Visibly transparent UV sunblock agents and methods of making same

摘要

Cosmetically acceptable physical sunscreens which remain visibly transparent upon the skin while remaining capable of absorbing substantial UV radiation. A first embodiment is directed to the use of a dispersion of micronized particles of zinc oxide having a diameter of less than about 0.2 mu and a very low trace metal content. A second embodiment utilizes substantially larger crystals of substantially pure zinc oxide, measuring between about 1-100 microns in diameter, formed by a process, such as chemical vapor deposition, which produces symmetrical, substantially optically perfect crystals with a relatively smooth outer surface and which are substantially free of internal fractures and imperfections. Visibly transparent glass particles having a diameter of between about 0.01-100 mu may also be utilized as the UV absorbing agent. A further embodiment utilizes visibly transparent plastic spheres measuring between about 0.01-100 microns in diameter and having incorporated therein at least one UV absorbing additive for adjusting the bandgap energy of such spheres to the border between the visible and the ultraviolet wavelength ranges. The particulate materials described above are preferably dispersed into an emulsion to facilitate their application onto the surface of the user's skin. The invention further comprises cosmetic formulations having incorporated therein the particulate sunblock agents described above.