System and method for controlling curl in multi-layer webs

Abstract

A system and method for controlling curl in multi-layer webs. The method can include providing a coated web, bending the web to induce a strain or pre-curl in the web, and curing the coating to form a multi-layer web. Some coatings at least partially shrink when cured such that curing the coating induces a curl in the multi-layer web. Bending the web occurs prior to curing the coating, and the pre-curl can be configured to at least partially counteract the curl induced by curing to form a multi-layer web having a desired curvature. The system can include a curing section configured to cure a coating, and can further include a web bending section configured to bend the web to induce a strain in the web. The web bending section can be positioned upstream of the curing section such that the web is bent prior to the coating being cured.

1 . A method for reducing strain-induced curl in a multi-layer web, the method comprising:
 providing a coated web comprising a coating applied to a web of indeterminate length;   bending the web to induce a strain in the web; and   curing the coating to form a multi-layer web, the coating being characterized by at least partially shrinking when cured such that curing the coating induces a curl in the multi-layer web,   wherein bending the web occurs prior to curing the coating, and wherein the strain induced by bending substantially cancels the curl induced by curing, said bending being accomplished by a means selected from:   i) passing the web partly around two co-rotating rollers having a gap between them, without a third roller to direct the web into the gap, holding the web against the rollers by holding means selected from electrostatic pinning wire, air pressure, vacuum, adhesive, and engagement members, so that the web is bent into a portion having a radius within or near the gap; and   ii) moving the web through and bending it within a gap between a first belt assembly and a second belt assembly to form a portion having a radius, each belt assembly including a moving, driven belt said belts being driven in opposite directions.   
     
     
         2 . A method for producing a multi-layer web having a desired curvature, the method comprising:
 providing a web of indeterminate length;   bending the web to induce a pre-curl in the web;   applying a coating to the web; and   curing the coating to form a multi-layer web, the coating being characterized by at least partially shrinking when cured such that curing the coating induces a curl in the multi-layer web,   wherein bending the web occurs prior to curing the coating, and wherein the pre-curl is configured to at least partially counteract the curl induced by curing to form a multi-layer web having a desired curvature.   
     
     
         3 . A web handling system for producing a multi-layer web having a desired curvature, the web handling system comprising:
 a curing section configured to cure a coating applied to a web of indeterminate length to form a multi-layer web; and   a web bending section configured to bend the web to induce a strain in the web, the web bending section being positioned upstream of the curing section such that the web is bent prior to the coating being cured.