Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
1998-11-20
2001-03-06
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S069000, C424S401000
Reexamination Certificate
active
06197282
ABSTRACT:
TECHNICAL FIELD
The present invention relates to ultraviolet shielding fine particles having substantially no catalytic activities and high shielding abilities in the ultraviolet light region, a method for producing the same, and cosmetics.
BACKGROUND ART
Of the sunlight reaching the earth (including infrared light, visible light, and ultraviolet light), 5 to 6% is ultraviolet light. The ultraviolet light has short wavelengths, and thus comprises high-energy electromagnetic waves. Therefore, the ultraviolet light has been widely known to have degradability against many kinds of substances, thereby causing damages to living bodies.
Therefore, ultraviolet shielding agents have been used for applications of protecting skin from causing inflammation or skin cancer due to the ultraviolet light by formulating them in cosmetics, or preventing a pigment from discoloration due to decomposition by ultraviolet light by mixing them in paints. By such applications, an unnatural whitening in cases of the cosmetics or a loss of coloration in cases of the paints can be prevented by increasing the transparency in the visible light region. Therefore, it is desired that the ultraviolet light is protected while the transparency in the visible light region is maintained.
The ultraviolet shielding agent comprising organic compounds as effective ingredients prevents the transmission of the ultraviolet light on account of the specific absorption of the composition against the ultraviolet light. For example, an ultraviolet absorbable composition comprising substituted N,N′-bis-aromatic formamidines, and the like are known (Japanese Patent Examined Publication No. 61-09993). However, while absorbing the ultraviolet light, the organic ultraviolet shielding agents have the problem of degradation on accounts of the absorption, with the result of an undesirable lowering of the shielding abilities with the passage of time. In their applications to cosmetics, the kinds and amounts of the ultraviolet shielding agents formulated are restricted owing to effects caused on human bodies, and thus it is difficult to achieve a good shielding performance within a controlled range.
On the other hand, in the ultraviolet shielding agent using an inorganic compound, the composition is formulated with inorganic fine particles, and the transmission of the ultraviolet light is prevented by the absorbing ability and the scattering ability against the ultraviolet light owned by the composition. In the inorganic ultraviolet shielding agent, the composition is not degraded with the passage of time and causes little damages on the human bodies, so that it is superior to the organic ultraviolet shielding agent. However, when compared with organic ultraviolet shielding agents, since the inorganic ultraviolet shielding agents are in the form of particles, it has been conventionally considered to be rather difficult to protect against the ultraviolet light with inorganic ultraviolet shielding agents while maintaining high transparency in the visible light region.
In order to effectively exhibit the shielding abilities in the ultraviolet light region while maintaining high transparency in the visible light region (light wavelengths of from 400 to 800 nm), the composition has to be made ultrafine to be in a state of high dispersion to thereby increase the shielding abilities against the ultraviolet light. However, in the case of using such ultrafine particles, problems may arise in the dispersion stability due to the aggregation ability of the ultrafine particles, and in the catalytic activities of the ultrafine particles.
In order to improve dispersibility, there have been known methods of improving surfaces of the ultrafine particles by coating with other substances, including, for instance, an invention concerned with cosmetics formulating powdery products of zinc oxide fine particles coated with an anionic surfactant (Japanese Patent Examined Publication No. 5-77644); an invention concerned with a method of producing powdery products of zinc oxide ultrafine particles coated with an anionic surfactant (Japanese Patent Laid-Open No. 62-260716), and the like. In the above publications, the method comprises the steps of surface-treating the particles in an aqueous solution, solvent-replacing with an organic solvent, and drying, in which the number of the production steps is large, and also process is complicated. Also, in publications other than those mentioned above, there have been known, for instance, an invention concerned with a composition for cosmetics comprising metal oxide fine particles coated with a surfactant and a method of producing the same (Japanese Patent Laid-Open No. 62-84017). In this publication, the method comprises the steps of surface-treating the particles in a liquid phase, aggregating and filtering, washing, dehydrating, and blending, in which the number of the production steps is extremely large as in the method mentioned above, and the process is very complicated.
In publications other than those mentioned above, there have been known, for instance, an invention concerned with a method of producing zinc oxide fine particles obtainable by heating a mixture comprising zinc or a zinc compound, a carboxyl group-containing compound, and an alcohol (Japanese Patent Laid-Open No. 7-232919); an invention concerned with composite oxides for shielding against ultraviolet light obtainable by the steps of reacting an acidic solution containing at least one member selected from zinc, lanthanum, cerium are the like with an alkali solution, filtering, washing, drying, firing, and subsequently surface-treating with a silicone oil or a fatty acid, and a method of producing the same (Japanese Patent Laid-Open No. 5-222317), and the like. In these publications, the reaction step is an essential step in the production processes, which is noted to accompanied the complication of controlling the reaction.
In publications other than those mentioned above, there have been known an invention concerned with cosmetics characterized by containing a powder obtainable by subjecting titanium oxide to a coating treatment with mixed hydrates comprising particular amounts of silicate hydrates and alumina hydrates, wherein the titanium oxide is nearly spherical or irregularly shaped and has an average particle size of from 30 to 70 nm, and further subjecting the surfaces to a coating treatment with a silicone oil (Japanese Patent Laid-Open No. 2-247109). However, the process of coating treatment with mixed hydrates comprising the silicate hydrates and the alumina hydrates before the particle surface is subjected to a surface treatment with a silicone oil is required, which is noted to be accompanied with the complication in the reaction control of the mixed hydrates.
Next, for the purpose of providing a material dispersed with fine particles as to be used as water-repellant, ultraviolet shielding agents for sunscreen cosmetics, there have been known, for instance, an invention concerned with an oily, dispersed material obtainable by the step of pulverizing a mixture containing an oil, titanium dioxide particles, and an organic dispersant in the presence of a granular pulverizing medium, and a method of producing the same (Japanese Patent Examined Publication No. 6-61457); an invention concerned with a method of producing sunscreen obtainable by the step of pulverizing a mixture containing an oil, zinc oxide, titanium dioxide, and an organic dispersant in the presence of a granular pulverizing medium (Japanese Patent Laid-Open No. 5-201844); an invention concerned with a material dispersed with zinc oxide fine particles obtainable by the step of pulverizing a mixture containing an oil, zinc oxide particles, and an organic dispersant in the presence of a granular pulverizing medium (Japanese Patent Laid-Open No. 5-213618), and the like. In these publications, since the particle concentration in the dispersed material is as high as not less than 30%, its production is difficult, and the stability of the dispersed material is low. In add
Imaizumi Yoshinobu
Kozaki Shunji
Miyake Toshio
Oshima Kentaro
Sugawara Satoshi
Birch & Stewart Kolasch & Birch, LLP
Dodson Shelley A.
Kao Corporation
Lamm Marina
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