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.

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.

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.

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.

The present disclosure is directed to lamina(e) comprising cube corner elements, a tool comprising an assembly of laminae and replicas thereof. The disclosure further relates to retroreflective sheeting.

The present disclosure is directed to lamina(e) comprising cube corner elements, a tool comprising an assembly of laminae and replicas thereof. The disclosure further relates to retroreflective sheeting.

The present disclosure is directed to lamina(e) comprising cube corner elements, a tool comprising an assembly of laminae and replicas thereof. The disclosure further relates to retroreflective sheeting.

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.

The present disclosure is directed to lamina(e) comprising cube corner elements, a tool comprising an assembly of laminae and replicas thereof. The disclosure further relates to retroreflective sheeting.

The present disclosure relates to end milling methods for making microstructures, and articles containing such microstructures. The end milling process comprises rotating an end mill (1410r) around an axis of rotation (1409) and translating the rotating end mill (1410r) in a working surface (1407) to form a first recess (1420) such that end mill (1410r) moves along an inclined path (1411) relative to the working surface (1409), or to a reference plane along which the working surface (1407) extends. The method forms flat faces (1441a, 1441b) that meet along a rounded edge (1451), the edge (1451) being inclined to the reference plane. Both truncated cube corner elements (see for instance FIGS. 47 and 48) and full cube corner elements (see for instance FIG. 56A) can be made in a substrate (4705, 4805, 5605) by forming at least part of an optical face of the cube corner element (4780, 4880, 5680) by cutting the substrate (4705, 4805, 5605) with a rotating end mill (1410r).