Used as a photochromic dye in light-responsive materials. Changes color when exposed to UV light, returning to original state in the dark. Commonly applied in photochromic lenses for eyeglasses, where it enables automatic darkening under sunlight. Also utilized in specialty inks, security printing, and optical switches due to its reversible color change. Suitable for polymer matrices like plastics and coatings where dynamic optical properties are needed. Offers good fatigue resistance and clear color contrast between activated and deactivated states.