optical brightener
blue fluorescent dye used to enhance apparent brightness of white paper, fabric, and plastics
en-GB/ˈɒptɪkəl bɹaɪtnə/
en-US/ˈɑptɪkəl ˈbɹaɪdənɚ/
blue fluorescent dye used to enhance apparent brightness of white paper, fabric, and plastics