Patent ID: 6936725
Filing Date: 2005-08-30
Classification: C07D,G03C

Abstract:
1. A method for producing a photochromic compound suitable for use as a single substance for photochromic tinting of a transparent article made of a plastic material, said tinted article having a neutral gray or brown color in the excited state, the method comprising the step of fusing at least two non-identical photochromic sections that are selected so that the different absorption wavelengths of the excited photochromic sections give rise to a neutral gray or brown color in the plastic material, and which photochromic sections are further selected from the group consisting of oxazines and pyrans and of which at least one is not an indolino spiropyran, to an aromatic structure selected from the group consisting of benzene, biphenyl, naphthalene, anthracene and phenanthrene, the positions of fusion on the aromatic structure being directly adjacent to the oxygen atom of the pyran or the oxygen or nitrogen atom of the oxazine.