3M Innovative Properties Company

Christopher S Grinde

Nelson D Sewall

Kenneth L Smith

Todd A Ballen

The present disclosure relates to end milling methods for making microstructures, a tool comprising such microstructures, the microstructures, and replications thereof, where the microstructures are part of a structured surface configured as a security article. Some of the microstructures are configured differently from others to define an optically detectable indicia in the structured surface. Microstructures in a first group may for example differ from microstructures in a second group in terms of one or more of size, orientation, cube corner type, and dihedral angle value(s), to define the indicia or a portion thereof. The microstructures may comprise full or truncated cube corner elements, and the article may be a retroreflective sheeting.

Security articles comprising groups of microstructures made by end milling

A new technique for making cube corner elements that involves end milling is used in the fabrication of cube corner elements having non-orthogonal dihedral angles and dihedral angle errors, and arrays of such cube corner elements. A given optical face of a cube corner element may be a compound face with two constituent faces. In some cases, the constituent faces may be parallel and coplanar such that a given dihedral angle error pertains to the entire optical face, while in other cases, the two constituent faces may not be parallel, and may be associated with different dihedral angle errors.

Growing community of inventors

Baldwin, WI, United States of America

Christopher S Grinde