The white substance generally absorbs the blue light of 450 to 480nm in visible light slightly, resulting in insufficient blue color, which makes it slightly yellowish and gives people a sense of staleness. To this end, people have taken different measures to whiten and brighten the items.
As usual,people will take the following measure,
1. Add blue and whitening method. Adding blue can whiten, but the effect is limited, and because the total amount of reflected light is reduced, the color of the item becomes darker.
2. The chemical bleaching method mainly discolors substances through oxidation-reduction reaction, so it will cause certain damage to cellulose, and the bleached objects often have yellow color, which affects the whitening effect.
3.OPTICAL BRIGHTENING AGENT(FWA) is an important functional additive. It is a colorless organic compound that can absorb ultraviolet light (wavelength range between 300-400nm) and then emit blue-violet visible to the naked eye. Fluorescence (wavelength range between 420 ~ 480nm), complementary to the yellow light on the substrate and has a whitening effect.