Retroreflective articles having microcubes, and tools and methods for forming microcubes
First Claim
1. An article comprising an array of microcubes, at least one of said microcubes being non-hexagonal, such that for every plane in space there are two adjacent microcubes for which at the place of the adjacency none of the face edges is parallel to that plane, said at least one microcube having a projected area of less than 1 mm2, said at least one microcube being canted edge-more-parallel.
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Abstract
A method for tooling a pattern of retroreflective microcubes, which pattern can be subdivided into smaller increments within which there are straight line tooling paths, none of which pass through an otherwise solid part of the incremental pattern. The tooling paths within the various increments need not be parallel to a common plane.
Various adaptions of the method enable the tooling of a number of specific microcube shapes and for modifying such optical properties of the microcubes as entrance angularity, incidence angularity, orientation angularity, observation angularity, percent active aperture and retroreflectance. Specific techniques govern the pre-selection of cube parameters such as cube axis cant, cube apex decentration, and cube boundary proportions, which parameters can be adjusted independently of each other. Designs tooled by the method can have 100% active aperture at near zero degrees entrance angle.
The method involves providing a plurality of plates of micro thickness, each plate having at least one end comprised of a material that can be tooled with polished surfaces by means of an appropriate tool, tooling on said end of each plate an increment of the pattern, and assembling the plates together in various ways to form a master.
Retroreflective articles made by means of this technique are expected to provide superior performance when used in pavement markers, highway signs and other applications.
73 Citations
26 Claims
- 1. An article comprising an array of microcubes, at least one of said microcubes being non-hexagonal, such that for every plane in space there are two adjacent microcubes for which at the place of the adjacency none of the face edges is parallel to that plane, said at least one microcube having a projected area of less than 1 mm2, said at least one microcube being canted edge-more-parallel.
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21. An article comprising an array of microcubes, at least one of said microcubes being non-hexagonal such that for every plane in space there are two adjacent microcubes for which at the place of the adjacency none of the face edges is parallel to that plane, in which array at least one said microcubes is canted, said array being formed of a material having a refractive index n, and the cant of at least one microcube in said array does not exceed about tan−
- 1{square root over (2)} −
sin−
1(1/n).
- 1{square root over (2)} −
- 22. An article comprising an array of rectangular microcubes, at least some of which have no dihedral face-edges collinear with any dihedral faces-edges of any adjacent microcrubes, at least one of said rectangular microcubes having a projected area of less than 1 mm2, said at least one microcube being canted edge-more-parallel.
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26. An article comprising an array of microcubes in which every region of three by three microcubes is nonrulable and in which at least one microcube in a said region of three by three microcubes is rectangular, said at least microcube having a projected area of less than 1 mm2, said at least one microcube being canted edge-more-parallel.
Specification