If you develop sunscreen products, you probably know that conventional ZnO fine particles with a diameter of less than 0.1 μm are at a disadvantage in that transmitted light increases as particles become smaller. This, in turn, means UV protection in the UVA range (i.e., 315 nm to 380 nm) is significantly reduced.
However, according to these inventors, ZnO particles used as UV filters in sunscreens and cosmetics are ultrafine, typically having an average diameter of 0.1 μm or less. This is largely due to the fact that particles having a diameter larger than 0.1 μm and with a large aspect ratio cannot stably provide high transparency. Therefore, today's featured patent meets the need for ZnO particles with improved properties.
Hexagonal prism-shaped ZnO particles for UV protection, heat release
U.S. Patent 9404195
Publication date: Aug. 2, 2016
Assignee: Sakai Chemical Industry Co., Ltd.
Provided here are hexagonal, prism-shaped ZnO particles having a primary diameter between 0.1 μm and 0.5 μm and an aspect ratio less than 2.5. These particles exhibit higher transparency and UV-filtering performance than conventional ZnO particles.
Furthermore, said particles have high thermal conductivity, and therefore can be used as heat-releasing fillers. Also disclosed is a method for producing the particles, comprising a step of aging ZnO fine particles as seeds in an aqueous solution in which a Zn salt is dissolved.