Retro reflective tape grey / silver construction

Does anyone know the physical construction differences between the silver (3M) reflective tape and the grey slightly less reflective tape that seems to be
produced by many manufacturers?
I tried Google but couldn't find any diagrams or electron microscope pictures. What key words should I be searching for?
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hi Mike, You might look at the patent data base.
A couple of things that could do this--using higher index glass beads, lower index plastic.
best regards mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 24 May 2008 10:07:04 -0700, Mark W. Lund wrote:

I work at a company that uses more 3m reflective sheeting than just about any other. I can't get into specific details a) because I'm not entirely certain and don't want to mis-inform, and b) because there are some things that I don't think I should tell. Having said that, I CAN tell you that the 3m products are built up in layers, and that at least one of those layers seems to be prismatic in its physical construction, sort of like a diffraction grating.
You might also want to take note, 3m and their competitors produce several different grades of retroreflective material, and one of the key differences between grades happens to be how reflective it is.
Hope this helps.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The following page gives some basic info. 'Retroreflective Sheetings Used for Sign Faces' http://www.trafficsign.us/signsheet.html
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Mark W. Lund" wrote:

Or corner reflectors. See U.S. patent 4,938,563.
http://www.uspto.gov/patft/index.html
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.