OPTICALLY CHANGEABLE ELEMENT AND ITS APPLICATION Russian patent published in 2008 - IPC B42D15/10 G02B3/00 G02B5/18 

FIELD: optically changeable elements and application thereof as protective element for preventing counterfeiting of valuable documents or objects.

SUBSTANCE: the optically changeable element at least on sections of surface contains a boundary plane, which constitutes an optically active structure, which projects spatially to the front or to the back relatively to imaginary supporting surface. The boundary surface has free form surface, which appears three-dimensional to observer. The free form surface is composed of a section of boundary surface which is lens-like, or, in other words, appears spatially convex or shifted backwards, with creation of magnification, reduction or distortion effects. The free form surface is made with a diffraction screen structure, lines of which practically follow the contour of free form surface.

EFFECT: the optically changeable element, as a part of decorative layered structure of transfer film or laminated film, due to creation of three-dimensional optical effects which obstruct counterfeiting, ensures protection of valuable documents or objects.

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