The present invention relates to a compound of the following formula (I). The invention also relates to uses thereof as a chromophore as such or for building pigments displaying special optical effects, including metal-like reflection. ##STR00001##

An azo compound excellent in solubility in solvent and having a high absorbance coefficient is disclosed, as well as an ink containing the azo compound. Such an ink contains a solvent having a relative permittivity at 22° C. and at a measurement frequency of 1 kHz of 3 or less and having a solubility in water at 25° C. of 20 mg/L or less, and an azo compound.

An azo compound excellent in solubility in solvent and having a high absorbance coefficient is disclosed, as well as an ink containing the azo compound. Such an ink contains a solvent having a relative permittivity at 22° C. and at a measurement frequency of 1 kHz of 3 or less and having a solubility in water at 25° C. of 20 mg/L or less, and an azo compound.

A compound comprises at least one fluorescent moiety covalently bound to at least one second moiety selected from the group consisting of leuco moieties and chromophore moieties.

A compound comprises at least one fluorescent moiety covalently bound to at least one second moiety selected from the group consisting of leuco moieties and chromophore moieties.

The present invention relates to a compound of the following formula (I). The invention also relates to uses thereof as a chromophore as such or for building pigments displaying special optical effects, including metal-like reflection.

##STR00001##

A compound comprises at least one fluorescent moiety covalently bound to at least one second moiety selected from the group consisting of leuco moieties and chromophore moieties.

A compound comprises at least one fluorescent moiety covalently bound to at least one second moiety selected from the group consisting of leuco moieties and chromophore moieties.

A method is described for exfoliating a microcrystal of an anthracene derivative by irradiation with short pulses of light having a wavelength of 220-420 nm. The irradiation induces a cis-trans isomerization of the anthracene derivative in a part of the microcrystal, which leads to the separation of an outer layer having a thickness of 200-600 nm. The exfoliated microcrystal may be irradiated again with pulses of light of a same or different wavelength.

A method is described for exfoliating a microcrystal of an anthracene derivative by irradiation with short pulses of light having a wavelength of 220-420 nm. The irradiation induces a cis-trans isomerization of the anthracene derivative in a part of the microcrystal, which leads to the separation of an outer layer having a thickness of 200-600 nm. The exfoliated microcrystal may be irradiated again with pulses of light of a same or different wavelength.