Patent ID: 7595107

Claim:
Algae-resistant roofing granules comprising: (a) a base particle comprising an inert mineral; (b) an exterior coating layer on the base particle, the exterior coating including biocidal particles selected from the group consisting of: (1) biocidal particles having an average size from about 0.1 micrometers to about 5 millimeters and having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds; and (2) microcapsules having an average size from about 200 micrometers and 5 millimeters, and having a capsule wall environmentally degradable in a controlled manner and a core comprising a plurality of biocidal particles having an average size from about 0.1 micrometers to about 0.5 millimeters, the biocidal particles having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds.