Security substrate for documents of value

A security substrate for a document of value comprising:

• a laminate having a generally transparent balanced biaxially oriented core layer, said core layer being oriented in at least a first direction at an orientation ratio of at least 4:1 and oriented in a second direction substantially normal to the first direction at an orientation ratio of at least 6:1;
• generally transparent imbalanced biaxially oriented outer layers on opposite sides of said core layer, said outer layers being oriented in at least a first direction to a degree which is at least three times less than the degree of orientation present in a second direction substantially normal to the first direction;
• and a laminating adhesive resin securing the outer layers to the core layer so that the first directions of orientation of the outer layers are substantially aligned;
• at least one optically variable device embedded within the laminate between said core layer and one of said cover layers, the at least one optically variable device having a highly reflective opaque layer on a surface of said core layer and an optically variable thin film multilayer overlying at least a portion of the opaque layer;
• and
• opacifying coatings on said outer layers, at least one window being formed in at least one of said opacifying coatings that is at a location corresponding to said at least one optically variable device.