Ultraviolet-screening zinc oxide excellent in transparency and composition containing the same
First Claim
1. Zinc oxide which is in the form of a plurality of primary particles each having an average particle diameter of 50-100 nm and said plurality of primary particles forming a planar shape, and which has a ratio of the natural logarithm of the transmittance of long-wavelength ultraviolet rays (Γ
- =360 nm) to the logarithm of the transmittance of visible light (Γ
=400 nm) is 10 or more.
1 Assignment
0 Petitions
Accused Products
Abstract
The present inventors conducted investigations in order to develop a metal oxide which enables effective UV-screening; i.e. which has excellent screening ability against ultraviolet rays, particularly against long-wavelength ultraviolet rays, as well as excellent visible-light transmission; and to provide a UV-screening composition that contains the metal oxide and can be applied to external use. As a result, the present inventors have found that zinc oxide produced by a particular method has a characteristic form; i.e., primary particles having an average particle diameter of 50-100 nm aggregate in a planer shape, and a ratio represented by lnT360nm/lnT400nm (Txnm: transmittance of transmitted light of X nm) of 10 or more, and exerts excellent screening effect against long-wavelength ultraviolet rays as well as excellent visible-light transmission. The present invention has been accomplished based on this finding. The zinc oxide of the present invention effectively exerts the above-described excellent characteristics; i.e. UV-screening effect and transparency, and can be applied to a composition for external use such as make-up cosmetics or sunscreen cosmetics.
-
Citations
38 Claims
-
1. Zinc oxide which is in the form of a plurality of primary particles each having an average particle diameter of 50-100 nm and said plurality of primary particles forming a planar shape, and which has a ratio of the natural logarithm of the transmittance of long-wavelength ultraviolet rays (Γ
- =360 nm) to the logarithm of the transmittance of visible light (Γ
=400 nm) is 10 or more. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
- =360 nm) to the logarithm of the transmittance of visible light (Γ
Specification