In one example of the disclosure, a substantially transparent substrate is provided at a printer. A primer layer is applied upon a first surface of the substrate. A security ink layer that includes security information is applied upon the primer layer. An opaque background ink layer is applied upon the security ink layer. A corona treatment is applied to a second surface, located on an opposite side of the substrate relative to the first surface. A release ink layer is applied upon the corona-treated second surface. An opaque cover image ink layer is applied upon the release ink layer.