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AssigneeMinnesota Mining and Manufacturing Company
InventorsKatharina J. Bischof, Luigi Pastore, Wilhelm Kuester, Lynn E. Faykish
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The invention provides a transparent multilayer film comprising a cover layer, a destructible or irreversibly deformable layer, respectively, a pattern of adhesion-regulating material between the cover layer and the damagable layer, and an adhesive layer for bonding with a substrate. The damagable layer has a thickness of at least 10 .mu.m. The following relationship applies to the cohesive strength as well as the adhesion between the layers: a and d>c>b whereby a is the adhesive strength between cover layer (1) and layer (3) in the areas where no adhesion-regulating material (2) is present, b is the adhesive strength between cover layer (1) and layer (3), in the areas where adhesion-regulating material (2) is present, c is the cohesive strength of layer (3), and d is the adhesive strength between layer (3) and adhesive layer (5). The invention also provides for the use of the transparent multilayer film for protection of data on documents, as well as its use as a tamper-proof label. The invention also provides for a tamperproof document or label, comprising a multilayer film of the present invention.
Transparent multilayer film, comprising a cover layer, a damagable layer, a pattern of adhesion-regulating material between said layers, and a first adhesive layer on the side of the film opposite that of the cover layer, for bonding with a substrate, characterized in that damagable layer (3) has a thickness of at least 10 .mu.m and that the cohesive strength of the damagable layer (3) and the adhesive strength between the layers obeys the following relationship:
Dependencies are inferred from the claim text.