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.

The present invention provides a security assembly for protecting a device includes first and second security wraps fitted to the device. The first security wrap covers a first area of the device. The second security wrap partially overlaps the first security wrap and covers a second area of the device. Each of the first and second security wraps has a security screen having first and second screen terminals and a conductive track extending between the first and second screen terminals. A conductive structure is disposed in an overlapping area between the first and second security wraps and coupled to the second screen terminal of the first security screen and to the first screen terminal of the second security screen.

A tamper-indicating device, the tamper-indicating device including: an elongate structure; a penetrant chamber coupled to the elongate structure; and a physical barrier (or other release mechanism) disposed between the elongate structure and the penetrant chamber; wherein the penetrant chamber is adapted to contain a penetrant material that selectively diffuses into the elongate structure at a predetermined rate when the physical barrier is ruptured (or the other release mechanism is actuated) by a tamper or environmental event; and wherein the penetrant material creates an overt or covert indication of the degree of diffusion into the elongate structure, the degree of diffusion indicating an amount of time since the tamper or environmental event. The tamper-indicating device further includes a substrate coupled to the elongate structure. Optionally, the tamper-indicating device further includes a visible time scale disposed on the substrate substantially adjacent to the elongate structure.

A security document with unidirectional visual illumination is disclosed. A security feature is positioned within the document and not visible in normal ambient lighting conditions but becomes visible under specialized lighting conditions, for example in the presence of ultraviolet light. The security feature is constructible such that it is visible only from a single side of the security document, with the side being predeterminable regardless of the orientation of the specialized light.

A security document with unidirectional visual illumination is disclosed. A security feature is positioned within the document and not visible in normal ambient lighting conditions but becomes visible under specialized lighting conditions, for example in the presence of ultraviolet light. The security feature is constructible such that it is visible only from a single side of the security document, with the side being predeterminable regardless of the orientation of the specialized light.

A tamper-indicating device, the tamper-indicating device including: an elongate structure; a penetrant chamber coupled to the elongate structure; and a physical barrier (or other release mechanism) disposed between the elongate structure and the penetrant chamber; wherein the penetrant chamber is adapted to contain a penetrant material that selectively diffuses into the elongate structure at a predetermined rate when the physical barrier is ruptured (or the other release mechanism is actuated) by a tamper or environmental event; and wherein the penetrant material creates an overt or covert indication of the degree of diffusion into the elongate structure, the degree of diffusion indicating an amount of time since the tamper or environmental event. The tamper-indicating device further includes a substrate coupled to the elongate structure. Optionally, the tamper-indicating device further includes a visible time scale disposed on the substrate substantially adjacent to the elongate structure.