Retroreflective articles having microcubes, and tools and methods for forming microcubes

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.

1. An article comprising an array of microcubes, such that for every plane in space there are two adjacent microcubes for which at the place of adjacency none of the face edges is parallel to that plane, and in which at least one microcube of said array is rectangular or pentagonal, said at least one microcube of said array having a projected area of less than  1  mm 2 , said at least one microcube of said array being canted face-more-parallel. 
     
     
       2. The article of  claim 1  in which at least one microcube of said array has a plane of symmetry in which lies the cube axis of said microcube, thereby increasing the entrance angularity of said array in a plane perpendicular to said plane of symmetry. 
     
     
       3. An article comprising an array of microcubes, such that for every plane in space there are two adjacent microcubes for which at the place of adjacency none of the face edges is parallel to that plane, and in which at least one of said  microcube shape  of said array is rectangular, and in which  said at least one microcube of said array having a projected area of less than  1  mm 2   , said  at least one face of said  rectangular microcube is  of said array having one pentagonal face. 
     
     
       4. An article comprising an array of male microcubes in which every three by three subarray of said microcubes is nonrulable, and  in which at least one microcube in a said three by three subarray  in said array of male microcubes is rectangular or pentagonal, said at least one microcube of said array having a projected area of less than  1  mm 2 , said at least one microcube being canted face-more-parallel. 
     
     
       5. The article of  claim 4  in which at least one microcube of said array has a plane of symmetry in which lies the cube axis with said microcube, thereby increasing the entrance angularity of said array in a plane perpendicular to said plane of symmetry. 
     
     
       6. The article of  claim 1  in which a plurality of said microcubes are male microcubes and said array of microcubes is nonrulable. 
     
     
       7. The article of  claim 1  in which a plurality of said microcubes of said array have a projected area of about  0 . 35  mm 2    or less.   
     
     
       8. The article of  claim 1  in which a plurality of said microcubes of said array have a projected area of  0 . 12  mm 2    or less.   
     
     
       9. The article of  claim 1  in which the article comprises retroreflective sheeting. 
     
     
       10. The article of  claim 1  in which said array comprises microcubes present as opposed paired microcubes. 
     
     
       11. The article of  claim 10  in which said array comprises pairs of rows of said rectangular microcubes, in which each pair of rows is a replica of a structure that has been ruled on the end of a microthick plate by a v- groove extending along the center of the plate, with opposed pairs of v - grooves extending substantially perpendicular to the sides of the center v - groove.   
     
     
       12. The article of  claim 1  in which one or more microcubes within said array have substantially  100 %  active aperture for incidence angles of about zero degrees.   
     
     
       13. The article of  claim 1  in which said array comprises at least three consecutive rows of said microcubes. 
     
     
       14. The article of  claim 1  in which said array of microcubes comprises rows of said microcubes in which each row of microcubes is a replica of a structure that has been ruled on the end of a microthick plate. 
     
     
       15. The article of  claim 14  in which the microthick plate has a thickness of ( a )-( b ):
 ( a )  less than  1  mm, or      ( b )    0 . 012  inch  (   0 . 305  mm )  or less.     
     
     
       16. The article of  claim 1  in which said array comprises rows of said rectangular microcubes, in which each row is a replica of a structure that has been ruled on the end of a microthick plate by a bevel face formed along the end of the plate and a plurality of v- grooves formed substantially perpendicular to the bevel face.   
     
     
       17. The article of  claim 16  in which adjacent rows of said microcubes correspond to adjacent plates oriented  180 ° to each other. 
     
     
       18. The article of  claim 4  in which at least one microcube of said array has a projected area of about  0 . 35  mm 2    or less.   
     
     
       19. The article of  claim 4  in which at least one microcube of said array has a projected area of  0 . 12  mm 2    or less.   
     
     
       20. The article of  claim 4  in which said article comprises retroreflective sheeting. 
     
     
       21. The article of  claim 4  in which the array comprises microcubes present in said subarray as opposed paired microcubes. 
     
     
       22. The article of  claim 21  in which said array comprises pairs of rows of said rectangular microcubes, in which each pair of rows is a replica of a structure that has been ruled on the end of a microthick plate by a v- groove extending along the center of the plate, with opposed pairs of v - grooves extending substantially perpendicular to the sides of the center v - groove.   
     
     
       23. The article of  claim 4  in which one or more microcubes within said array have substantially  100 %  active aperture for incidence angles of about zero degrees.   
     
     
       24. The article of  claim 4  in which said array comprises at least three consecutive rows of said microcubes. 
     
     
       25. The article of  claim 4  in which said array of microcubes comprises rows of said microcubes in which each row of microcubes is a replica of a structure that has been ruled on the end of a microthick plate. 
     
     
       26. The article of  claim 25  in which the microthick plate has a thickness of ( a )-( b ):
 ( a )  less than  1  mm, or      ( b )    0 . 012  inch  (   0 . 305  mm )  or less.     
     
     
       27. The article of  claim 4  in which said array comprises rows of said rectangular microcubes, in which each row is a replica of a structure that has been ruled on the end of a microthick plate by a bevel face formed along the end of the plate and a plurality of v- grooves formed substantially perpendicular to the bevel face.   
     
     
       28. The article of  claim 27  in which adjacent rows of said microcubes correspond to adjacent plates oriented  180 ° to each other. 
     
     
       29. An article comprising an array of male microcubes of which array every three by three subarray of said microcubes is nonrulable, and in which at least one microcube in a said three by three subarray of said microcubes is rectangular or pentagonal, canted face- more - parallel, and has a projected area of  0 . 12  mm   2    or less, in which said array of male microcubes comprises rows of said microcubes in which each row of microcubes is a replica of a structure that has been ruled on the end of a microthick plate, and in which one or more microcubes within the array have substantially  100   %  active aperture for incidence angles of about zero degrees, and in which the article comprises retroreflective sheeting.   
     
     
       30. The article of  claim 29  in which said array comprises rows of said rectangular microcubes, in which each row is a replica of a structure produced on the end of said microthick plate by a bevel face formed along the end of the plate and a plurality of v- grooves formed substantially perpendicular to the bevel face.   
     
     
       31. The article of  claim 30  in which adjacent rows of said microcubes correspond to adjacent plates oriented  180 ° to each other. 
     
     
       32. The article of  claim 29  in which said array comprises microcubes present as opposed paired microcubes, and in which said array comprises pairs of rows of said rectangular microcubes in which each pair of rows is a replica of a structure produced on the end of a microthick plate by a v- groove extending along the center of the plate, with opposed pairs of v - grooves extending substantially perpendicular to the sides of the center v - groove.   
     
     
       33. The article of  claim 29  in which the microthick plate has a thickness of ( a )-( b ):
 ( a )  less than  1  mm, or      ( b )    0 . 012  inch  (   0 . 305  mm )  or less.     
     
     
       34. An article comprising an array of male microcubes of which array every three by three subarray of said microcubes is nonrulable, in which at least one microcube in a said three by three subarray of said microcubes is rectangular or pentagonal, canted face- more - parallel, and has a projected area of less than  1  mm   2   , and in which said array of male microcubes comprises at least three consecutive rows of said microcubes in which each row of microcubes is a replica of a structure that has been ruled on the end of a microthick plate having a thickness of less than  1  mm.   
     
     
       35. The article of  claim 34  in which said array comprises rows of said rectangular microcubes, in which each row is a replica of a structure that has been ruled on the end of said microthick plate by a bevel face formed along the end of the plate and a plurality of v- grooves formed substantially perpendicular to the bevel face.   
     
     
       36. The article of  claim 35  in which adjacent rows of said microcubes correspond to adjacent plates oriented  180 ° to each other. 
     
     
       37. The article of  claim 34  in which said array comprises microcubes present as opposed paired microcubes, and in which said array comprises pairs of rows of said rectangular microcubes in which each pair of rows is a replica of a structure that has been ruled on the end of a microthick plate by a v- groove extending along the center of the plate, with opposed pairs of v - grooves extending substantially perpendicular to the sides of the center v - groove.   
     
     
       38. The article of  claim 34  in which the article comprises retroreflective sheeting. 
     
     
       39. The article of  claim 34  in which one or more microcubes within said array have substantially  100 %  active aperture for incidence angles of about zero degrees.   
     
     
       40. The article of  claim 34  in which the microthick plate has a thickness of  0 . 012  inch (   0 . 305  mm )  or less.   
     
     
       41. An article comprising an array of microcubes, such that for every plane in space there are two adjacent microcubes for which at the place of adjacency none of the face edges is parallel to that plane, in which a plurality of said microcubes are male microcubes at least some of which have no dihedral face edges collinear with any dihedral face edges of any adjacent microcubes, and in which at least one male microcube of said array is rectangular or pentagonal, has a projected area of less than  1  mm 2   , and is canted face - more - parallel.