3M Innovative Properties Company

Minnesota Mining and Manufacturing Company

Nelson D Sewall

Kenneth L Smith

Timothy L Hoopman

Todd A Ballen

John C Nelson

William J Bryan

Conrad V Anderson

David W Meitz

Lars A Smeenk

Jeffrey E Clements

Madeleine B Fleming

Christopher S Grinde

Jennifer L Trice

Charles N DeVore

Greg E Schrank

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.

Non-orthogonal cube corner elements and arrays thereof made by end milling

Cube corner articles such as retroreflective sheeting utilize multiple cube corner arrays in a tiled configuration, each tile containing one array of canted cube corner elements. The tiles may be long and narrow, and the array in each of at least two or three adjacent tiles, or even in every tile, may include at least one lengthwise groove that is parallel to an edge of the tile and parallel to a fixed in-plane axis. Each tile may have a width that is narrow (e.g. 0.2 to 5 mm), and equal to an integer multiple of a lengthwise groove pitch to avoid or reduce ineffective fragmented cube corners along the tile edge. Each array may have a plane of cant and a primary plane of entrance angularity, and the primary planes of entrance angularity for the multiple tiles may be more evenly distributed in azimuthal angle than the planes of cant.

Microtiled prismatic cube corner articles

In one embodiment, a cutting tool assembly used for creating grooves in a microreplication tool is described. The cutting tool assembly includes a mounting structure and multiple diamonds mounted in the mounting structure. For example, first and second tool shanks having first and second diamond tips can be positioned in the mounting structure such that a cutting location of a diamond cutting tip of the first tool shank is a defined distance from a cutting location of a diamond cutting tip of the second tool shank. The defined distance may correspond to an integer number of pitch spacings, and may be accurate to within a tolerance of less than approximately 10 microns.

Multi-diamond cutting tool assembly for creating microreplication tools

The present invention relates to methods of making microstructured laminae for replication and apparatus. In a preferred embodiment, the invention relates to machining V-shaped grooves on individual lamina forming cube-corner microstructures.

Methods of making microstructured lamina and apparatus

In one embodiment, a tool used for creating grooves in a microreplication tool is described. The tool includes a mounting structure and a multi-tipped diamond mounted in the mounting structure. The different tips of the diamond may correspond to different grooves to be created in the microreplication tool. In this manner, the creation of a microreplication tool using a diamond can be simplified and/or improved.

Diamond tool with a multi-tipped diamond

The invention relates to articles comprising a sheeting having a microstructured surface that reflects light in a moir&#xe9;-like pattern. The invention further relates to methods of making a master and replicas thereof including tooling that results in sheeting having such pattern. A preferred method comprises forming V-shaped grooves in a substrate (e.g. metal plate) wherein the intersections of three grooves form cube-corner elements. The cube-corner elements are formed in such a manner that adjacent parallel grooves have substantially the same groove spacing and groove depth throughout the array. The master as well as corresponding tooling and sheeting preferably have a groove spacing within the range of about 0.0005 inches (0.0127 mm) to about 0.007 inches (0.1778 mm) throughout the array and more preferably a groove spacing of less than about 0.004 inches (0.1016 mm).

Retroreflective articles having moire-like pattern

The invention relates to methods of making a master and replicas thereof including tooling and retroreflective sheeting. The invention further relates to the corresponding master, tooling and in particular retroreflective sheeting. The method comprises forming V-shaped grooves in a substrate (e.g. metal plate) wherein the intersections of three grooves form cube-corner elements. The cube-corner elements are substantially the same size throughout the array. The master as well as corresponding tooling and sheeting preferably have an average groove spacing within the range of about 0.0005 inches (0.0127 mm) to about 0.007 inches (0.1778 mm) throughout the array and more preferably an average groove spacing of less than about 0.004 inches (0.1016 mm).

Methods of making a master and replicas thereof

An abrasive article is provided having a sheet-like structure having a major surface having deployed in fixed position thereon a plurality of abrasive three-dimensional abrasive composites, each of the composites comprising abrasive particles dispersed in a binder and having a precise shape defined by a distinct and discernible boundary which includes specific dimensions, wherein the precise shapes are not all identical. The invention also relates to a method of manufacturing such an abrasive article, involving, generally, the steps of:

Production tool for an abrasive article and a method of making same

The present invention provides a master tool and method for making a master tool. The master tool includes a plurality of precise three-dimensional shapes upraised from the surface of the master tool. Each of the precise shapes is defined by a distinct and discernible boundary including specific dimensions, wherein not all said three-dimensional shapes are identical. The master tool of the present invention can be used to form a production tool containing a plurality of precise three-dimensional-shaped cavities. The production tool can be used in the manufacture of abrasive articles to shape an abrasive slurry into an array of precise three dimensional-shaped abrasive composites.

Growing community of inventors

Forest Lake, MN, United States of America

Nelson D Sewall