This patent document discloses physical documents including metameric ink pairs. One claim recites a document comprising: a first surface; a second surface, in which the first surface comprises a first set of print structures and a second set of print structures, in which the first set of print structures and the second set of print structures collective convey an encoded signal discernable from optical scan data representing at least a first portion of the first surface, in which the first set of print structures is provided on the first surface with a first ink and the second set of print structures is provided on the first surface with a second, different ink, and in which the first ink and the second, different ink comprise a metameric pair. Of course, other claims and combinations are described as well.

A security device is disclosed that has an image formed upon a substrate. The image has a first printed region and a second different printed region both printed with a same ink formulation of field alignable flakes. At least one of the printed regions has optically variable effects. One of the first and second printed regions at least partially surrounds the other. The second printed region is formed of thin parallel lines and the first printed region has substantially wider lines than are printed in the second printed region. The area density of the ink in a line in the first group of wider lines is greater than the area density of a line in the second group of narrower lines. A surprising effect of this image is that particles or flakes in the ink are field aligned so as to produce a visible kinematic dynamic effect visible in the first region and not visible in the second region when the image is tilted or rotated.

A security device is disclosed that has an image formed upon a substrate. The image has a first printed region and a second different printed region both printed with a same ink formulation of field alignable flakes. At least one of the printed regions has optically variable effects. One of the first and second printed regions at least partially surrounds the other. The second printed region is formed of thin parallel lines and the first printed region has substantially wider lines than are printed in the second printed region. The area density of the ink in a line in the first group of wider lines is greater than the area density of a line in the second group of narrower lines. A surprising effect of this image is that particles or flakes in the ink are field aligned so as to produce a visible kinematic dynamic effect visible in the first region and not visible in the second region when the image is tilted or rotated.

Methods and systems for optical effects in pigments, inks, and on media. One aspect of this disclosure involves a pigment particle which includes a core, having a fluorescent material and having a spherical shape, and a shell surrounding the core; the shell includes a photochromic material which has a first optical property in a first light source and a second optical property in a second light source which includes a set of wavelengths not sufficiently present in the first light source. The second optical property attenuates an emitted radiation from the fluorescent material. Other aspects are also described.

Described is a chiral liquid crystal polymer (CLCP) layer or pattern which comprises randomly distributed craters of controlled mean diameter and/or density. The density and/or mean diameter of the craters can be controlled, for example, by adjusting the wetting of a substrate by a CLCP precursor composition, the development time of the precursor composition, and the thickness of the applied precursor composition.

The invention relates to an optically variable element as well as a method for the production thereof. In a first area the optically variable element has at least one first color region which in the event of illumination generates a color dependent on the angle of observation and/or angle of illumination. The first color region has two or more zones (41 to 47) arranged next to each other. The two or more zones arranged next to each other have in each case a width and/or length dimension of less than 300 μm. In at least one first zone (41) of the zones (41 to 47) of the first color region a thin-film interference filter (15) is provided with at least one interference layer (17). The interference layer (17) of the thin-film interference filter (15) has a first average thickness (d.sub.1) in the first zone (41). The first average thickness is chosen such that the thin-film interference filter (15) in the event of illumination at least one particular angle of observation and/or angle of illumination generates, by means of interference, a color which differs from at least one color which is generated in the event of illumination at this angle of observation and/or angle of illumination in at least one of the other zones (42 to 47) of the first color region.

A document which may be a security document has a thermochromic coating which may be a thermochromic ink on the substrate of the document. The ink may include several thermochromic materials which transition from various different colors to substantially clear in appearance as the ink is warmed to various temperatures. The combination of the colors of the thermochromic materials can give the document a different color at a number of different temperatures, until the coating is warmed to the highest color change point. When at or above the highest color change temperature, the coating becomes substantially transparent and the printed area assumes the color of the underlying substrate. The coating may also include non-reactive materials of yet another color that mixes with the colors of the thermochromic materials. The document may additionally include printed indicia on the substrate that are masked by the thermochromic materials at certain temperatures, and not masked by the thermochromic materials at other temperatures.

According to one aspect, the invention relates to an optical safety component having a plasmonic effect intended to be observed by transmission, including two layers (101, 103) made of a transparent dielectric material, a metal layer (102) that is arranged between said layers made of dielectric material to form two dielectric-metal interfaces (105, 106), and is structured to form on at least a portion thereof corrugations (104) that are capable of coupling surface plasmon modes supported by said dielectric-metal interfaces with an incident light wave. The corrugations are arranged in a first coupling area in a first main direction and in at least one second coupling area separate from said first coupling area, in a second main direction that is substantially perpendicular to said first main direction, said metal layer being continuous on each one of said coupling areas.

Security documents often incorporate optically variable devices to prevent or hinder counterfeiters. Disclosed herein are layered optically variable devices such as color-shift foils, and methods for their production and use. Such devices afford new techniques for a user of a security document to check quickly and easily whether the security document is a legitimate document or a counterfeit copy.

A method and security device, including: a semi-transparent layer exhibiting a first pattern of regions having high optical density and/or raised surface profile relative to layer intervening regions; and a color layer exhibiting a second pattern of elements of at least one color. First and second patterns partially overlap and are configured so the device, appearance varies at different viewing angles. First pattern has color layer following the contours of raised regions. Security device includes: a photosensitive film exhibiting pattern of regions of relatively high and low optical density, the pattern arising from photosensitive film exposure to radiation of a responsive predetermined wavelength from the photosensitive film; and a color layer overlapping the pattern exhibited by photosensitive film, which exhibits increase in optical density upon radiation exposure of a predetermined wavelength and concurrent or subsequent heating. Increases in optical density being due to the bubbles formation within the photosensitive film.