Multilayer film structures for use in the production of banknotes or the like

A curl-resistant, cross-sectionally symmetrical, laminated multilayer film substrate for use in the production of banknotes, security papers and the like comprising:

• (a) an imbalanced biaxially oriented first layer having inner and outer sides, comprising at least about 50 weight percent of a high density polyethylene having a density of at least about 0.94, said first layer being oriented in at least a first direction to a degree which is at least three times greater than the degree of orientation present in a second direction substantially normal to the first direction;
• and
• (b) an imbalanced biaxially oriented second layer having inner and outer sides, comprising at least about 50 weight percent of a high density polyethylene having a density of at least about 0.94, said second layer being oriented in at least a first direction to a degree which is at least three times greater than the degree of orientation present in a second direction substantially normal to the first direction;
• (c) a laminating adhesive resin disposed between the inner sides of (a) and (b), which comprises a component selected from the group consisting of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE);
• said second layer being laminated to said first layer so that the first direction of orientation of said second layer is substantially aligned with the first direction of orientation of said first layer and wherein (a) further comprises a coextruded propylene copolymer skin on its inner side.