SECURITY THREAD

A narrow polymer or metallic stripe embedded in a paper web during the paper manufacturing process. It is verified in transmitted light.

Types of security threads:

• a latent security thread is completely embedded in paper;

• a windowed (diving) security thread appears partially on the paper surface. In reflected light it looks like a dashed line, in transmitted light — like a solid dark stripe.

Security threads may be colored and may incorporate microprinting, optically variable, UV and IR luminescent features.

a — front side; b, c —  Latent security thread. Transmitted light (b). Cross section of a document page (c)

a —front side; b, c, d —  Latent security thread. Transmitted light (b). IR light (c).  microprinting on the security thread (d)

a — front side; b — ecurity thread. UV light; c, d —  Transmitted light (c). White light (d). The image of a plane moves when changing the angle of observation or illumination (d)