Extrusion-to-sheet production line and method

Abstract

Extrusion-to-sheet production line and method comprise first and second rolls set to a predetermined gap through which a continuously-extruded sheet of molten plastic material passes to calender the sheet to a predetermined thickness. The sheet passes through a nip formed between the second roll and a continuous belt looped around a third roll and a fourth roll. The belt comprises an embossing pattern of optical element shapes that is an inverse pattern of optical element shapes to be embossed at a first major surface of the sheet. The sheet remains in contact with the second roll until the sheet passes through the nip, where the pattern of optical element shapes on the belt is embossed into the first major surfaces of the sheet. Downstream of the third roll is a cooling area through which the belt passes.

1 . (canceled) 
     
     
         2 . An extrusion-to-sheet production line, comprising:
 a first roll and a second roll set to a predetermined gap through which a continuously-extruded sheet of molten plastic material passes;   a heated third roll;   a continuous belt looped around the third roll and a fourth roll spaced apart from the third roll, the belt comprising an embossing pattern that is an inverse pattern of a pattern of optical element shapes to be embossed at a first major surface of the sheet, wherein the second roll and the belt at a closest point between the second roll and the third roll form a nip that transfers the pattern of optical element shapes on the belt to the first major surface of the sheet; and   a separation area where the belt separates from the sheet after completing the transfer of the pattern of optical element shapes into the sheet.   
     
     
         3 . The extrusion-to-sheet production line of  claim 2 , additionally comprising a pressure roller downstream of the nip for pressing the sheet against the embossing pattern on the belt. 
     
     
         4 . The extrusion-to-sheet production line of  claim 2 , wherein the optical element shapes of the pattern that are set into the sheet are micro-optical element shapes. 
     
     
         5 . The extrusion-to-sheet production line of  claim 2 , wherein the optical element shapes of the pattern that are set into the sheet are lenticular or prismatic. 
     
     
         6 . The extrusion-to-sheet production line of  claim 2 , wherein the first roll and the second roll are cooled. 
     
     
         7 . The extrusion-to-sheet production line of  claim 2 , wherein the second roll is heated. 
     
     
         8 . The extrusion-to-sheet production line of  claim 2 , additionally comprising a supply reel and a guide roller for superimposing a carrier film into direct contact with a second major surface of the sheet. 
     
     
         9 . The extrusion-to-sheet production line of  claim 8 , additionally comprising a pressure roller downstream of the nip for pressing the sheet against the embossing pattern on the belt. 
     
     
         10 . The extrusion-to-sheet production line of  claim 9 , wherein the supply reel and the guide roller are arranged to superimpose the carrier film into direct contact with the second major surface of the sheet upstream of the pressure roller. 
     
     
         11 . The extrusion-to-sheet production line of  claim 8 , wherein a surface of the carrier film that is superimposed into direct contact with the second major surface of the sheet comprises an embossing pattern that is an inverse pattern of a pattern of optical element shapes to be embossed at the second major surface of the sheet. 
     
     
         12 . The extrusion-to-sheet production line of  claim 8 , wherein a surface of the carrier film that is superimposed into direct contact with the second major surface of the sheet has a smooth finish. 
     
     
         13 . The extrusion-to-sheet production line of  claim 2 , additionally comprising a cooling area downstream of the third roll and upstream of the separation area through which the belt passes while the first major surface of the sheet is still in contact with the embossing pattern on the belt for cooling the sheet and completing the set of the pattern of optical element shapes. 
     
     
         14 . The extrusion-to-sheet production line of  claim 13 , additionally comprising a pressure roller downstream of the nip and upstream of the cooling area for pressing the sheet against the embossing pattern on the belt. 
     
     
         15 . The extrusion-to-sheet production line of  claim 2 , additionally comprising a gap die through which the sheet of molten plastic material is extruded into the gap between the first roll and the second roll. 
     
     
         16 . A method, comprising:
 passing an extruded sheet of molten plastic material between a first roll and a second roll set to a predetermined gap to calender the sheet to a thickness;   passing the sheet through a nip formed between the second roll and a belt looped around a heated third roll and a fourth roll spaced apart from the third roll, the nip being where the belt is at a closest point between the second roll and the third roll, the belt comprising an embossing pattern that is an inverse of a pattern of optical element shapes to be embossed at a first major surface of the sheet, where the pattern of optical element shapes on the belt is embossed into the first major surface of the sheet;   separating the belt from the sheet after setting the pattern of optical element shapes into the sheet.   
     
     
         17 . The method of  claim 16 , additionally comprising passing the belt through a cooling area downstream of the third roll while the first major surface of the sheet is still in contact with the embossing pattern on the belt to cool the sheet and set the pattern of optical element shapes into the sheet. 
     
     
         18 . The method of  claim 16 , additionally comprising maintaining the second roll at a temperature such that the sheet remains above the glass transition temperature of the plastic material upstream of the nip. 
     
     
         19 . The method of  claim 16 , additionally comprising superimposing a carrier film into direct contact with a second major surface of the sheet downstream of the nip. 
     
     
         20 . The method of  claim 19 , additionally comprising transferring a finish shape on a surface of the carrier film that is superimposed into direct contact with the second major surface of the sheet onto the second major surface of the sheet during pressing of the carrier film against the sheet. 
     
     
         21 . The method of  claim 19 , wherein a surface of the carrier film that is superimposed into direct contact with the second major surface of the sheet has a smooth finish.