To obtain the subject highly transparent dispersion high in ultraviolet- protective ability by dispersing a specific proportion of zinc oxide particles, in the form of primary particles, in a specific dispersion medium so as to bring the visible ray transmittance of the resulting dispersion to a specific value or greater.
This zinc oxide dispersion is such one as to contain zinc oxide microparticles at 5-50 wt.% which is dispersed in the form of primary particles, being ≥30% in visible ray transmittance under a thickness of 1 cm. The dispersion medium to be used is one or more kinds of substance selected from cosmetic oils, silicone oils, polyols, ethanol and water. The value of the ultraviolet- protective ability A per 1,000 nm thick (given by a specified formula) of a coating film obtained by casting this zinc oxide dispersion on a silica glass is ≥3. This dispersion is obtained, for example, by the following process: a zinc salt is dispersed or dissolved in ethanol followed by addition of an alkali to form a zinc oxide sol, and a hydrophobic acid is then adsorbed to the sol into a lipophilic sol, which, in turn, is treated with a polymer or surfactant to effect solubilization, and the resultant sol is dispersed in a dispersion medium.
UCHIDA HIROKO
YAMAZAKI SEIJI
INOMATA YUKIO
TAGUCHI KAZUO
HORIBATA TATSUYA
MIYATAKE YOSHIKAZU
