Ultraviolet light screening compositions
View Patent ↗A UV screening composition comprises particles which are capable of absorbing UV light so that electrons and positively charged holes are formed within the particles. The particles are adapted to minimize migration to the surface of the particles of the electrons and/or the positively charged holes when the particles are exposed to UV light in an aqueous environment.
1. A UV screening composition comprising particles which are capable of absorbing UV light so that electrons and positively charged holes are formed within the particles, characterised in that the particles are adapted to minimise migration to the surface of the particles of the electrons and/or the positively charged holes when said particles are exposed to UV light in an aqueous environment, wherein the particles comprise a host lattice comprising titanium dioxide in the rutile form, the host lattice incorporating manganese in the 3+ state to provide luminescence trap sites and/or killer sites, wherein said particles are obtained by heating titanium dioxide in the rutile form at from 600° C. to 1000° C. with a manganese component to incorporate manganese in the 3+ state in the host lattice.
2. A composition according to claim 1 wherein the second component is present in an amount of from about 0.05 to 10%.
3. A composition according to claim 2 wherein the second component is present in an amount of from about 0.05 to 5%.
4. A composition according to claim 3 wherein the second component is present in an amount of from about 0.1 to 1%.
5. A composition according to claim 1 wherein the size of the particles is from 1 to 200 nm.
6. A composition according to claim 1 wherein a population of the particles have an outer coating.
7. A composition according to claim 6 wherein the coating is one or more organic materials selected from polyols, amines, alkanolamines, polymeric organic silicon compounds, hydrophilic polymers and surfactants.
8. A composition according to claim 7 wherein the coating is a surfactant selected from trioctylphosphine oxide and sodium hexametaphosphate.
9. A method for preparing a composition as defined in claim 1 which comprises associating the particles with a carrier.
10. A composition according to claim 1 wherein said composition is for topical application.
11. A composition according to claim 10 wherein said composition is a sunscreen.
12. A composition according to claim 1 formulated as a paint, a plastics composition, a coating, a pigment or a dye composition.
13. A composition according to claim 1 formulated as a cosmetic composition.
14. A composition according to claim 1 further comprising UVA, UVB or broad band sunscreen agent.
15. A composition according to claim 1 , wherein the average primary size of the particles is 50 nm to 200 nm.