DE3006744A1 - PLEOCHROITIC COLORS CONTAINING LIQUID CRYSTALS - Google Patents

Description

Electro-optical ^ facilities in which liquid crystals Used to "order" usually two in one Spaced transparent flat plates with very thin transparent electrodes on their inside oriented surfaces, which are sealed on their periphery to form a closed cell. The space between the plates is filled with a liquid crystal mass. When exposed to an electric field on the liquid crystal, the optical properties of the liquid crystal layer are influenced.

Heilmeier and Zanoni, Applied Physics Letters, Vol. 13 (1968), pp. 91-92, have discovered that when pleochroic dyes are admixed with nematic liquid crystals in an electro-optical display system of the type described above, the pleochroic character the dye is then expressed when an electric field is applied and canceled. This means, that the display device appears to change color or change from clear to colored when that electric field is applied and canceled and the orientation of the pleochroic dye changes. The nematic liquid crystal compound is commonly referred to as the "host" and the pleochroic dye is commonly referred to as the "guest" and the combination is accordingly referred to as the guest-host connection. Presumably they will be in the host mix dissolved molecules of the pleochroism are oriented by the liquid crystal compound and result thereby a jointly aligned guest-host system. When the liquid crystal (host) by intermittent application of an electric field is oriented or reoriented, the orientation of the pleo-

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chroic dye (guest) as a result of the movement of the Host molecules. This phenomenon has been described in U.S. Patents 3,551,026, 3,597,044 and 3,960,751, for example.

Many pleochroic dyes suitable for use in host-guest combinations are elongated Molecules that absorb little or no light oscillating parallel to the long axis while they are Absorb light oscillating parallel to the short axis in different areas of the visible spectrum. Other pleochroic dyes can align in opposite directions and are colorless (non-absorbent) in relation to light that oscillates along the short axis of the molecule and colored (absorbing) in relation to parallel light oscillating along the long axis.

By combining two pleochroic dyes, Each one of the above two types, facilities can be created that differ from one Change color to another. Another effect is achieved by adding an isotropic, i.e. non-pleochroic Dye achieved together with a pleochroic dye. The colors of the two dyes add up at one level and the color of the isotropic Dye appears in the other stage of passing through the electric field.

In order to obtain a periodic sequence of colorless and colored or of two colors for a given device, the dye is favorably used in such an amount as that in the nematic liquid crystal is soluble, and not in excess of that amount which will align the amount of liquid crystal present able. In general, the pleochroism dyes can be used in various liquid crystal compositions in amounts up to about 25 percent by weight, based on the total mass

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the guest-host combination, be effective. In some cases the solubility of the pleochroism dye in the liquid crystal is insufficient to exceed concentrations to achieve about 5 percent by weight. Many well-known guest-host combinations can achieve contrasts from 0 to a maximum electric field of about 2: 1 to about 4: 1.

It is generally believed that there must be a dye suitable for use in liquid crystal display systems favorable properties with regard to pleochroism, the order parameter and the solubility in the liquid crystal mass exhibit. The structural properties of the molecules of the pleochroism dye that have such Have favorable parameters are usually similar to those of the liquid crystal host molecules. Accordingly were long, rod-shaped easily polymerizable molecules, large heavy residues and linearity of the dye molecules for important aspects kept. Examples of such dyes are, for example, in US Pat. Nos. 3,7,3,329, 3 833 287, 3 960 751 and 4 Ο32 219, as well as in the publications "Pleochroic dyes of high optical order parameters" by J. Constant et al., 6th International Liquid Crystal Conference, Kent, Ohio (1976), and by D.C. White et al., J. Applied Physics, Vol. 45 (1974), pp. 4718-4723.

The invention is based on the object of new liquid crystal compositions with positive dielectric anisotropy that contain dyes that are characterized by a particularly strong pleochroism, due to high solubility in usual positive nematic liquid crystal masses, due to a high degree of optical order and excellent chemical stability in combination with liquid crystal compounds distinguish. This object is achieved by the invention.

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The invention "accordingly relates to a liquid crystal composition with positive dielectric anisotropy, containing at least one nematic liquid crystal compound with positive dielectric anisotropy and an effective amount of a pleochroic dye, characterized thereby is that the pleochroism dye has the general formula I.

(R) ₁

(SQ) _n

in which a has the value 1 or 0, where, if a has the value 1,
η has the value 0,

m represents an integer from 1 to 4, R a methyl or methoxy group or a hydrogen off atom means and

the radicals Y, independently of one another, represent amino, nitro or hydroxyl groups or chlorine or fluorine atoms, and

if a has the value 0,

the radicals Y independently of one another amino, nitro or represent hydroxyl groups and the radicals Q independently of one another radicals of the general formula

or.

mean and are only in the 1-, 4-, 5- and / or 8-position, where the radicals R ¹ and R "independently represent hydrogen atoms or a nonionic substituent,
m is 0, 1, or 2

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ι η is an integer from 1 to 4 and the sum

of m + η has at most the value 4-,

with the proviso that when Q denotes the radical ~ M y, η denotes 2 and m denotes;

Have value O and get the leftovers

S-Q ntir in 1- and 4-, 1- and 5-, 1- and 8-, 4- and 5- or 5- and 8-positions.

The nature of the above-mentioned non-ionic radical is not critical for the pleochroic character of the compounds. However, the nonionic radical can to a certain extent influence the solubility of the dye in the liquid-crystal composition. Examples of the nonionic substituents R ¹ and R ″ are branched or unbranched alkyl radicals having 1 to 12, preferably 1 to 4 carbon atoms, alkoxy radicals having 1 to 12, preferably 1 to 4 carbon atoms, halogen atoms, such as chlorine, fluorine or bromine atoms , Trifluoromethyl, difluoromethyl and alkylsulphonyl groups with 1 to 12, preferably 1 to 4 carbon atoms, sulphonamide radicals, which are optionally substituted on the nitrogen atom by lower alkyl radicals, for example with 1 to 4 carbon atoms, or by benzyl groups, aralkoxy groups, preferably benzyloxy groups, or aryloxy groups, preferably The benzyloxy and phenoxy groups can in turn be substituted by halogen atoms or alkyl and alkoxy radicals having 1 to 4 carbon atoms.

Specific examples of the pleochroitis according to the invention Dyes are listed below:

1_ (2'-Benzothiazinyl) -thioanthraquinone, 1,5-bis- (2'-Benzothiazinyl ) -thioanthraquinone, 1,4-bis- (2'-benzothiazinyl) -thioanthraquinone, 1,8-bis- (2'-benzothiazinyl) -thioanthraquinone, 1,5,8-tris- (2'-benzothiazinyl) -thioanthraquinone, 4 ~ (2'-Benzothiazinyl) -thioanthraquinone, 1,4-, 5,8-tetra- (2'-benzothiazinyl) -thioanthraquinone, 1- (2 '- ^ "-

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thiazinyl) -thioanthraquinone, 1- (2 '- ^ 5 "-Methyl7-" b enzothiazinyl) -thioanthraquinone, 1- (2' - ^ "- ethoxyy-benzothiazinyl) -thioanthraquinone, 1- (2 ^f - / 5", 6 "-Dimethyl-ben ζ ο thiazinyl) -thioanthraquinone, 1- (2 '- ^" - Bienos ^ -fcenzothiazinyl) -thioanthraquinone, 1- (2'-Z5 "-Decylox27-benzothiazinyl) -thioanthraquinone, 1- (2 · -Z5 "- (4-"'-η-Butyl) -phenoxs7-benzothiazinyl) -tliioant] irachinon, 1- (2' - ^ 5 "-7 zinyl) -thioanthracliinon _i 1- (2 ^l - ^ 5 ^tl th.iazinyl) -th.ioanthracliinone, 1,5-bis- (2 '- / uonyloxy _ / - l-deizothiazinyl) -thioantlirac] iinone, 1,5-bis- (2 ^l - / decylsulfonyl7- "benzotliiazinyl) -thiaant] aracliinone , 1,5-Ms- (2 '- / 5 "-Hetlioxy_7- ■ benzothiazinyl ^ -tliioanthracliiiion, 1,5-bis- (2' - / 5" -Glilos7-Tjenzothiazinyl) -thioantlirac] iinon, 1,5- l3is- (2 · - / 5 "-JPh-eno3C27-tenzothiazinyl) -tliioantliracliinon, 1,5-Ms- (2 '- / 3 ^I!, 6" -Dimethy3, / - benzothiazinyl) -tliioant] iracliinon, 1, 8-t »is- (2 'benzothiazinyl) -thioantlirach.inone, 1,8-Ms- (2' - / 5", 6 "-Dimethyl7-benzothiazinyl) -thioanthraquinone, Λ , 8-ΐ» Ϊ3- (2 '-Ζ5 "-Decylbenzothiazinyl) -th.ioantlirach.inoii, 1,8-bis- (2' - / 5"-lTonyloxy7-'benzothiazinyl) -thioanthracliinone, 1,8-T3is- (2 '/ 5 "(4 × ¹¹ '-n-butyl) -plienox2 / -T3enzothiazinyl) -tliioanth.rach.inone _J - (2 ^l - / 5" -chloro ^ -l (eiizotliiazinyl) -thioanthracliinone, - (2 ¹ -25 ", 6" -Dimetliyl7-benzotliiazinyl) -thioantlu? Acliinone, 1- (2 '-BenzotMazinyl) -th.io-2-aminoanthrac] iinone, 1- (2' -Benzothiazinyl) -tiiio- ^/ i-amiiioantliracliinon _i 1 - (2 * Benzothiazinyl) -th.io-5-aminoaiitlirach.inon, 1- (2'-benzothiazinyl) -thio-5-chloroanthraquinone, 1- (2'-benzothiazinyl) -thio-4-chloroanthraquinone, 1- ( 2'-Benzothiazinyl) -thio-8-chloroanthraquinone, 1- (2'-Benzothiazinyl) -thio-4-hydroxoxyanthraquinone, 1- (2'-Benzothiazinyl) -thio-5-hydroxyanthraquinone, 1- (2 * -Benzothiazinyl) -thio-2,6-dihydroxyanthraquinone, 1- (2'-benzothiazinyl) -thio-4-amino, 5-nitroanthraquinone, 1- (2'-benzothiazinyl) -thio-4,8-dinitro, 5-chloroanthraquinone, 1 , 5-bis- (2 '- /! ^' - Butox ^ -benzothiazinyl) -thio - ^ -, 8-dihydroxyanthraquinone, 5,8-bis- (2 » S" , 6 "- Dimethyl7-'benzothiazinyl) -thio-1, ^ - aiaminoanthraquinone "1 j 8-Ms- (2 '- ^ 57

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anthraquinone, 4- (2 ^l - / 5 "-0hlor7-benzothiazinyl) -thio-1 ~ hydroxyanthraquinone, 1,4-bis- (4'-methylphenyl ^ thioanthraquinone, 1,8-bis- (4'-methylphenyl) - thioanthraquinone, 4,5-bis- (4-methylphenyl) -thioanthraquinone, 5,8-bis- (4-methyl-phenyl) -thioanthraquinone, 1,5-bis- (4'-methylphenyl) -thioanthraquinone, 1 , 4-bis- (4-decylphenyl) -thioanthraquinone, 1,5-bis- (4-decylphenyl) -thioanthraquinone, 1,8-bis- (4'-decylphenyl) -thioanthraquinone, 4,5-bis- (4'-decylphenyl) -thioanthraquinone, 5,8-bis- (4'-decylphenyl) -thioanthraquinone, 1,4-bis- (4'-methoxyphenyl) -thioanthraquinone, 1,4-bis- (4'-decyloxyphenyl ) -thioanthraquinone, 1,5-bis- (4'-methoxyphenyl) -thioanthraquinone, 1,5-bis- (4'-decyloxyphenyl) -thioanthraquinone, 1,8-bis- (4'-methoxyphenyl) -thioanthraquinone, 1 , 8-bis- (4'-decyloxyphenyl) -thioanthraquinone, 1,4-bis- (4 * -chlorophenyl) -thioanthraquinone, 1,5-bis- (4'-chlorophenyl) -thioanthraquinone, 1,8-bis- (4 · -Ghlorpheny 1) -thio anthraquinone, 1,4-bis- (4'-J-fluorophenyl) -thioanthraquinone, 1,5-bis- (4'-I'-fluorophenyl) -thioane thrachinone, 1,8-bis- (4'-fluorophenyl) -thioanthraquinone, 1,4-bis- (4'-bromophenyl) -thioanthraquinone, 1,5-bis- (4'-bromophenyl) -thioanthraquinone, 1,8 -bis- (4'-bromophenyl) -thioanthraquinone, 1,4-bis- (4 * -trifluoromethy1) -thioanthraquinone, 1,5-bis- (4'-trifluoromethy1) -thioanthraquinone, 1,8-bis- (4 '-Trif luormethy 1 ^ thioanthraquinone, 1,4-bis- (4'-benzylphenyl) -thioanthcachinone, 1,5-bis- (4-benzy! Phenyl) -thioanthraquinone, 1,8-bis- (4'- Benzylphenyl) thioanthraquinone, 1,4-bis (4 · -henoxyphenyl) -thio anthraquinone, 1,5-bis- (4 '-henoxypheny 1 ^ thioanthraquinone, Λ , 8-bis- (4' -phenoxyphenyl) -thioanthraquinone , 1,4-bis- (4 '- / 4 "-Methylphenyl7-phenyl) -thioanthraquinone, 1,4-bis- (4'-Z4" -Nonylphenyl7-phLenyl) -thioanthraquinone, 1,5-bis- (4 '- / 4 "-Methylphenyl7-phenyl) -thioanthraquinone, 1,5-bis- (4' - / 4" -Iionylphenyl7-pb.enyl) -thioanthraquinone, 1,8-bis- (4 '- / 4 "- Methylphenyl7-plienyl) -thioanthraquinone, 1,8-bis- (4 '-Z4 "-nonylplienyl7-plienyl) -thioanthraquinone, 1,4-bis- (4' - / 4" -methoxyphenyl7-phenyl) -thioanthraquin on, 1,4-bis (4'-Z4 "-Nonoxypheny! / - phenyl) -thioanthraquinone,

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1,5-bis- (4 '- ^ 4 "-Methoxypheny! / - phenyl) -thioanthr aquinone, 1,5-bis- (4' - / 4" -If onoxyphenyl7-phenyl) -thioanthr aquinone, 1,8 -bis- (4 ■ - $ ■ "-Methoxyphenyl7-phenyl) -thioanthr aquinone, 1,8-bis- (4 '- / 4" -Uonoxyphenyl7-pkenyl) -thioanthraquinone, 1,5-diamino anthraquinone, i-amino -5-chloroanthraquinone, i-amino-4-hydroxyanthraquinone, 1,4-diamino-5-nitroanthraquinone, i ^ -diamino ^ -hydroxyanthraquinone, 1-chloro-5-hydroxy anthraquinone, 1,8-dinitro-4,5 -düydroxyanthrachinon, 1-chloroanthraquinone, 2-methy 1-1,4-diaminoanthraquinone, 2-methyl-1-amino-4-hya ^ oxyanthraquinone, 2-methyl-1-amino-4-chloroanthraquinone, 2-methyl -1,4-diamino-5-nitroanthraquinone, 2-methy1-1,4-diamino-3-chloranthraquinone, 2-methyl-1,8-dichloroanthraquinone, 2-methy 1-1, 5-dichloroanthraquinone, 2-methy1- 1-chloroanthraquinone, 1,4-bis- (phenyl) -thioanthraquinone, 1,4-bis- (4'-butoxyphenyl) -thioanthraquinone, 1,4-bis- (4'-tert-buty! Phenyl) -thioanthraquinone , 1,5-bis- (4'-n-butylphenoxy) -thioanthraquinone, 1,8-bis- (phenyl) -thioanthraquinone, 2-meth oxy-1,4-diaminoanthraquinone, 2-methoxy-1-amino-4-hydroxyanthraquinone, 2-methoxy-1-amino-5-chloranthraquinone, 2-methoxy-1,4-dihydroxy-5-nitroanthraquinone, 2-methoxy 1,5 ~ dichloro-4,8-diaminoanthraquinone, 2-methoxy-1,5-dihydroxy-4,8-diaminoanthraquinone, 2-methoxy-1,5,6-trihydroxyanthraquinone, 2-methoxy-4,7-dichloro 5,8-dihydroxyanthraquinone, 2-meth-

'' ⁵ oxy-1-hydroxy anthraquinone.

Compounds of the general formula I in which a has the value are colored and are used industrially as intermediates used in the manufacture of more complex anthraquinone dyes. Surprisingly, they now own this . Compounds have excellent pleochroism properties in guest-host combinations, although they are not structural Have properties formerly used for the beneficial properties of the known pleochroism Dyes were deemed necessary. The pleochroic dyes of the general formula I in which a den

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Has value 1, "have surprisingly broad absorption bands in the visible range, for example at 400 to 650 nm. The high extinction coefficients of these compounds together with the broad absorption bands result in increased, visibly perceived contrast ratios. For example result in liquid-crystal compositions with a net-positive dielectric anisotropy and a content of the pleochroic dyes according to the invention as Gast generally has a contrast ratio of at least about 10: 1 when measured spectrophotometrically.

The pleochroic compounds of the general formula I according to the invention, in which a has the value 0, result hitherto difficult to obtain colors, especially bright yellows with improved hue and color purity. These pleochroism compounds have sharp light absorption maxima in the range from about 430 to 440 nm. The absorption spectra are relatively free of secondary maxima at the bottom of the absorption curve. This pleochroism Compounds with positive nematic liquid-crystal compositions have optical degrees of order of the order of magnitude from about 0.65 to 0.76 and can therefore, high contrast ratios, for example in the order of magnitude of at least 10: 1. This property is special in the manufacture of liquid crystal display systems he wishes.

The anthraquinone dyes used according to the invention of the general formula I, in which a has the value 1, are known and can easily be prepared by known processes will. For example, they can synthesize the desired o-benzoylbenzoic acids from one Phthalic anhydride and a substituted benzene among Use of aluminum chloride can be obtained. The ring closure is carried out using sulfuric acid or Oleum carried out. The implementation can be done by the following

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Equation can be reproduced

O +

Various other rearrangement and condensation processes can also be used to arrive at the corresponding o-benzoylbenzoic acid. Such methods are for example in GB-PS 334-166, in Gleason and Dougherty, J. Im. Ohem. Soc. 51 (1929), p. 310, IG! Farbenindustrie, Bios Reports 987, and in Marschalk, Bull. Soc. Chim. Prance, £ ζ / 2 (1935), p. 1810. Further compounds can be obtained by direct halogenation, elimination reactions, hydrolysis of haloanthraquinones or by nitration of the corresponding anthraquinone derivatives. A large number of such compounds are known and are described, for example, by HA Lubs, "The Chemistry of Synthetic Dyes and Pigments", Reinhold Publishing Company.

Thioanthraquinone-The pleochroic / derivatives of the general formula I, in which a has the value 0, can be prepared by known processes. For example, ^ in U.S. Pat 4,096,111, in which some of the pleochroic compounds and their suitability as dyes for dyeing polyesters are described Procedures are used. Generally run the process as a base-catalyzed condensation of anthraquinone with carbocyclic or heterocyclic Mercaptans.

For example, the yellow pleochroic anthraquinone

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derivative 1,5-bis- (phen; ylthio) - anthraquinone by reaction of two equivalents of mercaptobenzene with one equivalent of 1,5-dichloroanthraquinone with potassium carbonate in 'dimethyl- ■; formamide produced under reflux. The implementation product is crystallized and separated by filtration and chromatography. A number of dyes can be used by using various ρ-substituted mercaptobenzenes produced in the above-mentioned process

, will.
. ·. ::;

Depending on the process used for production or on the origin of the dyes, it can be recommended be to purify the pleochroism dyes prior to their use in a guest-host display device. One

} ⁵ Such purification is necessary due to the presence of undesirable reaction by-products, ionic salts and other impurities which can degrade or otherwise affect the properties of the guest-host-liquid crystal mixture.

The purification can be carried out by conventional methods, for example by precipitation from sulfuric acid, Crystallization from non-ionic solvents and separation using chromatographic methods.

Vacuum sublimation processes can also be used for cleaning. With a cheap cleaning process becomes liquid chromatography using alumina and eluting with a mixture of toluene and methanol or from toluene, methanol and acetic acid

³⁰ 'used. The collected fraction of the dye in question is then evaporated to dryness and

"" dried under reduced pressure for about 12 to 24 hours.

The substituted anthraquinone derivatives of the general

Formula I result in particularly good guest-host combinations

with the commonly used nematic liquid ^L 0-3 0036/0774

crystal masses with positive dielectric anisotropy or with compounds that contain positive anisotropic compounds in predominant quantities, i.e. those that are positive in the result exhibit dielectric anisotropy »The designation “Positive anisotropy” is accordingly used for mixtures which have a net positive dielectric anisotropy.

The pleochroic dyes used according to the invention can be used alone, in the form of a mixture of several of them and with other dyes, in guest-host combinations "; functions in a relatively wide proportion; can be used with the nematic liquid crystal compositions. The upper limit of the effective amount is generally one Function of the solubility of the pleochroic dye in the liquid crystal. The pleochroism according to the invention Dyes can be effective in concentrations up to about 25 percent by weight of the total guest-host combination can be used. In the case of liquid crystal display systems that convey information, the background color, i.e. the color in the "clean" state, generally be as low as possible. For such facilities the pleochroic dyes are therefore generally preferred in amounts of about 0.5 to 5% about 0.5 to 1.5 weight percent used.

Specific examples of liquid crystal compounds having positive anisotropy suitable for use with the Pleochroic dyes suitable in the liquid-crystal compositions according to the invention are:

trans-4 - n-pentyl- (4 '-cyanphenyl) -cyclohexane, trans-4 ~ n-pentyl- (V-cyanobiphenyl-4) -cyclohexane, p-n-hexylbenzylidene-p'-amino-benzonitrile, p-methoxybenzylidene-p'-aminobenzonitrile, p-lthoxybenzylidene-p'-aminobenzonitrile, p-cyanobenzylidene-p'-n-butoxyaniline, p-cyanobenzylidene-p'-oetyloxyaniline and compounds of the general formulas

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in which R is an alkyl or alkoxy radical having 1 to 7 carbon atoms and X is an alkyl or alkoxy radical having 1 to 10 carbon atoms.

The eutectic mixtures and combinations of all of the above-mentioned compounds are also suitable. Examples of eutectic mixtures are the 4'-substituted 4-cyanobiphenyls, in which the 4'-substituents are alkyl or alkoxy radicals having 3 to 8 carbon atoms. A special example of this is the mixture known as "E-7" from BDHLtd. Another suitable mixture of compounds contains mixtures of the pheny / cyclohexanes mentioned above, for example mixtures with a content of 4-alkyl- (4 ^l -cyanphenyl) -cyclohexanes, mixtures with a content of 4-alkyl- (4'-eyanbiphenylyl) -. Cyclohexanes and mixtures containing both types of compounds. A suitable known mixture contains four components and is available under the name Nematic Phase 1132 TNC "Licristal ¹¹ from EM Laboratories Inc. This mixture contains the following ingredients in approximately the specified amount (percent by weight): 14% trans-4-n-pentyl - (4'-cyanbiphenylyl-4) -cyclohexane, 26% trans-4-n-propy 1- (4'-cyanopheny 1) -cyclohexane, 36% trans-4-n-pentyl- (4 ⁱ -cyanphenyl) - cyclohexane and 24% trans-4-n-heptyl- (4 · cyanophenyl) -cyclohexane.

Examples of suitable groups of nematic liquid crystal compounds and masses with negative anisotropy are the following groups of compounds: p-methoxybenzylidene-p'-n-buty! aniline, p-methoxybenzylidene p'-aminophenylbenzoate, p-methoxybenzylidene-p'-aminophenyl acetate, p-azoxyanisole, p-n-buty! benzoic acid, p'-n-hexyl

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oxyphenyl ester, p (p ^f -ethoxyphenylazo) -phenylheptanoate, ρ (ρ '-ethoxyphenylazo) -phenylundecylenate, p-butoxybenzylidene-p'-penty! aniline and p-ethoxybenzylidene-p'-n-butylaniline.

The following connection groups also belong to this group: O O

and RO - ^^ - N = N- ^ jV R ¹

where R and R ^{1 are} lower alkyl radicals having 1 to 4 carbon atoms;

where R is an alkyl group having 1 to 7 and R is an alkoxy group having 1 to 7 or R is an alkoxy group having Λ to 7 and R is an alkyl group having Λ to 7 carbon atoms; O ο

oc 4 \ ο-ζ- (Γ \. _R i

ä— ^y b ^ ^J

where R and R are alkyl radicals having 1 to 7 carbon atoms and a and b represent hydrogen atoms or one of them represents a chlorine atom.

Some of the negative nematic liquid crystal compounds mentioned above are disclosed in U.S. Patents Re 29 34-9, 3 829 491, 3 809 656, 3 994 567 and 3 7-3 33I. When the negative nematic compounds are combined with positive nematic compounds, mixtures with a net positive anisotropy. This can be achieved by only relatively low proportions of compounds with high positive anisotropy are used when the others Compounds have a relatively low negative anisotropy.

The anthraquinone pleochroism parisons described above can be used to manufacture electro-optical

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see display systems such as liquid crystal displays being used. The pleochroic dyes can be used together with liquid crystal compounds or compositions with positive dielectric anisotropy in a guest-virt relationship. This is achieved by _s mixing the pleochroic dye and the liquid crystal and filling a conventional display cell with the mixture according to known methods. For example, the twist nematic field effect display systems can be made as described, for example, in US Pat. No. 3,918,796. In addition, other display systems that use positive liquid crystal compounds can be operated with the pleochroic dyes according to the invention, for example the devices according to TJS-PSs 3 7-3 329, 3 833 287, 3 960 751 and M- Ο32 219. The display devices are of particular interest with the known cholesteric nematic phase change device, in which the guest-host mixture contains a proportion of, for example, up to 50 percent by weight of a chiral or optically active cholesteric liquid crystal, such as cholesteryl nonanoate. In this mixture, the pleochroic dye (guest) absorbs all levels of light, so that there is no need for an external polarization direction.

The unusual properties of the pleochroic dyes according to the invention make them advantageous Suitability in mixtures with nematic liquid crystals in display systems, e.g. for computers and clocks, as well as for use as electronic locks, for example in cameras and projectors. When using In a mirror arrangement, mirrors are obtained with their help, which are from mirroring to darchsehen and used in cameras or other devices that use mirrors

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can be.

The substituted anthraquinone compounds used according to the invention are also exceptional because of their high values of the optical degree of order S are remarkable. This parameter is a measure of the effectiveness of the Orientation of a dye. It is calculated by measuring the absorption of polarized light as the log des reciprocal value of the percentage transmission at the wavelength and the angle of incidence of the maximum absorption by a solution of the dye in a liquid crystal in a liquid crystal cell according to the above Description is determined with and without the application of an orienting electric field. The degree of order S becomes by the equation

expressed in which A ^ and A _{Q represent} the absorption with and without an electric field. The degree of order S is given as a decimal number with a value below 1. It can vary within certain limits for a particular dye depending on the particular nematic liquid crystal used as the host. Many of the known pleochroism dyes have values for S on the order of about 0.3-0.5. The pleochroic dyes used according to the invention have optical degrees of order of at least 0.5, with the preferred compounds being able to achieve values of 0.7 and higher. This is a very large range of these values which cannot be expected for the compounds with the structure of the pleochroic dyes described.

The guest-host combinations according to the invention also yield very high contrast ratios as a result of the high Degree of order of the described pleochroic color

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Fabrics. When using the guest-host combinations according to the invention can easily contrast ratios of 10: 1 and even higher can be achieved.

The contrast ratio of a translucent display system defines the difference in optical density between the switched-on and the switched-off state of the display system measured at 25 ° C using the visible part of the spectrum at which maximum absorption occurs. In the case of a reflective display device the contrast ratio is generally determined using a directional light source measured at an angle of incidence of 20 ° and observed at a normal viewing angle.

The examples illustrate the invention.

Examples 1 to 13 A substituted anthraquinone dyes of the general formula I were purified and mixed in ¹ IUssigkristallmasse in an amount of 1 percent by weight in a positive nematic B comprising a mixture of three Cyanphenylcyclohexanen and a Cyanbiphenylylcyclohexan contains (Nematic Phase 1132 TUG Licristal) supplemented with 1 percent by weight of cholesteryl nonanoate was added. The values for calculating the optical degree of order S were determined in a spectrophotometer as described above. The results are shown in Table I below

summarized.
30th

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- 24 Table I.

■ 1 position in the anthraquinone ring 5 6 Cl - 7th 8th waves
length, S. example NH ₂ 2 3. 4th Cl - - _ _ no 0.62 1 NH ₂ - _ - Cl - 510 0.62 2 NH ₂ - - - 520 0.70 3 NH ₂ - ■ OH NH ₂ - - - 530 0.68 4th NH ₂ CH ₃ - OH NO ₂ - - - 540 0 ₇ 68 5 NH ₂ - - NH ₂ NO ₂ - - NH ₂ 540 0 _r 65 6th NH ₂ - - NH ₂ - - - - 600 0.71 7th NH ₂ - - NH ₂ - - - NO ₂ 620 0.70 8th NH ₂ _ _ NO ₂ - - - - 625 0 * 68 9 NC ₂ CH ₃ - NH ₂ Cl - - 550 0.60 10 NH ₂ CH ₃ - - - - 450 0.65 11 Cl Cl Cl NH ₂ -. - 600 0.56 12th Cl - - Cl 415 0.50 13th - - 415

30 example.

The yellow pleochroic 1,5-bis- (fhenylthio) -anthraquinone is produced according to the following process: 2.2 g (2 equivalents) of mercaptobenzene are dissolved in a solution of 5 g of potassium carbonate and 2.7 g (1 equivalent)

35 1, Jj-dichloroanthraquinone in 30 g of K, N'-dimethylformamide brought in. Thereafter, the reaction mixture is 4 hours

030036/0774

refluxed. After cooling to 80 ^° C., 100 ml of methanol are added to the mixture. The precipitated crystalline precipitate is then filtered off, purified by chromatography on aluminum dioxide with a mixture of toluene and methanol as the eluent and dried. A light yellow-orange crystalline product is obtained.

Following the procedure described above, the following p-substituted mercaptobenzenes for the preparation of the corresponding 1,5-substituted homologous dyes used:

p-ethyl mercaptobenzene,

p-octyl mercaptobenzene,
p-decyl mercaptobenzene,

p-propyloxymercaptobenzene,

p-hexyloxymercaptobenzene,

p-nonyloxymercaptobenzene,

p-phenyl mercaptobenzene.
20th

To determine the degree of optical order, the pleochroic dyes are dissolved in an amount of 0.5 percent by weight in a positive nematic liquid crystal composition that contains a mixture of three cyanophenylcyclohexanes and one cyanbiphenylylcyclohexane (Nematic Phase 1132! DNC Licristal), and to which 1 percent by weight of cholesteryl nonanoate has been added . The values for calculating the optical degree of order S are determined in a spectrophotometer as described above. Table II below summarizes the properties of 1,5-substituted anthraquinone dyes of the general formula I, in which m is the value and η is 2 and Q is the radical -f \ - R ¹ , where R ^{1 is} the in Table II has the meaning given.

030036/0774

¹⁰

R ¹

5 -

-OC ₃ H ₇

- 26 - S. Table II Absorption maximum, 0.7 nm 0.76 44-0 0.72 43O 0.65 43 0 0.7 440 0.75 440 0.7 43O 440

-H

Example 15

Tray, following this procedure, becomes the yellow pleochroism Dye 1,5-bis- (thiobenzothiazinyl) -anthraquinone produced. 60 g N, W'-dimethylformamide, 15 g 1,5-dichloroanthraquinone, 22 g of 2-mercaptobenzothiazole and 9 g of anhydrous potassium carbonate are refluxed together for 3 hours cooked. After cooling to room temperature, the dye turns into a yellow microcrystalline powder in quantitative terms Yield obtained. By prolonged washing with methanol and recrystallization from hot dimethylformamide the dye is obtained in pure form.

Numerous homologues of this dye can be made by the method described above. In the following table III are examples of substituents in the relevant positions of the anthraquinone ring listed.

35

03003 6/0774

- 27. 300B744

Table III Position in the anthraquinone ring

1_ 4th 5 8th r _M NH ₂ NH ₂ Cl Cl OH OH Cl Cl. NO ₂ NO ₂ Cl Cl OH Cl OH Cl NH ₂ Cl NH ₂ Cl NO ₂ Cl NO ₂ Cl Cl OH OH Cl H H Cl

Further homologs can be obtained by the method described above using substituted 2-mercapto-benzothiazoles can be obtained. Substituted anthraquinone derivatives of the general formula I are used obtained, in which Q is the remainder of the formula

means, where

R ¹ one of the radicals -OC ₀ Ht, -Cz-Hy ₁₂ , -CoH ^ r ₇ . -0, -Hi. or

-C ₇ H ₁₅ O and
R "represent a hydrogen atom.

according to the method for determination described above of the optical degree of order are measurements different connections made. In Table IV below are the results for a number of substituted Anthraquinone derivatives of the general formula I

03 0036/0774

1 summarized, in which Q is the remainder of the formula

5 denotes, where R "represents a hydrogen atom and m, n, R ¹ and T have the meanings given.

Table IV

10 Position of Q m η RJ YS

1.5 0 2

1.8 0 2

1.8 2 2

1.5 0 2

¹⁵ 1.5 1 2

1.8 0 2

H - 0.72 H - 0.70 H OH 0.68 OG ₂ H ₅ - 0.75 ° 8 ^H 17 NO ₂ 0.75 CH. - 0.72

(J 3 00 3 6/0774 -J

Claims (1)

VOSSIUS VOSSIUS TA UC nisi ER · HEUNEMANN- RAUH PATENT LAWYERS SIEBERTSTRASSE 4 8OOO MUNICH 86 PHONE: (O89) 47 4 <^ Q 06744 CABLE: BENZOLPATENT MÖNCHEN -TELEX 5-29 453 VOPAT D 5 oc: P 524- (Ea / H)
Case: 915 386 MIKIiESOTA MINHTG AND MANUFACTURING COMPANY Saint Paul, Minnesota, V.St.A. "Liquid-crystal compositions containing pleochroic dyes" Priority: February 23, 1979, V.St.A., No. 14-54-0 February 23, 1979, V.St.A., No. 1454-1 Claims 20 1. Liquid crystal mass with positive dielectric anisotropy, containing at least one nematic liquid crystal compound having positive dielectric anisotropy and an effective amount of a pleochroism Dye, characterized 25 that the pleochroic dye has the general formula I. (SQ) _n 35 in which a has the value 1 or 0, where, if a has the value 1, 030036/0774 η has the value 0, m represents an integer from 1 to 4-, R a methyl or methoxy group or a hydrogen atom means and the radicals Y, independently of one another, represent amino, nitro or hydroxyl groups or chlorine or fluorine atoms, and
if a has the value O, the radicals Γ independently of one another amino, nitro or represent hydroxyl groups and the radicals Q independently of one another radicals of the general !Formula f. —Λ N ^^ • ^ M \ SR 'or ^ ^{= J} and are only in the 1-, 4-, 5- and / or 8-position, where the radicals R ¹ and R "independently represent hydrogen atoms or a nonionic substituent, m has the value 0, 1 or 2, η is an integer from 1 to 4- and the sum of m + η is at most 4-, with the proviso that if Q is the remainder, η is 2 and m is O and the remainders are S-Q only in 1- and 4-, 1- and 5-j 1- and 8-, 4- and 5- or 5- and 8-positions. 2. Composition according to claim 1, characterized in that it is 1,4-diaminoanthraquinone as a pleochroitis-related dye 1,4-diamino-5-nitro-anthraquinone, 1-amino-4-hydroxyanthraquinone, 1-amino-5-chloroanthraquinone or their Contains mixtures.
35 030036/0774 3. Composition according to claim 1, characterized in that it is 1,5-bis-phenylthio) anthraquinone as the pleochroic dye 1,5-bis- (lhioethoxybenzothiazinyl) -anthraquinone, contains their stereoisomers or mixtures. 5 4 ·. Composition according to Claim 1, characterized in that the nematic liquid crystal composition is 4-phenyl) cyclohexane and ^ - alkyl-C
contains cyclohexane.
10 5. Composition according to claim 1, characterized in that the nematic liquid crystal mass is a eutectic mixture contains of 4'-substituted 4-cyanobiphenyls, where the 4'-substituents are alkyl and / or alkoxy radicals represent having 3 to 8 carbon atoms. 6. Composition according to claim 1, characterized in that it contains the pleochroic dye in an amount of about Contains 0.5 to 5jO percent by weight of the total mass. 7. Composition according to claim 1, characterized in that it also has a maximum of about 50 percent by weight contains chiral agent. 8. Composition according to claim 7 »characterized in that it contains cholesteryl nonanoate as a chiral agent. 9. Use of the liquid crystal compositions according to claims 1 to 8 in electro-optical devices, in particular electro-optical display systems. 10. Electro-optical device containing a transparent Enclosure with electrodes on a portion of their opposing surfaces and in the enclosure a positive nematic liquid crystal compound containing an effective amount of a pleochroic dye contains dissolved, characterized in that that the pleochroic dye is the general 030036/0774 Formula I. (SQ) _n (D. in which a has the value 1 or O ", where, if a has the value 1, η has the value O, m represents an integer from 1 to 4-, * E is a methyl or methoxy group or a hydrogen atom means and the radicals T independently of one another are amino, nitro or hydroxyl groups or chlorine or fluorine atoms represent, and if a has the value O, the radicals X independently of one another are amino, Mtro- or represent hydroxyl groups and the radicals Q independently of one another radicals of the general formula mean and are only in the 1-, 4-, 5- and / or 8-position, where the radicals R ¹ and R "independently represent hydrogen atoms or a nonionic substituent, m has 0, 1 or 2, η is an integer from 1 to 4- and the sum of m + η has at most the value 4-, with the caveat that if Q is the remainder _ / \ ^ _ _R t, η is 2 and m have the value 0 and get the remainder 030036/0774 SQ are only in 1- and 4-, 1- and 5-, 1- ™ ad ⁸ "» 4- and 5- or in 5- and 8-positions. 11. Device according to claim 10, characterized in that it is 1,4-diaminoanthraquinone, 1,4-diamino-5-nitro-anthraquinone, 1-amino-4-hydroxyanthraquinone, 1-amino-S-chloranthraquinone or theirs as the pleochroic dye Contains mixtures.
10 12. Device according to claim 10, characterized in that that they are 1,5-bis- (phenylthio) -anthraquinone as a pleochroic dye, 1,5-bis- (Thioethoxybenzothiazinyl) -anthraquinone, the stereoisomers or mixtures thereof. 13. Device according to claim 10, characterized in that the nematic liquid crystal ^{composition contains 4-alkyl- (4 1} -cyanphenyl) -cyclohexane and 4-alkyl- (4'-cyanbiphenylyl-4) -cyclohexane. 14. Device according to claim 10, characterized in that that the nematic liquid crystal mass is a eutectic mixture of 4'-substituted 4-cyanobiphenyls contains, the 4'-substituents alkyl and / or Represent alkoxy radicals having 3 to 8 carbon atoms. 15. Device according to claim 10, characterized in that that they have the pleochroism dye in an amount ^ Q contains from about 0.5 to 5.0 percent by weight of the -jescimfcen mass. 16. Device according to address 10, -J ^ rIur - .: h q &k'sun ::. O refuses that it divides i; u; - ..; iLzlieh hochü; tr-.; ·, '''>) Gei / l-.jht3pi, O ^ £ iilfc ■ ° of a ciiiraien means c? Nth; iit, Γ7, Einrichtüii'j to A -; - ^ ι Jiu.:u .... -.tdui h gch ^ iii- ^ elfiimeti, ^l - J (J ϊ -J i'i 3 W / 0 7 V;. ORIGINAL BATHROOM ¹ that it contains cholesteryl nonanoate as a chiral agent. 300 36/077 4 - ^J.