Patent ID: 8173079

Claim:
A method for forming a structured polymeric film having a plurality of longitudinally spaced structures on both sides of the structured polymeric film, comprising: providing a rotatable tool having an outer circumferential surface, the outer circumferential surface including a plurality of tool projections; providing a nip roll having a smooth conformable outer circumferential surface opposed to the outer circumferential surface of the tool, the nip roll having a conformable outer circumferential surface of a Shore A hardness in the range of 30 to 100; introducing a transparent polymer layer and an opaque polymer layer into a nip between the tool and the nip roll; pressing the polymer layers between the tool and the nip roll to form web recesses into a first side of the opaque polymer layer and web projections extending away from an opposing second side of the transparent polymer layer, with the tool projections on the circumferential surface of the tool and forming a structured web, the tool projections having a height greater than the total thickness of both polymer layers; and removing the structured web from the tool; said transparent polymer layer being further from the tool projections in the nip than the opaque polymer layer, whereby the resulting structured web has recesses having opaque side walls and transparent bottom surfaces.