Patent ID: 7678459

Claim:
A mirror comprising: a substrate supporting a coating, wherein the coating includes at least a reflective layer comprising aluminum, first and second dielectric layers, and at least one layer comprising silicon aluminum oxide, wherein the layer comprising silicon aluminum oxide is located closer to the substrate than are the reflective layer and the dielectric layers, and wherein the reflective layer comprising aluminum is located between the substrate and the dielectric layers; wherein the layer comprising silicon aluminum oxide is located directly under and contacting the reflective layer comprising aluminum in order to improve at least durability of the first surface mirror; and wherein the layer comprising silicon aluminum oxide is graded in at least three different respects so that the layer comprising silicon aluminum oxide (a) contains more oxygen at a location closer to the substrate than at a location further from the substrate; (b) contains more Si at a location closer to the substrate than at a location further from the substrate; and (c) contains more Al at a location closer to the reflective layer than at a location further from the reflective layer.