Crystallization and morphology of indanthrone converted from latent pigment in the solution with photo acid generator

• The boc-protective group on the boc-indanthrone could be removed by acidolytic treatment.
• The particle size of regenerated pigment in solution treated by acidolysis was significantly increases with the amount of PAG.
• The morphology of regenerated indanthrone changed from bar like to bar like/cubic and spherical.
• The regenerated indanthrone lose crystal structure as the conversion through acidolytic process resulting from the presence of the stibium.

The crystal phase, particle size, and morphology of organic pigments play an important role on the surface coating properties, such as substrate absorbency, surface smoothness, the light scattering properties, gloss, roughness, coating power, rheology and stability upon storage, etc. This paper aims to study the effect of photo acid generator (PAG) containing the stibium ion on the crystal structure and morphology of the regenerated pigment from the precursor of indanthrone in organic solvent. As measured from ultraviolet–visible spectroscopy and Fourier transform infrared spectroscopy, it was discovered that adding PAG accelerated the conversion of latent pigment to regenerated pigment. In addition, field emission scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis indicated that, as the amount of PAG increased, the regenerated pigment lost its crystal structure, which particle size is increased from 1 to 4 μm and morphology is changed from a bar like form to a cubic and spherical form.