Method and apparatus for embossing a precision optical pattern in a resinous sheet

摘要

Disclosed herein are a method and apparatus for continuously embossing a repeating pattern of precise detail, in particular, cube-corner type reflector elements, on one surface of a sheet of transparent thermoplastic material to form retroreflective sheeting. A continuous embossing tool in the form of a flexible thin metal belt or cylinder has on its outer surface an embossing pattern which is the reverse of the pattern to be formed. The embossing tool is continuously moved at a predetermined speed along a closed course through a heating station where the temperature of a portion of the embossing tool is raised to be above the glass transition temperature of the sheeting and a cooling station where the heated portion of the embossing tool is cooled to be below that glass transition temperature. The sheeting is continuously moved at the predetermined speed from a supply thereof into engagement with the embossing pattern on the tool and is pressed thereagainst continuously at a plurality of pressure points sequentially spaced along the heating station, with the one surface of the sheeting confronting and engaging the embossing pattern until the sheeting is raised above its glass transition temperature and conforms to the embossing pattern on one face. The sheeting is maintained in engagement with the tool until the tool passes the cooling station and the sheeting is lowered below its glass transition temperature and the pattern solidifies. The sheeting is thereafter stripped from the tool.