A flat security element with optical security features includes at least one first surface region with a first sub-wavelength structure. The structure elements that define the first sub-wavelength structure periodically repeat in the plane of the security element. In order to be able to convey a motif with increased forgery protection using at least two different color impressions, which motif is easy to produce, the first sub-wavelength structure of at least one partial region of the first surface region is additionally provided with an interference coating for producing a color-shifting effect.

A flat security element with optical security features includes at least one first surface region with a first sub-wavelength structure. The structure elements that define the first sub-wavelength structure periodically repeat in the plane of the security element. In order to be able to convey a motif with increased forgery protection using at least two different color impressions, which motif is easy to produce, the first sub-wavelength structure of at least one partial region of the first surface region is additionally provided with an interference coating for producing a color-shifting effect.

Provided are transaction cards including an infinity mirror. In some approaches, a transaction card may include a body comprising a first reflective layer and a second reflective layer, and a light source between the first reflective layer and the second reflective layer.

Disclosed is a composite particle for use in a marking that is suitable for identification/authentication purposes. The particle comprises at least one superparamagnetic portion and at least one thermoluminescent portion coated with an thermoisolating portion. Optionally also a thermoconductive portion between the superparamagnetic and thermoluminscent portions.

A method is disclosed. For example, the method includes applying a clear coat layer on a substrate, drying the clear coat layer to form random microstructures in the clear coat layer, dispensing a printing fluid to print a graphical pattern on the clear coat layer, and generating a physical unclonable function (PUF) pattern by drying the printing fluid that fills the random microstructures formed in the clear coat layer.

A digitally printed security document includes: a security document substrate; a first digitally printed print working on a first surface of the substrate in a first region, the first print working including a first array of printed elements arranged according to a first grid of lattice points having a first pitch; and a second digitally printed print working on the first surface of the substrate in a second region, the second print working including a second array of printed elements arranged across a second grid of lattice points having a second pitch different from the first pitch.

A digitally printed security document includes: a security document substrate; a first digitally printed print working on a first surface of the substrate in a first region, the first print working including a first array of printed elements arranged according to a first grid of lattice points having a first pitch; and a second digitally printed print working on the first surface of the substrate in a second region, the second print working including a second array of printed elements arranged across a second grid of lattice points having a second pitch different from the first pitch.

An IR and/or UV machine-readable optical security device (e.g., micro-optic security thread) that is made up of at least one IR-absorbing component with a characteristic IR signature detectable at two or more IR-wavelengths, at least one UV-absorbing component with a characteristic UV signature detectable at two or more UV-wavelengths, at least one IR-absorbing component that absorbs IR light and emits light at a different invisible wavelength, at least one UV-absorbing component that absorbs UV light and emits light at a different invisible wavelength, or a combination thereof, is provided. The IR and UV machine-readable features do not interfere with the optical effects projected by the optical material.

An IR and/or UV machine-readable optical security device (e.g., micro-optic security thread) that is made up of at least one IR-absorbing component with a characteristic IR signature detectable at two or more IR-wavelengths, at least one UV-absorbing component with a characteristic UV signature detectable at two or more UV-wavelengths, at least one IR-absorbing component that absorbs IR light and emits light at a different invisible wavelength, at least one UV-absorbing component that absorbs UV light and emits light at a different invisible wavelength, or a combination thereof, is provided. The IR and UV machine-readable features do not interfere with the optical effects projected by the optical material.

A security device is provided, comprising: a colour shifting element that exhibits different wavelengths of light at different viewing angles, and; an at least partially transparent light control layer covering at least a part of the colour shifting element and comprising a surface relief adapted to modify the angle of light from the colour shifting element, wherein; a first region of the light control layer comprises a first optical characteristic, whereby light at a first viewing angle from the first region of the light control layer is perceived to have a resultant optical effect that is the resultant of the wavelength of light exhibited at that viewing angle due to the combination of the colour shifting element and the surface relief of the light control layer, and the first optical characteristic, and; a second region of the light control layer either: (i) is substantially colourless such that light at the first viewing angle from the second region is perceived to have a resultant optical effect exhibited at that viewing angle due to the combination of the colour shifting element and the surface relief of the light control layer, or; (ii) comprises a second optical characteristic different from the first optical characteristic, whereby light at the first viewing angle from the second region of the light control layer is perceived to have a resultant optical effect that is the resultant of the wavelength of light exhibited at that viewing angle due to the combination of the colour shifting element and the surface relief of the light control layer, and the second optical characteristic. Methods of manufacture thereof are also disclosed.