The present disclosure relates to an encoding method and a decoding method using a chiral metal nanostructure. The encoding method according to an aspect of the present disclosure includes preparing a plurality of metal nanostructures having a chiral structure; obtaining the optical data of the plurality of metal nanostructures, and preparing a security medium including the plurality of metal.

An anti-counterfeiting medium includes a recording medium, a polarizer layer arranged on a part of the recording medium. The polarizer layer is formed thereon with a low extinction-ratio area that forms an image portion where a polarizer exhibits an extinction ratio lower than in a portion other than the low extinction-ratio area of the polarizer layer. The recording medium is formed thereon with an image portion that is a part of the recording medium and has a nature different from that of a portion other than the part of the recording medium.

An anti-counterfeiting medium includes a recording medium, a polarizer layer arranged on a part of the recording medium. The polarizer layer is formed thereon with a low extinction-ratio area that forms an image portion where a polarizer exhibits an extinction ratio lower than in a portion other than the low extinction-ratio area of the polarizer layer. The recording medium is formed thereon with an image portion that is a part of the recording medium and has a nature different from that of a portion other than the part of the recording medium.

A security device is provided including a first pattern of elements and a second, overlapping, pattern of elements spaced by a transparent layer, the first and second patterns in combination obstructing the passage of light transmitted to a viewer through the device to a varying degree depending on the viewing position. The first and second patterns of elements are configured such that a first region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a first tilt axis, and a second region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a second tilt axis which is not parallel to the first tilt axis.

A security device is provided including a first pattern of elements and a second, overlapping, pattern of elements spaced by a transparent layer, the first and second patterns in combination obstructing the passage of light transmitted to a viewer through the device to a varying degree depending on the viewing position. The first and second patterns of elements are configured such that a first region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a first tilt axis, and a second region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a second tilt axis which is not parallel to the first tilt axis.

An anti-counterfeiting medium includes a recording medium, a polarizer layer arranged on a part of the recording medium. The polarizer layer is formed thereon with a low extinction-ratio area that forms an image portion where a polarizer exhibits an extinction ratio lower than in a portion other than the low extinction-ratio area of the polarizer layer. The recording medium is formed thereon with an image portion that is a part of the recording medium and has a nature different from that of a portion other than the part of the recording medium.

An anti-counterfeiting medium includes a recording medium, a polarizer layer arranged on a part of the recording medium. The polarizer layer is formed thereon with a low extinction-ratio area that forms an image portion where a polarizer exhibits an extinction ratio lower than in a portion other than the low extinction-ratio area of the polarizer layer. The recording medium is formed thereon with an image portion that is a part of the recording medium and has a nature different from that of a portion other than the part of the recording medium.

An article may include a biodata page defining a perimeter including an edge and a hinge layer attached to at least a portion of the biodata page. The hinge layer comprises a cross-linked polyurethane. In some examples, the hinge layer may include a cross-linked thermoset polyurethane.

An article may include a biodata page defining a perimeter including an edge and a hinge layer attached to at least a portion of the biodata page. The hinge layer comprises a cross-linked polyurethane. In some examples, the hinge layer may include a cross-linked thermoset polyurethane.

A display medium including a first layer, a second layer, and a third layer, wherein: a part or an entirety of the first layer, a part or an entirety of the second layer, and a part or an entirety of the third layer are stacked in a thickness direction in this order; the first layer is a layer that is capable of reflecting circularly polarized light having a rotation direction D1 and allowing to pass therethrough circularly polarized light having a rotation direction D2, which is a direction opposite to the rotation direction D1; the second layer is a phase difference layer; and the third layer is a layer that is capable of reflecting circularly polarized light whose rotation direction is the rotation direction D1 and allowing to pass therethrough circularly polarized light whose rotation direction is the rotation direction D2.