The invention includes a radiation diffracting member having a crystalline structure comprising an ordered periodic array of hollow particles. The radiation diffracting member also includes a matrix material in which the array of particles is received.

The invention includes a radiation diffracting member having a crystalline structure comprising an ordered periodic array of hollow particles. The radiation diffracting member also includes a matrix material in which the array of particles is received.

The present invention relates to a process for the preparation of thin silver nanoparticle layers, which are produced directly on a substrate as part of a coating or printing process. The layers show different colours in transmittance and reflectance. The layers do not show the typical conductivity of metallic layers, since the particles are essentially discrete particles which are not sintered. The invention further relates to decorative and security elements. When the layers are applied over a security element, such as a hologram, the obtained products show also different colours in reflection and transmission, an extremely bright optically variable image (OVD image) and high purity and contrast. Depending on the thickness of the layer a more or less intensive metallic aspect appears.

A method is disclosed which is performed by at least one first apparatus. In the method, information indicative of at least one characteristic of a franking is obtained. It is determined whether or not the franking is a counterfeit franking and/or a reused franking based on the obtained information or based on the obtained information and based on reference information indicative of at least one characteristic of a franking. The at least one characteristic includes at least one of a physical characteristic of the franking, a visual characteristic of an image provided on the franking, and/or a characteristic based on at least one material of the franking.

A method is disclosed which is performed by at least one first apparatus. In the method, information indicative of at least one characteristic of a franking is obtained. It is determined whether or not the franking is a counterfeit franking and/or a reused franking based on the obtained information or based on the obtained information and based on reference information indicative of at least one characteristic of a franking. The at least one characteristic includes at least one of a physical characteristic of the franking, a visual characteristic of an image provided on the franking, and/or a characteristic based on at least one material of the franking.

Provided herein are organic long persistent luminescence compositions and methods of use and preparation thereof and articles comprising the same.

A method and system for reducing the appearance of a security feature viewed under UV (Ultra Violet) illumination can include selecting a colorant, wherein the colorant comprises a first UV spectral reflectance property, selecting a matching colored media, which matches a color of the colorant and which comprises a second UV spectral reflectance property that is different from the first UV spectral reflectance property, and adjusting the color of the colorant and a color of the matching color media to match one another and produce an adjusted colorant that facilitates a reduction in a visibility of the security feature based on the adjusted colorant.

A method and system for reducing the appearance of a security feature viewed under UV (Ultra Violet) illumination can include selecting a colorant, wherein the colorant comprises a first UV spectral reflectance property, selecting a matching colored media, which matches a color of the colorant and which comprises a second UV spectral reflectance property that is different from the first UV spectral reflectance property, and adjusting the color of the colorant and a color of the matching color media to match one another and produce an adjusted colorant that facilitates a reduction in a visibility of the security feature based on the adjusted colorant.

There is provided a luminescent medium which requires difficult analysis of light emitted from a luminescent material of the medium. A luminescent medium includes a substrate, and a luminescent material comprising a first luminescent material which, when irradiated with visible light, infrared light or ultraviolet light, emits first infrared light “a”, and a second luminescent material which, when irradiated with visible light, infrared light or ultraviolet light, emits second infrared light “b”. The first luminescent material is formed in a first planar area, and the second luminescent material is formed in a second planar area. The first planar area and the second planar area overlap each other, forming an overlapping planar area in which the luminescent materials each have a concentration gradation.

There is provided a luminescent medium which requires difficult analysis of light emitted from a luminescent material of the medium. A luminescent medium includes a substrate, and a luminescent material comprising a first luminescent material which, when irradiated with visible light, infrared light or ultraviolet light, emits first infrared light “a”, and a second luminescent material which, when irradiated with visible light, infrared light or ultraviolet light, emits second infrared light “b”. The first luminescent material is formed in a first planar area, and the second luminescent material is formed in a second planar area. The first planar area and the second planar area overlap each other, forming an overlapping planar area in which the luminescent materials each have a concentration gradation.