Patent ID: 7833576

Claim:
A method of making a punched product which comprises the steps of: (a) applying an anisotropic pressure sensitive adhesive having linear polymer chains to one or both sides of a carrier material with an extrusion die to form a single coated or double coated carrier material such that the linear polymer chains are oriented on the carrier material and crosslinking the anisotropic pressure sensitive adhesive by irradiation with electron beams and freezing the orientation of the polymer chains on the carrier material, wherein said anisotropic pressure sensitive adhesive: (i) is obtainable by a free-radical addition polymerization; (ii) is based of at least 65% by weight of at least one acrylic monomer from the group of compounds selected from the group consisting of: where R 1 is H or CH 3 and the radical R 2 is selected from the group consisting of H, CH 3 and branched or unbranched, saturated alkyl groups having 2 to 20 carbon atoms; (iii) has a weight-average molecular weight, as measured by gel permeation chromatography, of at least 650,000; (iv) when applied to a carrier, possesses a preferential direction, the refractive index measured in the preferential direction, n MD , being greater than the refractive index measured in a direction perpendicular to the preferential direction, n CD , and the difference Δn =n MD −n CD being at least 1·10 −5 ; and (v) exhibits shrinkback; (b) punching or partial-punching of said single or double coated material to form said punched product wherein the anisotropic pressure sensitive adhesive is slit during the punching or partial-punching and the anisotropic pressure sensitive adhesive at the slit does not coalesce after the punching or partial-punching.