A photocuring PUA material with adjustable flexibility used in the fast photochromic coating on ophthalmic lenses

To resolve the problem of inhomogeneous color depth during photochromism, the photochromic coating on the surface of a pre-molded lens as well as the photocuring process are proposed. The host polyurethane acryl (PUA) material with adjustable flexibility was constructed from isophorone diisocyanate trimer (t-IPDI). The polycarbonatediol (PCDL) was used for chain extension and the hydroxyethyl methylacrylate (HEMA) was introduced to the lateral chain for the subsequent photo-crosslinking. Multiple experimental conditions were optimized, which included selection of the photoinitiator (PI), operating spectral window for photocuring and the equivalent ratio of HEMA to NCO group. The spectrokinetics behavior of photochromic coating was investigated by monitoring relative grayscales (Gy*) with irradiation and fading time. The glass-transition temperature (Tg) was measured by the differential scanning calorimetry (DSC) as well. An attempt of application of this photochromic coating on the surface of a commercial lens blank was made tentatively.