Application of a photochromic dye in an automatic welding filter.

The main purposes of this study were to select a photochromic dye and to develop an active welding filter with a photochromic layer. A series of functionalized spirobenzopyranoindolins were synthesized and their photophysical and photochemical properties were investigated in a solution using absorption and emission spectroscopy. Time-resolved fluorescence spectroscopy measurements were used to characterize the decays and rate constants of fluorescence emission. One dye was selected as a suitable photoactive compound in automatic welding filters. A model of an active welding filter with a photochromic layer based on 1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indole] (6-nitroBIPS) was developed. The paper presents the results of tests of the filter conducted according to EN standards.