Abstract: A security device for security documents provides an angle-dependent Moiré effect. A security device for a security document and method for making the security device are provided. At least two interlaced laser engraved images form an angle dependent parallax effect. First and second images are laser engraved at a substrate of the security document. To render the security device more difficult to copy, a colour changing effect or a nonreciprocal transmission effect may be achieved by adding a coloured (absorptive or emissive) layer between or within non-laser engravable layers situated between the laser engravable layers, and/or by adding a patterned phase diffraction grating situated between the laser engravable layers.

Abstract: A security device for security documents provides an angle-dependent Moire effect. A security device for a security document and method for making the security device are provided. At least two interlaced laser engraved images form an angle dependent parallax effect. First and second images are laser engraved at a substrate of the security document. To render the security device more difficult to copy, a colour changing effect or a nonreciprocal transmission effect may be achieved by adding a coloured (absorptive or emissive) layer between or within non-laser engravable layers situated between the laser engravable layers, and/or by adding a patterned phase diffraction grating situated between the laser engravable layers.

Abstract: A method of encoding a hidden image in high frequency spatial frequencies of a line pattern of a host image. A set of host image spatial frequencies is generated based on a predefined mapping of a domain of a set of representative scalar values of the hidden image and a domain of the host image spatial frequencies. The line pattern of the host image is generated based on the set of host image spatial frequencies. The host image may be composed of tiles containing parallel line segments, with each tile encoding a corresponding one of the scalar values. The host image may be composed of a stochastic line pattern generated from a white noise image convolved with a space variable kernel based on the predefined domain mapping. The hidden image may be decoded algorithmically or optically in a single step.

Abstract: Ultraviolet light-curable deposits are printed onto a substrate in a predetermined pattern to make tactile marks (e.g. Braille-like resin dots) for use by people with impaired vision to, for example, recognize the denominations of banknotes. The deposit demonstrates high adhesion due to: (1) presence of 20-80% (wt.) of a low viscosity acrylate component to provide a substrate-penetrating property; and, (2) 2-30% (wt.) of an adhesion-promoting acid acrylate. The deposit material further includes 1-30% (wt.) of urethane acrylate, 1-30% by weight of reactive diluent, photoinitiator and 1-10% (wt.) of rheological adsorbing additive. Optimally, the adhesion promoter is added after the other components have been mixed with the rheological additive. The printing step may be followed by heating before the curing step to increase penetration of the ink into the substrate. The deposit may comprise a taggant for use as a security feature.

Abstract: A method of encoding a hidden image in high frequency spatial frequencies of a line pattern of a host image. A set of host image spatial frequencies is generated based on a predefined mapping of a domain of a set of representative scalar values of the hidden image mage and a domain of the host image spatial frequencies. The line pattern of the host image is generated based on the set of host image spatial frequencies. The host image may be composed of tiles containing parallel line segments, with each tile encoding a corresponding one of the scalar values. The host image may be composed of a stochastic line pattern generated from a white noise image convolved with a space variable kernel based on the predefined domain mapping. The hidden image may be decoded algorithmically or optically in a single step.

Abstract: Improved ultraviolet light-curable compositions are provided for printing onto a security document substrate in a predetermined pattern to make tactile features for use by people with impaired vision to, for example, recognize the denominations of banknotes. The improved compositions substantially comprise an acidic trifunctional acrylate ester, preferably in an amount of 60-80 wt %, and include urethane acrylate and effective amounts of flexibilizer (e.g. low viscosity aromatic monoacrylate having an elongation parameter of about 200), photoinitiator and a rheological additive (e.g. silica). The composition unexpectedly provides flexibility and is particular useful for printing tactile features in the form of relatively large continuous graphical patterns.

Abstract: Ultraviolet light-curable deposits are printed onto a substrate in a predetermined pattern to make tactile marks (e.g. Braille-like resin dots) for use by people with impaired vision to, for example, recognize the denominations of banknotes. The deposit demonstrates high adhesion due to: (1) presence of 20-80% (wt.) of a low viscosity acrylate component to provide a substrate-penetrating property; and, (2) 2-30% (wt.) of an adhesion-promoting acid acrylate. The deposit material further includes 1-30% (wt.) of urethane acrylate, 1-30% by weight of reactive diluent, photoinitiator and 1-10% (wt.) of rheological adsorbing additive. Optimally, the adhesion promoter is added after the other components have been mixed with the rheological additive. The printing step may be followed by heating before the curing step to increase penetration of the ink into the substrate. The deposit may comprise a taggant for use as a security feature.