Patent ID: 8696032
Filing Date: 2014-04-15
Classification: B42D

Abstract:
1. A security device comprising: a substrate having a transparent region, wherein: at least one optical element comprising a diffraction grating is provided in part of the transparent region, the optical element causing an incident off-axis light beam incident on the device in a direction offset from a perpendicular to the plane of the substrate and transmitted through the optical element to be redirected away from a line parallel with the incident light beam whereby when the device is viewed in transmission directly against a backlight defined by a light beam of higher intensity than the ambient light level and which is in line with the device and the observer, the presence of the optical element cannot be discerned but when the device is moved relative to the backlight such that lines of sight from the viewer to the transparent region and from the transparent region to the backlight form an obtuse angle at which redirected light is visible to the viewer, a first contrast is viewed between the part of the transparent region including the optical element and another part of the transparent region, and when the security device is viewed in reflection under diffuse lighting conditions either no contrast can be discerned between the two parts or a second contrast, different from the first contrast, can be discerned between the two parts; and the security device further comprises an image, viewable in both reflection and transmission, on a part of the transparent region, the image being arranged at least partially over a portion of the at least one optical element.