WHITE POWDER AND METHOD FOR PRODUCING THEREOF

摘要

1. A white powder characterized by comprising base particles having on the surface thereof at least one coating film comprising a crystallized-particle aggregate which is capable of imparting a white color based on the scattering reflection of light. 2. The white powder of claim 1, characterized in that the crystallized particles are ones irregular in particle diameter. 3. The white powder of claim 1, characterized in that the coating film is a multilayered film. 4. The white powder of claim 1 or 2, characterized by having, on the surface of the coating film, a coating film comprising particles capable of filling up the voids present in said surface. 5. The white powder of claim 1, characterized in that the coating film is a high-refractive-index film. 6. The white powder of claim 4, characterized in that the coating film is a silica film or a titania film. 7. The white powder of claim 1, characterized in that the coating film is one formed by forming solid-phase particles in an aqueous solution to coat the base particles with the solid-phase particles and then burning the coated base particles. 8. The white powder of claim 7, characterized in that before the burning is conducted, the coating layer is coated with particles capable of constituting a film which fills up the voids present in the surface of the coating layer. 9. The white powder of claim 1, characterized in that the coating layer is one formed by adhering crystallized particles to the surface of a base powder in a liquid containing the crystallized particles and the base powder dispersed therein. 10. A process for producing a white powder, characterized by coating the surface of base particles with at least one coating film comprising a crystallized-particle aggregate which is capable of imparting a white color based on the scattering reflection of light. 11. A process for producing a white powder, characterized by coating the surface of base particles with at least one coating film comprising a crystallized-particle aggregate which is capable of imparting a white color based on the scattering reflection of light, wherein the coating film is formed forming solid-phase particles in an aqueous solution and then burning the coated base particles. 12. The process of claim 10 or 11, characterized in that the crystallized particles are ones irregular in particle diameter. 13. The process of claim 10 or 11, characterized in that the coating film is a multilayered film. 14. The process of claim 10 or 11, characterized by coating the surface of the coating layer with a coating film comprising particles capable of filling up the voids present in said surface. 15. The process of claim 10 or 11, characterized in that the coating film is a high-refractive-index film. 16. The process of claim 14, characterized in that the coating film is a silica film or a titania film. 17. The process of claim 11, characterized in that before the burning is conducted, the coating film is coated with particles capable of constituting a film which fills up the voids present in the surface of the coating film. 18. The process of claim 10 or 11, characterized in that the coating layer is one formed by adhering crystallized particles to the surface of a base powder in a liquid containing the crystallized particles and the base powder dispersed therein.