A security device is disclosed including a substrate and one or more focusing elements or lens structures located on one side of the substrate. The security device includes a plurality of image elements associated with each focusing element wherein the image elements include at least first and second groups of image elements. Each image element may be composed of pixels located in an object plane to be viewable through the associated focusing element. Each image element comprises a diffractive grating element or sub-wavelength grating element which when illuminated by a light source generates a diffraction image observable at a range of viewing angles around the device. Image elements of the first group are visible in a first range of viewing angles and image elements of the second group are visible in a second range of viewing angles. The security device is particularly suitable for use on security documents, such as banknotes. A method of forming a security device is also disclosed.

The present invention is directed to a sealing layer that comprises a combination of polyurethane and poly(vinyl alcohol), the poly(vinyl alcohol) containing an acetoacetate functional group in its molecular structure. The sealing layer is formed from an aqueous sealing composition and shows water resistance and good barrier properties to non-polar fluids. The sealing layer can be used to seal microcells of electro-optic displays.

The present invention is directed to a sealing layer that comprises a combination of polyurethane and poly(vinyl alcohol), the poly(vinyl alcohol) containing an acetoacetate functional group in its molecular structure. The sealing layer is formed from an aqueous sealing composition and shows water resistance and good barrier properties to non-polar fluids. The sealing layer can be used to seal microcells of electro-optic displays.

A security marking has a physically unclonable function (PUF) wherein the PUF includes a disordered multilayer photonic crystal structure having an electromagnetic transmission and/or reflection spectrum and/or spectra upon receipt of electromagnetic radiation within a photonic bandgap region of the structure that is unique to the structure.

The invention relates to an optical structure (5) having a relief effect, comprising: - a support (7) adapted for aligning liquid crystals, - a deposit (9) in contact with the support of a substance in the form of at least one pattern (11), which partially covers the support, and - a liquid crystal layer (13) which at least partially covers the support and said pattern and is in contact with the support.

The invention relates to an optical structure (5) having a relief effect, comprising: - a support (7) adapted for aligning liquid crystals, - a deposit (9) in contact with the support of a substance in the form of at least one pattern (11), which partially covers the support, and - a liquid crystal layer (13) which at least partially covers the support and said pattern and is in contact with the support.

The present invention relates to the field of security inks suitable for printing machine readable security features on substrate, security documents or articles as well as machine readable security feature made from said security inks, and security documents comprising a machine readable security feature made from said security inks. In particular, the invention provides security inks comprising one or more IR absorbing materials wherein said security ink allows the production of a machine readable security feature having the following optical properties: a lightness L* equal to or higher than about 80, a chroma C* smaller than or equal to about 15 and a reflectance at 900 nm smaller than or equal to about 60%.

The present invention relates to the field of security inks suitable for printing machine readable security features on substrate, security documents or articles as well as machine readable security feature made from said security inks, and security documents comprising a machine readable security feature made from said security inks. In particular, the invention provides security inks comprising one or more IR absorbing materials wherein said security ink allows the production of a machine readable security feature having the following optical properties: a lightness L* equal to or higher than about 80, a chroma C* smaller than or equal to about 15 and a reflectance at 900 nm smaller than or equal to about 60%.

In a general aspect, unique unclonable physical identifiers are applied and used. A method of applying the unique marker can include receiving an object having a surface feature and forming a unique marker on the surface feature of the object. The unique marker includes a distribution of elements and conforms with a morphology of the surface feature. The method further includes extracting orientation information from the unique marker. The orientation information can indicate relative spatial orientations of the respective elements. The method additionally includes generating a unique code for the object based on the orientation information. The surface feature can be facets, surface patterns, textures, or other indentations of the object. The surface feature can include a region of the object that is susceptible to tampering.

The present invention relates to security, or decorative elements, comprising a transparent, or translucent substrate, which may contain indicia or other visible features in or on its surface, and on at least part of the substrate surface, a first layer, comprising transition metal particles having an average diameter of from 5 nm to 500 nm and a binder, on at least part of the first layer a second layer, comprising an organic material and having a refractive index of from 1.2 to 2.3 and having a thickness of from 20 to 1000 nm, wherein the transition metal is silver, copper, gold and palladium, wherein the weight ratio of transition metal particles to binder in the first layer is in the range from 20:1 to 1:2 in case the binder is a polymeric binder, or wherein the weight ratio of transition metal particles to binder in the first layer is in the range from 5:1 to 1:15 in case the binder is an UV curable binder. The security or decorative element show a certain color in transmission and a different color in reflection and a color flop on the coating side. The color in reflection and the color flop of the security or decorative elements are controlled by adjusting the refractive index and thickness of the second layer.