Method for protective film lamination with curl control

Claim 1

The method of laminating a protective transparent film to a document substrate, without producing appreciable curl in the finished laminate, comprising the following steps: A. preparing a composite protective film comprising an outer layer of tough, transparent abrasion resistant resin and an inner layer of transparent thermoplastic bonding resin, including the addition of a limited quantity of a radiant-heat-blocking pigment to the bonding resin in an amount sufficient to increase the radiant heat absorption of the bonding resin and to decrease its radiant heat transmission but small enough to preclude material degradation of the transparency of the composite film to visible light; B. heating the bonding resin layer of the composite film by directing radiant heat to impinge directly upon the bonding resin; C. laminating the composite protective film to a substrate by passing the composite film and the substrate between first and second pressure rolls, promptly after heating of the adhesive, with the adhesive surface of the film in engagement with an inner surface of the substrate, the outer surface of the film engaging the first pressure roll, and the outer surface of the substrate engaging the second pressure roll; and D. maintaining the resulting laminate in engagement with the second pressure roll through an appreciable arcuate distance on the second pressure roll after clearing its engagement with the first pressure roll.

Claim 2

The method of laminating a protective transparent film to a document substrate, without producing appreciable curl in the finished laminate, comprising the following steps: A. preparing a composite protective film comprising an outer layer of tough, transparent abrasion resistant resin and an inner layer of transparent thermoplastic bonding resin, including the addition of a limited quantity of a radiant-heat-blocking pigment to the bonding resin in an amount sufficient to increase the radiant heat absorption of the bonding resin and to decrease its radiant heat transmission but small enough to preclude material degradation of the transparency of the composite film to visible light; B. heating the bonding resin layer of the composite film by directing radiant heat to impinge directly upon the bonding resin; C. laminating the composite protective film to a substrate by passing the composite film and the substrate between first and second pressure rolls, promptly after heating of the adhesive, with the adhesive surface of the film in engagement with an inner surface of the substrate, the outer surface of the film engaging the first pressure roll, and the outer surface of the substrate engaging the second pressure roll; and D. maintaining the resulting laminate in engagement with the second pressure roll through an appreciable arcuate distance on the second pressure roll after clearing its engagement with the first pressure roll.