A variety of organic UV-absorbers and inorganic UV-shielders are used for sunscreen cosmetics these days. As inorganic UV-shielders, ultra-fine metal oxide powders such as titanium dioxide and zinc oxide are commonly used. Both titanium dioxide and zinc oxide have been manufactured and commercially used for years and have become typical raw materials for sunscreen cosmetics.
It is widely known that ultra-fine titanium dioxide is used in order to shield UV-B which causes sunburn, while zinc oxide is used to shield UV-A which causes suntan. In the present paper the background to the different usages of the two oxides is explained by considering the difference in their optical properties.
In addition, the special features and design concept of ultra-fine particles, which differ from pigment products, are explained by describing their basic properties, production process and photo-catalytic activity.
View full abstract