Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Patent
1996-04-01
1998-10-27
Dodson, Shelley A.
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
423462, 423592, 424 60, 424400, 424401, A61K 742, A61K 700, C01B 719, C01B 1314
Patent
active
058275070
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to ultraviolet shielding composite fine particles having high transparency in the visible light region and a high shielding ability in the ultraviolet region. It also relates to a method for producing the composite fine particles, and cosmetics containing such composite fine particles.
BACKGROUND ART
The sunlight reaching the earth includes infrared light, visible light, and ultraviolet light, of which 5 to 6% is ultraviolet light. The ultraviolet light has short wavelengths, and thus are electromagnetic waves with high energies. Therefore, ultraviolet light is known to decompose many kinds of materials and to cause various damages to a living body.
Therefore, ultraviolet shielding agents are used for the purpose of protecting skin from inflammation or skin cancer due to exposure of skins to harmful ultraviolet light by adding the ultraviolet shielding agents to the cosmetics. Also, they are used for the purpose of preventing a pigment from fading due to decomposition by ultraviolet light by mixing the ultraviolet shielding agents with paints. In these cases, by increasing transparency of such cosmetics or paints in the visible light region, unnatural skin whitening can be prevented, and change of coloring of paints can be prevented. Therefore, ultraviolet blocking is desirably carried out while maintaining transparency in the visible region.
The ultraviolet shielding agent using organic compounds as an effective component prevents transmission of the ultraviolet light by characteristic absorption of ultraviolet light by the component. For example, an ultraviolet absorbent composition comprising substituted N,N'-bis-aromatic formamidines is known (Japanese Patent Examined Publication No. 61-09993). However, the organic ultraviolet shielding agents have a problem that although they can absorb the ultraviolet light, at the same time they are likely to be decomposed by the light, and thereby the shielding ability undesirably lowers with the passage of time. As for their applications to cosmetics, the kinds and amounts of the ultraviolet shielding agents are restricted owing to effects caused on human bodies, making it difficult to achieve a good shielding performance within the regulated range.
On the other hand, the ultraviolet shielding agent using an inorganic compound contains inorganic fine particles in its composition and prevents transmission of the ultraviolet light by the absorbing ability and the scattering ability of the composition to the ultraviolet light. The inorganic ultraviolet shielding agent is superior to the organic ultraviolet shielding agent from the viewpoint that the composition containing the inorganic ultraviolet shielding agent is not decomposed by the ultraviolet light with the passage of time and has little effects to the human body.
However, since the inorganic ultraviolet shielding agents are in the form of particles, blocking of the ultraviolet light while maintaining high transparency in the visible light region by using the inorganic ultraviolet shielding agent has been known to be difficult when compared with the organic ultraviolet shielding agent.
In order to effectively exhibit light shielding ability in the ultraviolet region while maintaining high transparency in the visible light region, the composition has to be microgranulated to give ultrafine particles capable of being in a highly dispersed state to increase ultraviolet scattering ability. However, in the case of using ultrafine particles, problems may occur in dispersion stability due to aggregation of the ultrafine particles.
In order to improve dispersability, a surface of the ultrafine particles may be coated with other materials. For example, skin cosmetics comprising an oily cosmetic base material and a hydrophobic titanium oxide powder are known (Japanese Patent Examined Publication No. 59-15885). However, a solvent has to be suitably selected depending upon the properties of the coating materials coated on the surface. Also, even if the surface treatment is
REFERENCES:
Derwent WPI English Abstract of JP-A-1-143821, Jun. 6, 1989.
Derwent WPI English Abstract of JP-A-5-132662, May 28, 1993.
Derwent WPI English Abstract of JP-A-3-17011, Jan. 25, 1991.
Derwent WPI English Abstract of JP-B-59-15885, Apr. 12, 1984.
Derwent WPI English Abstract of JP-A-63-126818, May 30, 1988.
Derwent WPI English Abstract of JP-A-4-56312, Mar. 2, 1992.
Imaizumi Yoshinobu
Kozaki Shunji
Nishimura Toru
Oshima Kentaro
Sugawara Satoshi
Dodson Shelley A.
Kao Corporation
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