetrical product, both alone and in admixture with the corresponding symmetrical compounds, has a considerably higher solubility in the liquid crystal medium than the symmetrical products or their mixtures. Not only is this higher solubility totally unexpected, but it is also of considerable commercial interest in light of the present need for practical guest-host based liquid crystal display devices.

The following five analogous compositions were prepared in a similar manner to Example 10 using equivalent amounts of the corresponding substituted thiols in place of the thiols used in Example 10.

Example 11

Thiol 1: thiophenol

Thiol 2: 3-methylphenylthiol.

Main component of the product:

1-phenylthio-5- (3-methylphenylthio]

anthraquinone

Content of main component in the product: 81% F. 227 ⁰ C.

Example 12

Thiol 1: thiophenol

Thiol 2: 4-methylphenylthiol

t / 6

-S3 "-

237666 7

Main component of the product:

1-phenylthio-5- (4-methylphenylthio)

anthraquinone

Content of main component in the product: 83% F. 269 ⁰ C.

Example 13

Thiol 1: Thiophenol Thiol 2: n-butylthiol Main component of the product:

1-phenylthio-5- (n-butylthio) -

anthraquinone

Content of main constituent in the product: F. 163 ⁰ C. '

Beispiel.14

Thiol · 1: Thiophenol Thiol 2: 4-phenylphenylthiol

Main component of the product ^

1-phenylthio-5- (4-phenyl-phenylthio) -

anthraquinone content of main constituent in the product: 91%

Example 15

Thiol 1: Thiophenol Thiol 2: Cyclohexylthiol

237666 7

Main component of the product:

1-phenylthio-S-cyclohexylthioanthrachinon.

Example 16

A solution of thiophenol (1.98 g), 4-t-butylphenylthiol (2.99 g) and potassium carbonate (2.48 g) in dimethylformamide (20 ml) was heated to 115 ^° C. and stirred for 1 h at this temperature. The solution was then treated with 1.5-dinitro-4.8-diaminoanthraquinone (3.28 g); the mixture was stirred at 115 ^° C. for 8 h. It was then cooled to room temperature, filtered, washed successively with DMF, water and ethanol and dried to give 1.7 g of crude product.

The crude product was purified by trituration in hot chloroform and then passed through a chromatographic column with SiO ,, filling after cooling. As the eluent, chloroform was used; the blue major band was collected and evaporated to dryness. The dry material was triturated with methanol (20 ml) for purification; then it was filtered, washed with methanol and dried at 80 ⁰ C. There was obtained 0.2 g of the purified composition containing 6% 3-1-phenylthio-5- (4-t-butylphenylthio) -4,8-diaminoanthraquinone.

The 1.5-dinitro-4.8-diaminoanthraquinone was

/ UUU

from 1. 5-diaminoanthraquinone bis (N, N-dimethyl oriramidium chloride) was prepared by the method of Example 2 of British Patent 1041528. The 1, 5-diaminoanthraquinone bis (N, N-dimethylformamidiuirchloride) 'was recovered after the

Method of Example 2 der.DE-PS 11 32 931 made of 1.5-diaminoanthraquinone ..

Example 17

Thiophenol (1.98 g), 3-methylphenylthiol (2.33 g) and potassium carbonate (2.02 g) were stirred at 115 ^° C. for 1 h in DMF (15 ml) and then cooled to room temperature. The mixture was spiked with 5-dibromo-4,8-dimethylaminoanthraquinone (4.24 g) for 5 minutes; The mixture was heated again to 120 ⁰ C and stirred at this temperature for 16 h. After cooling to room temperature and adding ethanol (25 ml), the crude material was worked up as in Example 3; Yield 4.35g.

The material obtained in the work-up was dissolved in chloroform and purified by column chromatography on silica gel, using chloroform as eluent and collecting the main red band. After evaporation of the chloroform, washing with methanol and drying at 80 ^° C, the yield of purified material was 4.09 g containing 48.9% of 1-phenylthio-5- (4-t-butylphenylthio) -4,8-dimethylaminoanthraquinone; the remainder consisted of the two symmetrical substituted dithioanthraquinones.

- 56 -

56 6

Example 18 . , ·

A mixture of thiophenol (1.24g), 4-t-butylphenylthiol (1.87g) and potassium carbonate (1.56g) in DMF (10ml) was stirred at 120 ^° C for 1h and then cooled to room temperature. The cooled mixture was added with 1-nitro-5,8-dichloro-4-anilinoanthraquinone (1- / 73 g); the mixture was stirred at 120 ^° C. for 5 h. After allowing to cool to room temperature and adding ethanol (27 ml) and water (40 ml), the resulting solid was filtered off, washed with water and ethanol, and dried to give 3.55 g of crude material.

The crude material was dissolved in chloroform and purified by column chromatography on silica gel using chloroform as eluent and collecting the orange major band. After evaporation of the solvent, 30 ml of methanol were added; The solid material was filtered off, washed with methanol and at. Dried 50 ⁰ C; Yield 2.95 g. , .-

The purified material contained 65% unsymmetrical substituted trithioanthraquinones; the remainder consisted mainly of the two symmetrical substituted trithioanthraquinones.

The 1-nitro-4-anilino-5,8-dichloroanthraquinone was prepared as follows:

A mixture of aniline (7.83 g) and 1.4.5-trichloro-8-nitroanthraquinone (10 g) in 2-ethoxyethanol (75 ml)

was heated at 120 ⁰ C for 18 h. The product obtained was filtered, washed with ethanol, reslurried in 50 ml of ethanol and filtered again. The product was then stirred into 2N HCl (50 ml), filtered, washed acid-free with water and dried at 80 ^° C. In the final stage of cleaning, the dry material was 20 min in chloroform (50 ml) .gerührt, then filtered, washed with chloroform and dried at 80 ⁰ C. The product (yield 5.9 g, mp 216-217 ⁰ C) had a purity of 90.5% (determined by liquid chromatography Höchdruck).

Example 19

A mixture of thiophenol (1.48 g), 4-t-butylphenylthiol (2.24 g) and. KOH (1.5 g) was refluxed in ethanol (15 ml) for 1 h and then cooled to room temperature. The cooled mixture was treated with 1.4.5-trichloroanthraquinone (1.5 g); the mixture was refluxed for 16 hours. After cooling to room temperature, the mixture was worked up as in Example 3.

The obtained 2.3 g of the worked-up product contained 6-2% unsymmetrical substituted trithioanthraquinones, ie bis (phenylthio) 4-t-butylphenylthioanthraquinone and phenylthio-bis (4-t-butylphenylthio) -anthraquinone; the remainder consisted mainly of the two symmetrical substituted trithioanthraquinones

Example 20

A mixture of. Thiophenol (0.127 g) and KOH (0.065 g) in ethanol (15 ml) were refluxed for 1 h and then cooled to room temperature. The cooled mixture was treated with 1-5-bis (4-t-butylphenylthio) -4-chloroanthraquinone (0.66 g); The mixture was refluxed for 16 hours and then cooled to room temperature.

After working up as in Example 3, the yield of dry product was 0.6 g. The material contained 78% of 1,5-bis (4-t-butylphenylthio) -4-phenylthioanthraquinone.

The 1,5-bis (4-t-butylphenylthio) -4-chloroanthraquinone was prepared as follows:

A mixture of 4-t-butylphenylthiol (2.98 g) and KOH (0.51 g) in ethanol (10 ml) was heated at reflux for 1 h and then cooled to room temperature. The mixture was · (1.56 g) was added 1.4.5-trichloroanthraquinone, stirred for 16 h at 40 ⁰ C and then cooled to room temperature.

After work-up of the crude product as in Example 3, by dissolving the crude product in 100 ml of petroleum ether (boiling range 60-80 ⁰ C), screening and chromatography type silica gel with elution with the same solvent and collecting the middle orange band further purified. After

-237666

evaporation of the solvent, washing with methanol and drying, the purified product was obtained in a yield of 0.9 g.

Example 21

A mixture of thiophenol (1.1 ml, 0.01 mol) and 1 .. 5-dihydroxy-2. 6-dinonyl-4. 8-dinitroanthraquinone (5.8 g, 0.01 mol) in pyridine (50 ml) was stirred at room temperature for 30 min and then introduced into 100 ml of water. Thereafter, concentrated HCl (75 ml) was added; the precipitated solid was filtered, washed with water and dried; the yield of crude product was 6 g.

A portion of this (3 g) was recrystallized from petroleum ether (boiling range 100-120 ⁰ C). The yield of intermediate 1,5-dihydroxy-2,6-dinonyl-4-nitro-8-phenylthioanthraquinone, whose structure was confirmed by mass spectrometry, was 1.3 g. '.

A mixture of the above intermediate (0.65 g) and 4-t-butylphenylthiol (0.2 g) in pyridine (10 ml) was for 16 h at 90 - 95 ⁰ C and then stirred into dilute hydrochloric acid (50 ml) is poured. The precipitated solid was filtered off, washed successively with water and methanol and dried. The solid was then recrystallized from petroleum ether (boiling range 40 - 60 ⁰ C) to give, after which the product obtained in a yield of 0.1 g

237666

which consisted mainly of 1,5-dihydroxy-2,6-dinonyl-4- (4-t-butylphenylthio) -8-phenylthioanthraquinone (structure confirmed by mass spectrometry).

The 1,5-dihydroxy-2,6-dinonyl-4,8-dinitroanthraquinone was prepared by the method of GB-PS 2O388O9A by reacting 1, 5-Dihydroxyanthrachinon with nonylaldehyde and nitration of the dinonyl derivative.

Example 22

A mixture of 1. 8-Dihydroxy-2,7-didodecyl-4,5-dinitroanthraquinone. (6, 6 g), thiophenol (1.1 g) and pyridine (100 ml) was stirred for 2 h at room temperature and then introduced into 200 ml of water. The precipitated solid was filtered off, washed successively with water and methanol, and dried to give 4.5 g of crude product.

After recrystallization from petroleum ether (boiling range 100-120 ⁰ C) as the product of 1.8-dihydroxy-2.7-didodecyl-4-phenylthio-5-nitroanthraquinone (yield 4.15 g; structure confirmed by mass spectrometry) was obtained.

A portion of this intermediate (3.7g) was added to a solution of 4-t-butylphenylthiol (0.83g) and KOH (0.3g) in isopropanol (50ml) at 65 ^° C. After 3 h heating of the mixture at the rear

/ WWW

flow (83 ⁰ C) was cooled to room temperature, filtered / washed successively with isopropanol and methanol, dried and recrystallized from petroleum ether (boiling range 100 - 120 ⁰ C). The product (2.75 g) consisted essentially of 1,8-dihydroxy-2,7-didodecyl-4-phenylthio-5- (4-t-butylphenylthioanthraquinone).

The 1,8-dihydroxy-2,7-didodecyl-4,5-dinitroanthraquinone was prepared by the method of GB-PS 2O388O9A by reacting 1. 8-Dihydroxyanthrachinon with dodecyl aldehyde and nitration of the didodecyl derivative.

Example 23

A sample of the product prepared according to the procedure of Example 1 was measured at room temperature (20 ⁰ C) was purified by high pressure liquid chromatography (column packing material Partisil 5u (250x4,6mm), eluent 99: 1 mixture of hexane and acetonitrile, flow rate at least 2 / ml). Detection was with a UV source (254 nm); All peaks in the chromatogram corresponding samples were collected. The collected fractions are identified in Table 3.

- .54- 237666 7

Table 3

fraction

  connection

Absorption .Löslich-order maximum

(%) parameter λ,> ^ ,, - ,, max (nm)

Tetrakis (phenylthio) anthraquinone 1.8

Tris (phenylthio) -4-butylphenylthioanthraquinone 10.7

Diphenylthio-bis (4-t-butylphenyl thiolane thraquinone <0.5

3a diphenylthio bis (4-t

butylphenylthicjanthra-. quinone 1, 0

Diphenylthio-bis (4-t-butylphenyl thic) anthraquinone. 2.9

Phenylthio-tris (4-t-butylphenylthic) anthraquinone 1, 0

Tetrakis (4-t-butylphenylthio) anthraquinone <'1.0 0.78

0.78

0.78 0.77

0.78 0.7 8

550 550 550 550 550

550 550

Fractions 3 and 3a had the same retention time and were separated due to their different solubility in the eluent.

The following composition was prepared in a manner similar to Example 10 using equivalent amounts of the corresponding substituted ones. Thiols prepared in place of the thiols used in Example 10.

Example 24

Thiel 1: thiophene1

Thiol 2: 4-methoxyphenylthiol.

Main component of the product:

1-phenylthio-5- (4-methoxyphenylthio) anthraquinone. ,

Example 25

The procedure was as in Example 4 with the difference that the cyclohexylthiol was replaced by the equivalent weight of 4-methoxyphenylthiol. The main components of the product were unsymmetrical substituted tetrathioanthraquinones present in the positions. 1, 4, 5 and 8 had phenylthio and... 4-Methoxyphenylthio groups.

In Table 4, the properties of the products obtained in Examples 1 to 25 are given in solution in the above-mentioned liquid crystal material E4 3. The values for the order parameter S and the absorption maxima λ given in Table 4 and the following tables are each at 20 ^° C.

Max

measured.

* w / WWW

table

_,,, Absorption order parameter

Product of, .., . ,,., . ~

_. , Solubility maximum '

example

No.

10 11 12 13 14 15 2.4-16 17 18 19 20 21 22

Solubility (%) ' Absorption maximum 'λ · (nm) max 14.7 550 1.0 550 3.0 550th. 4.7 550 3.2 464 3.3 464 2.4 464 2.5 464 2.9 464 .8.6 464 2.4 464 1.8 464 3.1 470 4.0 460 9.2 465 0.8 605 1.0 648 7.8 615 2.0 5 20 14.3 520 4.6 580 3.Ö 578

0 .80 0 .80 0 .77 0 .75 0 .80 0th .78 0th .73 0 .80 0 .78 0th .79 0 .78 0th 80 0th .75 0th , 78 0th , 81 0th 73 0th 72 0th 71 0th 77 0th 81 0th 79 0th 83

- Ö-7 -

£ 0/000 /

The solubility is defined in this case for a dye solution in the liquid crystal material and indicated as "wt .-% dye in the solution at 20 ⁰ C.

In this context is. determine that solubilities for the preparation of liquid crystal materials are important for convenient guest-host applications for the following reasons:

a) The optical properties at 20 ⁰ C are with increasing dye content in the. Dye-liquid crystal solution improved at 20 ⁰ G;

b) the optical properties at low temperatures are improved with increasing dye content in the dye-liquid crystal solution at 20 ⁰ C, since the higher solubility of a given dye in a given matrix material at 20 ⁰ C normally also a higher solubility of the dye in this! Matrix material at low temperatures corresponds.

Other properties were determined for some of the products listed above; they are listed in Tables 5 to 7.

In Tables 5 to 7, the following liquid crystal materials were used as matrix materials:

237666 7

(1) Matrix Λ consisting of the commercially available liquid crystal material E7 (BDH Chemicals Ltd.), which consists of a mixture of the following compounds:

weight N 51 N 25 CN 16

(2) matrix 2, consisting of the commercial material ZLI 1132 (E. Merck Co.), which consists of a mixture of the following compounds:

CN

(3) matrix 3, consisting of the commercial material ZLI 1695 (E. Merck & Co., Darmstadt), which has a clearing point (transition temperature from nematic to isotropic state) of 72 ⁰ C. The material consists of a mixture with Cyanophenylcyclohexanverbindungen (PCH compounds).

(4) Matrix 4 consisting of a commercial material containing phenyl dioxane. The material has a clearing point of 87 ⁰ C and consists of a mixture.

-. & -? - - -w / W '

(5) Matrix 5 consisting of the commercial material ZLI 1565 (E. Merck & Co.). It has a clearing point of 85 ⁰ C and consisting of a mixture with Cyanocyclohexylcyclohexanverbindungen (CCH connections]

(6) Matrix 6, consisting of the commercial material ZLI 1624 (E. Merck & Co.). It has a clearing point of 87 ⁰ C and consists of a mixture with PCH compounds.

(7) Matrix 7, consisting of the commercially available material RO TN 403 (Hoffman La Roche & Co., Basel)

It has a clearing point of 82 ⁰ C and exists

from a mixture with cyanophenylpyrimidine compounds (PPM compounds)

(8) Matrix 8, consisting of the commercial one

Material RO TN 430 (Hoffman, La Roche & Co., Basel). It has a clearing point of 6 9 ⁰ C and consists of a mixture 'with PPN compounds.

(9) Matrix 9, consisting of a mixture of the following bicyclo (2.2.2.) Octane derivatives (cf. GB patent application 7926902):

~ CN Wt.% 30 - CN 40 - CN 30th

(10) matrix 10 consisting of a mixture of the following compounds:

ⁿ ~ ^C 5 ^H 1

This material is an example of a matrix material that itself has a high order parameter.

(11) matrix 11 consisting of a mixture of the following compounds:

Wt .-%

3 3 14 18

7 10

C00 ~ @ - @ - CN 4

nC ₅ H ₁

- 70a -

(12) Matrix '12 consisting of a mixture of the following compounds:. ,

Component A: 90% by weight

Wt .-%

ⁿ ~ ^C 3 ^H 7 "W" ^C00 ~ O / ⁿ ~ ^C 5 ^H 11 ⁴⁵

ⁿ " ^C 5 ^H 1 'i \ ^' ^Q00 - \ J) ~ ⁿ " ^C 5 ^H 1 1 ⁵⁵

F component B: TO% by weight

- 71 -

This material is an example of a matrix material that itself has a high order parameter.

Table 5

Further properties of the products of Examples 1 and 5

at 20 ^° C

property

Molar extinction coefficient (CHCl ₀ )

Product of Beisp.5 Product of

example 1

χ 10 "

1 χ

Absence of UV radiation (time to absorption drop to 90% of initial value)

a. In the 'black light' (UV, 20 ⁰ C)

b. In xenon arc lamp light (UV + visible light, 40 ' ⁰ C)

10000 h

H

20000 h

5000 h

ti //

table

Further properties of the products of Examples 1, 5 and 10 in various other matrix materials

20 ⁰ C

Matrix product of

No. Example 1

Product of Example 5

Ordering Lot Λ Ordering Solver

parameck. , ,. parameck. ter S (% by weight) ^lnm 'ter S max

(Wt%) (run)

1 0.73 2 0.80 3 0.79 4 0, 7 5 5 0.75 6 0.78 7 > 0.7 8th 0.78 9 0.70 10 0.78 1 1 0.78 12 3.0

0.72 0.80

0.81

0.68 0.78

0.75 0.81

2,0 1,5.

3.1 · 2.0 463 463

3 463

463

Product of Example 10

Ord- Lösnungsk. para- (wt .-%) meter

 S

0.73

O, 76 4.0

0.79 2.5

0.81

0.94

4.6 550 550 550 550 550 550 550

7.2 550 550

550 550

A suitable dark gray dye mixture of the above individual dyes for 12 μΐη-ΖεΙΙεη (see below) has the following composition:

46 3 0 81 46 3 46 3 46 3 0 77 2.0

Product of Example 5 Product of Example 1 Product of Example

Weight ⁵ 2.5

2.0 1, 0 ... - ^ max (nm

463 463 463 463

463

463

(OO

Dye No. 9 is an example of a dye described in GB Patent Application 8123185 and has the formula

HO 0 pH

^ CH, CH (CH

3'2

In the following the invention with reference to inventive liquid crystal display devices is explained in more detail with reference to the drawing; show it:

1 shows an exploded view of a display device based on the Freedericksz effect according to the invention;

2 shows a cross section through the display device of Fig. 1 and

3 shows a front view of a wristwatch with a liquid crystal display according to FIGS. 1 and 2.

As is apparent from Fig. 1, a Freedericksz effect-based liquid crystal display device having a nematic liquid crystal having positive dielectric anistropy has a liquid crystal cell 3_ comprising two glass plates 4 , 5 and a layer 6_ of one

#: 237666

Liquid matrix stalagmite based on a neraatic material with positive dielectric anisotropy together with a pleochroic dye. On the inner surfaces of the glass plates 4, electrodes ] _, 8-, for example of tin oxide, are provided. · Behind the glass plate 5_, a brushed aluminum reflector 2J_ can be provided. Before assembling the cell. 3_ the glass plates 4_, 5_, which already carry the electrodes 1_, <3, coated on the inner surfaces with silicon monoxide or magnesium fluoride. These. Coating is formed by vapor deposition of, for example, silicon monoxide on the glass plate at an angle of about 5 ° to the surface, as described, for example, in GB Patent Application No. 1 454. When assembling the glass plates 4_, 5_ are arranged so that their evaporation directions are parallel to each other. Due to such coatings, the molecules on the coated surfaces lie in a single direction (parallel to the deposition direction) and at an angle of about 25-35 ° and typically about 30 ° to the adjacent plate surface. The liquid crystal molecules are therefore in a parallel homogeneous texture, as indicated by the arrow 13 in Fig. 1. The dye molecules in guest-host relationship to the liquid crystal molecules are also approximately in this texture, which is why the cell 3_ appears relatively strongly colored (black or gray when the dye absorbs uniformly over the visible spectrum).

-G-

237666 7

In front of or behind the cell _3, a single polarizer A_ is provided (in front of the cell 3 in FIG. 1) whose transmission axis is parallel to the direction of orientation of the liquid crystal material 6; This enhances the color of the device in this state, the OFF state. By this arrangement, the electrical vector of the incident or reflected light is set approximately parallel to the transition of the dye molecules.

When an appropriate voltage of, for example, a few volts higher than the threshold voltage required to obtain the effect is applied to the electrodes 2 ^and 8, which corresponds to the ON state, the molecules of the liquid crystal material are switched to the high texture ', which means that they are oriented parallel to the electric field along an axis perpendicular to the glass plates 4_, 5_ standing. Due to the guest-host effect, the dye molecules are also 'switched over' into this texture and orient their longitudinal axes substantially parallel to the light incident on the cell 3_ in a direction perpendicular to the glass plates 4_, 5, ie substantially end-to-end , which effectively reduces their absorption from ambient light. As a result, the cell _3 appears relatively bright or only slightly colored.

When the electrodes 7 and 8 cover only a part of the inner surface of the glass plates 4_ and S_ , the entire cell 3_ appears strongly colored in the OFF state, that is, it reflects strongly, while in the ON state

237666

only the area of the liquid crystal material 6_. between the electrodes ] _, 3_ appears bright or only slightly colored, while the remaining cell 3 appears strongly colored, ie remains in the OFF state. (If the pleochroic dye absorbs uniformly over the visible spectrum, the strong color appears black or gray).

By suitably shaping the electrodes 1_, 8_ in the form of discrete, opposing parts, ie strips or segments, of a digit, which can be connected separately to a voltage source (not shown), corresponding symbols or letters can be displayed be achieved by (known per se) photoetching of, for example, SnO-existing layers used for the electrodes ] _, 8_ before assembly.

When in FIG. For example, in the clock display shown in FIG. 3, the electrodes 7, 8 are arranged to give numerical seven-segment digits for time display; as an example of such a digital display is shown in Fig. 3, the time 12.45. Such displays may further include a periodically pulsating point P as in conventional clock displays indicating the operation of the device.

Examples of suitable colored liquid crystal materials which can be used as liquid crystal material 6, for example for display devices as in FIG. 1, are solutions of the abovementioned

-ist-

in the liquid crystal material E43 and the matrix 1 given above, wherein the layer thickness of the liquid crystal layer 6_ 1 is 2 μηη.

According to an alternative embodiment of the device according to the invention also display devices can be constructed in a conventional manner, based on the phase change from the cholesteric to the nematic state. The structure is the same as in the apparatuses shown in Figs. 1-3, except that the inner surfaces of the electrodes, supporting plates 4, 5 are not coated with MgF, - or SiO, no polarizer is required, and the liquid crystal material 6_ in this case is essentially a cholesteric material with a long helix pitch (molecular helix pitch on the order of about 2 μm with a pleochroic dye). Suitable materials are the liquid crystal materials E43 and, for example, the matrix 1 as defined above containing the above-mentioned dye mixture, which was used in the described on the Fig. 1-3, based on the Freedericksz effect device, wherein the thickness of the liquid crystal layer 6_ turn 12 μΐΐι amounts.

In the OFF state, ie without applied voltage, the cell 3 appears as in the case of the

237666

Freedericksz effect based display device. strongly colored. The liquid crystal material 6_ is in this state in the focal conic texture consisting of an array of random molecular helices. The dye molecules assume the same arrangement due to the guest-host effect. The strong coloration, which may be black or dark gray, is caused by the partial absorption of the ambient light incident on the liquid crystal material 6 ' by the plate A_ from the dye molecules oriented perpendicular or oblique to the propagation direction of the light.

In the ON state, a voltage (typically 10 to 15 V) is applied to the electrodes 1, 8, which is sufficient to achieve the homeotropic texture, in which the liquid crystal molecules between the electrodes 1 , 8 are substantially reoriented and are aligned perpendicular to the plates 4_, 5_. The dye molecules between the electrodes 1_, 8 ^ are also reoriented to this arrangement due to the guest-host effect. The region between the electrodes 7_, 8 appears in this state, as well as in the devices based on the Freedericksz effect, bright or only weakly colored, since the dye molecules with respect to the ambient light, in the direction perpendicular to the cell 3_, ie perpendicular to the plates 4_, 5_ propagates through the plate 4_, are substantially oriented with their ends in advance.

- ys -

237566 7

Liquid crystal materials suitable for this application are the commercially available liquid crystal material E43 or about the matrix 1 as indicated above (96% by weight) containing the commercial material CB15 (4% by weight). As the dye dissolved in this matrix, the above-mentioned dye mixture can be used. The commercially available liquid crystal material CB 15 consists of

the compound (+ J-CH ₃ CH ₂ CH (CH ₃ ) CH ₉ (BDH Chemicals Ltd.).

Claims (43)

237666 Inventory Review _ T. liquid crystal material for guest-host liquid crystal devices based on a liquid crystal material and a pleochroic dye, marked by at least one Anthrachinonverbindung without water solubility causing and ionic substituents of the formula I. X Ö X
as a pleochroic dye, where: Each Q is independently NH ₂ , OH, alkyl, aryl, NO ₂ or halogen, Each X is independently H, -SR, where R independently is in each case alkyl, aryl or cycloalkyl, <Z ¹ '
² where Z ₁ and Z _{2 are} independently H, Alkyl, aryl or cycloalkyl, or Q and η 0 or an integer from 1 to 4, inclusive, 237666 wherein at least two of the groups X are different -SR groups. 2. Liquid crystal material according to item Π, characterized by an anthraquinone compound of the formula I, in which one of the groups Q, X, R and Z, which represents an alkyl group, a substituent selected from oxygen, alkoxy, halogen or monocyclic aryl substituent in the alkyl group. 3. Liquid crystal material according to item 1 or 2, characterized by an anthraquinone dye of the formula I in which one of the groups Q, X, R or Z is an alkyl group having at most 20 C atoms. 4. Liquid crystal material according to item 3, characterized by an anthraquinone dye of the formula I in which one of the groups Q, X, R or Z is an alkyl group having at most 10 C atoms. 5. Liquid crystal material according to item "4, characterized by an anthraquinone dye of the formula I in which one of the groups Q, X, R or Z is C-- to C, -alkyl. 6. Liquid crystal material according to one of the points ^ to 5, characterized by an anthraquinone dye of the formula I, in which one of the groups Q, X, R or Z is an aryl group having at most 15 C-atoms. 7. Liquid crystal material according to item 1 6, characterized by an anthraquinone dye of the formula I in which .j ?. 237666 one of the substituents Q. X, R or Z is a phenyl group. 8. Liquid crystal material according to Pun.kt_j. 7, characterized by an anthraquinone dye of the formula I in which one of the groups Q, X, R or Z is a phenyl group substituted by lower alkyl, lower alkoxy, halogen, cyclohexyl and / or phenyl. 9. Liquid crystal material according to one of. Points 1 to 8, characterized by an anthraquinone dye of the formula I ,. in which one of the groups R or Z is a cycloalkyl group having at most 15 C atoms. 10. Liquid crystal material according to Funkt. i-9, characterized by an anthraquinone dye of the formula I in which one of the groups R or Z is a lower alkyl, lower alkoxy, halogen and / or monocyclic aryl substituted cyclohexyl group. 11. Liquid crystal material according to one of the items 1 to 10, characterized by a dye of the formula Aryl and Alkyl, aryl or cycloalkyl and R. and R ₂ are different from each other. 237666 12. liquid crystal material according to point 11, characterized by a dye of the formula 0 SR, are R. and R ₂ are phenyl groups which are different from each other as to their nature or the position of a substituent thereon. 13. Liquid crystal material by point; 11 or 12, characterized by a dye of the formula in the R-phenyl and R _{0 is} 4-t-butylphenyl, 14. liquid crystal material according to one of the items to 10, characterized by a dye of the formula '2 237666 7 in which T-, T ", Τ, and ¹ → _{4 are} each independently alkyl, aryl or cycloalkyl and not more than three of these substituents are identical. 15. Liquid crystal material according to one of the items 1 to 10, characterized by a dye of the formula -S 0 S- Ti -so s- 10 / in the T _g H and mean t-butyl. 16. Liquid crystal material according to one of the items 1 to 10, characterized by a dye of the formula SY. wherein Y ₁ , Y ₂ and Y ^ are each independently alkyl, aryl or cycloalkyl. 17. Liquid crystal material according to > point '· 1 / characterized by an anthraquinone dye of the formula I in which η- 23 7 66 6 7 two of the substituents X are -SR, the other substituents X are OH or NH- and the substituent; Q are alkyl, where η is 1 or 2. 18. Liquid crystal material after . Point; , 17, characterized by an anthraquinone dye of the formula I, in which two of the substituents X are differently substituted phenylthio groups, the other two substituents X are OH and the substituents Q are each C, - to C_ alkyl, where η is 2. 19. A liquid crystal material according to item 18, characterized by an anthraquinone dye of the formula I in which the OH groups are in the 1- and 5- or 1- and 8-positions of the anthraquinone skeleton and the alkyl groups Q are adjacent to the OH groups. 20. Liquid crystal material according to one of: dots to 19, characterized by a dye composition containing one or more unsymmetrical substituted polythioanthraquinone dyes according to any one of claims 1 to 11, wherein at least two differently substituted thio groups are present, and one or more symmetrical substituted Polythioanthrachinonfarbstoffe, where all substituted thio groups are identical. 21. A liquid crystal material according to item 20, characterized by a dye composition which is at least 237666 7 50 wt .-% of one or more unsymmetrical substituted Polythioanthrachinonfarbstoffen. 22. Liquid crystal material according to item .1, characterized by an anthraquinone dye of the formula C (CH. 23. Liquid crystal material after. Item 1, characterized by an anthraquinone dye of the formula C (CH 3 ⁷ 3 C (CH 24. Liquid crystal material according to point ^ _l characterized by an anthraquinone dye of the formula Ίβ 237666 7 25. Liquid crystal material according to point \ _t characterized by an anthraquinone dye of the formula O S S O 26. Liquid crystal material according to claim 1 / characterized by an anthraquinone dye of the formula 27. Liquid crystal material according to item 1, characterized by an anthraquinone dye of the formula (CH 3'3 237666 28. Liquid crystal material according to: P ^u £ JL 1 / characterized by an anthraquinone dye of the formula C (CH ₃ ) H \ S 0 29. A liquid crystal material according to any one of claims to 28, characterized by 0.75 to 10 wt .-% pleochroic dye. 30. Liquid crystal material according to item 29, characterized by 2 to S wt .-% pleochroic dye. 31. Liquid crystal material according to one of claims 30, characterized by a mixture of dyes, at least one of which is an anthraquinone dye of the formula I according to claim 1, as a pleochroic dye. 32. Liquid crystal material according to item: 31, characterized by a mixture of a blue dye and an orange dye, which is an anthraquinone compound of the formula I according to claim, as a pleochroic dye. 33. The liquid crystal material according to item -32, characterized in that the mixture further comprises a yellow dye and / or a red dye and comprises a neutral-colored mixture. 237666 34. liquid crystal material according to ^ point ^ Λ, characterized by a neutral-colored mixture of a yellow dye, a red dye and a blue dye, at least one of which is an anthraquinone compound of formula I according to claim 1, as a pleochroic dye. 35. The liquid crystal material according to any one of items 1 to 34, characterized in that the liquid crystal material mainly comprises 4-n-alkyl or -alkoxy-4'-cyanodiphenyl compounds. 36. The liquid crystal material according to any one of items 1 to 34, characterized in that the liquid crystal material mainly comprises 1- (4'-cyanodiphenyl) -4-n-alkylcyclohexane compounds. 37. A liquid crystal material according to any one of the items - \ 34, characterized by a liquid crystal material comprising a nematic liquid crystal material together with a chiral agent and suitable for cholesteric to nematic state-based device switching. 38. A liquid crystal material according to item _35, characterized by a liquid crystal material comprising a nematic liquid crystal material together with a chiral agent and suitable for cholesteric to nematic state-based device switching. -M- 3 9 Γ Γ Γ «/ boo 39. A liquid crystal material according to item 36, characterized by a liquid crystal material comprising a nematic liquid crystal material together with a chiral agent and suitable for cholesteric to nematic state-based device switching. 40. An electro-optical liquid crystal device having two electrically insulating substrates, at least one of which is optically transparent, on the inner surfaces of the substrates provided electrodes and an interposed layer of a dielectric material, characterized by a liquid crystal material according to any one of claims 1 to 40 as a dielectric material. 41. A liquid crystal device according to item 40 _f, characterized in that it is based on the cholesteric to nematic state phase change device. 42. Liquid crystal device according to ^; Item 40, characterized in that it is a device based on the Freedericksz effect. 43. A liquid crystal device according to item 40, characterized in that it is a device based on the twisted nematic structure. See 1 drawings