Abstract: High refractive index coatings having metal oxide particles are disclosed. Dispersions of metal oxide particles in solvent are also disclosed. These find use in the protection of surface relief structures. In some disclosed embodiments, the coatings or dispersions contain UV-curable resins. The coatings and dispersions find application in the field of security devices and documents and tokens incorporating security devices.

Abstract: A method for producing an optical device, preferably a security device, including the steps of: forming a planar relief structure on a substantially planar first surface of a substrate, preferably a transparent substrate, the planar relief structure having a first alignment direction and including a plurality of relief structure elements each having the same height; and applying a liquid crystal polymer (LCP) layer onto the planar relief structure such that the LCP layer is aligned with the relief structure, wherein the LCP layer includes at least one or more first LCP regions having a first height and one or more second LCP regions having a second height above the substantially planar first surface of the substrate, wherein the second height is different to the first height, and an optical device formed by such a method.

Abstract: An optically variable device and method of manufacturing the device is disclosed, the device including a plurality of zero-order diffraction grating elements some of which are modulated such that a coloured at least partially polarized image is visible to a person viewing the device, observing a first optically variable effect when the device is rotated about an axis substantially perpendicular to the plane, and a second optically variable effect when the device is viewed under polarized light and rotated about an axis substantially perpendicular to or parallel with the plane. The device is particularly suitable for security documents such as bank notes. Preferably, the first optically variable effect is produced by a change in brightness and/or color of the grating elements and the second optically variable effect may likewise be produced by a change in brightness and/or color of the grating elements.

Abstract: An optical security device is disclosed which includes a diffraction layer having a plurality of diffraction elements and a high refractive index layer, wherein the high refractive index layer is applied on the diffraction layer such that selected regions of the diffraction layer have the corresponding diffraction elements partially uncovered by the high refractive index layer and other regions are substantially covered by the high refractive index layer. Accordingly, the optical security device has a first security feature associated with the diffraction layer and a second security feature associated with the high refractive index layer. An image is viewable from the regions of the high refractive index layer, either, covertly by placed an index matched item over the device or, overtly, through selection of the thickness of the high refractive index layer.

Abstract: An optical device including: a first surface; and an arrangement of pixels on the first surface, wherein a plurality of the pixels includes a zero-order diffraction element, such that each zero-order diffraction element is configured for providing a zero-order diffractive effect.

Abstract: A security device comprises a transparent substrate having an opacifying layer disposed on at least one surface. A reflective grating layer comprises one or more arrangements of grooves, and a liquid crystal material layer is disposed over at least a portion of the grating layer. The arrangements of grooves have a groove spacing such that liquid crystal molecules within the liquid crystal material layer are substantially aligned so as to polarise optical radiation passing therethrough. The security device further includes apertures formed in the opacifying layer and the grating layer comprising a transmissive diffractive optical element (DOE). The security device thereby comprises a transmissive security feature, visible when viewed in transmission mode by the naked eye, in combination with a covert, reflective security feature, visible only using a suitably oriented polariser.

Abstract: An optical security device is disclosed which includes a diffraction layer having a plurality of diffraction elements and a high refractive index layer, wherein the high refractive index layer is applied on the diffraction layer such that selected regions of the diffraction layer have the corresponding diffraction elements partially uncovered by the high refractive index layer and other regions are substantially covered by the high refractive index layer. Accordingly, the optical security device has a first security feature associated with the diffraction layer and a second security feature associated with the high refractive index layer. An image is viewable from the regions of the high refractive index layer, either, covertly by placed an index matched item over the device or, overtly, through selection of the thickness of the high refractive index layer.

Abstract: An optical security device, including a substrate (102) having a first surface and a second surface; and a metallic nanoparticle ink (104) provided intermittently in at least one area on the first surface (102) to produce a reflective or partially reflective patch or patches; wherein a high refractive index coating (106) is applied over the area or areas (108) in which the metallic nanoparticle ink is provided, the high refractive index coating (106) adhering to the first surface (102) where the metallic nanoparticle ink is not present, thereby retaining the metallic nanoparticle ink (104) between the first surface (102) and the high refractive index coating (106).

Abstract: A polarising security element for polarising light of a predetermined wavelength including a first dielectric material having a refractive index nb and at least one polarising region of mutually parallel segments of a second material having a refractive index np which is different from nb, the second material being a dielectric or conducting material. The segments of the second material are in contact with the first material and the segments have a width and/or an average spacing which is less than a predetermined range of wavelengths. A method of manufacturing such a security element in which a relief structure is embossed in the layer of the first dielectric material, the relief structure includes mutually parallel peaks and troughs, and the second layer of dielectric or conducting material is applied on the relief structure to form the at least one polarising region of mutually parallel segments.

Abstract: An optically variable device and method of manufacturing the device is disclosed, the device including a plurality of zero-order diffraction grating elements some of which are modulated such that a coloured at least partially polarised image is visible to a person viewing the device, observing a first optically variable effect when the device is rotated about an axis substantially perpendicular to the plane, and a second optically variable effect when the device is viewed under polarised light and rotated about an axis substantially perpendicular to or parallel with the plane. The device is particularly suitable for security documents such as bank notes. Preferably, the first optically variable effect is produced by a change in brightness and/or colour of the grating elements and the second optically variable effect may likewise be produced by a change in brightness and/or colour of the grating elements.

Abstract: High refractive index coatings having metal oxide particles are disclosed. Dispersions of metal oxide particles in solvent are also disclosed. These find use in the protection of surface relief structures. In some disclosed embodiments, the coatings or dispersions contain UV-curable resins. The coatings and dispersions find application in the field of security devices and documents and tokens incorporating security devices.