A guest-host smectic cell incorporates an alkyl 1,4-diaminoanthraquinone-2-carboxylate blue dye which is relatively highly resistant to degradation when exposed to the fields and current densities typically employed for switching by means of electrohydrodynamic induced instability effects. Such dyes may be employed admixed with other stable dyes to provide a black dye.

2,3-Dicyano-anthrachinone der Formel worin R Wasserstoff, Alkyl oder Cycloalkyl bedeutet, erhält man in guten Ausbeuten und hoher Reinheit durch Umsetzung von Verbindungen der Formel worin X Wasserstoff oder die Sulfonsäuregruppe bedeutet, mit Cyaniden in Gegenwart von Formamid oder N-Methyl-formamid und gegebenenfalls Oxidationsmittelns sowie Schwermetallkatalysatoren.

Anthrachinonfarbstoffe der Formel

in der

R¹ und R² jeweils für Cyano oder zusammen für einen Rest der Formel

stehen, worin

n

0 oder 1,

X¹ und X²

unabhängig voneinander Wasserstoff, C₁-C₄-Alkyl oder Halogen und

X³

Wasserstoff oder gegebenenfalls substituiertes C₁-C₂₆-Alkyl

A process for producing 1,4-diaminoanthraquinone-2,3- disulfonic acid or a salt thereof comprises reacting a 1,4-diamino-2,3-dihalogenoanthraquinone with a sulfonating agent in an aqueous medium in the presence of at least one of a quaternary ammonium compound and a quaternary phosphonium compound and, optionally, an inert organic solvent. The thus-obtained 1,4-diaminoanthraquinone-2,3- disulfonic acid or salt thereof may be reacted with a cyanogenation agent to produce 1,4-diamino-2,3-dicyano- anthraquinone.

57 Dichroitisches Material, vorwiegend in Form flüssigkri_- stalliner Phasen, enthaltend mindestens einen Anthrachinonfarbstoff der Formel in der

• Y₁, Y₂, Y₃, Y₄ die in der Beschreibung angegebenen Bedeutungen haben,

neue Anthrachinonfarbstoffe sowie ihre Verwendung zum Färben von synthetischen Polymeren.

The present liquid crystal composition is characterized by containing a dye of anthraquinone series represented by the following general formula (1) dissolved as a guest in a host liquid crystal: wherein R represents an alkyl group or a cycloalkyl group. The alkyl group or the cycloalkyl group of the dye of anthraquinone series includes those substituted by alkyl, hydroxyl, alkoxy, cycloalkyl, aryl, aryloxy, dialkylamino, or heterocyclic residue. Furthermore, the liquid crystal composition can contain two or more other kinds of the dye of anthraquinqne series, or can be used in combination with other dyes. In the dye of anthraquinone series, the group -COOR at the 2-position and the group -CN at the 3-position are particularly important for realization of cyan color and a high S value.

The dye of anthraquinone series is particularly effective 'for preparation of a black dye.

The present liquid crystal display device is characterized by comprising a liquid crystal cell comprising two transpa. rent juxtaposed substrate plates (1), transparent electrodes (2) formed each on the opposite inner surfaces of the substrate plates (1), alignment films formed each on the opposite inner surfaces of the substrate plates to cover the transparent electrodes and align liquid crystal molecules, sealing members for keeping the two substrate plates (1) at a predetermined distance, a liquid crystal composition (3) containing the dye (4) represented by the said general formula (1) being filled in the liquid crystal cell, and a light source (5) being provided outside the liquid crystal cell.

The present invention relates to an optical recording medium comprising a visible information recording layer comprising a dye denoted by the following general formula (I) on a support. In general formula (I), A denotes a substituted or unsubstituted heterocyclic group, substituted aliphatic group, or substituted or unsubstituted carbon ring group, and B denotes a substituted or unsubstituted heterocyclic group or a substituted or unsubstituted aryl group. The optical recording medium may further comprise a recording layer capable of recording and/or reproducing information by irradiation of a laser beam. The present invention further relates to a method of recording visible information on the visible information recording layer of the optical recording medium, wherein the visible information is recorded by using the same laser bean as that used in recording on the above recording layer.

The present invention relates to novel colorants based on monoanthraquinone azamethine derivatives for the mass coloring of polymers, either for polar polymers such as polyamides, polyesters, polycarbonates and ABS; or for non-polar polymers such as polyethylene and polypropylene.

The novel colorants are characterized by a substituted or unsubstituted annealed aromatic ring system comprising at least one heteroatom.

The novel colorants provide for excellent compatibility with the polymer substrate, excellent heat stability and light fastness.

Verfahren zur Halogenierung von polycyclischen Küpenfarbstoffen oder deren polycyclischen Vorprodukten mit Chlor oder Brom als Halogenierungsmittel in Gegenwart eines verdünnungsmittels bei einer Temperatur von 123 bis 200°C, wobei man geschmolzene Benzoesäure als Verdünnungsmittel verwendet.