Retroflective device and method of manufacture thereof

Abstract

A retroreflective device 1, for use in creating a retroreflective surface, comprises an agglomeration of glass beads 2, formed by binding together glass beads 2 of a specific size with an adhesive material 3. Selected properties, for example refractive index, of each glass bead 2 are chosen in accordance with the desired retroreflectivity of the device 1. The adhesive material 3 may be pigmented, thereby to colour light retroreflected from the device 1. Preferably, the agglomeration of glass beads 2 is approximately spherical or ovoid and the glass beads 2 are approximately spherical. A retroreflective road marking coating may comprise a road marking material applied to the surface of a road and a plurality of the retroreflective devices 1 embedded in the road marking material so as to protrude partially therefrom. The retroreflective devices 1 may also be used with a coating from which they protrude so as to provide a road surfacing material.

1 . A reflective device for use in creating a retroreflective surface, including first refractive index beads, second, different, refractive index beads and binder, the binder holding the first and second beads together with the first and second beads being distributed throughout the device.  
   
   
       2 . A device as claimed in  claim 1  in which the beads are in close proximity to each other.  
   
   
       3 . A device as claimed in  claim 1  in which the spacing between adjacent beads is less than two times the mean cross-sectional dimension of the beads.  
   
   
       4 . A device as claimed in  claim 1  in which the ratio of the combined volume of the beads to the volume of the binder is more than 1:10.  
   
   
       5 . A device as claimed in  claim 4  in which the ratio is more than 6:10.  
   
   
       6 . A device as claimed in  claim 1  in which the combined number of first and second beads in the device is more than 20.  
   
   
       7 . A device as claimed in  claim 6  in which the combined number of first and second beads in the device is more than 40.  
   
   
       8 . A device as claimed in  claim 1  in which the first beads have a refractive index of more than 2.0.  
   
   
       9 . A device as claimed in  claim 1  in which the second beads have a refractive index of less than 2.0.  
   
   
       10 . A device as claimed in  claim 1  which is ovoid.  
   
   
       11 . A device as claimed in  claim 1  in which the first and second beads are from 100 to 700 microns in their mean cross-sectional extent.  
   
   
       12 . A device as claimed in  claim 1  in which the first and second beads are spherical.  
   
   
       13 . Use of a plurality of retroreflective devices as claimed in  claim 1  in combination with road marking material as a retroreflective road marking coating or road surfacing material.  
   
   
       14 . Use of a plurality of retroreflective devices as claimed in  claim 1  in combination with a binder material as a retroreflective surface dressing.  
   
   
       15 . A retroreflective road marking coating comprising a road marking material applied to the surface of a road and a plurality of retroreflective devices as claimed in  claim 1  embedded in the road marking material so as to protrude partially therefrom.  
   
   
       16 . A reflective device for use in forming a retroreflective device including first beads having a refractive index of more than 2.0 and second reflection beads having a refractive index of less than 2.0 and binder, the binder holding the first and second beads together with the first and second beads being distributed throughout the device, the number of first and the number of second beads being selected to give the required refractive properties of the device.  
   
   
       17 . A method of forming a reflective device having a retroreflective surface comprising determining the number of beads having a first refractive index and determining the number of beads having a second, different, refractive index in order to give a device having the required reflective properties and holding the beads together with binder with the beads being caused to be distributed throughout the device.  
   
   
       18 . A method as claimed in  claim 17  comprising stocking only first and second beads.  
   
   
       19 . A method as claimed in  claim 17  comprising choosing first beads having a refractive value of more than 2.0 and the second beads having an index of less than 2.0.  
   
   
       20 . A method as claimed in  claim 17  comprising binding more than 40 beads into the device.  
   
   
       21 . A method as claimed in  claim 17  comprising varying the reflective properties of at least two batches of devices by altering the ratio of first and second beads that are bound by the binder.  
   
   
       22 . A method as claimed in  claim 17  comprising dropping liquid binder onto the first and second beads and causing the binder to set.