A nonlinear optical dye includes a compound represented by the general formula (1) below. ##STR00001## In the above general formula (1), each of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 independently represents a hydrogen atom, an alkyl group having a carbon number of 1 to 6, a halogen atom, a hydroxyl group, a nitro group, a cyano group, or a methylsulfonyl group. In the present invention, it is preferred that each of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 independently represents a hydrogen atom, an alkyl group having a carbon number of 1 to 6, or a halogen atom. In the present invention, it is also preferred that the nonlinear optical dye has a dipole moment of 2.1 D or less and a maximum absorption wavelength within a range of 315 to 360 nm.

Disclosed is a mono-azo dichroic dye compound represented by the following Chemical Formula 1, a composition for polarizing plate, a polarizing plate, and an optical device. ##STR00001## In Chemical Formula 1, R.sub.3 represents a substituted or non-substituted heterocyclic group having 1-20 carbon atoms. The mono-azo dichroic dye compound shows excellent dichroic properties, and has excellent heat resistance and photo-resistance, and thus may be used advantageously for a dye-based polarizing plate.

The invention concerns a new class of tubulin polymerisation inhibitors and their applications in research and medicine, notably in chemotherapy. The invention proposes new azoaryl derivatives of formula (I):

##STR00001##

as defined in Claim 1, which may be fully reversibly interconverted between non-tubulin-binding trans and tubulin-binding as isomeric forms, either by irradiation or spontaneously. The invention also concerns compounds with a azoaryl structure for use in studying the cytoskeleton and/or its associated processes, or in the treatment of a disease for which a tubulin polymerisation inhibition activity has a beneficial effect, wherein the compound is administered to the cell, organism or patient in need of such treatment in the trans form of the diazenyl bond, and where this trans form is inactive as regards a tubulin polymerisation inhibition effect, and where after photoisomerisation in vitro, in cellulo or in vivo to an azoaryl compound in its cis isomeric form of the diazenyl bond by the application of light, optionally with modification in vitro, in cellulo or in vivo of one or more substituents, the resultant cis form is active as regards a tubulin polymerisation inhibition effect.

The present invention refers to dyes of the formula (I) and mixtures thereof ##STR00001##
a process for their production and to their use.