A security element (100, 101) and a value document (200, 201) having such a security element (100, 101) in the form of a strip having a first (1) and second polymer layer (2) are shown, baying a visually recognizable grid primed image (3), which is luminescent under UV radiation, between the first (1) and second layer (2), wherein the grid printed image (3) has an opacity and forms at least one imprint area (5) having a boundary contour (4) within the security element (100, 101). To increase the forgery protection, it is proposed that at least one of the two polymer layers (1, 2) have an opacity at least in the region of the boundary contour (4) of the imprint area (5) and be adapted in its opacity to the opacity of the imprint area (5), in order to diminish the visual recognizability of the boundary contour (4) of the imprint area (5) of the luminescent grid printed image (3) on the security element (100, 101).

The current invention relates to a patterned optical device comprises a patterned cholesteric liquid crystal polymer layer where different domains of the pattern reflect different colors and where luminescent molecules are embedded in a subset of said reflective domains or in a separate layer. The current invention also relates to an optical security device comprises overt reflective OVD images and covert luminescent images with multiple authentication levels including detection of polarized reflections and emissions.

The current invention relates to a patterned optical device comprises a patterned cholesteric liquid crystal polymer layer where different domains of the pattern reflect different colors and where luminescent molecules are embedded in a subset of said reflective domains or in a separate layer. The current invention also relates to an optical security device comprises overt reflective OVD images and covert luminescent images with multiple authentication levels including detection of polarized reflections and emissions.

A security device is provided including a first pattern of elements and a second, overlapping, pattern of elements spaced by a transparent layer, the first and second patterns in combination obstructing the passage of light transmitted to a viewer through the device to a varying degree depending on the viewing position. The first and second patterns of elements are configured such that a first region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a first tilt axis, and a second region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a second tilt axis which is not parallel to the first tilt axis.

A security device is provided including a first pattern of elements and a second, overlapping, pattern of elements spaced by a transparent layer, the first and second patterns in combination obstructing the passage of light transmitted to a viewer through the device to a varying degree depending on the viewing position. The first and second patterns of elements are configured such that a first region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a first tilt axis, and a second region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a second tilt axis which is not parallel to the first tilt axis.

An event detection composite in embodiments of the present invention may have one or more of the following features: (a) a plurality of solid and/or hollow and/or porous-wall microspheres, (b) a functional material disposed on or within the plurality of microspheres, wherein the functional material can have unique optical, electrical, magnetic, thermal, or chemical properties, where these properties can be realized upon the plurality of microspheres being exposed to a physical, optical, electrical, magnetic, thermal or chemical stimuli, and (c) a host matrix containing the plurality of microspheres.

A method of illuminating an item is disclosed. The method includes applying adhesive to the item, interspersing a taggant in the adhesive, illuminating the item with an excitation signal, sensing luminescence emitted by the taggant in response to illumination by the excitation signal, and determining the authenticity of the item based on the sensed emitted luminescence. The item can include any item benefited by authentication, and can include a postage stamp. A method of customizing an item is disclosed. This can include the steps of preparing a substrate, applying a security feature to the substrate, printing non-customized information on the substrate, receiving image information, and printing the image information on the substrate.

A method of illuminating an item is disclosed. The method includes applying adhesive to the item, interspersing a taggant in the adhesive, illuminating the item with an excitation signal, sensing luminescence emitted by the taggant in response to illumination by the excitation signal, and determining the authenticity of the item based on the sensed emitted luminescence. The item can include any item benefited by authentication, and can include a postage stamp. A method of customizing an item is disclosed. This can include the steps of preparing a substrate, applying a security feature to the substrate, printing non-customized information on the substrate, receiving image information, and printing the image information on the substrate.

Security of a printed matter is enhanced, and a visual image is made to clear if a latent image formed by a coat printed on a matter to be printed for a security enhancement of the printed matter becomes the visual image. A security ink pigment contains a powder. A main constituent of the powder is a perovskite-type oxide. The perovskite-type oxide has a composition expressed as a general formula of ABO.sub.3. A is mainly made of Ba. B is mainly made of Sn. The powder emits infrared fluorescence when being irradiated with ultraviolet excitation light. The perovskite-type oxide has a crystal lattice constant having a difference equal to or smaller than 0.002 angstrom from a theoretical crystal lattice constant of the perovskite-type oxide having a composition expressed as a composition formula of BaSnO.sub.3.

Security of a printed matter is enhanced, and a visual image is made to clear if a latent image formed by a coat printed on a matter to be printed for a security enhancement of the printed matter becomes the visual image. A security ink pigment contains a powder. A main constituent of the powder is a perovskite-type oxide. The perovskite-type oxide has a composition expressed as a general formula of ABO.sub.3. A is mainly made of Ba. B is mainly made of Sn. The powder emits infrared fluorescence when being irradiated with ultraviolet excitation light. The perovskite-type oxide has a crystal lattice constant having a difference equal to or smaller than 0.002 angstrom from a theoretical crystal lattice constant of the perovskite-type oxide having a composition expressed as a composition formula of BaSnO.sub.3.