Compound mold and structured surface articles containing geometric structures with compound faces and method of making same

Abstract

A structured surface articles such as molds or sheeting are formed on a compound substrate including a machined substrate and a replicated substrate. In one embodiment, the structured surface is a cube corner element on a compound substrate. In another embodiment, the structured surface is a geometric structure that has a plurality of faces, where one face is located on the machined substrate and another face is located on the replicated substrate. In yet another embodiment, at least some of the faces include a compound face with a portion formed on the machined substrate and a portion formed on the replicated substrate. The method of making a structured surface article including a geometric structure having a plurality of faces includes forming an array of geometric structures in a first surface of a machined substrate; passivating selected locations of the first surface of the machined substrate; forming a replicated substrate of the machined substrate to form a compound substrate; forming an array of second geometric structures on a second surface opposite the first surface on the machined substrate; and removing selected portions from the second surface of the machined substrate.

1 . A geometric structure having a plurality of faces disposed on a compound substrate, the compound substrate comprising a machined substrate and a substantially replicated substrate, wherein at least one of the faces is located on the machined substrate and at least one of the faces is located on the replicated substrate.  
   
   
       2 . The geometric structure of  claim 1 , wherein the geometric structure comprises a cube corner element.  
   
   
       3 . The geometric structure of  claim 1 , wherein at least one of the faces comprises a compound face, wherein a portion of the compound face is located on the machined substrate and a portion of the compound face is located on the replicated substrate.  
   
   
       4 . The geometric structure of  claim 3 , wherein the portion of the compound face on the machined substrate is substantially aligned with the portion on the replicated substrate.  
   
   
       5 . The geometric structure of  claim 3 , wherein the portion of the compound face on the machined substrate and the portion on the replicated substrate have angular orientations that differ by less than 10 degrees of arc.  
   
   
       6 . The geometric structure of  claim 3 , wherein the compound face has a transition line separating the portion on the machined substrate from the portion on the replicated substrate.  
   
   
       7 . The geometric structure of  claim 6 , wherein the compound face terminates at a nondihedral edge of a cube corner element, and wherein the transition line is nonparallel to the nondihedral edge.  
   
   
       8 . The geometric structure of  claim 1 , wherein the geometric structure comprises a cube corner element having an outline in plan view selected from the group of shapes consisting of a hexagon and a rectangle.  
   
   
       9 . A method of making a geometric structure in an article, comprising the steps of: 
 providing a compound substrate having a structured surface formed along an internal interface between two substrates; and    forming grooved side surfaces in an exposed surface of the compound substrate to form a geometric structure, the geometric structure comprising a portion of the internal interface and a portion of the grooved side surfaces.    
   
   
       10 . The method of  claim 9 , wherein the geometric structure comprises one of a cube corner element or a PG cube corner element.  
   
   
       11 . The method of  claim 9 , wherein the providing step comprises the steps of: 
 passivating a surface of at least one of the two substrates; and    selectively removing portions of the passivated surface.    
   
   
       12 . The method of  claim 9 , wherein the forming step comprises forming an array of cube corner elements, which array includes the geometric structure.  
   
   
       13 . The method of  claim 9 , wherein at least some of the cube corner elements are canted and arranged in opposing orientations.  
   
   
       14 . The method of  claim 9 , further comprising forming at least one reference mark in at least one of the two substrates.  
   
   
       15 . The method of  claim 9 , wherein the grooved side surfaces extend along axes that are parallel to a common plane.  
   
   
       16 . The method of  claim 9 , wherein the providing step comprises: 
 providing a first substrate;    forming a plurality of faces in a first surface of the first substrate; and    forming a second substrate over the plurality of faces as a replica.    
   
   
       17 . The method of  claim 16 , wherein the forming a plurality of faces in the first surface comprises forming at least two intersecting sets of parallel v-shaped grooves.  
   
   
       18 . The method of  claim 9 , wherein the step of forming grooved side surfaces produces discrete pieces of one of the two substrates on the other substrate, the method further comprising the step of: 
 removing at least some of the discrete pieces to expose portions of the internal interface.    
   
   
       19 . The method of  claim 9 , further comprising the step of: 
 replicating the geometric structure to form retroreflective sheeting.    
   
   
       20 . The method of  claim 9 , wherein the step of forming grooved side surfaces comprises the step of forming a plurality of geometric structures selected from the group consisting of three-sided geometric structures and four-sided geometric structures.  
   
   
       21 . A method of making a structured surface article comprising a geometric structure having a plurality of faces, the method comprising the steps of: 
 forming a plurality of faces in a first surface of a machined substrate;    forming a replicated substrate of the machined substrate to form a compound substrate;    forming a plurality of faces in a second surface of the machined substrate opposite the first surface; and    removing selected portions of the machined substrate to form a geometric structure having at least a first face disposed on the machined substrate and at least a second face disposed on the replicated substrate.    
   
   
       22 . The method of  claim 21 , wherein the geometric structure is one of a plurality of geometric structures each comprising a cube corner element, at least some of the cube corner elements being arranged in opposing orientations.